CA3150312C

CA3150312C - Pillaring of clay-containing fine tailings for enhanced post-deposition dewatering and consolidation

Info

Publication number: CA3150312C
Application number: CA3150312A
Authority: CA
Inventors: Oladipo Omotoso
Original assignee: Suncor Energy Inc
Current assignee: Suncor Energy Inc
Priority date: 2022-02-28
Filing date: 2022-02-28
Publication date: 2024-05-07
Anticipated expiration: 2042-02-28
Also published as: CA3150312A1

Abstract

Process/method implementations for treating fine tailings containing clay platelets including addition of a pillaring agent, comprising trivalent cations and/or tetravalent cations, to fine tailings to convert at least a portion of the clay platelets into pillared layered solids. Adjustment of at least one of a solubilizing pH, a zeta potential, and a concentration of the pillaring agent can be performed to facilitate solubilization of the trivalent cations and/or tetravalent cations and further diffusion for intercalation between basal surfaces of the clay platelets to form a thermally stable interlayer of pillars. The treated tailings are further deposited for further consolidation over time to form a consolidated deposit that results in a geotechnically and geochemically stable landform in a shorter period than according to conventional deposition/consolidation techniques.

Description

PILLARING OF CLAY-CONTAINING FINE TAILINGS FOR ENHANCED POST-DEPOSITION DEWATERING AND CONSOLIDATION
TECHNICAL FIELD
[001] The present techniques relate to dewatering and consolidation of clay-containing fine tailings, and more particularly relate to the treatment of clay-containing fine tailings to encourage pillaring of clay platelets for enhancing the dewatering and consolidation of the treated tailings into a reclaimable landform.
BACKGROUND

[002] Post-deposition management of fluid fine tailings is an ongoing challenge in oil sands and mineral extraction industries, where large volumes of fluid fine tailings are generated.

[003] Conventionally, tailings are transported to a deposition site generally referred to as a "tailings pond" located close to the mining and extraction facilities to facilitate pipeline transportation, deposition and management of the tailings. Due to the scale of operations, tailings ponds can cover vast tracts of land. In accordance with some standing regulations, the land must be reclaimable after a certain period of time which can be a complex undertaking given the slow consolidation rates of fluid fine tailings.

[004] Certain methods have been proposed to improve and accelerate the dewatering and consolidation of fluid fine tailings, including mature fine tailings (MFTs) which can be recovered from oil sands tailings ponds or other sources. MFTs are formed in the pond over time and are often characterized as being high in clay content and having relatively slow consolidation rates. For example, MFTs can be co-deposited with sand to encourage strength development after the end of the deposition to produce consolidated tailings. In another example, flocculation of the MFTs has been proposed to aggregate fine clays, optionally co-currently with coagulation, thereby providing a rapid initial dewatering.

[005] However, challenges remain to be overcome to accelerate post-deposition consolidation of fluid fine tailings and facilitate terrestrial reclamation.

Date Recue/Date Received 2023-05-11 SUMMARY

[006] The present techniques are directed to treatment of fine tailings containing clay platelets by pillaring to form a consolidated deposit that can be reclaimed as a landform, that is sufficiently geotechnically and geochemically stable in accordance with a specific land use,

[007] More particularly, there is provided a process for treating fine tailings containing clay platelets. The process includes treatment of the fine tailings to produce treated tailings comprising pillared layered solids. The treatment includes addition of a pillaring agent releasing trivalent cations and/or tetravalent cations that intercalate between basal surfaces of the clay platelets to form a thermally stable interlayer of pillars, thereby converting at least a portion of the clay platelets into pillared layered solids. The process further includes deposition of the treated tailings within a dedicated deposition area to produce a consolidated deposit by allowing separation of the water from solids of the treated tailings to form a pillared deposit comprising the pillared layered solids; and consolidation of the pillared deposit into the consolidated deposit over time, the consolidation comprising forming additional thermally stable interlayers of pillars that grow from the trivalent cations and/or tetravalent cations intercalated between the basal surfaces of the clay platelets.

[008] In some implementations, the treating of the fine tailings can include adjusting a pH of the fine tailings to a solubilizing pH encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets.
For example, the solubilizing pH can be at most 5 or at least 9 in accordance with a nature of the trivalent cations and/or tetravalent cations.

[009] In some implementations, the treating of the fine tailings can include adjusting a zeta potential of the fine tailings to encourage diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets. For example, the zeta potential can be adjusted to at least ¨40 mV, -50 my, or -60 mV.

[010] In some implementations, the treating of the fine tailings can include adjusting a concentration of the pillaring agent to a pillaring concentration being at most 0.06 wt%, at most 0.08 wt%, at most 0.1 wt%, at most 0.3 wt%, at most 0.5 wt%, at most 0.7 wt%, at most 0.9 wt%, at most 1.1 wt%, at most 1.3 wt%, at most 1.5 wt%, at most 1.7 wt%, at most 1.9 wt%, or at most 2 wt% of the total solids content in the fine tailings.

Date Recue/Date Received 2022-02-28

[011] In some implementations of the process, the pillaring agent comprises an exogenous source of silicon. For example, the pillaring agent can be hydraulic cement, activated pozzolan, activated silica fume, activated fumed silica, or a combination thereof.
The pillaring agent can be added at a pH of at least 9, at least 10, at least 11, at least 12 or at least 13 in the treated tailings.

[012] In some implementations of the process, the pillaring agent can be an acid coagulant comprising at least one of an aluminum cation and a ferric cation.
For example, the pillaring agent can include aluminum sulfate, ferric sulfate or a combination thereof.
The pillaring agent can be added at a pH of at most 3, at most 4, at most 5, or at most 6.

[013] In some implementations of the process, the treatment of the fine tailings can further includes flocculating the fine tailings by adding a flocculation agent to form flocculated tailings. For example, the pillaring agent can be added after the flocculation agent into the flocculated tailings, and optionally, the flocculation agent can be an anionic water-soluble polymer, such as a polyacrylamide, or a non-ionic polymer. In another example, the pillaring agent can be added before the flocculation agent to the fine tailings, and optionally the flocculation agent can be a non-ionic polymer, such as a polyethylene oxide polymer.

[014] In some implementations of the process, the pillaring agent can be a flocculant including pillaring moieties releasing the trivalent cations and/or tetravalent cations for intercalation between the clay platelets, and the treatment of the fine tailings thereby comprises the addition of the pillaring agent to flocculate the fine tailings into flocculated fine tailings and pillar the flocculated fine tailings for forming the treated tailings. For example, the flocculant can be a polyethylene oxide copolymer comprising siloxane units.

[015] In some implementations of the process, the fine tailings can include contaminants of concern (CoCs) and the treatment further includes immobilizing the CoCs to produce the landform comprising the pillared layered solids and immobilized CoCs. For example, the immobilizing can be performed by addition of an immobilization agent that is added after the pillaring agent. Optionally, the immobilization agent can be an acid coagulant comprising at least one of aluminum cations and ferric cations, such as aluminum sulfate, ferric sulfate or a combination thereof. Further optionally, the acid coagulant can be added at an immobilizing concentration that is at most 5 meq/L, at most 10 meq/L, at most 15 meq/L, or at most 20 meq/L of a pore water in the fine tailings.

Date Recue/Date Received 2022-02-28

[016] In some implementations of the process, the fine tailings can include contaminants of concern (CoCs) and the pillaring agent can be an acid coagulant releasing aluminum and/or ferric cations performing both the pillaring of the clay platelets and the immobilizing of the CoCs to produce the landform comprising the pillared layered solids and immobilized CoCs. Optionally, the acid coagulant can be added at a concentration between 20 and 40 meq/L of a pore water in the fine tailings.

[017] In some implementations, the addition of the pillaring agent can be performed under a turbulent micro-mixing regime to minimize formation of secondary products from the trivalent cations and/or tetravalent cations.

[018] In some implementations of the process, the treated tailings can include at least 10, 20, 30, 40, 50, 60, 70 or 80 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

[019] In some implementations of the process, the consolidated deposit can include at least 50, 60, 70, 80 or 90 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

[020] In some implementations of the process, the deposition of the treated tailings can be performed until the pillared deposit reaches a target height. For example, the deposition of the treated tailings can be performed at a deposition rate of at most 20 meters per year.
Optionally, the target height can be between 20 m and 75 m.

[021] In some implementations of the process, the consolidated deposit can be reclaimed as a landform once the consolidated deposit is geotechnically stable after a consolidation period for a given end use. For example, geotechnical stability of the consolidated deposit can be achieved by consolidation when the consolidated deposit has a shear strength greater than 15, 20, 25, 30 or 35 kPa. For example, geotechnical stability of the consolidated deposit can be achieved by consolidation when the consolidated deposit has a solids content of at least 50, 55, 60 or 65 wt%. Optionally, the consolidation period can be at most 50 years when the pillared deposit is initially at most 75-meter high.

[022] In some implementations of the process, the pillared deposit can have a post-deposition hydraulic conductivity greater than 10-9 m/s.

[023] In some implementations of the process, the dedicated deposition area can be below or above grade. The process can include capping the consolidated deposit with a layer of sand or coke to form a solid top cap. Optionally, the solid top cap can have a Date Recue/Date Received 2022-02-28 thickness between 2 m and 5 m. The process can further include draining a top layer of the consolidated deposit for further dewatering of the top layer. The consolidated deposit can be reclaimed as a landform that comprises a dryland, or solid ground.

[024] In some implementations of the process, the dedicated deposition area can be below grade. Optionally, the dedicated deposition area can include a containment structure, such as a mine pit. The process can include capping the consolidated deposit with a layer of water to form a top water cap. The top water cap can include at least a portion of the water released from the treated tailings during the dewatering.
For example, the consolidated deposit can be reclaimed as a landform that comprises a floor or sediment of a lake, or a wetland.

[025] In some implementations of the process, the fine tailings can have a clay content being at least 50, 60, 70, 80 or 90 wt% of a total solids content of the fine tailings.

[026] In some implementations of the process, the fine tailings can be oil sands fine tailings.

[027] In some implementations of the process, the fine tailings can be mature fine tailings.

[028] In some implementations of the process, the fine tailings can be thin fine tailings

[029] In some implementations of the process, the fine tailings can be thick fine tailings.

[030] There is also provided a method for converting fine tailings containing clay platelets and contaminants of concern (CoCs) into a consolidated deposit. The method includes forming treated tailings by flocculating the fine tailings to form aggregates of the clay platelets; pillaring the clay platelets by intercalating trivalent cations and/or tetravalent cations between basal surfaces of the clay platelets to grow pillared layered solids comprising thermally stable interlayers of pillars between the clay platelets;
and immobilizing the CoCs. The method further includes depositing the treated tailings within a dedicated deposition area to convert the treated tailings into the consolidated deposit by releasing water from the treated tailings pores to produce a pillared deposit comprising the pillared layered solids and immobilized CoCs; and consolidating the pillared deposit over a consolidation period to produce the consolidated deposit, the consolidating comprising forming additional pillared layered solids from the aggregates of the clay platelets.
Date Recue/Date Received 2022-02-28

[031] In some implementations, the pillaring of the clay platelets can be performed at a solubilizing pH encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets. For example, the solubilizing pH can be at most 5 or at least 9 in accordance with a nature of the trivalent cations and/or tetravalent cations.

[032] In some implementations, the flocculating can be performed to achieve a zeta potential of the aggregates encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets. For example, the zeta potential can be at least ¨40 mV, -50 my or -60 mV.

[033] In some implementations of the method, the trivalent cations can be at least one of aluminum cations and ferric cations, and the tetravalent cations are silicon cations.

[034] In some implementations of the method, the flocculating can be performed before or after the pillaring via separate addition of a flocculation agent and a pillaring agent to the fine tailings.

[035] In some implementations, the addition of the pillaring agent can be performed under a turbulent micro-mixing regime to minimize formation of secondary products from the trivalent cations and/or tetravalent cations.

[036] In some implementations of the method, the pillaring agent can be added at a pillaring concentration being at most 0.06 wt%, at most 0.08 wt%, at most 0.1 wt%, at most 0.3 wt%, at most 0.5 wt%, at most 0.7 wt%, at most 0.9 wt%, at most 1.1 wt%, at most 1.3 wt%, at most 1.5 wt%, at most 1.7 wt%, at most 1.9 wt%, or at most 2 wt% of the total solids content in the fine tailings.

[037] In some implementations of the method, the flocculation agent can be an anionic polymer. For example, the anionic polymer can be polyacrylamide (PAM).

[038] In some implementations of the method, the flocculation agent can be a non-ionic polymer. For example, the non-ionic polymer can be a polyethylene oxide polymer.

[039] In some implementations of the method, the pillaring agent can be an acid coagulant releasing aluminum cations and/or ferric cations. The acid coagulant can include aluminum sulfate, ferric sulfate or a combination thereof. For example, the pillaring agent can be added at a pH of at most 3, at most 4, at most 5, or at most 6.

Date Recue/Date Received 2022-02-28

[040] In some implementations of the method, the pillaring agent can be hydraulic cement, activated pozzolan, activated fumed silica, activated silica fume, or any combinations thereof.

[041] In some implementations of the method, the flocculating and pillaring can be co-currently performed via in-line addition of a flocculant to the fine tailings, with the flocculant comprising pillaring moieties releasing the trivalent and/or tetravalent cations. The flocculant can be a non-ionic polymer comprising pillaring moieties releasing silicon cations. For example, the flocculant can be a polyethylene oxide copolymer comprising siloxane units. For example, the flocculant can be added at a pH of at least 9, at least 10, at least 11, at least 12 or at least 13 in the treated tailings.

[042] In some implementations of the method, immobilizing the CoCs can be performed via in-line addition of an immobilization agent, wherein the immobilization agent is added after the pillaring agent. For example, the immobilization agent can be an acid coagulant releasing aluminum and/or ferric cations, such as aluminum sulfate, ferric sulfate or a combination thereof. For example, the acid coagulant can be added at an immobilizing concentration that is at most 5 meq/L, at most 10 meq/L, at most 15 meq/L, or at most 20 meq/L of a pore water in the tine tailings.

[043] In some implementations of the method, immobilizing the CoCs can be performed via in-line addition of the pillaring agent, wherein the trivalent and/or tetravalent cations released by the pillaring agent participate in both the pillaring of the clay platelets and the immobilizing of the CoCs. For example, the pillaring agent can be added at a concentration between 20 and 40 meq/L of a pore water in the fine tailings.

[044] In some implementations of the method, the treated tailings can include at least 10, 20, 30, 40, 50, 60, 70 or 80 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

[045] In some implementations of the method, the consolidated deposit can comprise at least 50, 60, 70, 80 or 90 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

[046] In some implementations of the method, the method can include capping the consolidated deposit with a layer of sand or coke to form a top cap. The top cap can have a thickness between 2 m and 5 m.

Date Recue/Date Received 2022-02-28

[047] In some implementations of the method, the method can include capping the consolidated deposit with a layer of water to form a top water cap. The top water cap can include at least a portion of the water released from the treated tailings following deposition.

[048] In some implementations of the method, the dedicated deposition area can be above grade.

[049] In some implementations of the method, the dedicated deposition area can be below grade. Optionally, the dedicated deposition area can include a containment structure. For example, the dedicated deposition area can be a mine pit.

[050] In some implementations of the method, the method can include reclaiming the consolidated deposit when the consolidated deposit is geotechnically and geochemically stable for a given land use after the consolidation period. For example, geotechnical stability of the consolidated deposit can be achieved by consolidation when the consolidated deposit has a shear strength greater than 15, 20, 25, 30 or 35 kPa. For example, geotechnical stability of the consolidated deposit can be achieved by consolidation when the consolidated deposit has a solids content of at least 50, 55, 60 or 65 wt%. Optionally, the consolidation period can be at most 50 years when the pillared deposit is initially at most 75-meter high.

[051] In some implementations of the method, the geotechnically and geochemically stable consolidated deposit can be reclaimed as a landform that is a floor of a lake, a wetland, or a dryland.

[052] In some implementations of the method, the fine tailings can have a clay content being at least 50, 60, 70, 80 or 90 wt% of a total solids content of the fine tailings.

[053] In some implementations of the method, the fine tailings can be oil sands fine tailings.

[054] In some implementations of the method, the fine tailings can be mature fine tailings.

[055] In some implementations of the method, the fine tailings can be thin fine tailings.

[056] In some implementations of the method, the fine tailings can be thick fine tailings.

Date Recue/Date Received 2022-02-28

[057] It should also be noted that various features, step and implementations summarized above may be combined with other features, step and implementations of the described above or herein.
BRIEF DESCRIPTION OF THE DRAWINGS

[058] Figure 1 is a schematic representation of the crystalline structure of two adjacent clay platelets of a 2:1 clay mineral and a cation interlayer, each clay platelet comprising a layer of cations in octahedral coordination and cations in tetrahedral coordination.

[059] Figure 2 is a schematic representation of a pillared layered solid including oxy-hydroxide pillars being formed from intercalation of trivalent and/or tetravalent cations in clay aggregates from flocculated fluid fine tailings.

[060] Figure 3 is a schematic process flow diagram of treatment and deposition of MTF
according to an embodiment of the present techniques.

[061] Figure 4 is a schematic process flow diagram of treatment and deposition of MTF
according to another embodiment of the present techniques.

[062] Figure 5 is a schematic process flow diagram of treatment and deposition of MTF
according to another embodiment of the present techniques.

[063] Figure 6 is a schematic process flow diagram of treatment and deposition of MTF
according to another embodiment of the present techniques.

[064] Figure 7 is a graph of deposit elevation versus years after the start of the deposition and indicating the elevation at the end of deposition and the elevation when the deposit is sufficiently dewatered and consolidated for reclamation, for five different tailings materials, two of which being treated according to the present techniques (f/c and pillared FFT_PEO
and f/c and pillared FFT_pozzolan) and the three remaining streams being handled according to conventional techniques (CT 3:1, c/f FFT, and untreated (FFT)).
FFT refers to fluid fine tailings.
DETAILED DESCRIPTION

[065] The present techniques include treating clay-containing fine tailings to form treated tailings, and depositing the treated tailings to dewater and consolidate the treated tailings for supporting aquatic and terrestrial reclamation activities. The treatment particularly Date Recue/Date Received 2022-02-28 allows for the conversion of clay platelets into pillared layered solids as will be explained in further detail below.

[066] The fine tailings that can be treated by the techniques described herein include clay-containing fine tailings, which can be oil sands fine tailings derived from oil sands extraction operations. Fine tailings that are notably suitable for treatment using the pillaring techniques include a high fines content, e.g., a fines fraction including clay that is greater than 60 wt%, 70 wt%, 80 wt%, 90 wt% of the solids content of the fine tailings. For example, the oil sands fine tailings can be thin fine tailings having a solids content below wt% or thick fine tailings having a solids content above 10 wt% and typically in the range of 20 wt% to 45 wt%. The thick fine tailings can be mature fine tailings (MFT) retrieved from a tailings pond. The fine tailings that can be treated include solid components, such as clays, that are pillarable. It is also noted that, although the abbreviation MFT is used herein, it should be understood that the fine tailings encompassed in the present description are not necessarily obtained from a tailings pond and can be any clay-containing fine tailings that are derived from a mining operation.

[067] The treatment of the fine tailings is tailored to encourage formation of heterostructures between clay platelets of the treated fine tailings. Such heterostructures can be referred to as pillars, and the resulting partially pillared clays can be referred to as pillared layered solids. The pillared layered solids are clay structures of larger discrete particle size and of higher porosity than those in untreated fine tailings.
The larger discrete particle size and greater porosity advantageously enable quicker consolidation of the deposit to support reclamation activities.
Solids and clay

[068] The oil sands industry has adopted a convention with respect to mineral particle sizing. Mineral fractions with a particle diameter greater than 44 microns are referred to as "sand". Mineral fractions with a particle diameter less than 44 microns are referred to as "fines". The "clay" mineral fraction is usually characterized as having a particle diameter less than 2 microns.

[069] Clay or clay mineral is defined herein as a phyllosilicate comprising silicate tetrahedral and aluminum octahedral sheets arranged into platelets, referred to as clay platelets. Typically, clay platelets can include repetitive layers of one tetrahedral sheet and one octahedral sheet (1:1 structures), or one octahedral sheet sandwiched between two Date Recue/Date Received 2022-02-28 tetrahedral sheets (2:1 structures), with the repetitive layers being chemically bonded to one another (e.g., via secondary bonds such as hydrogen bonds). Additional variable amounts of iron, magnesium, alkali metals, and/or alkaline earth metals can be further part of crystalline structure of the clay platelets. Depending on the composition of the tetrahedral and octahedral sheets of the clay platelets, different atoms are available at basal surfaces of the platelets, which can change the surface chemistry of the clay platelets.
Pillaring

[070] Pillaring as described herein includes inserting vertically spaced, thermally stable, inorganic molecular compounds/moieties between external layers of adjacent clay platelets, so as to form multiple pillars generating a thermally stable interlayer between clay platelets. Each pillar is a heterostructure that is formed between basal surfaces of two clay platelets, and can include one or more of Fe, Al or Si atoms. Pillaring can be understood as intercalating inorganic moieties between clay platelets to create a porous structure having an increased interlamellar distance and an increased pore volume. The initial layer configuration is thus retained but further pillared and spaced apart, and the formed porous structure can be referred to as the pillared layered solid or pillared compound.

[071] Tailings treated according to the present techniques can be referred to as treated tailings including water and pillared layered solids. Advantageously, upon deposition of the treated tailings, the pillared layered solids can maintain an interlayer spacing thereof while releasing water from the treated tailings via pores of the pillared layered solids. The clay platelets within the pillared layered solids are thus propped apart vertically (as in a stack configuration) and the pillared layered solids do not collapse upon removal of the water by dewatering of the treated tailings. If the pillaring agent has an immobilizing effect with respect to contaminants of concern present in the fine tailings, or if a separate immobilization agent is added subsequently to the pillaring agent, the treated tailings can further include immobilized contaminants of concern (CoCs), as will be described in further detail below.

[072] In some implementations, the techniques include in-line addition of a pillaring agent to fine tailings to form thermally stable interlayers between clay platelets, producing treated tailings including the pillared layered solids. The treated tailings are then subjected to dewatering and consolidation.

Date Recue/Date Received 2022-02-28

[073] The pillaring agent refers to an inorganic or organic compound having a pillaring effect, i.e., being able to intercalate atoms/moieties and serving as a pillar seed/nuclei to grow a pillar between external layers of clay platelets. Referring to Figure 1, the pillaring agent can liberate at least one of a trivalent cation (M3+) and a tetravalent cation (M4+) for intercalation between clay platelets to serve as the pillar seed, e.g., a hydroxy cation (referred to in Figure 1 as M3+/M4+ hydroxy islands in interlayer). For example, the pillaring agent can release at least one of Al, Fe, and Si in ionic form. More particularly, referring to Figure 2, the intercalated trivalent (A13+ or Fe3+) and tetravalent (Si4+) ions can further react with oxygen to form solid heterostructures comprising oxyhydroxides distributed in interlayers between the clay platelets. The interlayers have lower compressibility than mere hydrated exchangeable cations while maintaining high permeability.
Pillaring allows for creation of micropores and mesopores of controlled sizing between stacked clay platelets having a lamellar structure, thereby facilitating dewatering of the clay-containing tailings. In some implementations, the pillaring is performed via the in-line addition of an exogenous source of silicon to fine tailings. When referring to the Si element from an exogenous source, it is understood that the provided silicon is not initially part of the clay platelet itself or the original tailings material.

[074] Silicon in the clay platelets is available at the basal surfaces and edges of the platelets but is not to be considered as a pillaring agent or as having a pillaring effect. It should further be noted that pillars as encompassed herein are to be distinguished from hydrates, although pillars and hydrates can co-exist within the formed interlayers.

[075] The present techniques thus include controlling the water chemistry of the treated fine tailings prior to deposition to facilitate their diffusion in a pore water environment between the clay platelets. The diffused pillaring ions act as pillar seeds/nuclei (e.g., metal hydroxy cations) and can then react with oxygen to form solid pillars growing between clay platelets of the fine tailings upon deposition and overtime. Controlling the water chemistry can include adjusting at least one of a concentration of the pillaring agent, a pH of the pore water and a zeta potential of treated fine tailings.

[076] The treated fine tailings formed according to the present techniques can be characterized by including at least 10, 20, 30, 40, 50, 60, 70, or 80 wt% of the pillarable clay from the fine tailings being pillared in the treated fine tailings, i.e., being stabilized as a pillared layered solid.
Tailings flocculation Date Recue/Date Received 2022-02-28

[077] Flocculation of the tailings is used herein to facilitate formation of the pillars between clay platelets by bringing the clay platelets closer together into aggregates, and to further facilitate dewatering of the treated tailings upon deposition.

[078] It was noted that flocculation of the fine tailings into clay aggregates can produce flocculated tailings having a highly negative zeta potential and a good stability. Such negative zeta potential can encourage intercalation of the pillaring moieties (Al, Fe, and/or Si) of the pillaring agent when added to the flocculated fine tailings.

[079] For example, the pillaring agent can be added to flocculated fine tailings having a zeta potential of at least ¨40 mV, -50 mV, or - 60 mV.

[080] The techniques can thus include in-line addition of a flocculation agent to the fine tailings to form aggregates of clay platelets that are pillarable into pillared layered solids.
The flocculation agent can be a non-ionic polymer or an anionic polymer, for example.

[081] Addition of the flocculation agent can be performed before, after or simultaneously with the addition of the pillaring agent. The sequence of the addition can be selected in accordance with various factors, such as the nature of the flocculation agent for encouraging seeding and growth of the pillars between the clay platelets upon adding the pillaring agent. Depending on properties of the tailings, the flocculation agent and the pillaring agent along with operating variables of the process, the order of the pillaring and flocculation steps can be selected for a given implementation.

[082] The pillaring agent can be added at a pillaring concentration being at most 0.06 wt%, at most 0.08 wt%, at most 0.1 wt%, at most 0.3 wt%, at most 0.5 wt%, at most 0.7 wt%, at most 0.9 wt%, at most 1.1 wt%, at most 1.3 wt%, at most 1.5 wt%, at most 1.7 wt%, at most 1.9 wt%, or at most 2 wt% of the total solids content in the fine tailings, for example. The pillaring concentration can also have a lower bound of, for example, 0.05 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.25 wt% or 1.5 wt%.

[083] In some implementations, the pillaring agent can be added subsequently to the flocculation agent (e.g., anionic polymer), and thus added to flocculated tailings. Figures 3 and 4 provide two example process implementations including in-line addition of an anionic polymer as the flocculation agent, prior to the in-line addition of a pillaring agent (Si-based in Figure 3 and Al/Fe-based in Figure 4). The anionic polymer can be an anionic polyacrylamide When using an anionic polymer as the flocculation agent to form clay aggregates, a highly negative zeta potential is generated around the clay aggregates.

Date Recue/Date Received 2022-02-28

[084] Referring to Figure 3, the pillaring agent can include an exogenous source of silicon that can participate in the formation of thermally stable heterostructures between clay platelets. For example, the pillaring agent can be an activated pozzolan.
In another example, the pillaring agent can be hydraulic cement. In another example, the pillaring agent can be activated fumed silica or activated silica fume.

[085] Referring to Figure 4, the pillaring agent can include a source aluminum or ferric ions that can participate in the formation of thermally stable heterostructures between clay platelets. For example, the pillaring agent can be an acid coagulant. The pillaring agent is added in an amount avoiding precipitation of the pillaring ions away from the clay platelets, and facilitating diffusion of the pillaring ions to intra-aggregate pore water and basal surfaces of the clay platelets.

[086] In other implementations, the pillaring agent can be added to the fine tailings prior to or with the flocculation agent. Figures 5 and 6 provide two example process implementations including in-line addition of a non-ionic polymer as the flocculation agent, while adding the pillaring agent (e.g., siloxane units of the flocculant in Figure 5) or after the in-line addition of the pillaring agent (e.g., acid coagulant in Figure 6). The non-ionic polymer can be a polyethylene oxide polymer, or a non-ionic polyacrylamide.

[087] It should be noted that simultaneous addition of the pillaring agent and the flocculation agent can include the addition of a flocculation agent having a pillaring effect.
In other words, the flocculation agent and the pillaring agent would be one and the same compound with both flocculation and pillaring functionalities. Optionally, the flocculation agent can include a pillaring moiety. For example, the flocculation agent can be a non-ionic polymer including Si-containing moieties that can participate in the formation of thermally stable heterostructures between clay platelets. Referring to Figure 5, the flocculation agent having a pillaring effect can be a polyethylene oxide copolymer including siloxane units. Advantageously, non-ionic polymers can bind to the basal surface of the clay platelets (rather than edges for anionic polymers) which brings the siloxane units to the adequate locations of the clay platelets for the desired pillaring.

[088] Referring to Figure 6, the pillaring agent can be an acid coagulant that includes aluminum cations, ferric cations or a combination thereof, and that is added prior to the non-ionic polymer that can be a polyethylene oxide polymer. The acid coagulant can be aluminum sulfate, ferric sulfate, or a mixture thereof, for example. When using a non-ionic polymer as the flocculation agent to form clay aggregates, the pH can be lowered by Date Recue/Date Received 2022-02-28 adding an acid coagulant as the pillaring agent before the flocculation agent, thereby encouraging the pillaring ions to remain in solution and to diffuse into pore water between clay platelets for promoting heterostructure bridges that grow into oxy-hydroxide pillars over time. Optionally, the non-ionic polymer can include silicon moieties that can further serve as pillaring moieties, in addition to diffused Al and/or Fe moieties, to participate in the pillaring reactions (not illustrated), such that the process includes an initial pillaring step using a pillaring agent followed by a second pillaring step using pillaring moieties that are part of the flocculation agent.

[089] The residence time for the pillaring ions to diffuse to the basal surfaces of the clay platelets can be in the order of seconds. To minimize formation of secondary products from the pillaring ions that would not thus be involved in pillaring, a turbulent micro mixing regime can be sustained to facilitate pillaring, and the process and equipment can be designed accordingly.

[090] The process includes adjusting a pH of the fine tailings to a solubilizing pH, with the solubilizing pH being selected to ensure solubilization of the pillaring ions and diffusion of the pillaring ions between the basal surfaces of the clay platelets. In accordance with the nature of the pillaring ions, the solubilizing pH can be of at most 5 or at least 9.

[091] In some implementations, the pillaring agent is added to the fine tailings to achieve a solubilizing pH that favours solubilizing and diffusion of the pillaring moieties/ions between clay platelets. For example, depending on the nature of the pillaring moieties, the pillaring agent can be added at a solubilizing pH of at most 3, at most 4, at most 5, at least 9, at least 10, at least 11, at least 12 or least 13. For example, due to the buffering effect of MFTs, the pH generally returns to about 8 after some time.

[092] Optionally, the shearing energy provided to the treated tailings during pipeline transport can be controlled by an energy dissipation rate to tailor the aggregate size required for settlement and consolidation. The shearing energy can be controlled by adjusting the flow rate, pipeline diameter, and the presence or absence of in-line mixing elements, for example.
Immobilization

[093] The in-line treatment of the fine tailings is performed to generate pillared layered solids over time, and the treated tailings are converted into a pillared deposit after deposition and dewatering. The content of pillared layered solids in the pillared deposit Date Recue/Date Received 2022-02-28 can also increase over time via consolidation to form a reclaimable geotechnically and geochemically stable landform. Using techniques disclosed herein, the reclamation timelines to terrestrial or aquatic land use can be measured in decades instead of centuries as has been the case for some conventional tailings treatment solutions.

[094] Fine tailings as discussed herein, such as MFT and especially fine tailings derived from oil sands processing operations, can include CoCs that include organic acids, residual hydrocarbons and regulated dissolved metals. In some implementations of the in-line treatment, the quality of the water released from the treated tailings by dewatering can be enhanced by immobilizing the CoCs within the pillared deposit.
Immobilization of the CoCs can be performed via in-line addition of an immobilization agent into the fine tailings to achieve insolubilization of dissolved or soluble CoCs. The water released from the treated tailings thus has a reduced level of CoCs or is substantially free of CoCs, and the resulting pillared deposit comprises the immobilized CoCs. Immobilization of CoCs in fine tailings is described in further detail in Canadian patent No. 2,958,873 (Omotoso et al.) and can be used in conjunction with techniques described herein.

[095] In some implementations, the pillaring agent can differ from the immobilization agent that is used to immobilize the CoCs. For example, referring to Figures 3 and 5, the pillaring agent can be an external source of silicon (e.g., cement in Figure 3 or polyethylene oxide with siloxane units in Figure 5) and the immobilizing agent can be an acid coagulant including aluminum cations, ferric cations or a combination thereof, that is added subsequently to the pillaring agent.

[096] In some implementations, the pillaring agent can have an immobilizing effect and acts as an immobilization agent. The pillaring agent can indeed release at least one of a trivalent cation or a tetravalent cation that can participate in the formation of the thermally stable heterostructures between the clay platelets, and/or in the immobilization of CoCs.
The pillaring trivalent and tetravalent cations that are exemplified herein, i.e., Al3+, Fe3+, and Si4+, can concurrently immobilize CoCs from the pore water between the clay platelets.

[097] Referring to Figure 4, the pillaring agent having the immobilizing effect can thus be an acid coagulant including aluminum cations, ferric cations or a combination thereof. The acid coagulant can be added after the flocculation agent (e.g., anionic polymer) in an amount tailored to reduce or avoid precipitation of aluminum or ferric moieties, to facilitate diffusion of the Al3+ or Fe3+ ions into the pore water between clay platelets, and to co-Date Recue/Date Received 2022-02-28 currently immobilize CoCs from the pore water. Referring to Figure 6, the same agent can be added before and after the flocculation agent so as to be used as a pillaring agent and as an immobilization agent, respectively. More particularly, an acid coagulant including aluminum cations, ferric cations or a combination thereof can be added before and after the non-ionic polyethylene oxide.

[098] It should be noted that the concentration of the acid coagulant can be controlled and tailored for use as the immobilization agent or as the pillaring agent.
More particularly, the concentration of the acid coagulant that is used for immobilization of the CoCs (e.g., when added after the flocculation agent/pillaring agent) can be lower in comparison to an implementation where the acid coagulant is used as a pillaring agent (e.g., before a non-ionic polymer flocculant or after an anionic polymer flocculant). For example, the immobilizing concentration of the acid coagulant that is used as an immobilization agent can be at most 5 meq/L, at most 10 meq/L, at most 15 meq/L, or at most 20 meq/L of the pore water and can be adjusted according to the extent of contaminant immobilization desired, e.g., to a concentration between 1 and 15 meq/L, between 2 and 12 meq/L, or between 5 and 10 meq/L. The pillaring concentration of the acid coagulant that is used as a pillaring agent can be above 20, 25, 30, 35, 40, 45, 50, 55, 60, 65 or 70 meq/L of the pore water, thereby facilitating Al3+ or Fe3+ migration within the pore water between clay particles. Optionally, the concentration of the acid coagulant serving as both pillaring and immobilizing agent can be between 20 and 40 meq/L of the pore water.
Example process implementations

[099] Referring to the process implementation illustrated in Figure 3, the in-line treatment of the fine tailings, such as MFT, can include in-line addition of an anionic polymer as the flocculation agent, an external source of silicon as the pillaring agent, and an acid coagulant as the immobilization agent to produce treated tailings. The treated tailings are transported by pipeline to a deposition site. The MFTs initially have a pH of 8.0 and the anionic polymer, e.g., anionic polyacrylamide, is added to flocculate the clay platelets into aggregates and bring the clay platelets closer together. The anionic polymer does not have an impact on the pore water pH, but the anionic polymer creates a highly negative zeta potential around the clay aggregates. The anionic polymer addition is followed by the addition of an external source of silicon to the flocculated tailings. The dissolved silicon ions, Si4+, which are the primary pillaring ions are added at a concentration of at most 2 wt% of the solids in the MFTs. In this implementation, dissolved Si4+ ions can be added Date Recue/Date Received 2022-02-28 either through ordinary Portland cement, activated pozzolan, activated fumed silica or activated silica fume. Upon addition of the pillaring agent, the pH of the MFTs increases to 11, which ensures that Si4+ ions remain in solution during pipeline transport for diffusion into the intra-aggregate pore space and specifically diffuse to the basal surfaces of the clay platelets. Because the high pH of about 11 mobilizes organic acids in the bitumen from the MFTs, the toxicity of the water that is releasable from the treated tailings increases as CoCs would remain in solution. The CoCs are thus immobilized by further adding an acid coagulant just before deposition (and after Si4+ has diffused into the pore space of the clay aggregates) to reduce the pH to below 9 and improve the water quality.
Optionally, the amount of acid coagulant that is added as immobilization agent can be at most 20 meq/L of the pore water and can depend on the level of contaminant immobilization that is desired. In the implementation schematized in Figure 3, the aluminum or ferric cations (Al or Fe) of the acid coagulant do not participate in the pillar formation because at pH > 5, they rapidly form hydroxide precipitates. It should further be noted that, if added at high concentrations (typically above 1, 1.5, or 2 wt%), and over time in the deposit, the pillaring agent (ordinary Portland cement, activated pozzolan, activated silica fume, or fumed silica) can react with water to form calcium alumina-or-silicate hydrate network in the pore space to further strengthen the mineral matrix.
While this strengthening mechanism is not the primary focus of the present techniques, the strength gain through cement reactions can further accelerate the consolidation of the treated tailings once deposited.

[100] Referring to the process implementation illustrated in Figure 4, the in-line treatment can include the addition of an anionic polymer as the flocculation agent and an acid coagulant as the pillaring agent to the MFTs during pipeline transport.
Anionic polyacrylamide can be used as the flocculation agent to aggregate the clay platelets. The addition of the anionic polymer does not have an impact on the pH of the MFTs, but creates a highly negative zeta potential around the clay aggregates. This potential favours the diffusion of the pillaring cations provided by the subsequent addition of the acid coagulant comprising at least one of aluminum ions and ferric ions. The pillaring ions intercalate between the clay platelets to serve as seeds for forming heterostructures (pillars). The acid coagulant can co-currently immobilize the CoCs that have solubilized in the pore water between aggregates due to the pH lowering. Over time and before deposition, the pH can increase back to about 8 due to the buffering capacity of MFTs.

Date Recue/Date Received 2022-02-28

[101] Referring to the process implementation illustrated in Figure 5, the in-line treatment of the MFTs includes addition of a polyethylene oxide copolymer including siloxane units as the flocculation agent having a pillaring effect, and of the acid coagulant as the immobilization agent during pipeline transport. The polyethylene oxide copolymer is a non-ionic polymer that flocculates the clay platelets into clay aggregates by bonding to the basal surfaces of the clay platelets. The pillaring ions are provided simultaneously as the siloxane units are part of the flocculation agent. Using a Si-containing non-ionic polymer can result in a faster Si4+ pillaring action, because the polymer locates the siloxane units to the basal clay surface. The acid coagulant is then added in-line to the flocculated tailings to immobilize CoCs that are in solution in the water. Due to the lowering of the pH to below 4, the aluminum and/or ferric cations released by the acid coagulant can co-currently serve as pillaring ions by diffusion to the intra-aggregate pore water between clay platelets.
Although not illustrated, the acid coagulant can be added before the non-ionic polymer such that the aluminum and/or ferric ions would become the primary source of pillaring ions, and the siloxane units of the non-ionic polymer would become a secondary source of pillaring ions.

[102] Referring to the process implementation illustrated in Figure 6, the in-line treatment of the fine tailings, such as MFTs, can include successive in-line addition of the pillaring agent, the flocculation agent and the immobilization agent. An acid coagulant is first added inline to the MTFs during pipeline transport to provide aluminum and/or ferric pillaring ions.
The presence of the acid coagulant lowers the pH immediately after addition from about 8 to below about 4. This lower pH is suitable for the Al3+ and/or Fe3+ ions to diffuse to the pore space between clay platelets. The Al3+ and/or Fe3+ are added to provide a pillaring effect, and their concentration is of at most 30 meq/L, and optionally of at most 40 meq/L
of the pore water, to ensure that sufficient Al3+ and/or Fe3+ migrate to the pore space between clay platelets prior to precipitating as hydroxides as the pH buffers up during transport of the treated tailings. The non-ionic polyethylene oxide is then added as the flocculation agent to flocculate and aggregate the clay platelets. The non-ionic PEO can serve two purposes which are to (i) promote rapid dewatering of the treated tailings once deposited and (ii) promote pillaring by adsorbing on the basal surfaces (or siloxane surface) of clay platelets, such that a near parallel configuration of the clay platelets can favour the growth of heterostructure bridges as oxy-hydroxide pillars over time. Although not illustrated in Figure 6, the non-ionic polymer can include silicon in a backbone thereof, and the silicon can participate in the pillaring reactions as a secondary pillaring ion.

Date Recue/Date Received 2022-02-28

[103] When using an anionic polymer, the anionic polymer rather adsorbs on the edges of the clay platelets and may thus not be as effective as a non-ionic polymer to seed the pillars between clay platelets. The nature of the flocculation agent is thus a key parameter impacting the order of the addition sequence of the pillaring agent to favour seeding of the pillars by intercalation of pillaring ions between clay platelets.

[104] The treatment can be an in-line treatment, including the in-line addition of at least one of the agents. Regarding in-line addition, the agents can be added into a flow of the fine tailings via a pipe T-junction, a pipe Y-junction, an in-line static mixer, a co-annular injection device, or various other addition apparatuses. It could also be possible in some implementations to add the agents using a tank mixer that includes a dynamic mixing element, such as an impeller. While in-line addition of the pillaring, flocculation and immobilization agents is described herein and illustrated in the figures, it is also noted that one or more of the agents can be added to the fine tailings in other ways. For example, the pillaring agent could be added in a batch addition and mixing stage, in a vessel or other containment structure, and the resulting tailings material could then be pipelined for in-line addition of the flocculation agent followed by in-line transport to the deposition site.
For example, batch addition can involve the use of a dynamic mixer or a continuous stirred-tank reactor (CSR).
Consolidation and reclamation

[105] The present techniques can further include deposition of the treated tailings at a dedicated deposition area to allow water to separate from the treated tailings, and to produce a pillared deposit including pillared layered solids. The pillared deposit is further allowed to stand within the dedicated deposition area for consolidation into a consolidated deposit over time by further pillaring and optionally by other consolidation mechanisms (e.g., via placing a sand or coke surcharge on top). Once sufficiently consolidated, the consolidated deposit can be reclaimed as at least part of a landform that can sustain terrestrial or aquatic activities. The landform should be understood as a man-made geostructure within a landscape. For example, the landform can be a sub-aerial beach-like structure formed from one or more layers of deposited material or a lakebed below a water cap forming an in-pit lake structure.

[106] The consolidated deposit can be characterized as including at least 50 wt%, 60 wt%, 70 wt%, 80 wt%, or 90 wt% of the pillarable clay initially present in the fine tailings being pillared, for example.
Date Recue/Date Received 2022-02-28

[107] Deposition can include discharging the treated tailings within the dedicated deposition area over a period of time. The discharging can be performed in a manner to avoid over-shearing the treated tailings, and thus to maintain the clay platelets within flocculated aggregates. One way of managing this is to discharge the treated tailings close onto a slope and/or relatively close to the contact point of the deposition area, and to use an outlet that is sized sufficiently large to avoid notable acceleration or spraying of the discharged material. The discharging can be performed continuously over a deposition period at a given rise rate (e.g about 20 meters per year) until a certain height of the deposited material is reached. Discharge could also be a seasonal operation with material placed until a final elevation is reached.

[108] It should be noted that the treated tailings can be discharged in various ways, in accordance with the structure and properties of the chosen dedicated deposition area, as well as the long term reclamation strategy for the tailings. The dedicated deposition area can be below or above grade, and the consolidated deposit results in a landform (above original ground and optionally below a water cap) that can be geotechnically and geochemically stable.

[109] For example, the dedicated deposition area can be a subaerial pit, with the water being released from the pillared deposit and coming to the surface, while the solids settle to the bottom and further consolidate. The pillared deposit provides for a lower solids-rich stratum including pillared layered solids below an upper water cap. The lower solids-rich stratum can further dewater with consolidation by pillaring as a significant dewatering mechanism. The lower solids-rich stratum becomes consolidated into a consolidated deposit that can be reclaimed as a lakebed or lake floor, for example. This structure can be referred to as a permanent aquatic storage structure (PASS) where a water cap is maintained above a consolidated lower stratum including the pillared layered solids.

[110] In another example, deposition can be performed according to thin lift deposition wherein the treated tailings are deposited as "lifts" or layers which are stacked on top of each other on a sloped area to form the pillared deposit, which is allowed to drain in accordance with an initial water release. The released water flows away from the pillared deposit mainly by drainage, and the pillared deposit is allowed to stand and further dewater by evaporation and other mechanisms. Once deposition is ceased, the pillared deposit is further allowed to stand as a beach-like structure to form additional pillars between clay platelets and consolidate the pillared deposit including the pillared layered Date Recue/Date Received 2022-02-28 solids into the consolidated deposit. Dewatering of the pillared deposit can further happen by consolidation (including the further pillaring), freeze-thaw, evaporation, and/or permeation mechanisms.

[111] The pillared deposit should thus be understood herein as being formed by deposition of the treated tailings and as resulting from an initial water release of the deposited treated tailings. The treated tailings can already include some pillared layered solids, and additional pillars can form over time to densify the pillared layered solids that are already present and generate newly formed pillared layered solids. The pillared deposit resulting from the initial dewatering of the treated tailings includes the formed pillared layered solids, and the level of pillaring of the pillared deposit varies and can increase over time after deposition. When referring to the pillared deposit, one can thus understand that, upon dewatering, the tailings are partially pillared and the pillaring is further encouraged and develops after deposition for consolidation. The consolidated deposit can be reclaimed as a landform including the pillared layered solids, being for example a lower solid-enriched stratum below a water cap or a solid-enriched deposit above ground.

[112] Stability of the consolidated deposit can be achieved when the tailings are sufficiently dewatered and consolidated, thereby forming a geotechnically and geochemically stable landform. Geochemical stability can refer to the chemistry of the mineral and pore water released from the consolidated deposit meeting specifications allowing a specific land use. Geotechnical stability can refer to the strength and the density of the consolidated deposit being sufficient for use as a structural fill without requiring additional containment. For example, geotechnical stability of the consolidated deposit can be considered to be achieved when the consolidated deposit has a shear strength greater than 15, 20, 25, 30 or 35 kPa and/or when the consolidated deposit has a solids content of at least 50, 55, 60 or 65 wt%. The required stability can vary depending on the planned end use of the consolidated deposit as a landform, that can be a sediment/floor of a lake or wetland, or a dryland, for example.

[113] Stability of the consolidated deposit can be achieved faster according to techniques described herein than according to various conventional dewatering and consolidation methods. The pillaring can thus aid in the acceleration of tailings reclamation.

Date Recue/Date Received 2022-02-28

[114] Figure 7 provides a comparison of the time after which stability of the consolidated deposit can be achieved following the end of the deposition of treated tailings produced according to five treatment options. A reference case illustrating behavior fluid fine tailings (FFT) is provided, in addition to coagulated and flocculated fluid fine tailings (c/f FFT) and consolidated tailings (CT 3:1) which are produced according to conventional techniques known in the art. Figure 7 further provides the behavior of flocculated, coagulated and pillared fluid fine tailings (f/c and pillared FFT) produced in accordance with the techniques described herein with the pillaring ions being Si4+ that were provided with a polyethylene oxide polymer (PEO) or with activated pozzolan. Figure 7 shows that the time in which sufficient consolidation of the consolidated deposit can be achieved for use as a stable landform in accordance with the present treatment techniques is sooner (within decades) than for conventional treatment solutions (close to 100 years or several centuries). For example, the consolidation period can be at most 50 years when stability is reached for a post-deposition pillared deposit of initially 75-meter high, based on an MFT
volume before dewatering.

[115] One can see that the consolidation rate is generally faster in the implementation where activated pozzolan is added than in the implementation where siloxane units are added, such that stability of the consolidated deposit is achieved sooner than in other studied cases. This could be explained by the fact that pozzolanic reactions can further form hydrates that also strengthen the landform.

[116] A more rapid dewatering and consolidation can be explained at least in part by the conversion of the clay platelets aggregates into pillared layered solids. The porosity of the pillared layered solids confers a permeability and a hydraulic conductivity that improve the initial water release upon deposition of the treated tailings, and thus contributes to the acceleration the overall dewatering of the treated tailings. For example, the pillared deposit can be characterized as having a post-deposition hydraulic conductivity greater than 10-9 m/s. In addition, the multiplication of the pillars and the lower compressibility of the resulting pillared layered solids confer a strength and a density that improve a consolidation rate of the treated tailings.

[117] The process steps including treatment, deposition, dewatering and consolidation, with a pillaring feature, can be used to convert fine tailings into a stable reclaimed landform.

Date Recue/Date Received 2022-02-28

[118] Reclamation can be understood herein as resulting from the physical reconstruction of soils and terrain on a disturbed site to achieve a land use capability that can be equivalent as to what existed before disturbance.

[119] In the context of planned terrestrial reclamation, the process can include deposition of the treated tailings in a dedicated deposition area below or above grade, with the released water being directed away from the treated tailings as the material dewaters and further dries. The water can be recovered and reused in the mining and extraction operation, either directly or after pre-treatments; the water can be reused in the context of in situ recovery operations after pre-treatment; or the water can be treated and reintroduced into the environment. The dewatered treated tailings form the pillared deposit including the pillared layered solids and the immobilized CoCs. The pillared deposit further consolidates over time to form the consolidated deposit that can be reclaimed as a geotechnically and geochemically stable landform after a shortened consolidation period.
Terrestrial reclamation can comprise reclaiming the consolidated deposit as a landform including a dryland or other solid ground.

[120] Optionally, other post-deposition strengthening activities can be performed to further consolidate the deposit and achieve stability of the landform sooner for reclamation. For example, the consolidated deposit can be capped with a layer of sand or coke, or another material, to form a top cap. The top cap can have a thickness between 2 m and 5 m, for example. The top cap can provide weight that enhances consolidation and/or enable water absorption into the top cap from the consolidated deposit.
Another optional post-deposition strengthening activity can include draining a top layer of the consolidated deposit, including using wick drains to further dewater the top layer.

[121] In the context of planned aquatic reclamation, the process can include deposition of the treated tailings in a dedicated deposition area below grade, for example in a containment structure such as a mine pit, with at least some of the released water being maintained above the dewatered treated tailings, thus forming a water cap at the end of deposition. The dewatered treated tailings form the pillared deposit which remains below the water cap and includes pillared layered solids and immobilized CoCs. Over time, the lower pillared deposit can further consolidate which can include further pillaring, thereby forming a consolidated deposit being a lower solids-rich stratum below the water cap.
Once sufficiently consolidated, the consolidated deposit can be reclaimed as a landform being, for example, a sediment layer of a lake or a wetland. With the CoCs being Date Recue/Date Received 2022-02-28 immobilized within the lower stable landform, the quality of the water is such that aquatic recreational activities can be performed on site, and/or that aquatic life can be sustained.
Optionally, fresh water can be added to the water cap to maintain a level and a quality of the water cap.

[122] In some implementations, the aquatic reclamation is such that a lake is formed where the floor of the lake includes the solids-rich stratum and water is allowed to flow into and out of the lake such that the lower solids-rich stratum remains water capped. For example, the water cap can be further connected to a surrounding watershed, to establish a fresh water flow through the connected watershed.
Date Recue/Date Received 2022-02-28

Claims

1. A process for treating fine tailings containing clay platelets, the process comprisi ng:
treating the fine tailings to produce treated tailings comprising pillared layered solids, the treatment comprising:
adding a pillaring agent comprising trivalent cations and/or tetravalent cations that intercalate between basal surfaces of the clay platelets to form a thermally stable interlayer of pillars, thereby converting at least a portion of the clay platelets into pillared layered solids; and depositing the treated tailings within a dedicated deposition area to produce a consolidated deposit by:
separating water from the treated tailings to form a pillared deposit comprising the pillared layered solids; and consolidating the pillared deposit over time to form the consolidated deposit, the consolidation comprising forming additional thermally stable interlayers of pillars that grow from the trivalent cations and/or tetravalent cations intercalated between the basal surfaces of the clay platelets.

2. The process of claim 1, wherein the treating of the fine tailings comprises adjusting a pH of the fine tailings to a solubilizing pH encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets.

3. The process of claim 2, wherein the solubilizing pH is at most 5 or at least 9 in accordance with a nature of the trivalent cations and/or tetravalent cations.

4. The process of any one of claims 1 to 3, wherein the treating of the fine tailings comprises adjusting a zeta potential of the fine tailings to encourage diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets.

5. The process of claim 4, wherein the zeta potential is adjusted to at least ¨ 40 mV, -50 mv, or -60 mV.

6. The process of any one of claims 1 to 5, wherein the treating of the fine tailings comprises adjusting a concentration of the pillaring agent to a pillaring Date Recue/Date Received 2023-05-11 concentration being at most 0.06 wt%, at most 0.08 wt%, at most 0.1 wt%, at most 0.3 wt%, at most 0.5 wt%, at most 0.7 wt%, at most 0.9 wt%, at most 1.1 wt%, at most 1.3 wt%, at most 1.5 wt%, at most 1.7 wt%, at most 1.9 wt%, or at most 2 lid% of the total solids content in the fine tailings.

7. The process of any one of claims 1 to 6, wherein the pillaring agent comprises an exogenous source of silicon.

8. The process of any one of claims 1 to 7, wherein the pillaring agent is hydraulic cement, activated pozzolan, activated silica fume, activated fumed silica, or a combination thereof.

9. The process of claim 7 or 8, wherein the pillaring agent is added at a pH
of at least 9, at least 10, at least 11, at least 12 or at least 13 in the treated tailings.

10. The process of any one of claims 1 to 6, wherein the pillaring agent is an acid coagulant comprising at least one of an aluminum cation and a ferric cation.

11. The process of claim 10, wherein the pillaring agent comprises aluminum sulfate, ferric sulfate or a combination thereof.

12. The process of claim 10 or 11, wherein the pillaring agent is added at a pH of at most 3, at most 4, or at most 5.

13. The process of any one of claims 1 to 12, wherein the treatment further comprises flocculating the fine tailings by adding a flocculation agent to form flocculated tail ings.

14. The process of claim 13, wherein the pillaring agent is added after the flocculation agent into the flocculated tailings.

15. The process of claim 14, wherein the flocculation agent is an anionic water-soluble polymer.

16. The process of claim 15, wherein the anionic water-soluble polymer is a polyacrylamide.

17. The process of claim 14, wherein the flocculation agent is a non-ionic polymer.

18. The process of claim 13, wherein the pillaring agent is added before the flocculation agent to the fine tailings.

19. The process of claim 18, wherein the flocculation agent is a non-ionic polymer.

Date Recue/Date Received 2023-05-11

20. The process of claim 19, wherein the non-ionic polymer is a polyethylene oxide polymer.

21. The process of any one of claims 1 to 6, wherein the pillaring agent is a flocculant comprising pillaring moieties releasing the trivalent cations and/or tetravalent cations for intercalation between the clay platelets, and the treatment of the fine tailings thereby comprises the addition of the pillaring agent to flocculate the fine tailings into flocculated fine tailings and pillar the flocculated fine tailings for forming the treated tailings.

22. The process of claim 21, wherein the flocculant is a polyethylene oxide copolymer comprising siloxane units.

23. The process of any one of claims 1 to 22, wherein the fine tailings comprise contaminants of concern (CoCs) and the treatment further comprises immobilizing the CoCs to produce the consolidated deposit comprising the pillared layered solids and immobilized CoCs.

24. The process of claim 23, wherein the immobilizing is performed by addition of an immobilization agent that is added after the pillaring agent.

25. The process of claim 24, wherein the immobilization agent is an acid coagulant comprising at least one of aluminum cations and ferric cations.

26. The process of claim 25, wherein the acid coagulant comprises aluminum sulfate, ferric sulfate or a combination thereof.

27. The process of claim 25 or 26, wherein the acid coagulant is added at an immobilizing concentration that is at most 5 meq/L, at most 10 meq/L, at most meq/L, or at most 20 meq/L of a pore water in the fine tailings.

28. The process of any one of claims 1 to 6, wherein the fine tailings comprise contaminants of concern (CoCs) and the pillaring agent is an acid coagulant releasing aluminum and/or ferric cations performing both the pillaring of the clay platelets and immobilizing of the CoCs to produce the consolidated deposit comprising the pillared layered solids and immobilized CoCs.

29. The process of claim 28, wherein the acid coagulant is added at a concentration between 20 and 40 meq/L of a pore water in the fine tailings.

Date Recue/Date Received 2023-05-11

30. The process of any one of claims Ito 29, wherein the addition of the pillaring agent is performed under a turbulent micro-mixing regime to minimize formation of secondary products from the trivalent cations and/or tetravalent cations.

31. The process of any one of claims 1 to 30, wherein the treated tailings comprise at least 10, 20, 30, 40, 50, 60, 70 or 80 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

32. The process of any one of claims 1 to 30, wherein the consolidated deposit comprises at least 50, 60, 70, 80 or 90 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

33. The process of any one of claims 1 to 32, wherein the deposition of the treated tailings is performed until the pillared deposit reaches a target height.

34. The process of claim 33, wherein the deposition of the treated tailings is performed at a deposition rate of at most 20 meters per year.

35. The process of claim 33 or 34, wherein the target height is between 20 m and 75 m.

36. The process of any one of claims 1 to 35, comprising reclamation of the consolidated deposit once the consolidated deposit is geotechnically stable after a consolidation period for a given end use.

37. The process of claim 36, wherein geotechnical stability of the consolidated deposit is achieved by consolidation when the consolidated deposit has a shear strength greater than 15, 20, 25, 30 or 35 kPa.

38. The process of claim 36, wherein geotechnical stability of the consolidated deposit is achieved by consolidation when the consolidated deposit has a solids content of at least 50, 55, 60 or 65 wt%.

39. The process of any one of claims 36 to 38, wherein the consolidation period is at most 50 years when the pillared deposit is initially at most 75-meter high.

40. The process of any one of claims 1 to 39, wherein the pillared deposit has a post-deposition hydraulic conductivity greater than 10-9 m/s.

41. The process of any one of claims 1 to 40, wherein the dedicated deposition area is below or above grade.

Date Recue/Date Received 2023-05-11

42. The process of claim 40, further comprising capping the consolidated deposit with a layer of sand or coke to form a solid top cap.

43. The process of claim 42, wherein the solid top cap has a thickness between 2 m and 5 m.

44. The process of any one of claims 41 to 43, further comprising draining a top layer of the consolidated deposit for further dewatering of the top layer.

45. The process of any one of claims 41 to 44, comprising reclaiming the consolidated deposit as a landform that comprises a dry land or solid ground.

46. The process of any one of claims 1 to 40, wherein the dedicated deposition area is below grade.

47. The process of claim 46, wherein the dedicated deposition area comprises a containment structure.

48. The process of claim 47, wherein the dedicated deposition area is a mine pit.

49. The process of any one of claims 45 to 48, comprising capping the consolidated deposit with a layer of water to form a top water cap.

50. The process of claim 49, wherein the top water cap comprises at least a portion of the water released from the treated tailings during the separating.

51. The process of any one of claims 46 to 50, comprising reclaiming the consolidated deposit as a landform that comprises a floor or sediment of a lake or a wetland.

52. The process of any one of claims 1 to 51, wherein the fine tailings have a clay content being at least 50, 60, 70, 80 or 90 wt% of a total solids content of the fine tail ings.

53. The process of any one of claims 1 to 52, wherein the fine tailings are oil sands fine tailings.

54. The process of any one of claims 1 to 53, wherein the fine tailings are mature fine tail ings.

55. The process of any one of claims 1 to 53, wherein the fine tailings are thin fine tail ings.

56. The process of any one of claims 1 to 53, wherein the fine tailings are thick fine tail ings.
Date Recue/Date Received 2023-05-11

57. A method for converting fine tailings containing clay platelets and contaminants of concern (CoCs) into a consolidated deposit, the method comprising:
forming treated tailings by:
flocculating the fine tailings to form aggregates of the clay platelets;
pillaring the clay platelets by intercalating trivalent cations and/or tetravalent cations between basal surfaces of the clay platelets to grow pillared layered solids comprising thermally stable interlayers of pillars between the clay platelets; and immobilizing the CoCs; and depositing the treated tailings within a dedicated deposition area to convert the treated tailings into the consolidated deposit by:
releasing water from the treated tailings pores to produce a pillared deposit comprising the pillared layered solids and immobilized CoCs; and consolidating the pillared deposit over a consolidation period to produce the consolidated deposit, the consolidating comprising forming additional pillared layered solids from the aggregates of the clay platelets.

58. The method of claim 57, wherein the pillaring of the clay platelets is performed at a solubilizing pH encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets.

59. The method of claim 58, wherein the solubilizing pH is at most 5 or at least 9 in accordance with a nature of the trivalent cations and/or tetravalent cations.

60. The method of any one of claims 57 to 59, wherein the flocculating is performed to achieve a zeta potential of the aggregates encouraging diffusion of the trivalent cations and/or tetravalent cations between the basal surfaces of the clay platelets.

61. The method of claim 60, wherein the zeta potential is at least ¨ 40 mV, -50 mv or -60 mV.

62. The method of any one of claims 57 to 62, wherein the trivalent cations are at least one of aluminum cations and ferric cations, and the tetravalent cations are silicon cations.

Date Recue/Date Received 2023-05-11

63. The method of any one of claims 57 to 63, wherein the flocculating is performed before or after the pillaring via separate addition of a flocculation agent and a pillaring agent to the fine tailings.

64. The method of claim 63, wherein the addition of the pillaring agent is performed under a turbulent micro-mixing regime to minimize formation of secondary products from the trivalent cations and/or tetravalent cations.

65. The method of claim 63 or 64, wherein the pillaring agent is added at a pillaring concentration being at most 0.06 wt%, at most 0.08 wt%, at most 0.1 wt%, at most 0.3 wt%, at most 0.5 wt%, at most 0.7 wt%, at most 0.9 wt%, at most 1.1 wt%, at most 1.3 wt%, at most 1.5 wt%, at most 1.7 wt%, at most 1.9 wt%, or at most 2 wt% of the total solids content in the fine tailings.

66. The method of any one of claims 63 to 65, wherein flocculation agent is an anionic polymer.

67. The method of claim 66, wherein the anionic polymer is polyacrylamide (PAM).

68. The method of any one of claims 63 to 65, wherein flocculation agent is a non-ionic polymer.

69. The method of claim 68, wherein the non-ionic polymer is a polyethylene oxide polymer.

70. The method of any one of claims 63 to 69, wherein the pillaring agent is an acid coagulant releasing aluminum cations and/or ferric cations.

71. The method of claim 70, wherein the acid coagulant comprises aluminum sulfate, ferric sulfate or a combination thereof.

72. The method of claim 70 or 71, wherein the pillaring agent is added at a pH
of at most 3, at most 4, at most 5, or at most 6.

73. The method of any one of claims 63 to 69, wherein the pillaring agent is hydraulic cement, activated pozzolan, activated fumed silica, activated silica fume, or any combinations thereof.

74. The method of any one of claims 57 to 62, wherein the flocculating and pillaring are co-currently performed via addition of a flocculant to the fine tailings, with the flocculant comprising pillaring moieties releasing the trivalent and/or tetravalent cations.

Date Recue/Date Received 2023-05-11

75. The method of claim 74, wherein the flocculant is a non-ionic polymer comprising pillaring moieties releasing silicon cations.

76. The method of claim 75, wherein the flocculant is a polyethylene oxide copolymer comprising siloxane units.

77. The method of claim 75 or 76, wherein the flocculant is added at a pH of at least 9, at least 10, at least 11, at least 12 or at least 13 in the treated tailings.

78. The method of any one of claims 57 to 77, wherein immobilizing the CoCs is performed via addition of an immobilization agent, wherein the immobilization agent is added after the pillaring agent.

79. The method of claim 78, wherein the immobilization agent is an acid coagulant releasing aluminum and/or ferric cations.

80. The method of claim 79, wherein the immobilization agent is aluminum sulfate, ferric sulfate or a combination thereof.

81. The method of claim 80 or 81, wherein the acid coagulant is added at an immobilizing concentration that is at most 5 meq/L, at most 10 meq/L, at most meq/L, or at most 20 meq/L of a pore water in the fine tailings.

82. The method of any one of claims 57 to 77, wherein immobilizing the CoCs is performed via addition of the pillaring agent, wherein the trivalent and/or tetravalent cations released by the pillaring agent participate in both the pillaring of the clay platelets and the immobilizing of the CoCs.

83. The method of claim 82, wherein the pillaring agent is added at a concentration between 20 and 40 meq/L of a pore water in the fine tailings.

84. The method of any one of claims 57 to 83, wherein the treated tailings comprise at least 10, 20, 30, 40, 50, 60, 70 or 80 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

85. The method of any one of claims 57 to 83, wherein the consolidated deposit comprises at least 50, 60, 70, 80 or 90 wt% of pillarable clay platelets initially present in the fine tailings being pillared into the pillared layered solids.

86. The method of any one of claims 57 to 85, further comprising capping the consolidated deposit with a layer of sand or coke to form a top cap.

Date Recue/Date Received 2023-05-11

87. The method of claim 86, wherein the top cap has a thickness between 2 m and 5 m.

88. The method of any one of claims 57 to 85, further comprising capping the consolidated deposit with a layer of water to form a top water cap.

89. The method of claim 88, wherein the top water cap comprises at least a portion of the water released from the treated tailings following deposition.

90. The method of any one of claims 57 to 89, wherein the dedicated deposition area is above grade.

91. The method of any one of claims 57 to 89, wherein the dedicated deposition area is below grade.

92. The method of claim 91, wherein the dedicated deposition area comprises a containment structure.

93. The method of claim 92, wherein the dedicated deposition area is a mine pit.

94. The method of any one of claims 57 to 93, comprising reclaiming the consolidated deposit when the consolidated deposit is geotechnically and geochemically stable for a given land use after the consolidation period.

95. The method of claims 94, wherein geotechnical stability of the consolidated deposit is achieved by consolidation when the consolidated deposit has a shear strength greater than 15, 20, 25, 30 or 35 kPa.

96. The method of claims 94, wherein geotechnical stability of the consolidated deposit is achieved by consolidation when the consolidated deposit has a solids content of at least 50, 55, 60 or 65 wt%.

97. The method of any one of claims 94 to 96, wherein the consolidation period is at most 50 years when the pillared deposit is initially at most 75-meter high.

98. The method of any one of claims 94 to 97, wherein the geotechnically and geochemically stable consolidated deposit is reclaimed as a landform that is a floor of a lake, a wetland, or a dryland.

99. The method of any one of claims 57 to 98, wherein the fine tailings have a clay content being at least 50, 60, 70, 80 or 90 wt% of a total solids content of the fine tail ings.

Date Recue/Date Received 2023-05-11

100. The method of any one of claims 57 to 99, wherein the fine tailings are oil sands fine tailings.

101. The method of claim 100, wherein the fine tailings are mature fine tailings.

102. The method of any one of claims 57 to 100, wherein the fine tailings are thin fine tailings.

103. The method of any one of claims 57 to 100, wherein the fine tailings are thick fine tailings.
Date Recue/Date Received 2023-05-11