CA3117346A1

CA3117346A1 - Enhanced dewatering of mining tailings employing chemical pre-treatment

Info

Publication number: CA3117346A1
Application number: CA3117346A
Authority: CA
Inventors: Mitchell CATLING; Lois BOXILL; John BELLWOOD; Carlos SILVA GAXIOLA; Coralys TORRES LOPEZ
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2018-10-31
Filing date: 2019-10-30
Publication date: 2020-05-07
Also published as: WO2020089271A1

Abstract

The invention relates to a process for separating solids from an aqueous slurry containing particulate material, which particulate material comprises sand particles and fines particles and contains clay particles, which aqueous suspension has a solids content of from 25 to 70% by weight and a sand to fines ratio of from 0.5:1 to 5:1, which process comprises applying a treatment system to the aqueous slurry to cause flocculation of the particulate material, and subsequently separating the so formed flocculated particulate material as solids from the slurry, in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol; (b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (measured at 25°C in 1 M NaCI) and (c) optionally, at least one cationic coagulant.

Description

Enhanced Dewatering of Mining Tailings Employing Chemical Pre-treatment Background of the Invention Field of the Invention The present invention, in one of its aspects, relates to a process for treating an aqueous slurry .. such as a tailings stream from a mineral processing operation. Said process employs a treat-ment system that includes at least one ionic polymeric de-coagulant and at least one polymeric flocculent. In another of its aspects, the present invention also relates to an aqueous composi-tion containing an aqueous slurry of particulate material comprising sand particles and fines particles and also contains at least one ionic polymeric de-coagulant and at least one polymeric flocculent.
Description of the Prior Art Processes of treating mineral ores, coal or oil sands to extract mineral values or in the case of coal and oil sands to recover the hydrocarbons, will normally result in waste material from the beneficiation process. Often the waste material is an aqueous slurry or sludge comprising par-ticulate mineral material, for instance clay, shale, sand, grit, oil sands tailings, metal oxides etc.
admixed with water.
Typically, the slurry of waste material would be thickened in one or more gravity sedimentation vessels, which are sometimes referred to as thickeners, to concentrate the solids and recover some of the water content. In some processes where the valuable metal is recovered by disso-lution or leaching, the waste solid material may be separated from the liquor containing the min-eral values by a series of counter current sedimentation vessels, sometimes referred to as a recovery circuit. In the Bayer alumina process for example, following an initial digestion stage, the solids, often referred to as red mud, would be passed to an initial gravity sedimentation ves-sel, often referred to as a thickener, and washed in the liquor from subsequent gravity sedimen-tation vessels, often referred to as washer vessels. The solids from the initial thickener stage would be passed from the base of the vessel as an underflow and into the first of a series of counter current sedimentation vessels (washer vessels), in which the solids from each washer vessel would be passed as an underflow successively to each subsequent washer vessel and in which an aqueous liquor is used to wash the solids in each stage before being passed to each previous washer stage and then finally into the first thickener stage.
Polymeric flocculants may be added into any one or more thickener or water stages to assist with the solids liquid separa-tion. The waste solids from the last washer stage would then be passed as an underflow to a disposal area, for example a lake or tailings dam.
GB 2080272 describes aqueous suspensions of red mud being removed from the Bayer pro-cess for making alumina by the addition of at least the first stage of the recovery circuit of a flocculants selected from starch, homopolymers of acrylic acid or acrylates, copolymers of acryl-ic acid or acrylates containing at least 80 molar percent acrylic acid or acrylate monomers and

2 combinations thereof and subsequent addition to later, more dilute stages in the recovery circuit of a copolymer containing from about 35 to 75 molar percent of acrylic acid or acrylate and from about 65 to 25 molar percent of acrylamide monomers.
US 5653946 refers to a process for fluidifying flocculated aqueous suspensions of red muds in the production of alumina from bauxite by the Bayer process, which consists:
in dissolving baux-ite using sodium hydroxide; then, in decanting and in washing the red muds formed in order to separate them from the alumina in successive vats, while recycling the washing water up-stream; and finally, in eliminating the red muds thus treated; and in which a flocculant consisting of a polyacrylamide of molecular weight greater than 10 million is introduced into the suspen-sion of one of the successive vats; wherein a dispersing agent formed by an anionic acrylic acid polymer of molecular weight lower than 50,000 is added simultaneously with said flocculant to the suspension in the same vat.
In a typical mineral, coal or oil sands processing operation, waste solids are separated from solids that contain mineral valuables or hydrocarbon in an aqueous process.
The aqueous sus-pensions of waste solids often contain clays and other minerals and are usually referred to as tailings. These solids are often concentrated by a flocculation process in a gravity thickener to give a higher density underflow and to recover some of the process water.
In some cases, the waste material such as mine tailings can be conveniently disposed of in an underground mine as backfill. Generally, this waste comprises a high proportion of coarse large sized particles together with other smaller sized particles and is pumped into the mine as a slur-ry, occasionally with the addition of a pozzolan, where it is allowed to dewater leaving a sedi-mented solid in place. It is commonplace to use flocculant to assist this process by flocculating the fine material to increase the rate of sedimentation. However, in this instance, the coarse material will normally sediment at a faster rate than the flocculated fines, resulting in a hetero-geneous deposit of coarse and fine solids.
For other applications it may not be possible to dispose of the waste in an underground mine. In these cases, it is common practice to dispose of the material, by pumping the aqueous slurry or underflow to lagoons, heaps or stacks, which may be above ground, or into open mine voids, or even purpose-built dams or containment areas. It is usual to pump the aqueous slurry to a sur-face holding area, often referred to as a tailings pit or dam or more usually a tailings pond in the case of oil sands. This initial placement of the mining waste into the disposal area may be as a free-flowing liquid, thickened paste or the material may be further treated to remove much of the water, allowing it to be stacked and handled as a solid-like material. Once deposited at this sur-face holding area, water will continue to be released from the aqueous suspension resulting in further concentration of the solids over a period of time through the actions of sedimentation, drainage and evaporation. Once a sufficient volume of water has been collected this is usually pumped back to the mineral or oil sands processing plant.
For example, in the case where the tailings are sent to the disposal area in a liquid and fluid form, they must be contained in a lagoon by dams or similar impoundment structures. The tail-

3 ings may have been pretreated by adding flocculating agents and thickened in a gravity thick-ener to remove and recover some of the water content, but the overall solids content is such that the fluid has no, or a low yield stress, and hence the material behaves largely as a liquid on deposition. These lagoons may be relatively shallow, or relatively deep, depending upon how much land is available, the location for building impoundment area and other geotechnical fac-tors generally within the vicinity of the mine site. Dependent upon the nature of the solid parti-cles in the waste, often the particles will gradually settle from the aqueous slurry and form a compact bed at the bottom of the deposition area. Released water may be recovered by pump-ing or is lost to the atmosphere through evaporation and groundwater through drainage. It is desirable to remove the aqueous phase from the tailings whereby the geotechnical moisture content is below the liquid limit of tailings solids, in order to manage the remaining tailings in a form that has a predominantly solid or semi-solid handling characteristic.
Numerous methods can be employed to achieve this, the most common, when the material properties of the tailings allow, is self-weight consolidation in a tailings dam, whereby the permeability of tailings is enough to overcome the filling rate of the dam and water can be freely released from the tail-ings. Where the permeability of the tailings is not sufficient for water to escape freely, polymers are typically used to improve permeability thereby making the tailings more suitable for a self-weight consolidation process. Eventually, it may be possible to rehabilitate the land containing the dewatered solids when they are sufficiently dry and compact. However, in other cases, the nature of the waste solids will be such that the particles are too fine to settle completely into a compact bed, and although the slurry will thicken and become more concentrated over time, it will reach a stable equilibrium whereby the material is viscous but still fluid, making the land very difficult to rehabilitate. It is known that the flocculants are sometimes used to treat the tail-ings before depositing them into the disposal area, to increase the sedimentation rate and in-crease the release of water for recovery or evaporation.
In an alternative method, the tailings may be additionally thickened, often by the treatment with polymeric agents, such that the yield stress of the material increases so that the slurry forms heaps or stacks when it is pumped into the deposition area. Specialised thickening devices such as Paste Thickeners or Deep Cone Thickeners may be used to produce an underflow with the required properties. Alternatively, the polymeric agents may be added the tailings slurry dur-ing the transfer or discharge into the disposal area, to render the material less mobile and achieve the required yield stress. This heaped geometry aids more rapid dewatering and drying of the material to a solid-like consistency as the water is removed and recovered more rapidly through run-off and drainage, and the compaction of the solids may occur more rapidly through the increased weight and pressure of the solids when formed into a heap or a stack. In some instances, the deposition of the solids is controlled to build up relatively narrow bands of tailings which can also dewater quickly through evaporation, prior to adding a new layer of treated waste material on top. This is sometimes referred to as thin lift or dry stacking. Typically, each relatively narrow band of tailings (i.e. each layer of treated waste material) would tend to have a thickness of from 0.1 to 0.5 m. In the case of red mud, this material often has sufficient yield stress to form the layered stacks without further polymer treatment and this method has been widely used to dispose of tailings from alumina processing for a number of years. Air drying of

4 tailings can be used to great effect where the environment has some evaporation potential and there is enough land area to spread the tailings thinly enough for this process to be effective.
Where the area for evaporation is limited it is possible for the polymers to be added to the tail-ings to improve this process. The addition of the polymer may increase the permeability of the tailings whereby at least about 20% by weight of water can be allowed to drain, while another 20% of the water that is typically more associated with the particle surfaces and the clay matrix can be removed through evaporation.
It is often useful for the tailings pond or dam to be of limited size to minimise the impact on the environment. In addition, providing larger tailings ponds can be expensive due to the high costs of earthmoving and the building of containment walls. These ponds tend to have a gently slop-ing bottom which allows any water released from the solids to collect in one area and which can be pumped back to the plant. A problem that frequently occurs is when the size of the tailings pond and the dam are not large enough to cope with the output of tailings from the mineral pro-cessing operation. Another problem that frequently occurs is when fine particles of solids are carried away with the run-off water. Thus, the released water containing the fine particles could have a detrimental impact on recycling and subsequent uses of the water.
Another method for disposal of the mine tailings is to use mechanical dewatering devices such as filters and centrifuges. Such mechanical dewatering devices are able to remove a significant amount of water from the aqueous minerals slurry, such that the waste material may be depos-ited in the disposal area directly with a solid like consistency. In many cases, it is necessary to treat the tailings with polymeric flocculating agent immediately prior to the mechanical dewater-ing step, to enable this equipment to perform efficiently and achieve the degree of dewatering required.
A further method for disposal of the mine waste is through filtration in a Geotube , whereby the aqueous slurry placed into a permeable geotextile bag which retains the solids particles and some of the water is released by a filtration process, escaping through the walls of the geotex-tile bag. In some cases, where the starting permeability of the mine tailings is low, it may be desirable to add a flocculating agent in order to increase the filtration rate and improve the re-tention of fine solids within the Geotube .
For example, in oil sands mining, the ore is processed to recover the hydrocarbon fraction, and the remaining material, constitutes the tailings. In the oil sands extraction process, the main process material is water, and the tailings are mostly sand with some silt and clay, with some residual bitumen. Physically, the tailings consist of an easily dewatered, solid part (sand tailings) and a more fluid part (sludge). The most satisfactory place to dispose of the tailings, is of course in the existing excavated hole in the ground. Nevertheless, the sand tailings alone from the one cubic foot of ore occupy just about one cubic foot. The amount of sludge is variable, depending on the quality and process conditions, but average about 0.3 ft3. The tailings simply will not fit into the hole in the ground. Therefore, there is generally a requirement to build additional im-poundment areas for the tailings.

Within the oil sands industry, there are many different types of process tailings streams as de-fined in Technical Guide for Fluid Fine Tailings Management, COSIA 2012, which may require treatment with polymeric agents. One example is "fine fluid tailings" (FFT) which is the fines fraction (mainly silt and clay) from the process after the hydrocarbon content has been largely

5 recovered, and the sand fraction has been largely removed, usually by passing the "whole tail-ings" (WT) through a cyclone. The solids content of the fine fluid tailings may vary significantly, depending upon if material has been thickened by gravity sedimentation. Whole Tailings (WT) may be regarded as tailings produced from primary or secondary separation vessels of the ex-traction plant and contains sand, fines and water. In general, the sand to fines ratio of the WT
are greater than 4:1 and may be as high as 20:1.
Another example is "composite tails" (CT) in which all the particle size ranges are present (sand, silt and clay). This may be the whole tailings, prior to the removal of the sand, or other tailings streams which may be formed by subsequent mixing of fine tailings with sand fractions, to varying degrees. The sand to fines ratio of CT tend to be greater than 3:1 and may be as high as 6:1 or 7:1. A further example is "mature fines tailings" (MFT) which are formed after storage of fluid fine tailings, or in some cases combine tailings, in a tailings pond for several years. FFT tends to have sand to fines ratios significantly below 1:1 and MFT
tend have much lower sand contents typically less than 0.3:1, for instance less than 0.25:1.
In the oil sands fine tailings pond, the process water, any residual hydrocarbons and minerals settle naturally to form different strata. The upper stratum can be predominantly water that may be recycled as process water to the extraction process. The lower strata can contain settled residual hydrocarbon and minerals which are predominantly fines, usually clay.
It is usual to refer to this lower stratum as mature fines tailings. It is known that mature fines tailings consoli-date extremely slowly and may take many hundreds of years to settle into a consolidated solid mass. Consequently, mature fines tailings and the ponds containing them are a major chal-lenge to tailings management and the mining industry.
The composition of mature fines tailings tends to be variable. The upper part of the stratum may have a mineral content of about 10% by weight but at the bottom of the stratum the miner-al content may be as high as 50% by weight. The variation in the solids content is believed to be because of the slow settling of the solids and consolidation occurring over time. The aver-age mineral content of the MFT tends to be of about 30% by weight. MFT
behaviour is typically dominated by clay behaviour, with the solids portion of the MFT behaving more as a plastic-type material than that of a coarser, more friable sand.
The MFT frequently comprises a mixture of sand, fines and clay. Generally, the sand is defined as siliceous particles of any size greater than 44 pm and may be a component of the MFT sol-ids in an amount of up to 50% by weight. The remainder of the mineral content of the MFT
tends to be made up of a mixture of clay and fines (silts). Generally, fines refer to mineral parti-cles no greater than 44 pm. The clay may be any material traditionally referred to as clays by virtue of its mineralogy and will generally have a particle size of below 2 pm. Typically, the clays

6 tend to be a blend of kaolin, illite, chlorite and water swelling clays, such as smectites which are sometimes referred to as montmorillonites and may be interlayered with the other types of clay.
Additional variations in the composition of MFT may be as a result of the residual hydrocarbon which may be dispersed in the mineral tailings and may segregate in the tailings pond into mat layers of hydrocarbon. The MFT in a pond not only has a wide variation of compositions distrib-uted from top to bottom of the pond but there may also be pockets of different compositions at random locations throughout the pond.
It has been known to treat aqueous slurry such as tailings using polymer flocculants. See, for example, any of:
EP-A-388108;
WO 96/05146;

7;
WO 04/060819;
WO 01/05712; and W097/06111.
Canadian patent 2,803,904 teaches the use of high molecular weight multi valent anionic poly-mers for clay aggregation. Specifically, a polymer comprising an anionic water-soluble multiva-lent cation-containing acrylate copolymer is described.
Canadian patent 2,803,025 teaches a polymer similar to the polymer taught in Canadian patent 2,803,904 with the proviso that the polymer has an intrinsic viscosity of less than 5 dl/gm.
WO 2017/084986 describes a multivalent cation containing copolymer derived from one or more ethylenically unsaturated acids. The copolymer has the following characteristics: (a) an intrinsic viscosity of at least about 3 dl/g when measured in 1 M NaCI
solution at 25 C; (b) the copolymer is derived from a monomer mixture comprising an ethylenically unsaturated acid and at least one comonomer, the ethylenically unsaturated acid present in an amount in the range of from about 5% to about 65% by weight; and (c) a residual comonomer content of less than 1000 ppm when the comonomer is an acrylamide. The copolymer, inter-alia, is useful as a floc-culent for treating an aqueous slurry comprising particulate material, preferably tailings from a mining operation.
US 2018/0201528 describes a method of dewatering an aqueous mineral suspension compris-ing introducing into the suspension flocculating system comprising a mixture of polyethylene glycol and polyethylene oxide polymers. The mixture of polyethylene glycol and polyethylene oxide polymers is said to be useful for the treatment of suspensions of particulate material, es-pecially waste mineral slurries and is said to be particularly suitable for the treatment of tailings and other waste material resulting from mineral processing, in particular, the processing of oil sands tailings.
Clay-based minerals are known to cause problems in mineral processing operations. When the mined ore contains significant amounts of clay, then treatment and disposal of the waste (gangue) material after the recovery (beneficiation) of the valuables is often problematic. This is because the stacked platelets of a clay mineral particle tend to delaminate (or break apart) when contacted with water and these delaminated platelets form (or rearrange into) network type structures held together by electrostatic forces between the edges and the faces of the clay platelets. The high specific surface area, combined with the hydrophilic nature of the surfaces, causes water to become trapped with solids, and the waste is then difficult to concentrate and dewater. This can result in both excessive volumes of waste material, soft deposits which do not compact readily over time, and loss of process water.
Polymeric flocculants, such as Magnafloc and Rheomax ETD ranges, supplied by BASF, have been used to enhance the rate of settling and dewatering of tailings deposits. However, in some cases, whilst the polymers do improve the rate and extent of water removal to some de-gree, this is not sufficient to increase the solids content of the material beyond the plastic limit of the system and, further self-weight compaction does not occur, leading to the creation of soft deposits which are not suitable for rehabilitation.
One such example is the Canadian oil sands industry, where it is well documented that their fine tailings will remain semi-fluid for many hundreds of years, except where the process allows for a significant amount of water evaporation and atmospheric drying. This problem is especially the case for deep pour deposits of tailings, which make the most effective use of land and mining voids but have limited opportunity for evaporative dewatering. Evaporation to dewater tailings to a solids content above the plastic point can only be used on relatively thin layers of deposited tailings, which requires a massive area of land to operate effectively.
Another industry which also produces problematic high clay containing tailings is the phosphate industry, for example in Florida, USA.
There is a need for a more effective process for dewatering waste solids containing clays, es-pecially one that improves upon or overcomes the aforementioned problems.
Summary of the Invention In accordance with the present invention we provide a process for separating solids from an aqueous slurry containing particulate material, which particulate material comprises sand parti-cles and fines particles and contains clay particles, which aqueous slurry has a solids content of from 25 to 70%, preferably 30 to 70%, by weight and a sand to fines ratio of from 0.5:1 to 5:1,

8 which process comprises applying a treatment system to the aqueous slurry to cause floccula-tion of the particulate material, and subsequently separating the so formed flocculated particu-late material as solids from the slurry, in which the treatment system comprises (a) at least one ionic polymeric de-coagulant which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculent, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCI); and (c) optionally, at least one cationic coagulant.
By applying a treatment system to the aqueous slurry, the process of the present invention in-cludes applying the treatment system, including the components thereof, to any one or more components used to form the aqueous slurry. Further, the treatment system may be applied to the aqueous slurry by addition of at least one of the treatment system components to a compo-nent forming the aqueous slurry and at least one of the treatment system components to anoth-er component forming the aqueous slurry. In addition, the treatment system may be applied to the aqueous slurry by addition of at least one of the treatment system components to at least one component forming the aqueous slurry and the remainder of the treatment system compo-nents may be added to the aqueous slurry to be treated according to the present invention.
Thus, where, for instance, the aqueous slurry is formed by combining any one or more of whole tailings (WT), composite tailings (CT), mature fines tailings (MFT), fluid fines tailings (FFT), thin fines tailings (TFT) and/or thickened fines tailings (ThFT) together with other components of the aqueous slurry such as sand, the treatment system may be applied to any one or more of these component streams forming the aqueous slurry or maybe split across different component streams or a combination of different component streams and the final aqueous slurry and dif-ferent components of the treatment system may be added to different component streams of the aqueous slurry.
The invention also relates to a composition formed from an aqueous slurry containing particu-late material, which particulate material comprises sand particles and fines particles and con-tains clay particles, which aqueous slurry has a solids content of from 25 to 70%, preferably 30 to 70%, by weight and a sand to fines ratio of from 0.5:1 to 5:1, in which the composition comprises flocculated particulate solids and a treatment system in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculent, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCI); and

9 (c) optionally, at least one cationic coagulant The invention further relates to a treatment system for separating solids from an aqueous slurry containing particulate material, which particulate material comprises sand particles and fines particles and contains clay particles, which aqueous slurry has a solids content of from 25 to 70%, preferably 30 to 70%, by weight and a sand fines ratio of 0.5:1 to 5:1, in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCI); and (c) optionally, at least one cationic coagulant.
The invention additionally relates to the use of said treatment system for separating solids from an aqueous slurry.
Description of the Drawings Figure 1 provides a graphical representation of the natural coagulation state of clays, showing a plot of suspension (aqueous slurry) viscosity (mPas) versus pH and providing two-dimensional representations of the respective coagulated structure of the clay platelets.
Figure 2 illustrates filtration apparatus employed in the test work of the examples.
Figure 3 is a graphical representation of the results of the filter cake moisture content variance on the dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of Flocculant 1 from Table 1 of Example 1.
Figure 4 is a graphical representation of the results of release of water solids variance on the dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of Flocculant 1 from Ta-ble 1 of Example 1.
Figure 5 is a graphical representation of the results of the variance of turbidity of released water on the dose of ionic polymeric de-coagulant Product 1 and employing 800 g/t of Flocculant 1 from Table 1 of Example 1.
Figure 6 is a graphical representation of the results of the filter cake moisture content variance in response to the dose of ionic polymeric de-coagulant Product 1 and employing 360 g/t Floc-culant 1 from Table 2 of Example 2.

Figure 7 is a graphical representation of the results of the release water solids variance in re-sponse to the dose of ionic polymeric de-coagulant Product 1 and employing 360 g/t Flocculent 1 from Table 2 of Example 2.
Figure 8 is a graphical representation of the results of the turbidity of released water variance in 5 response to the dose of ionic polymeric de-coagulant Product 1 and employing 360 g/t Floccu-lent 1 from Table 2 of Example 2.
Figure 9 is a graphical representation of the results of the filter cake moisture content variance in response to the dose of ionic polymeric de-coagulant Product 1 and employing 150 g/t Floc-culent 1 from Table 3 of Example 3.

10 Figure 10 is a graphical representation of the results of the release water solids variance in re-sponse to the dose of ionic polymeric de-coagulant Product 1 and employing 150 g/t Flocculent 1 from Table 3 of Example 3.
Figure 11 is a graphical representation of the results of the turbidity of released water variance in response to the dose of ionic polymeric de-coagulant Product 1 and employing 150 g/t Floc-culant 1 from Table 3 of Example 3.
Figure 12 is a graphical representation of the results of the filter cake moisture content variance in response to the dose of ionic polymeric de-coagulant Product 1 and employing 715 g/t Floc-culent 3 from Table 6 of Example 6.
Figure 13 is a graphical representation of the results of the turbidity of released water variance in response to the dose of ionic polymeric de-coagulant Product 1 and employing 715 g/t Floc-culent 1 from Table 6 of Example 6.
Detailed Description The aqueous slurry should have a solids content of from 25 % to 70% by weight of the aqueous slurry. The aqueous slurry to be treated may already have a solids content within this range.
Typically, however, an aqueous slurry may have undergone some sort of initial thickening stage where an amount of the aqueous liquid may have been removed. Such an initial thickening stage may, for instance, be a sedimentation stage, such as in a thickening or sedimentation vessel or in a pit. Alternatively, the thickening stage may include a belt thickener or a centrifuge.
Other means of bringing the solids content to within the required range may also be possible.
By particulate mineral solids we mean that the solids include mineral or mining solids, typically from a mining or mineral processing operation. The particulate solids in the slurry may, for in-stance, contain filter cake solids or tailings. Often, the particulate mineral material comprises tailings. Suitably, the aqueous slurry may comprise phosphate slimes, gold slimes or wastes from diamond processing. Typically, the particulate mineral material is selected from the group consisting of coal fines tailings, mineral sands tailings, red mud (alumina Bayer process tail-

11 ings), oil sands tailings, mature fines tailings, zinc ore tailings, lead ore tailings, copper ore tail-ings, silver ore tailings, uranium ore tailings, nickel ore tailings and iron ore tailings.
Suitably the at least one ionic polymeric de-coagulant (a) should be added to the aqueous slurry before adding the at least one polymeric flocculent (b). Typically, the at least one ionic polymer-ic de-coagulant (a) may be added to the aqueous slurry first and subsequently the at least one polymeric flocculent (b) should be added. The optional component (c) of the treatment system, the at least one cationic coagulant, may be added to the aqueous slurry after the addition of the at least one ionic polymeric de-coagulant (a) but before the addition of the at least one polymer-ic flocculent (b) or alternatively the optional at least one cationic coagulant (c) may be added subsequently to the at least one polymeric flocculent (b). In some cases, it may even be desira-ble to add the optional at least one cationic coagulant (c) simultaneously with the addition of the at least one polymeric flocculent (b). Suitably, the aqueous slurry employed in the present in-vention may comprise clay in a coagulated state and the treatment system comprises adding to the aqueous slurry ionic polymeric de-coagulant (a) to reduce the coagulated state of the clay particles to a less coagulated state within the aqueous slurry and then addition of the polymeric flocculent (b) to flocculate the sand and de-coagulate treated clay particles.
By clay being in a coagulated state, we mean that clay platelets are linked to each other, typi-cally by electrostatic forces on the platelet faces and/or edges. Clays may exist in a number of coagulated states and typically these include arrangements where the platelets are linked in a face-to-face structure; a mixture of face-to-face and edge to face structures;
a mixture of edge to face and edge-to-edge structures; and edge-to-edge structures. When the clay is in a sub-stantially un-coagulated form the clay platelets tend to be substantially separated. Aqueous slur-ries tend to exhibit highest viscosity when the clay platelets contain edge to face structures, for instance mixtures of edge to face and edge-to-edge structures and especially mixtures of edge to face and edge-to-edge structures. This is illustrated in Figure 1.
Those aqueous slurries which contain clay in a coagulated form, particularly where the coagu-lated structure induces high viscosities, for instance as understood often to be the case when the slurries are oil sands MFT slurries or oil sands FFT slurries, tend to be particularly difficult to dewater.
The inventors realised that by employing a treatment system that includes an ionic polymeric de-coagulant as part of the treatment system in conjunction with a polymeric flocculent for clay containing aqueous slurries, more effective dewatering can be achieved.
Without being limited to theory, the inventors believe that the effectiveness of the present process involving the spe-cial treatment system may be as a result of breaking down the electrostatic forces between co-agulated clay platelets so as to allow the polymer chains of the flocculent to attach to a greater proportion of the suspended solids without interference from the coagulated clay. This allows for the improved release of water which would have been otherwise trapped inside of the coagulat-ed clay structures. The inventors believe that the de-coagulant is acting on the coagulated clay particles by breaking down or diminishing electrostatic attractive forces between them and

12 hence transferring the clay particles into a form of fully and/or partially separated particles (as depicted in Figure 1). Thus, by de-coagulant we mean a chemical additive which reduces elec-trostatic attractive forces between coagulated clay particles to render the particles fully and/or partially separated. In addition, the inventors have found that the employment of the treatment system facilitates the co-disposal of the fines and the sand. Desirably, this treatment enables the deposited solids separated from the aqueous slurry to contain both the fines and sand parti-cles forming a relatively homogenous deposit with minimal segregation of fines and sand parti-cles. Prevention of segregation during co-disposal of the fines and sand particles is important because otherwise the heavier sand particles would tend to settle faster while the fines would take longer to settle and would tend to be washed away with the liquid separated from the slur-ry. Thus, in the process according to the invention the liquid separated from the aqueous slurry tends to have a lower fines particles content. This can be measured by well-known filtration techniques. Suitably, the liquid separated from the aqueous slurry should have a solids content of less than 5% by weight of the total separated liquid. Preferably the solids content is less than 2% by weight of the total separated liquid, more preferably less than 1% by weight of the total separated liquid, even more preferably from 0.001% to 0.75% by total weight of the separated liquid, still more preferably from 0.01% to 0.5% by total weight of the separated liquid, often from 0.01% to 0.1% by total weight of separated liquid.
The particulate material contained in the aqueous slurry includes sand and fines. By sand we mean mineral solids (excluding gravel) with a particle size greater than 44 pm and generally less than 2 mm (not including bitumen). By fines we mean mineral solids, such as silts, with a particle size of equal to or less than 44 pm (not including bitumen). In general, the clay compo-nent of the aqueous slurry is part of the fines component. Thus, fines include the clay compo-nent as well as any other non-clayey mineral particles of the aforementioned size range. The particulate solid material contained in the aqueous slurry usually comprises a sand to fines ratio of from 1:1 to 5:1. Often the sand to fines ratio may be from 1:1 to 4:1, such as from 2:1 to 3:1.
The aqueous slurry may have a fines solids content of from 10% to 45%, by total weight of the aqueous slurry.
The invention is of particular applicability where the aqueous slurry is derived from an oil sands fluid fines tailings (FFT), thickened fine tailings (ThFT) or a mature fines tailings (MFT). Fluid fine tailings (FFT) are generally understood to mean a liquid suspension of oil sands fine tailings or fines dominated tailings in water, with a solids content greater than 2%
but less than the sol-ids content corresponding to the Liquid Limit. Mature fines tailings are understood to be a more specific category of fluid fine tailings with a sand to fines ratio of less than 0.3 and a solids con-tent typically greater than 30%. Thin fine tails (TFT) may be understood to be a category of fluid fine tailings with a sand to fines ratio of less than 0.3 and a solids content typically between 15 and 30%. Thickened fine tailings (ThFT) mean fluid fine tailings (FFT) or thin fine tailings (TFT) that have been thickened by removal of some of the aqueous content. However, the solids con-tent of such thickened fine tailings would not be above the liquid limit and therefore remain fluid.

13 Typically, the aqueous slurry comprises from 10% to 70% clay particles based on the total weight of solids. In general, the clay particles tend to be predominantly kaolinite and illite. The clay frequently also contains smectite and chlorite. The proportions of the clay components of oil sands clays in marine deposits tend to vary according to depth within the deposit. Generally, illite species slightly dominates in the top end of the deposits. The smectite species are general-ly interlayered with either the kaolinite or illite species, and this tends to induce additional sepa-ration of particles.
The at least one ionic polymeric de-coagulant (a) suitably may include water-soluble polymers exhibiting a weight average molar mass of below 1.5 million g/mol, for instance below 1 million g/mol, such as below 500,000 g/mol or below 100,000 g/mol. In general, the at least one ionic polymeric de-coagulant would tend to have a lower weight average molar mass, typically up to 50,000 g/mol. Desirably, the weight average molar mass of the at least one ionic polymeric de-coagulant may tend to be in the range of from 500 to 50,000 g/mol, for instance from 1000 to 40,000 g/mol, such as 2000 to 30,000 g/mol, or 3000 to 20,000 g/mol.
The at least one ionic polymeric de-coagulant (a) may typically be a combination of different ionic polymeric de-coagulants each having a weight average molar mass of below 1 million g/mol or any of the more precise ranges of molar mass referred to herein.
The at least one ionic polymeric de-coagulant (a) may be cationic, anionic, amphoteric or zwit-terionic. In the context of the present invention cationic means that the ionic polymeric de-coagulant (a) carries positive charges, anionic means that the ionic polymeric de-coagulant (a) carries negative charges and amphoteric means that the ionic polymeric de-coagulant (a) car-ries both positive and negative charges. By zwitterionic we mean that the ionic polymeric de-coagulant (a) contains positive and negative charges carried on the same repeating monomeric units. Preferably, however, the at least one ionic polymeric de-coagulant (a) is anionic.
Typical polymers which may be used as the ionic polymeric de-coagulant (a) include poly(naphthalene sulphonate), prepared for instance by reacting formaldehyde and naphthalene sulphonate. Other possible ionic polymeric de-coagulants include polymers based on melamine sulphonates and acetone/formaldehyde sulphonates. Generally, these materials may be pre-pared by a condensation reaction. Suitable polymers of this category may be those described in US 4725665 and US 3277162 which disclose the synthesis of naphthalene sulphonic ac-id/formaldehyde condensates starting from naphthalene, sulphuric acid and formaldehyde. In the synthesis naphthalene is initially reacted with concentrated sulphuric acid to form naphtha-lene sulphonic acid which is reacted with formaldehyde in a polycondensation reaction and then finally neutralisation utilising a suitable base, such as sodium hydroxide or calcium hydroxide.
The use for improving the flowability of inorganic binders like cement and as fluid (water) loss additives in cements for oil wells, respectively, is described. Suitable polymers based on mela-mine sulphonates are described in US 6555683. This document describes the preparation of the polycondensate based on melamine sulphonates and their use to liquefy inorganic binder suspensions. These may be synthesised by reacting melamine with formaldehyde and a sul-

14 phite at alkaline pH followed by a polycondensation reaction at acidic pH and finally neutralising the polymer with sodium hydroxide. Suitable polymers based on acetone, formaldehyde sul-phonate condensates are described in US 4818288 and US 4657593 which describe such con-densates for use as dispersants for inorganic binders and US 4657593 describes the use of these compounds as dispersion agents for kaolin and clay suspensions. The condensates are produced by reacting acetone and sodium sulphite with formaldehyde in a polycondensation reaction to give directly the desired polycondensate.
Preferably, however, the ionic polymeric de-coagulant (a) is a water-soluble polymer derived from ethylenically unsaturated monomers. One preferred category of water-soluble polymers includes those polymers prepared from one or more ethylenically unsaturated acid monomers or salts thereof. These polymers may be homopolymers of the one or more ethylenically unsatu-rated acid monomers (or salts thereof) or they may be copolymers of said one or more ethyleni-cally unsaturated acid monomers (or salts thereof) and one or more ethylenically unsaturated non-ionic monomers. Typically, these ethylenically unsaturated non-ionic monomers may be selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, vinyl acetate, vinyl alcohol, vinyl alkyl ether, allyl alkyl ether, styrene and 01-8 alkyl acrylates.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable hydroxyalkyl methacry-lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxybutyl methac-rylate.
Suitable 01_8 alkyl acrylates as non-ionic comonomers may include methyl acrylate, ethyl acry-late, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or cyclohexyl acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl ether, ally! ethyl ether, allyl n-propyl ether or allyl isopropyl ether.
The ethylenically unsaturated acid monomers for preparing the aforesaid homopolymers or co-polymers as the ionic polymeric de-coagulant (a), may be any suitable ethylenically unsaturated monomer bearing an acid group. Suitable acid groups may include carboxylic acids, sulphonic acids, sulphuric acids, phosphoric acids or phosphonic acids. By referring to the specific eth-ylenically unsaturated acid monomers we also include the corresponding salts thereof by this definition. We also include the corresponding anhydride of an acid group in the definition of eth-ylenically unsaturated acid monomers. Suitable monomers in this category include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, ethacrylic acid, crotonic acid, mono esters of ethylenically unsaturated dicarboxylic acids, such as mono methyl maleate, mono me-thyl fumarate, mono ethyl maleate, mono n butyl maleate, and mono n butyl fumarate, styrene carboxylic acids, maleic anhydride, itaconic anhydride, 2-acrylamido-2-methylpropylene acid, vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid, 2-hydroxy ethyl methacrylate phosphate.

Preferred ionic polymeric de-coagulants (a) are selected from the group consisting of a homo-polymer of acrylic acid (or salts thereof) and a copolymer of a monomer mixture consisting of acrylic acid (or salts thereof) and acrylamide. Suitable ionic polymeric de-coagulants (a) of this category may include polymers in the Dispex or Sokalan product ranges supplied by BASF.
5 Another particularly suitable category of ionic polymeric de-coagulants (a) include anionic poly-mers derived from ethylenically unsaturated monomers and said polymer comprising repeating monomeric units carrying pendant polyalkyleneoxy groups. Suitable ionic polymeric de-coagulants (a) may be prepared in accordance with US 6777517, US 2012/0035301 or CA
2521173.
10 Preferred ionic polymeric de-coagulants (a) include polymers comprising repeating units derived from monomers, (i) an ethylenically unsaturated anionic or non-ionic monomer containing a polymerisable moiety (M) and having the structure M ¨ R2¨ X ¨ (- CH2¨ CHR5¨ 0 -)i ( ¨ CH2¨ CH2¨ 0 ¨)m - ( - CH2 ¨ CHR3 ¨ 0 -),-, ¨ R4 (I)

15 in which X is 0 or NH, R2 is independently a single bond or a divalent linking group selected from the group consisting of ¨(CH2¨)p- and ¨0¨(CH2¨)s where p is a number from 1 to 6 and s is a number from 1 to 6, R3 and R5 are each independently a hydrogen or hydrocarbyl radical having 1-4 carbon atoms, R4 is independently a hydrogen or a hydrocarbyl radical having 1-4 carbon atoms or a moiety having the structure ¨ ( ¨ CH 2¨ CH2¨ 0 ¨)k-Y
k is a number from 1 to 20 I is a number from 0 to 250;
m is a number from 1 to 300, n is a number from 0 to 250;
Y is hydrogen or a hydrocarbyl radical having 1-4 carbon atoms, and (ii) at least one ethylenically unsaturated monomer carrying at least one anionic functional group different from component (i);
and

16 (iii) optionally at least one ethylenically unsaturated non-ionic monomer, different from component (i).
In the present invention, M maybe any suitable polymerisable ethylenically unsaturated moiety.
Preferably, M is selected from a vinyl moiety, an ethylenically unsaturated carboxylic moiety, an ethylenically unsaturated amide moiety, an allyl moiety or isoprenyl moiety.
More preferably, M is selected from the group consisting of:
H2C=C(R1)¨ (II);
H2C=C(R1)¨CH2¨ (Ill);
H2C=C(R1)¨00¨ (IV);
H000¨HC=C(R1)¨00¨ (V); and ¨0C¨HC=C(R1)¨00¨(V1), in which R1 is hydrogen or methyl.
It will be apparent to the person skilled in the art in the field of polyalkylene oxides that the num-bers in regard to I, m and n mentioned are mean values of distributions.
It will be apparent to the person skilled in the art in the field of polyalkylene oxides that the ori-entation of the respective hydrocarbyl radicals R3 and R5 may depend on the conditions in the alkoxylation, for example on the catalyst selected for the alkoxylation in the polymerisation reac-tion of the copolymer of the present invention. The alkyleneoxy groups can thus be incorporated into the monomer (i) in the orientation ¨(¨CH2¨CH(R5)-0-)1¨ or else the inverse orientation ¨(-CH(R5)-0H2-0-)1¨ and the orientation ¨(¨CH2¨CH(R3)-0-),-,¨ or else the inverse orientation ¨(¨
CH(R3)-CH2-0-)n¨. The representation in formula (I) shall therefore not be regarded as being restricted to a particular orientation of the R3 or R5 groups.
Monomer (i) of general formula (I) suitably contains the following preferred features:
Preferably integers I and n are each zero.
Integer m is preferably from 5 to 250, more preferably from 10 to 200, even more preferably from 45 to 175 and most preferably from 45 to 175.
Preferably, R1 is hydrogen.
If R2 is not a single bond then preferably integer s is 4; or integer p is 1 or 2.
Preferably, M is a vinyl, or maleic mono ester group.

17 One suitable group of monomers as monomer (i) of the general formula (I) is vinyloxybutyl poly-ethylene glycol, in which the polyethylene glycol moiety contains from 45 to 175 repeating eth-ylenoxide units, preferably containing from 75 to 150 repeating ethylenoxide units, more prefer-ably containing from 100 to 150 repeating ethylenoxide units, particularly from 110 to 140 re-peating ethylenoxide units, more particularly from 120 to 140 repeating ethylenoxide units. An especially preferred monomer (i) of general formula (I)is the adduct of 129 moles of ethylene oxide with 4-hydroxy butyl mono vinyl ether.
A further suitable group of monomers as monomer unit (i) of general formula (I) is based on the reaction of 4-hydroxy butyl vinyl ether which has been ethoxylated, then butoxylated and then ethoxylated. This group of monomers may be described as vinyloxybutyl polyethylene glycol polybutadiene glycol polyethylene glycol or may be defined as vinyloxybutyloxy (E0)a (B0)b (E0)c, in which EO represents repeating ethylenoxide units, BO represents repeating butylene units and each of a, b, c independently represents numbers. Suitably, a may be from 5 to 75, b may be from 1 to 30 and c may be from 0 to 20. Preferably, a may be from 10 to 50, b may be .. from 2 to 20 and c may be from 0 to 20. More preferably, a may be from 15 to 40, b may be from 5 to 20 and c may be from 0 to 10. More preferably still, a may be from 24 to 25, b may be from 10 to 20 and c may be from 0 to 5. One particularly suitable monomer is where a is from 24-25, b is from 15-17 and c is from 3-4.
Another suitable monomer (i) of the general formula (I) is poly (PO block-EO) maleamide which may be prepared by the reaction of Jeffamine Monoamines (M series) (available from Hunts-man) with maleic anhydride in the ratio of 1:1 to give the mono amide. By PO
block-EO it is un-derstood that this means a block of propylene oxide units and a block of ethylene oxide units.
The at least one ethylenically unsaturated monomers that carries an anionic functional group of category (ii) may be any suitable anionic ethylenically unsaturated monomer.
Suitable anionic functional groups may include carboxylic acids, sulphonic acids, sulphuric acids, phosphoric acids or phosphonic acids. By referring to the specific ethylenically unsaturated anionic mono-mers we also include the corresponding salts thereof by this definition. We also include the cor-responding anhydride of an acid group in the definition of ethylenically unsaturated anionic monomers. Suitable monomers in this category include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, ethacrylic acid, crotonic acid, mono esters of ethylenically un-saturated dicarboxylic acids, such as mono methyl maleate, mono methyl fumarate, mono ethyl maleate, mono n butyl maleate, and mono n butyl fumarate, styrene carboxylic acids, maleic anhydride, itaconic anhydride, 2-acrylamido-2-methylpropylene acid, vinylsulfonic acid, allyl sul-phonic acid, vinyl phosphonic acid, 2-hydroxy ethyl methacrylate phosphate.
A still further type of suitable monomers (i) of general formula (I) are based on methacrylic es-ters and acrylic esters. Examples of these are mono methacrylate adduct of ethylene oxide units. Typical examples of these may be found in US 5707445, particularly in the examples in column 7 by reference to monomers A-1 (mono methacrylate of adduct of methanol with eth-ylene oxide (EO) units (average number of EO units of 115)); A-2 (mono methacrylate adduct of methanol with EO repeating units (average number 220)); A-3 (mono methacrylate adduct of

18 methanol with repeating EO units (average number 280)); A-5 (block adduct of acrylic acid with propylene oxide (PO) units and EO units (average number 135)); A-6 (block adduct of acrylic acid with E0 and PO (average number of E0 molecules 135 and average number of PO mole-cules added 5)); and A-8 (mono methacrylate of adduct of methanol with EO
(average number 5 of EO molecules 100)).Preferably monomer component of category (ii) is either acrylic acid (or salts thereof), maleic anhydride or maleic acid (or salts thereof).
Suitable ethylenically unsaturated non-ionic monomers of category (iii) may be any suitable non-ionic ethylenically unsaturated monomer that is different from the monomers of category (i) and be copolymerisable with the monomers of categories (i) and (ii).
Desirably, these mono-10 .. mers may be selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, hydroxy alkyl methyl acrylate, vinyl acetate, vinyl alcohol, allyl alkyl ether, styrene, and alkyl acrylates.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable hydroxyalkyl methacry-lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxybutyl methac-rylate.
Suitable 01-8 alkyl acrylates as non-ionic comonomers may include methyl acrylate, ethyl acry-late, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or cyclohexyl acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl ether, allyl ethyl ether, allyl n-propyl ether or allyl isopropyl ether.
The ranges of the respective repeating units are suitably as follows:
Monomer (i) is preferably from 1 to 50 moles %; monomer (ii) is preferably from 50 to 99 mole %; and monomer (iii) is preferably from 0 to 33 mole %. More preferably, monomer (i) is from 5 to 40 mole %; monomer (ii) from 60 to 95 mole %; and monomer (iii) from 0 to 25 mole %. Even more preferably, monomer (i) is from 10 to 30 mole %; monomer (ii) from 70 to 90 mole %; and monomer (iii) is preferably 0%.
The weight average molar mass of the ionic polymeric de-coagulant (a) formed from monomers (i), (ii) and optionally (iii) is preferably from 1000 to 100,000 g/mole, more preferably from 5000 to 70,000 g/mole, even more preferably from 10,000 to 65,000 g/mole, more preferably still from 20,000 to 60,000 g/mole, especially from 25,000 to 60,000 g/mole and most preferably from 30,000 to 60,000 g/mole.
The weight average molar mass may be determined by gel permeation chromatography (GPO) with the following method: column combination: Shodex OH-Pak SB 804 HQ and OH-Pak SB
802.5 HQ from Showa Denko, Japan; eluent: 80 vol % aqueous solution of HCO2NH4 (0.05 mo1/1) and 20 vol% Me0H; injection volume 100 pl; flow rate 0.5 ml/min. The weight average

19 molar mass may be calibrated using standards from PSS Polymer Standard Service, Germany.
For the UV detector, poly(styrene-sulfonate) standards may be used, and poly(ethylene oxide) standards for the RI detector. The weight average molar mass may then be determined using the results of the RI detector.
The preparation of suitable polymeric products containing monomers (i) and (ii) and optionally containing component (iii) is described in US 6777517, US 2012/0035301 or CA
2521173.
One particularly suitable group of ionic polymeric de-coagulant (a) is formed from the terpolymer of vinyloxybutyl polyethylene glycol (i); acrylic acid as a monomer (ii); and maleic anhydride as a further monomer (ii). The polyethylene glycol moiety preferably contains from 45 to 175 repeat-ing ethylenoxide units, preferably containing from 75 to 150 repeating ethylenoxide units, more preferably containing from 100 to 150 repeating ethylenoxide units, particularly from 110 to 140 repeating ethylenoxide units, more particularly from 120 to 140 repeating ethylenoxide units.
Particularly preferably the monomer (i) is the adduct of 129 moles of ethylene oxide with 4-hydroxybutyl monovinyl ether. The molar ratio of the aforesaid three monomers is preferably 0.8-1.2/4/0.4-0.8 and suitably has a weight average molar mass of from 45,000 to 60,000 g/mole. The preparation of a particularly suitable polymer for use as the ionic polymeric de-coagulant (a) is described in US 2012/0035301 on page 4 under heading Polymer 1.
Another suitable group of ionic polymeric de-coagulant (a) is formed from the terpolymer of vi-nyloxy butyl polyethylene glycol polybutylene glycol polyethylene glycol (as described above) (i):
acrylic acid as a monomer (ii); and maleic anhydride as a further monomer (ii). The monomer (i) vinyloxybutyloxy (E0)a (B0)b (E0)c, in which EO and BO have each been defined above and in which suitably a may be from 5 to 75, b may be from 1 to 30 and c may be from 0 to 20. Pref-erably, a may be from 10 to 50, b may be from 2 to 20 and c may be from 0 to

20. More prefer-ably, a may be from 15 to 40, b may be from 5 to 20 and c may be from 0 to 10.
More preferably still, a may be from 24 to 25, b may be from 10 to 20 and c may be from 0 to 5. One particularly suitable monomer is where a is from 24-25, b is from 15-17 and c is from 3-4.
The molar ratio of the aforesaid three monomers is suitably 2-5/4/0.8-1.2 and the weight average molar mass of from 15,000 to 45,000 g/mole.
Other suitable polymers as ionic polymeric de-coagulants (a) are described in US
2012/0035301, particularly the examples.
Further suitable polymers as ionic polymeric de-coagulants (a) include copolymers of methacryl-ic or acrylic esters of formula (I) with ethylenically unsaturated carboxylic acids or corresponding salts such as acrylic acid (or salts thereof), methacrylic acid (or salts thereof) or maleic acid (or salts thereof or the anhydride). Suitable methacrylic esters of formula (I) would include mono-mers A-1, A-2, A-3, A-5, A-6 and A-8 given in US 5707445 (described above).
Suitable exam-ples of such suitable polymers for this application are given in US 5707445 for instance the Preparative Example 3 and Preparative Example 5. Examples of other suitable polymers are also given in EP 1142847 A2 and particularly in Reference Example 3 and Reference Example 4.

Yet further suitable polymers as ionic polymeric de-coagulants (a) include copolymers of poly-ethylene glycol mono methyl ether methacrylate copolymers with ethylene glycol methacrylate phosphate optionally with methacrylic acid. Desirable examples of these polymers are given in US 2008/146700 and with specific reference to Table 1 and in particular Polymer Numbers 5-8, 5 14 and 15.
By water-soluble in respect of the ionic polymeric de-coagulant (a), we mean that the polymers exhibit a solubility in water of at least 5 g per 100 ml of water at 25 C.
The ionic polymeric de-coagulant (a) may suitably have a charge density of from 0.2 to 10 meq/g (milliequivalents per gram), preferably from 0.3 to 8 meq/g, more preferably from 0.5 to 5 10 meq/g and most preferably from 0.8 to 3 meq/g.
The at least one ionic polymeric de-coagulant (a) may be used in conjunction with other addi-tives. This may be by the inclusion of one or more additives together with the at least one ionic polymeric de-coagulant (a), for instance as at least one compound present as a mixture togeth-er with the at least one ionic polymeric de-coagulant (a). Examples of typical additives that may 15 be used in conjunction with the at least one ionic polymeric de-coagulant (a) include polyeth-ylene glycol (PEG), polyethylene glycol derivatives (such as monofunctional polyethylene glycol monoalkyl ethers) or polyvinyl alcohol. Suitable polyethylene glycols may have weight average molar masses of up to 50,000 g/mol but are usually within the range of from 50 g/mol to 30,000 g/mol, typically in the range of from 100 to 20,000 g/mol, for instance from 200 to 20,000 g/mol 20 or 200 to 10,000 g/mol, such as from 200 to 5000 g/mol, typically from 200 to 1000 g/mol or from 300 to 500 g/mol. The polyethylene glycols may have any particular geometry, for instance linear, branched, star, comb structures. Suitable polyethylene glycols are commercially availa-ble and may be available, for instance from Dow Chemical under the tradename Carbowax 0, or from BASF under the tradename Pluriol 0 E or from Clariant under the name Polyglykol 0 M.
The at least one ionic polymeric de-coagulant (a) may be a mixture of different ionic polymeric de-coagulants. Such a mixture may include a first mixture component based on one or more of any of the aforementioned ionic, especially anionic, polymers derived from ethylenically unsatu-rated monomers and being a polymer comprising repeating monomeric units carrying pendant polyalkyleneoxy groups and a second mixture component being one or more different ionic pol-ymeric de-coagulants as described herein. Such different ionic polymeric de-coagulant as sec-ond mixture component may be a homopolymer or copolymer of acrylic acid (or salts thereof), for instance any of those polymer types analogous to the Dispex or Sokalan product ranges.
Preferably the mixture of different ionic polymeric de-coagulants comprises as first mixture component being a polymer in the aforementioned category formed from monomers (i), (ii), and optionally (iii) and the second mixture component being an anionic copolymer or anionic homo-polymer, particularly of the polymer types analogous to Dispex or Sokalan product ranges.
The polymeric flocculent (b) should be a polymer having an intrinsic viscosity of at least 5 dl/g (measured at 25 C in 1 M NaCI). The polymer may be non-ionic, anionic, amphoteric or cation-ic. Typically, this may be formed from ethylenically unsaturated monomers. In the case of a non-

21 ionic polymeric flocculent the polymer may be derived from at least one non-ionic ethylenically unsaturated monomer. In the case of an anionic polymeric flocculent, the polymer may be de-rived from at least one anionic ethylenically unsaturated monomer, optionally including at least one ethylenically unsaturated non-ionic monomer. When the polymeric flocculent is cationic, it may be derived from one or more ethylenically unsaturated cationic monomers, optionally in combination with an ethylenically unsaturated non-ionic monomer. Where the polymeric floccu-lent is amphoteric, this may be derived from ethylenically unsaturated anionic monomers and ethylenically unsaturated cationic monomers, optionally in combination with ethylenically un-saturated non-ionic monomers. Preferably, the polymeric flocculent (b) is a polymer formed from repeating units derived from at least one ethylenically unsaturated monomer bearing an anionic group and optionally at least one ethylenically unsaturated non-ionic monomer.
Preferably still, the polymeric flocculent (b) is a water-soluble polymer derived from ethylenically unsaturated monomers selected from the group consisting of homopolymers of one or more ethylenically unsaturated acid monomers (or salts thereof); and copolymers formed from a monomer mixture comprising of (A) one or more ethylenically unsaturated acid monomers (or salts thereof), (B) one or more ethylenically unsaturated non-ionic monomers selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, vinyl acetate, vinyl al-cohol, allyl alkyl ether, styrene and 01-8 alkyl acrylates (C) one or more other ethylenically un-saturated monomers different from (A) and (B). Ethylenically unsaturated monomers in category (C) may include other ethylenically unsaturated non-ionic monomers not specified in category (B) or alternatively it may be ethylenically unsaturated monomers bearing a cationic functional group.
Suitable hydroxy alkyl acrylates as non-ionic comonomers may include any of hydroxyethyl acrylate, hydroxypropyl acrylate and hydroxybutyl acrylate; and suitable hydroxyalkyl methacry-lates include hydroxyethyl methacrylate, hydroxypropyl methacrylate and hydroxybutyl methac-rylate. Suitable 01_8 alkyl acrylates as non-ionic comonomers may include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, isobutyl acry-late, tert-butyl acrylate, ethylhexyl acrylate, n-octyl acrylate, or cyclohexyl acrylate.
Suitable allyl alkyl ethers as non-ionic monomers may include allyl methyl ether, ally! ethyl ether, allyl n-propyl ether or allyl isopropyl ether.
The at least one ethylenically unsaturated acid monomers of category (A) may be any suitable anionic ethylenically unsaturated monomer. Suitable acid groups may include carboxylic acids, sulphonic acids, sulphuric acids, phosphoric acids or phosphonic acids. By referring to the spe-cific ethylenically unsaturated acid monomers we also include the corresponding salts thereof by this definition. We also include the corresponding anhydride of an acid group in the definition of ethylenically unsaturated acid monomers. Suitable monomers in this category include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, ethacrylic acid, crotonic acid, mono esters of ethylenically unsaturated dicarboxylic acids, such as mono methyl maleate, mono methyl fumarate, mono ethyl maleate, mono n-butyl maleate, and mono n-butyl fumarate,

22 styrene carboxylic acids, maleic anhydride, itaconic anhydride, 2-acrylamido-2-methylpropylene acid, vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid, 2-hydroxy ethyl methacrylate phosphate.
When the polymeric flocculant (b) is a polymer comprising components (A), (B) and contains component (C), desirably the other ethylenically unsaturated monomers (C) may be selected from one or more cationic monomers, provided that the overall anionic equivalent content is greater than the overall cationic equivalent content. Suitably, the one or more cationic mono-mers are included in the monomer mixture in an amount of up to 10 mol % total cationic mono-mer based on the total molar content of monomers in the monomer mixture.
More preferably, the polymeric flocculant (b) is a copolymer of acrylamide with (meth)acrylic acid (or salt thereof) or a homopolymer of (meth)acrylic acid (or salt thereof).
The polymeric flocculant (b) may desirably be any anionic homopolymer or anionic copolymer that contains multivalent or monovalent counterion. Typically, the multivalent or monovalent counterion containing homopolymer or copolymer would be the multivalent or monovalent salt of the copolymer. Suitably, the multivalent counterion may be formed from alkaline earth metals, group IIla metals, transition metal etc. Preferable multivalent counterions include magnesium ions, calcium ions, aluminium ions etc. Desirably, the monovalent counterion may be formed from alkali metals or ammonium. Preferable monovalent counterions include lithium ions, sodi-um ions, potassium ions, ammonium ions etc. Suitable homopolymers or copolymers containing multivalent counterions may include repeating units of magnesium diacrylate, calcium diacrylate and aluminium triacrylate. Suitable copolymers containing monovalent counterions include lithi-um acrylate, sodium acrylate, potassium acrylate and ammonium acrylate.
Desirably, the copolymer comprises repeating units of (meth)acrylamide and an ethylenically unsaturated anionic monomer contains a sodium counterion, a potassium counterion, an am-monium counterion, a calcium counterion or a magnesium counterion. Preferably, the copoly-mer contains a calcium counterion. More preferably, the copolymer is of acrylamide and an eth-ylenically unsaturated anionic monomer containing a calcium counterion.
Typically, the multivalent or monovalent counterion is contained in the homopolymer or copoly-mer of the polymeric flocculant (b) in a significant amount relative to the number of repeating units of the ethylenically unsaturated anionic monomer. Normally, the molar equivalent of multi-valent or monovalent counterion to repeating anionic monomer units is at least 0.10:1. Suitably, the molar ratio equivalent may be from 0.15:1 to 1.6:1, normally from 0.20:1 to 1.2:1, preferably from 0.25:1 to 1:1.
The multivalent or monovalent counterion containing copolymer may be obtainable by copoly-.. merisation of ethylenically unsaturated anionic monomer which is already in association with the multivalent or monovalent counterion, for instance multivalent or monovalent cation salts of eth-ylenically unsaturated anionic monomer with (meth)acrylamide.

23 Thus, the multivalent or monovalent counterion containing copolymer, may be derived from a monomer mixture comprising a multivalent or monovalent cation salt of an ethylenically unsatu-rated anionic monomer and (meth)acrylamide. The ethylenically unsaturated anionic monomer salt may be present in an amount in the range of from 5% to 95% by weight, based on the total weight of the monomers. Desirably, the amounts of the respective monomers used to form the copolymer may be, for instance, from 5% to 95% by weight of multivalent or monovalent cation salt of an ethylenically un-saturated anionic monomer; and from 5% to 95% by weight of (meth) acrylamide.
Preferably, the amount of multivalent or monovalent cation salt of the ethylenically unsaturated anionic monomer may be from 5% to 85% by weight, such as from 5% to 70% by weight, typi-cally from 10% to 60% by weight, often from 15% to 50% by weight, desirably from 20% to 45%
by weight, for instance from 25% to 40% by weight; and the amount of (meth)acrylamide may be from 50% to 95% by weight, such as 30% to 95% by weight, typically from 40%
to 90% by weight, often from 50% to 85% by weight, desirably from 55% to 80% by weight, for instance from 60% to 75% by weight.
Preferably, polymerisation is effected by reacting the aforementioned monomer mixture using redox initiators and/or thermal initiators. Typically, redox initiators include a reducing agent such as sodium sulphite, sodium metabisulphite, sulphur dioxide and an oxidising compound such as ammonium persulphate or a suitable peroxy compound, such as tertiary butyl hydroperoxide etc. Redox initiation may employ up to 10,000 ppm (based on weight of aqueous monomer) of each component of the redox couple. Preferably though, each component of the redox couple is often less than 1000 ppm, typically in the range from 1 to 100 ppm, normally in the range from 4 to 50 ppm. The ratio of reducing agent to oxidising agent may be from 10:1 to 1:10, preferably in the range from 5:1 to 1:5, more preferably from 2:1 to 1:2 for instance around 1:1.
The polymerisation of the monomer mixture may be conducted by employing a thermal initiator alone or in combination with other initiator systems, for instance redox initiators. Thermal initia-tors would include suitable initiator compound that releases radicals at an elevated temperature, for instance azo compounds, such as azobisisobutyronintrile (Al BN), 4,4'-azo bis-(4-cyanovalereic acid) (ACVA). Typically, thermal initiators are used in an amount of up to 10,000 ppm, based on weight of aqueous monomer. In most cases, however, thermal initiators are used in the range from 100 to 5000 ppm, preferably from 200 to 2000 ppm, more preferably from 300 to 700 ppm, usually around from 400 to 600 ppm, based on the weight of the aqueous monomer mixture.
Typical methods of preparation of the multivalent or monovalent counterion containing copoly-mer are given in WO 2017084986.

24 Intrinsic viscosity of the polymeric flocculent (b) may be determined by first preparing a stock solution. This may be achieved by placing 1.0 g of copolymer in a bottle and adding 199 ml of deionised water. This mixture may then be mixed for 4 hours, for instance on a tumble wheel, at ambient temperature (25 C). Diluted solutions may then be prepared by, for instance, taking .. 0.0g, 4.0 g, 8.0 g, 12.0 g and 16.0 g, respectively, of the aforementioned stock solution and placing each into 100 ml volumetric flasks. In each case, 50 ml of sodium chloride solution (2 M) should then be added by pipette and the flask then filled to the 100 ml mark with deionised wa-ter and in each case the mixtures shaken for five minutes until homogenous. In each case, the respective diluted copolymer solutions are in turn transferred to an Ubbelohde viscometer and .. the measurement carried out at 25 C with the capillary viscometer Lauda iVisc. As such, the reduced specific viscosity of each of the dilute solution may be calculated and then extrapolated to determine the intrinsic viscosity of the polymer, as described in the literature.
Suitably, polymeric flocculent (b) may have an intrinsic viscosity in the range of from 5 to 30 dl/g, desirably from 5 to 25 dl/g, such as from 6 to 20 dl/g, for instance from 7 to 20 dl/g, often .. from 9 to 19 dl/g, typically from 10 to 18 dl/g, normally from 12 to 18 dl/g.
In one preferred form, the polymeric flocculent (b) is water-soluble. By water-soluble we mean that the polymer has a gel content measurement of less than 50% gel. The gel content meas-urement is described below.
The gel content may be determined by filtering a stock solution (preparation of a stock solution is described above in the method of measuring intrinsic viscosity) through a sieve with a 190 pm mesh size. The residue which stays in the filter is washed, recovered, dried (110 C) and weighed, and the percentage of undissolved polymer is calculated (weight of dry residue from the filter [g] /weight of dry polymer before filtration [g]). Where necessary, this provides a quan-tifiable confirmation of the visual solubility evaluation.
.. The optional cationic coagulant (c) is suitably a polymeric material having a weight average mo-lar mass of from 10,000 to 2 million g/mol. Suitable polymers include polymers of diallyl dialkyl ammonium halide, for instance the homopolymers of diallyl dimethyl ammonium chloride (DADMAC). Suitable polymers may be formed from other cationic monomers such as quater-nary ammonium salts of acrylate esters, for instance quaternary ammonium salts of dialkyl .. amino alkyl (meth) acrylate, such as the methyl chloride quaternary ammonium salt of dimethyl amino ethyl acrylate (DMAEA-q) or the methyl chloride quaternary ammonium salt of dimethyl amino ethyl methacrylate (DMAEMA-q). Further suitable polymers may be formed from cationic monomers based on the quaternary ammonium salts of amino alkyl acrylamides, including the quaternary ammonium salts of dialkyl amino alkyl (meth) acrylamides, for instance acrylamido propyl trimethylammonium chloride (APTAC) or methacrylamido propyl trimethylammonium chloride (MAPTAC). The aforesaid cationic monomers may be as homopolymers or as copoly-mers, for instance copolymers with acrylamide, such as DADMAC acrylamide copolymers, AP-TAC acrylamide copolymers, MAPTAC acrylamide copolymers, DMAEA-q acrylamide copoly-mers, and DMAEMA-q acrylamide copolymers.

Other suitable polymers include polyamines, for instance partially or fully hydrolysed polyvinyl formamides containing repeating vinyl amine units. Other polymers include polyethyleneimines, polymers of alkyl amines with formaldehyde and/or epichlorohydrin, and polycyandiamides.
Typical doses of the polymeric de-coagulant(a) may range from 0.1 to 1000 g polymer per 5 tonne of solids content of the aqueous slurry, suitably from 1 to 800 g per tonne, such as 10 to 600 g per tonne, for instance 20 to 500 g per tonne, desirably from 50 to 400 g per tonne, for instance from 75 to 350 g per tonne, suitably from 100 to 300 g per tonne, for instance from 150 to 250 g per tonne.
Typical doses of the polymeric flocculant (b) may range from 20 to 2000 g of polymer per tonne 10 of solids content of the aqueous slurry. Desirably, this may be from 40 or 50 to 1500 g per tonne, suitably from 75 to 1000 g per tonne, often from 90 to 750 g per tonne, usually from 100 to 500 g per tonne.
The exact doses of each of the two components may depend on the particular aqueous slurry, including the particular particulate mineral material of the slurry and the solids content of the 15 slurry. The optional cationic coagulant (c) may be applied to the aqueous suspension in doses in the ranges from 10 to 1000 g/tonne based on active weight of coagulant on dry weight of aqueous slurry, for instance in the range of from 25 to 750 g/tonne, or from 50 to 500 g/tonne, or from 100 to 250 g/tonne.
Suitably, the particulate solids of the aqueous slurry comprise mineral solids. Typically, the par-20 ticulate solids may for instance contain filter cake solids or tailings.
Often, the aqueous slurry may be an underflow from a gravimetric thickener, a thickened plant waste stream or alterna-tively may be an unthickened plant waste stream. For instance, the aqueous slurry may com-prise phosphate slimes, gold slimes or wastes from diamond processing. Typical aqueous slur-ries include slurries of mineral sands tailings, zinc ore tailings, lead ore tailings, copper ore tail-

25 ings, silver ore tailings, uranium ore tailings, nickel ore tailings, iron ore tailings, coal fines tail-ings, oil sands tailings or red mud. The aqueous slurry suitable for treatment in accordance with the present invention may include the concentrated suspension from the final thickener or wash stage of a mineral processing operation. Thus, the aqueous slurry may desirably result from a mineral processing operation. Preferably, the suspension comprises tailings.
Suitably, the par-ticulate solids contained in the aqueous slurry may comprise at least some solids which are hy-drophilic, for instance water swelling clays. More preferably, the particulate solids of the aque-ous slurry may be derived from tailings from a mineral sands process, coal fines tailings, oil sands tailings, phosphate tailings or red mud.
The concentration of the aqueous slurry will tend to vary according to the particular type of sub-strate. In general, the aqueous slurry can often be a slurry of thickened tailings, for instance a thickened tailings suspension flowing as an underflow from a thickener, for instance a gravimet-ric thickener, or other stirred sedimentation vessel. Suitably, the aqueous slurry may have a solids content in the range of from 25 to 70 % by total weight of aqueous slurry, preferably from 30 to 70% by weight, for instance from 45% to 65% by weight. Preferably, the solids content of

26 the aqueous slurry will often be from 30 to 50%, frequently from 30 to 45% by total weight of the aqueous slurry. When a pre-thickening stage occurs, the sand fraction (<44pm) solids may already be combined with the fine solids fraction, or may be combined with the tailings stream subsequently, after the thickening stage.
Suitably, the aqueous slurry containing the particulate material may be an underflow stream which flows from a sedimentation vessel in which a first suspension of the particulate mineral material is separated into a supernatant layer comprising an aqueous liquor and a thickened layer which is removed from the vessel as an underflow. It would be this underflow which would be subjected to the treatment according to the present invention. It would not be possible to achieve the objectives of the invention by adapting the separation in a conventional sedimenta-tion vessel as the yield stress of the thickened layer would be so high that it would be impossi-ble to stir the thickened layer or remove the thickened layer from the conventional sedimenta-tion vessel as an underflow. Furthermore, such solids would not be able to flow as an underflow from the vessel.
Aqueous slurries may not necessarily have a sand to fines ratio within the range of 0.5:1 to 5:1.
For instance, whole tailings (WT) have sand to fines ratios of greater than 4:1 and mostly tend to be greater than 5:1 and may be as high as 20:1. Composite tailings (CT) also have high sand to fines ratios typically more than 3:1 and in some cases more than 5:1 and may be as high as 6:1 or 7:1. On the other hand fluid fines tailings (FFT), thin fines tailings (TFT), thick-ened fines tailings (ThFT) and mature fines tailings (MFT) all tend to have very low sand to fines ratios. FFT tend to have sand to fine ratios significantly below 1:1 and MFT tend to have much lower sand contents typically less than 0.3:1, for instance less than 0.25:1.
The sand to fines ratios of aqueous slurries not having a sand to fines ratio within the range of 0.5:1 to 5:1, or 1:1 to 4:1 or 1:1 to 3:1 may be adjusted to a sand to fines ratio within the scope of the present invention, including any of the preferred sand to fines ratios recited herein.
For aqueous slurries where the sand to fines ratios fall below 0.5:1, for instance, as in the case of MFT slurries, and desirably even where the sand to fines ratios fall below 1:1, for instance, as in the case of FFT slurries, TFT slurries and ThFT slurries, the sand to fines ratio may be increased. One way of achieving this is to combine sand with the aforesaid MFT, FFT, TFT or ThFT slurries. The sand may be a concentrated sand fraction, for instance the underflow from a cyclone processing whole tailings (WT). Another way of carrying this out would be to mix the aforesaid MFT, FFT, TFT or ThFT slurries with whole tailings (WT). In both cases the propor-tions of sand fraction or whole tailings to the MFT, FFT, TFT or ThFT slurries should be such that the so formed composite tailings (CT) should have a sand to fines ratio of from 0.5:1 to 5:1, preferably from 1:1 to 4:1, more preferably from 1:1 to 3:1 and more preferably still be-tween 1:1 and 2:1.
Where the aqueous slurries have a sand to fines ratio greater than 5:1, preferably greater than 4:1 and more preferably greater than 3:1, as in the case of whole tailings (WT) or even some conventional composite tailings (CT), the adjustment of the sand to fines ratio should be a re-

27 duction of the sand content. One way of conducting this would be to pass whole tailings (WT) through a screen which filters out large coarse size sand particles such as greater than 120 pm or preferably greater than 100 pm. This may also be achieved by passing the aqueous slurry, for instance whole tailings, through a cyclone which cuts at the desired particle size, for in-stance 120 pm or 100 pm, to remove the larger particle size sand. This removal of some of the sand would serve to reduce the sand to fines ratio to the desired level.
There are a number of ways in which the treatment system can be applied to the aqueous slurry including addition to any of the components forming the aqueous slurry such as precursor slur-ries or other components such as sand.
In accordance with one aspect of the inventive process the aqueous slurry may be formed from a first precursor aqueous slurry in which the sand to fines ratio is below 0.5:1, suitably below 1:1, and the sand to fines ratio may be adjusted to increase the sand to fines ratio by either, (a) combining the first precursor aqueous slurry with sand; and/or (b) combining the first precursor aqueous slurry with a second precursor aqueous slurry, which second precursor aqueous slurry has a sand to fines ratio of greater than 3:1, suitably greater than 4:1 and especially suitably greater than 5:1, and thereby forming the aqueous slurry, in which the treatment system or components thereof desirably would be applied to any one or more of the first precursor aqueous slurry, the sand component, the second precursor aqueous slurry and/or the aqueous slurry.
In one suitable embodiment of this aspect of the invention the sand in (a) may be in the form of a sand stream, preferably the underflow sand stream from a cyclone processing whole tailings (WT). Desirably, the first precursor aqueous slurry is selected from the group consisting of ma-ture fines tailings (MFT), fluid fines tailings (FFT), thin fines tailings (TFT), thickened fines tail-ings (ThFT). The second precursor aqueous slurry may desirably be whole tailings (WT).
In accordance with a further aspect of the inventive process the aqueous slurry may be formed from a second precursor aqueous slurry in which the sand to fines ratio is greater than 3:1, suit-ably greater than 4:1 and especially suitably greater than 5:1, and the sand to fines ratio desira-bly would be adjusted to decrease the sand to fines ratio by separating sand particles having a particle size greater than a predetermined size limit, preferably greater than 100 pm, from the second precursor aqueous slurry thereby, and thereby forming the aqueous slurry, in which the treatment system or components thereof are applied to any one or more of the second precursor aqueous slurry and/or the aqueous slurry. The predetermined size limit may be set at any level sufficient to remove sufficient sand particles in order to provide an aqueous

28 slurry of the desired sand to fines ratio in accordance with the invention.
This may, for instance, be greater than 100 pm or in some cases greater than 110 pm or in other cases greater than 120 pm, depending upon the particle size distribution and sand content of the second precursor aqueous slurry. The second precursor aqueous slurry may, for instance, be whole tailings (WT).
-- Preferably, the separation of the sand from the second precursor aqueous slurry is conducted using a cyclone having a screen having a mesh size sufficient to remove the sand particles hav-ing a particle size greater than the predetermined size limit.
Preferably, the aqueous slurry of particulate material comprises flowing as slurry of mature fines tailings (MFT) and/or fluid fines tailings (FFT) and/or thickened fines tailings (ThFT) along a -- conduit and in which a slurry of sand is combined with the slurry of mature fines tailings and/or fluid fines tailings and/or thickened fines tailings (ThFT) to provide a combined tailings stream (CbT) having the desired sand to fines ratio of from 0.5:1 to 5:1, wherein the components of the treatment system are applied to (i) the mature fines tailings and/or fluid fines tailings and/or thickened fines tailings (ThFT); and/or (ii) the combined tailings (CbT) stream, and in which the -- so treated combined tailings (CbT) stream is fed to a deposition area.
Preferably the ionic poly-meric de-coagulant (a) is either fed into the slurry of MFT and/or FFT and/or ThFT; fed into the sand slurry; or fed into the combined tailings stream (CbT) and thereafter the polymeric floccu-lant (b) is added to the so treated combined tailings stream (CbT).
Optionally, the cationic coag-ulant (c) may be added to the combined tailings stream (CbT) either before, or preferably after -- the addition of the flocculant (b).
It may be desirable in some cases to add the polymeric flocculant (b) to the aqueous slurry as it exits the conduit for instance pipeline. In other cases, it may be desirable to add the flocculant prior to the aqueous slurry exiting the outlet of the conduit, or more specifically pipeline, for in-stance less than 100 m, less than 50 m and desirably less than 10 m from the outlet. In gen--- eral, the polymeric flocculant (b) desirably would be added to the aqueous slurry in the conduit or pipeline and close to the outlet, for instance less than 50 m from the outlet, for instance from 0.1 to 30 m from the outlet, or from 0.5 to 20 m from the outlet, or from 1 to 10 m from the out-let, or even from 1 to 5 m from the outlet.
Typically, the aqueous slurry is transferred by pumping along a conduit to a deposition area.
-- The conduit can be any convenient means for transferring the aqueous slurry to the deposition area and may, for instance, be a pipeline or even a trench. The deposition area may be a tail-ings dam or lagoon or may be adjacent to a tailings dam or lagoon, or preferably an open min-ing void or pit.
Normally the aqueous slurry would be transferred continuously to the deposition area i.e. with--- out interruption of the flow. However, in some cases it may be desirable to transfer the aqueous slurry first to a holding vessel or pond, before being transferred to the deposition area.
Suitably, the aqueous slurry is transferred to the deposition area through a conduit, for instance a pipeline. Normally, such a conduit, for instance pipeline, would have an outlet from which the

29 aqueous slurry exits as it flows to the deposition area. Typically, the outlet of the conduit, for instance pipeline, is at the deposition area or may be close to the deposition area, for instance less than 20 m, usually less than 10 m and desirably less than 5 m from the deposition area. In such cases where the conduit or more specifically pipeline is close to the deposition area, the aqueous slurry should be able to flow into the deposition area.
Desirably the so treated combined tailings stream (CbT) is fed into a void or impoundment at the deposition area, in which the void or impoundment has a depth of at least 5 m and the de-posited solids are allowed to separate from the released supernatant liquid and consolidate.
Desirably, the separated solids form a relatively homogeneous deposit with minimal segregation of the fines and sand particles. The void or impoundment area may have a depth of at least 10 m, for instance at least 15 m or suitably at least 20 m. The depth may be as much as 50 m or even as much as 75 m or as much as 100 m or more. Thus, the void or impoundment may have a depth in the range of from 5 m to 100 m, from 10 m to 75 m, from 15 m to 50 m or from 20 m to 40 m. This method of deep void disposal is sometimes referred to as Deep Pour. Deep Pour technique is believed by the inventors to be analogous to the technique described in Section 4 of the COSIA document entitled, "Deep Fines-Dominated (Cohesive) Deposits" and available on the 005 IA website (https://www.cosia.ca/uploads/documents/id7/TechGuideFluidTailingsMgmt_Aug2012.
pdf).
The supernatant liquid separated from the so treated slurry should form above the particulate solids deposited in the void or impoundment. Generally, the supernatant liquid may desirably be continually or periodically removed from the void or impoundment area.
Alternatively, the so treated combined tailings stream may be fed onto a beach surface at the deposition area and form thin layers of newly deposited beach material which dewaters through drainage and evaporation. The beached surface may have an angle of incline of from 0.50 and 10 .
In some instances, in accordance with the invention, the deposition of the solids is controlled to build up relatively narrow bands of tailings which can also dewater quickly through evaporation, prior to adding a new layer of treated waste material on top. This technique of using narrow band disposal may sometimes be referred to as "Thin Lift". In general, the deposition of the so treated aqueous slurry may be onto a beached surface, for instance as described in the previ-ous paragraph. The inventors believe that the "Thin Lift" method of disposal in regard to the oil sands industry is analogous to the technique described in section 3 of the aforementioned CO-SIA document, entitled, "Thin Layered Fines Dominated Deposits". This document uses from 0.1 to 0.5 m as a typical thickness for each lift.
Outside the oil sands industry, for instance in the alumina industry, the invention may also be employed by the deposition of thin layers, having a thickness of up to 0.5 m.
For instance, the so treated material at a deposition area, such as onto a beached surface, as described above, the analogous technique may be referred to as "Dry Stacking". A general description for this type of technique in the alumina industry is described, particularly in section 3, in the paper giv-en by DJ Cooling (Alcoa World Alumina Australia) to the Paste 2007 Conference in Perth, Aus-tralia. The paper is entitled, "Improving the Sustainability of Residue Management Practices ¨
Alcoa World Alumina Australia", Australian Centre for Geo-mechanics, Perth, 7-2.
5 In one aspect of the invention the treatment system may comprise adding the ionic polymeric de-coagulant (a) to the aqueous slurry of particulate material before adding the polymeric floc-culent (b). Typically, aqueous slurry of particulate material may first be treated by the addition of the ionic polymeric de-coagulant (a) and then the so treated slurry subjected to a mixing stage followed by the addition of the polymeric flocculent (b). Alternatively, the aqueous slurry of par-10 ticulate material may be treated by the addition of the whole treatment system followed by sub-jecting the so treated aqueous slurry to a mixing stage. Nevertheless, it may be desirable that the aqueous slurry of particulate material is subjected to a mixing stage after the addition of each of the ionic polymeric de-coagulant (a) and the polymeric flocculent (b) of the treatment system. Optionally, cationic coagulant (c) may be added between the addition of the ionic poly-15 meric de-coagulant (a) and the polymeric flocculent (b), simultaneously with the addition of the polymeric flocculent (b) or subsequent to the addition of the polymeric flocculent (b).
The ionic polymeric de-coagulant (a) may be added as an aqueous solution or as dry particles to the aqueous slurry.
Typically, the ionic polymeric de-coagulant is manufactured directly as an aqueous solution, or it 20 may be in the form of dry particles and then pre-dissolved in water to prepare an aqueous solu-tion. In the latter case, generally the solid particulate ionic polymeric de-coagulant, for instance in the form of powder, beads or substantially spherical particles, may be dispersed in water and allowed to dissolve with agitation. This may be achieved using suitable make-up equipment (as described below regarding flocculent (b)). It is also possible that the ionic polymeric de-25 coagulant is manufactured directly as an aqueous solution of higher concentration, and then diluted with water and mixing to form a lower concentration aqueous solution.
The concentration of the aqueous solution of the ionic polymeric de-coagulant (a) may be any suitable concentration which would facilitate the ionic polymeric de-coagulant solution to be fed into and to mix with the aqueous slurry. Although it is conceivable that the aqueous ionic poly-

30 meric de-coagulant concentration solution may be 60% weight/volume or higher, it is usual that the concentration be lower than 60% weight/volume. Usually the ionic polymeric de-coagulant solution will be from 0.1% to 50% weight/volume. Suitably, the aqueous ionic polymeric de-coagulant solution concentration will be from 1% to 40%, often from 5% to 25%.
The flocculent (b) may be added as an aqueous solution or as dry particles directly to the ague-ous slurry.
The aqueous solution of flocculent (b) is typically obtained by dissolving the polymer in water or by diluting a more concentrated solution of the polymer. Generally solid particulate polymer, for instance in the form of powder, beads or substantially spherical particles, is dispersed in water

31 and allowed to dissolve with agitation. This may be achieved using conventional make up equipment. Desirably, the polymer solution can be prepared using the Auto Jet Wet (trade-mark) supplied by BASF, for example as described in GB 1501938. The polymer solution may also be prepared according to any of the disclosures of US 4518261, US
5857773, US
6039470, US 5580168, US 5540499, US 5164429, US 5344619. The polymer solution may even be prepared using polymer slicing/shearing equipment, for instance as described by US
4529794, US 4874588, or even any of the disclosures CA 2667277, CA 2667281, CA
2700239, CA 2700244, CA 2775168, CA 2787175, CA 2821558 or US 2009/095688.
Alternatively, the polymer may be supplied in the form of a reverse phase emulsion or dispersion which can then be inverted into water by conventional techniques.
The concentration of the aqueous solution of the polymer of flocculent (b) may be any suitable concentration which would facilitate the polymer solution to be fed into and mix with the aque-ous slurry. Although it is conceivable that the aqueous polymer solution may be 5%
weight/volume or more, it is usual that the concentration be less than 5%
weight/volume. Typi-cally, the polymer solution will tend to be below 3% weight/volume. Usually the aqueous poly-mer concentration will be at least 0.01% weight/volume. Suitably the aqueous polymer concen-tration may be from 0.01% to 5% weight/volume, typically from 0.02% to 3%, often from 0.05%
to 1%.
The polymeric cationic coagulant (c) may be added as an aqueous solution or as dry particles to the aqueous slurry.
Typically, the cationic coagulant is manufactured directly as an aqueous solution, or it may be in the form of dry particles and then pre-dissolved in water to prepare an aqueous solution. In the latter case, generally the solid particulate cationic coagulant, for instance in the form of powder, beads or substantially spherical particles, can be dispersed in water and allowed to dissolve with agitation. This may be achieved using suitable make-up equipment (as described above in regard to flocculent (b)) It is also possible that the cationic coagulant is manufactured directly as an aqueous solution of higher concentration, and then diluted with water and mixing to form a lower concentration aqueous solution.
The concentration of the aqueous solution of the cationic coagulant (c) may be any suitable concentration which would facilitate the ionic polymeric de-coagulant solution to be fed into and to mix with the aqueous slurry. Although it is conceivable that the aqueous cationic coagulant concentration solution may be greater than 50% weight/volume, it is usual that the concentra-tion be equal to or lower than 50% weight/volume. Usually the cationic coagulant solution will be from 0.01% to 50% weight/volume. Suitably, the aqueous cationic coagulant solution concentra-tion will be from 0.1% to 30%, often from 1 to 10%.
The examples that follow are intended to illustrate the invention without in any way being limit-ing.

32 Examples Description of additives used in the examples Ionic Polymeric De-coagulants Products 1-6 Product 1 is the terpolymer of vinyloxybutyl polyethylene glycol (adduct of 129 moles of eth-ylene oxide with 4-hydroxy butyl mono vinyl ether) with acrylic acid and maleic anhydride. The molar ratio of these monomers is 1/4/0.6 and the weight average molar mass approximately 53,500 g/mole. The preparation of the polymer was as described in US
2012/0035301 on page 4 under heading Polymer 1.
Product 2 is a copolymer of sodium acrylate and acrylamide in a weight ratio of 75/25 weight %
having a weight average molecular weight of about 1 million Da and a charge density of about 8 mmol/g in the form of a bead and prepared by a traditional reverse-phase suspension polymeri-sation process.
Product 3 is a homopolymer of sodium acrylate having a weight average molecular weight of about 5000 Da and a charge density of about 10.6 mmol/g. The product is in the form of an aqueous solution of concentration 40 % by weight and prepared as an aqueous solution polymerisation of sodium acrylate in the presence of chain transfer agent.
Product 4 is a copolymer of 80/20 weight % sodium acrylate and sodium salt of ATBS (2-acrylamido-2-methyl propane sulphonic acid) of weight average molecular weight of about 5000 Da and charge density of about 9.5 mmol/g. The product is in the form of an aqueous solution of concentration 40 % by weight and prepared as an aqueous solution polymerisation of sodium acrylate in the presence of chain transfer agent.
Product 5 is a sulphonated melamine formaldehyde (SMF) polycondensate having a theoretical charge density of 3.5 mmol/g based on a repeating unit of 284 g/mol. The weight average mo-lecular weight is below 100,000 Da!tons. This SMF was synthesised according to the general procedure given in US 6555683. The molar ratio of melamine formaldehyde to sodium hydrogen sulphite was 1:3.19:1.53 Product 6 is a copolymer of vinyloxy butyl polyethylene glycol and acrylic acid. The preparation of this copolymer involves the copolymerisation of vinyloxy butyl polyethylene glycol and acrylic acid in an analogous procedure to Preparation Example 3 in EP 1902085 with the exception that a higher amount of acrylic acid was used (0.468 mole acrylic acid). The molecular weight is about 50,000 Da and the molar ratio of vinyloxy butyl polyethylene glycol to acrylic acid was 1:7.8. The vinyloxy butyl polyethylene glycol was a polyethylene glycol-5800-mono vinyl ether.
Flocculants 1-3

33 Flocculant 1 is a copolymer of calcium diacrylate and acrylamide having a weight ratio of 40/60 and exhibiting an intrinsic viscosity of 15 dl/g in the form of a powder and prepared according to W02017084986.
Flocculant 2 is a copolymer of sodium acrylate and acrylamide having a weight ratio of 40/60 and exhibiting an intrinsic viscosity of 20 dl/g and in the form of a powder prepared by standard solution polymerisation to provide a gel which is cut and dried and then ground to form the pow-der.
Flocculant 3 is a copolymer of sodium acrylate and acrylamide having a weight ratio of 40/60 and exhibiting an intrinsic viscosity of 10 dl/g and in the form of a bead having been prepared by traditional reverse-phase suspension polymerisation.
Coagulant Coagulant 1 is the homopolymer of diallyl dimethyl ammonium chloride (DADMAC) exhibiting an intrinsic viscosity of 1.0 dl/g in the form of a bead and prepared by traditional reverse-phase suspension polymerisation.

34 Example 1 ¨ Treatment of tailings from an oilsands, bitumen extraction process.
Oi!sands process water, as used below, typically has a similar chemical composition to the aqueous phase of the MFT slurry used to prepared the test substrate.
A substrate sample with 1:1 SFR (sand/fines ratio) was prepared by blending 220 parts (wt) of MFT, 81 parts (wt) of wet coarse tailings and 5 parts (wt) of oilsands process water to yield a combined tailings material (CbT) of the following composition:
Sand (particulates > 44 pm) 24.6 % wt Fines (particulates <44 pm) 25.4 % wt Process Water 50.0 % wt .. The combined tailings material (CbT) was mixed continuously to ensure homogeneity, and sub-sampled into individual aliquots (50 g) for subsequent testing. Note, as both the MFT and the coarse tailings contain a small proportion of sands and fines respectively, the final calculation of the SFR (above) is adjusted to include sand and fines from both materials.
Part A ¨ testing for substrate dewaterability and consolidation:
De-coagulant solution, Product 1 was prepared to contain 0.5 %wt/vol of polymer in oilsands process water. Flocculent 1 solution was prepared to contain 0.5 %wt/vol of polymer in oilsands process water.
The 50 g aliquot of the combined tailings substrate (CbT) is placed in a 120 ml beaker and mixed with a flat blade stirrer at 400 rpm. After 10 seconds, the required amount of Product 1 solution is added and subsequently, after 10 seconds, the required amount of flocculent solution is added, and mixing is continued until the sample is conditioned to the visual point of optimum flocculation / net water release (NWR), at which time the mixer is stopped.
The mixing time after the flocculent addition required to reach the point of optimum conditioning is recorded, and it may differ significantly for different types and dosages of de-coagulant and flocculent.
After conditioning, the treated substrate is transferred into a pressure filter apparatus consisting of a cylindrical chamber of diameter 3.25 cm, fitted with fine filter media at one end, and a solid sliding piston at the other. (see Figure 2). A force equal to an internal pressure of 6 psi is then applied to the piston for a period of 10 mins, during which the water expelled through the filter media is collected. The particulate solids content of the release water was determined gravimetrically by drying at 110 C for 2 hrs. The dry weight value obtained was adjusted for the electrolyte content of the process water (0.27 %wt/vol). The moisture content of the filtercake was determined by drying at 110 C for 24 hours.
Part B ¨ testing for fines capture during sub-aqueous deposition 50 g aliquot of the combined tailings substrate (CbT) is treated with de-coagulant and flocculant as has been previously described in Part A. After conditioning, the treated substrate is transferred into a 250 ml measuring cylinder which already contains 200 ml of water. The cylinder is then inverted vigorously three times to disperse the treated substrate into the bulk of 5 the water. The cylinder is then left to stand for 10 mins before sampling the supernatant water and measuring the residual turbidity.
Table 1: (See Figures 3 - 5) Part A Part B
Product 1 Flocculant 1 Cake Filtrate Mixing Mixing Turbidity Dose (g/t) Dose (g/t) Moisture Solids Time (s) (%wt) (%wt) Time (s) (NTU) 0 800 22.2 45.9 1.16 24.1 50 800 22.1 46.7 1.15 29.6 838 100 800 27.1 40.5 0.98 32.5 252 150 800 24.8 40.7 0.97 27.7 579 200 800 27.3 41.6 0.70 35.3 331 240 800 31.3 36.0 0.67 31.3 321 280 800 30.9 34.2 0.76 33.1 323 The results show that for the substrate mixture with a 1:1 SFR, the addition of Product 1 significantly reduced the residual moisture in the dewatered solids, and improved the retention 10 and capture of fine particles during both dewatering and sub-aqueous deposition.
Example 2 - Treatment of tailings from an oilsands, bitumen extraction process Testing was carried out as previously described in example 1 above except that a substrate sample with 1.75:1 SFR (sand/fines ratio) was prepared by blending 57 parts (wt) of MFT, 42 parts (wt) of wet coarse tailings and 20 parts (wt) of oilsands process water to yield a combined 15 tailings material (CbT) of the following composition:
Sand (particulates >44 pm) 31.8 %wt Fines (particulates <44 pm) 18.2 %wt Process Water 50.0 %wt Table 2: (See Figures 6 - 8) Part A Part B
Product 1 Flocculent 1 Cake Filtrate Mixing Mixing Turbidity Dose (g/t) Dose (g/t) Moisture Solids Time (s) (%wt) (%wt) Time (s) (NTU) 0 360 12.3 37.3 2.10 12.3 50 360 11.9 25.0 1.19 11.3 100 360 11.7 25.7 1.24 11.9 150 360 11.7 29.7 1.32 12.6 200 360 14.9 23.9 0.92 12.0 954 240 360 14.5 23.7 0.85 12.0 713 280 360 14.4 26.4 0.86 12.5 380 0 400 12.0 34.5 1.41 14.4 200 400 15.9 24.9 0.84 15.8 339 The results show that for the substrate mixture with a 1.75:1 SFR, the addition of Product 1 significantly reduced the residual moisture in the dewatered solids, and improved the retention and capture of fine particles during both dewatering and sub-aqueous deposition. The combination dosage of 50 g/t Product 1 with 360 g/t flocculent also achieved significantly better results than 400 g/t flocculent alone. For example, the residual cake moisture was only 25 % for the combination, whereas the similar dose of flocculent alone had a residual cake moisture of 34.5 %.
Example 3 - Treatment of tailings from an oilsands, bitumen extraction process Testing was carried out as previously described in example 1 above except that a substrate sample with 3:1 SFR (sand/fines ratio) was prepared by blending 60 parts (wt) of MFT, 88 parts (wt) of wet coarse tailings and 60 parts (wt) of oilsands process water to yield a combined tailings material (CbT) of the following composition:
Sand (particulates > 44 pm) 37.5 %wt Fines (particulates <44 pm) 12.5 %wt Process Water 50.0 %wt Table 3: (See Figures 9 - 11) Part A Part B
Product 1 Flocculant 1 Cake Filtrate Mixing Mixing Turbidity Dose (g/t) Dose (g/t) Time (s) Moisture Solids (%wt) (%wt) Time (s) (NTU) 0 150 8.8 32.6 3.64 7.2 50 150 9.1 32.2 2.75 8.6 100 150 9.1 23.9 1.68 9.1 150 150 8.1 22.8 1.11 8.1 200 150 10.8 29.4 1.06 9.6 240 150 12.3 28.3 1.05 6.6 280 150 9.2 23.8 0.68 5.9 572 The results show that for the substrate mixture with a 3:1 SFR, the addition of Product 1 reduced the residual moisture in the dewatered solids and improved the retention and capture of fine particles during both dewatering and sub-aqueous deposition.
Example 4 - Treatment of tailings from an oilsands, bitumen extraction process Testing was carried out as previously described in example 2 above using the substrate sample with 1.75:1 SFR (sand/fines ratio). A number of different de-coagulant and flocculant chemistry combinations were tested.
Table 4:
Product Flocculant Part A Part B
Cake Filtrate Dose Dose Mixing Mixing Turbidity # # Moisture Solids (g/t) (g/t) Time (s) (%wt) (%wt) Time (s) (NTU) n/a 0 2 360 37.1 47.9 2.04 43.8 1 200 2 360 36.5 34.1 1.49 34.3 n/a 0 1 360 12.3 37.3 2.10 12.3 2 100 1 360 17.1 24.9 0.67 11.2 2 200 1 360 15.0 23.7 0.54 12.3 3 50 1 360 15.1 44.3 1.17 13.0 4 40 1 360 12.0 42.6 1.33 12.2 4 96 1 360 15.0 51.2 0.12 NT
NT
5 100 1 360 11.8 40.0 2.77 9.5 5 200 1 360 12.0 39.0 2.49 11.3 6 100 1 360 11.8 39.1 1.92 9.7 6 200 1 360 12.0 31.0 1.20 10.6 The results show that in all cases the addition of the de-coagulant products improved the fines solids capture in the sub-aqueous deposition test compared to the corresponding treatment with flocculant alone. Products 1 and 2 are particular effective in improving both the dewatering and fines capture. Although de-coagulants with very high anionic charge densities, such as Product .. 3, 4 and 5 were effective they were not as effective as Products 1 and 2, especially in respect to facilitating the rapid separation of water from the solids. Product 6 improved dewatering and fines capture at lower doses. Fines capture was improved at greater doses of Product 6.
Example 5 ¨ treatment of tailings from an oilsands, bitumen extraction process Testing was carried out as previously described in example 2 above using the substrate sample with 1.75:1 SFR (sand/fines ratio). The effect of adding a coagulant, in the form of a 0.5%
wt/vol solution in process water, after the flocculation step, was evaluated.
Table 5:
Product 1 Cake Filtrate Flocculant 1 Coagulant 1 Mixing Mixing Turbidity Dose Moisture Solids (g/t) Dose (g/t) Dose (g/t) Time (s) (%wt) (%wt) Time (s) (NTU) 100 360 0 11.7 25.7 1.24 11.9 100 360 100 10.8 24.9 0.42 12.4 200 360 0 14.9 23.9 0.92 12.0 200 360 100 12.0 22.6 0.15 11.1 The results show that the further addition of a coagulant may be beneficial to further improve the fine capture and retention during the dewatering of the substrate.
Example 6 Testing was carried out as previously described in example 1 above except that a substrate sample with 1.6:1 SFR (sand/fines ratio) was prepared by blending 200 parts (wt) of MFT, 110 parts (wt) of wet coarse tailings to yield a combined tailings material (CbT) of the following composition:
Sand (particulates > 44 pm) 34.5 %wt Fines (particulates <44 pm) 21.5 %wt Process Water 44.0 %wt Table 6: (See Figures 12¨ 13) Part A Part B
Product 1 Flocculant 3 Cake Filtrate Mixing Mixing Turbidity Dose (g/t) Dose (g/t) Moisture Solids Time (s) (%wt) (%wt) Time (s) (NTU) 0 715 42.9 44.8 NT 46.0 36 715 46.4 36.6 NT 47.0 804 71 715 51.1 32.5 NT 45.1 448 107 715 46.8 32.9 NT 42.8 181 143 715 45.0 26.0 NT 45.5 224 179 715 49.4 24.3 NT 43.7 61 214 715 56.9 24.7 NT 55.0 65 The results show that for the substrate mixture with a 1.6:1 SFR, the addition of Product 1 reduced the residual moisture in the dewatered solids and improved the retention and capture of fine particles during both dewatering and sub-aqueous deposition.

Claims

Claims 1.
A process for separating solids from an aqueous slurry containing particulate material, which particulate material comprises sand particles and fines particles and contains clay parti-5 cles, which aqueous suspension has a solids content of from 25 to 70% by weight and a sand to fines ratio of from 0.5:1 to 5:1, which process comprises applying a treatment system to the aqueous slurry to cause floccula-tion of the particulate material, and subsequently separating the so formed flocculated particu-late material as solids from the slurry, 10 in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCl); and 15 (c) optionally, at least one cationic coagulant.
2. A process according to claim 1 in which the which aqueous suspension has a solids con-tent of from 30 to 70% by weight 3. A process according to claim 1 or claim 2 in which the aqueous slurry comprises clay in a coagulated state and the treatment system comprises adding to the aqueous slurry ionic poly-20 meric de-coagulant (a) to reduce the coagulated state of the clay particles to a less coagulated state within the aqueous slurry and then addition of the polymeric flocculant (b) to flocculate the sand and de-coagulate treated clay particles.
4. A process according to any preceding claims in which the aqueous slurry comprises a sand to fines ratio of from 1:1 to 5:1.
25 5. A process according to any preceding claims in which the aqueous slurry has a fines solids content of from 10% to 45% by total weight of aqueous slurry.
6. A process according to any preceding claim in which the aqueous slurry has been derived from an oil sands fluid fines tailings (FFT), thickened fine tailings or a mature fines tailings (MFT).
30 7. A process according to any preceding claim in which the aqueous slurry comprises from 10 percent to 70 percent clay particles based on the total weight of solids.

8. A process according to any preceding claim in which the clay particles contained in the aqueous slurry are predominantly kaolinite and illite, additionally comprises smectite and chlo-rite.
9. A process according to any preceding claim in which the ionic polymeric de-coagulant (a) is a water-soluble polymer derived from ethylenically unsaturated monomers and exhibiting a weight average molar mass of below 100,000 g/mol, preferably below 50,000 g/mol.
10. A process according to any preceding claim in which the ionic polymeric de-coagulant (a) is an anionic or non-ionic polymer derived from ethylenically unsaturated monomers and said polymer comprising repeating monomeric units carrying pendant polyalkyleneoxy groups.
11. A process according to any preceding claim in which the ionic polymeric de-coagulant (a) is a polymer comprising repeating units derived from (i) an ethylenically unsaturated anionic or non-ionic monomer containing a polymerisable moiety (M) and having the structure M ¨ R2¨ X ¨ ( - CH2 ¨ CHR5 ¨ 0 -)i ( ¨ CH2 ¨ CH2 ¨ 0 ¨)m - ( - CH2 ¨ CHR3 ¨ 0 -),-, ¨ R4 (l) in which X is 0 or NH, R2 is independently a single bond or a divalent linking group selected from the group consisting of ¨(CH2¨)p- and ¨0¨(CH2¨)s where p is a number from 1 to 6 and s is a number from 1 to 6, R3 and R5 are each a hydrogen or hydrocarbyl radical having 1-4 carbon atoms, R4 is independently a hydrogen or a hydrocarbyl radical having 1-4 carbon atoms or a moiety having the structure ¨ ( ¨ CH2 ¨ CH2 ¨ 0 ¨)k-Y, k is a number from 1 to 20, l is a number from 0 to 250;
m is a number from 1 to 300, n is a number from 0 to 250;
Y is hydrogen or a hydrocarbyl radical having 1-4 carbon atoms, and (ii) at least one ethylenically unsaturated monomer carrying at least one anionic functional group different from component (i);
and (iii) optionally at least one ethylenically unsaturated non-ionic monomer, different from component (i).
12. A process according to any preceding claim in which M is selected from a vinyl moiety, an ethylenically unsaturated carboxylic moiety, an ethylenically unsaturated amide moiety, an allyl moiety or isoprenyl moiety.
13. A process according to any preceding claim in which M is selected from the group consist-ing of:
H2C=C(R1)¨ (II);
H2C=C(R1)¨CH2¨ (III);
H2C=C(R1)¨00¨ (IV);
HOOC¨HC=C(R1)¨00¨ (V); and 0C¨HC=C(R1)¨00¨ (VI), in which R1 is hydrogen or methyl.
14. A process according to any preceding claim in which the ethylenically unsaturated mono-mer (ii) is selected from the group consisting of acrylic acid (or salts thereof), methacrylic acid (or salts thereof) maleic acid (or salts thereof), fumaric acid (or salts thereof), itaconic acid (or salts thereof), 2-acrylamido-2-methyl propane sulphonic acid (or salts thereof), vinylsulfonic acid (or salts thereof), allyl sulphonic acid (or salts thereof), vinylphosphonic acid (or salts thereof) and 2-hydroxyethyl methacrylate phosphate (or salts thereof).
15. A process according to any preceding claim in which the ethylenically unsaturated mono-mer (iii) is selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acry-late, hydroxy alkyl methyl acrylate, vinyl acetate, vinyl alcohol, allyl alkyl ether, styrene, and al-kyl acrylates.
16. A process according to claim 9 in which the ionic polymeric de-coagulant (a) is a water-soluble polymer derived from ethylenically unsaturated monomers selected from the group con-sisting of homopolymers of one or more ethylenically unsaturated acid monomers (or salts thereof); and copolymers formed from a monomer mixture consisting of one or more ethylenical-ly unsaturated acid monomers (or salts thereof) and one or more ethylenically unsaturated non-ionic monomers selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, vinyl acetate, vinyl alcohol, allyl alkyl ether, styrene and Ci_s alkyl acrylates.

17. A process according to claim 16 in which the one or more ethylenically unsaturated acid monomers are selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, 2-acrylamido-2-methyl propane sulphonic acid, vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid and 2-hydroxy ethyl methacrylate phosphate.
18. A process according to claim 16 or claim 17 in which the ionic polymeric de-coagulant (a) is selected from the group consisting of a homopolymer of acrylic acid (or salts thereof) and a co-polymer of a monomer mixture consisting of acrylic acid (or salts thereof) and acrylamide.
19. A process according to any preceding claim in which the polymeric flocculant (b) is a poly-mer formed from repeating units derived from at least one ethylenically unsaturated monomer bearing an anionic group and optionally at least one ethylenically unsaturated non-ionic mono-mer.
20. A process according to any preceding claim in which the polymeric flocculant (b) is a water-soluble polymer derived from ethylenically unsaturated monomers selected from the group con-sisting of homopolymers of one or more ethylenically unsaturated acid monomers (or salts thereof); and copolymers formed from a monomer mixture comprising of (A) one or more eth-ylenically unsaturated acid monomers (or salts thereof), (B) one or more ethylenically unsatu-rated non-ionic monomers selected from the group consisting of acrylamide, methacrylamide, hydroxy alkyl acrylate, vinyl acetate, vinyl alcohol, allyl alkyl ether, styrene and 01-8 alkyl acry-lates (C) one or more other ethylenically unsaturated monomers different from (A) and (B).
21. A process according to claim 20 in which the one or more ethylenically unsaturated acid monomers are selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, 2-acrylamido-2-methyl propane sulphonic acid, vinylsulfonic acid, allyl sulphonic acid, vinylphosphonic acid and 2-hydroxy ethyl methacrylate phosphate.
22. A process according to claim 20 or claim 21 in which the one or more other ethylenically unsaturated monomers (C) are selected from one or more cationic monomers, provided that overall anionic equivalent content is greater than the overall cationic equivalent content and preferably the one or more cationic monomers are included in the monomer mixture in an amount of up to 10 mol % total cationic monomer based on the total molar content of monomers in the monomer mixture.
23. A process according to any preceding claim in which the polymeric flocculant (b) is a co-polymer of acrylamide with (meth)acrylic acid (or salt thereof) or a homopolymer of (meth)acrylic acid (or salt thereof).
24. A process according to any preceding claim in which the polymeric flocculant (b) exhibits an intrinsic viscosity of at least 6 dl/g.
25. A process according to any preceding claim in which the cationic coagulant (c) is selected from the group consisting of homopolymers of diallyldimethylammonium chloride (DADMAC);

copolymers of diallyldimethylammonium chloride (DADMAC) and acrylamide;
homopolymers of methyl chloride quaternised dimethyl amino ethyl acrylate (DMAEA-q);
copolymers of methyl chloride quaternised dimethyl amino ethyl acrylate (DMAEA-q) and acrylamide;
homopolymers of methyl chloride quaternised dimethyl amino ethyl methacrylate (DMEMA-q);
copolymers of methyl chloride quaternised dimethyl amino ethyl methacrylate (DMEMA-q) and acrylamide;
homopolymers of acrylamido propyl trimethylammonium chloride (APTAC);
copolymers of acrylamido propyl trimethylammonium chloride (APTAC) and acrylamide;
homopolymers of methacrylamido propyl trimethylammonium chloride (MAPTAC); copolymers of methacrylamido propyl trimethylammonium chloride (MAPTAC) and acrylamide; partially or fully hydrolysed pol-yvinyl formamides containing repeating vinyl amine units; polyethyleneimines;
alkyl amines with formaldehyde and/or epichlorohydrin; and polycyandiamides.
26. A process according to any preceding claim in which the aqueous slurry is formed from a first precursor aqueous slurry in which the sand to fines ratio is below 0.5:1, suitably below 1:1, and the sand to fines ratio is adjusted to increase the sand to fines ratio by either, (a) combining the first precursor aqueous slurry with sand; and/or (b) combining the first precursor aqueous slurry with a second precursor aqueous slurry, which second precursor aqueous slurry has a sand to fines ratio of greater than 3:1, suitably greater than 4:1 and especially suitably greater than 5:1, and thereby forming the aqueous slurry, in which the treatment system or components thereof are applied to any one or more of the first precursor aqueous slurry, the sand component, the second precursor aqueous slurry and/or the aqueous slurry.
27. A process according to claim 26 in which the sand in (a) is in the form of a sand stream, preferably the underflow sand stream from a cyclone processing whole tailings (WT).
28. A process according to claim 26 or claim 27 in which the first precursor aqueous slurry is selected from the group consisting of mature fines tailings (MFT), fluid fines tailings (FFT), thin fines tailings (TFT), thickened fines tailings (ThFT).
29. A process according to any of claims 1 to 25 in which the aqueous slurry is formed from a second precursor aqueous slurry in which the sand to fines ratio is greater than 3:1, suitably greater than 4:1 and especially suitably greater than 5:1, and the sand to fines ratio is adjusted to decrease the sand to fines ratio by separating sand particles having a particle size greater than a predetermined size limit, preferably greater than 100 pm, from the second precursor aqueous slurry thereby, and thereby forming the aqueous slurry, in which the treatment system or components thereof are applied to any one or more of the second precursor aqueous slurry and/or the aqueous slurry.
30. A process according to any of claims 26 to 29 in which the second precursor aqueous slur-ry is whole tailings (WT).
5 31. A process according to claim 29 in which the separation of the sand from the second pre-cursor aqueous slurry is conducted using a cyclone or a screen sufficient to remove the sand particles having a particle size greater than the predetermined size limit.
32. A process according to any preceding claim in which the aqueous slurry of particulate ma-terial comprises flowing as slurry of mature fines tailings (MFT) and/or fluid fines tailings (FFT) 10 along a conduit and in which a slurry of sand is combined with the slurry of mature fines tailings and/or fluid fines tailings to provide a combined tailings stream (CbT), wherein the components of the treatment system are applied to (i) the mature fines tailings and/or fluid fines tailings;
and/or (ii) the combined tailings stream (CbT), and in which the so treated combined tailings stream (CbT) is fed to a deposition area.
15 33. A process according to claim 32 in which ionic polymeric de-coagulant (a) is either fed into the slurry of MFT and/or FFT, fed into the sand slurry or fed into the combined tailings stream (CbT) and thereafter the polymeric flocculent (b) is added to the so treated combined tailings stream (CbT).
34. A process according to claim 32 or claim 33 in which the so treated combined tailings 20 stream (CbT) is fed into a void or impoundment at the deposition area, in which the void or im-poundment has a depth of at least 5 m, preferably at least 20 m, and the deposited solids are allowed to separate from the released supernatant liquid and consolidate.
35. A process according to claim 34 in which a supernatant liquid separated from the so treated slurry forms above the particulate solids deposited in the void or impoundment and in which the 25 supernatant liquid is continually or periodically removed from the void.
36. A process according to claim 34 or claim 35 in which the so treated combined tailings stream (CbT) is fed onto a beach surface at the deposition area and form thin layers of newly deposited beach material which dewaters through drainage and evaporation.
37. A process according to claim 36 in which the beached surface has an angle of incline of 30 between 0.5 and 10 .
38. A process according to any preceding claim in which the aqueous slurry of particulate ma-terial is first treated by the addition of the ionic polymeric de-coagulant (a) and then subjecting the so treated aqueous slurry to a mixing stage followed by addition of the polymeric flocculent (b).

39. A process according to any preceding claim in which the aqueous slurry of particulate ma-terial is treated by the addition of the treatment system and then subjecting the so treated aque-ous slurry to a mixing stage.
40. A process according to any preceding claim in which the aqueous slurry of particulate ma-terial is subjected to a mixing stage after the addition of each of the ionic polymeric de-coagulant (a) and the polymeric flocculant (b) of the treatment system.
41. A composition formed from an aqueous slurry containing particulate material, which par-ticulate material comprises sand particles and fines particles and contains clay particles, which aqueous suspension has a solids content of from 25 to 70% by weight and a sand to fines ratio of from 0.5:1 to 5:1, which composition comprises flocculated particulate solids and a treatment system in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCl); and (c) optionally, at least one cationic coagulant.
42. A composition according to claim 41 incorporating one or more of the features of any of claims 2 to 40.
43. A treatment system for separating solids from an aqueous slurry containing particulate ma-terial, which particulate material comprises sand particles and fines particles and contains clay particles, which aqueous slurry has a solids content of from 25 to 70% by weight and a sand fines ratio of 0.5:1 to 5:1, in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCl); and (c) optionally, at least one cationic coagulant.
44. A treatment system according to claim 43 incorporating one or more features of any of claims 2 to 40.

45. Use of a treatment system for separating solids from an aqueous slurry containing particu-late material, which particulate material comprises sand particles and fines particles and con-tains clay particles, which aqueous slurry has a solids content of from 25 to 70% by weight and a sand fines ratio of 0.5:1 to 5:1, in which the treatment system comprises (a) at least one ionic polymeric de-coagulant, which exhibits a weight average molar mass of below 2 million g/mol;
(b) at least one polymeric flocculant, which has an intrinsic viscosity of at least 5 dl/g (meas-ured at 25 C in 1 M NaCl); and (c) optionally, at least one cationic coagulant.
46. Use according to claim 45 incorporating one or more features of any of claims 2 to 40.