GB2371296A - Aluminium chloride and zirconium-containing coagulant compositions - Google Patents

Abstract

A composition which comprises an aqueous solution of aluminium chloride and/or basic aluminium chloride, a zirconium-containing compound (from a range of zirconium salts) and optionally a boron-containing compound. The composition can further contain polyacrylamides and/or charge bearing starches. The composition may be used as a coagulant in water treatment, particle retention aids and water drainage aids in paper manufacture and as sludge dewatering aids.

Description

Aluminium Chloride Containing Compositions This invention relates to aluminium chloride and/or basic aluminium chloride containing compositions, a method for their production, and their use in industrial applications.

Coagulants, that is, substances which induce coagulation, are used in precipitating solids or semi-solids from solution. Many industrial processes commonly use coagulants to treat the effluents or process liquids to aid the removal of suspended or colloidal negatively charged particles known as"anionic trash". Examples include the paper manufacturing process; food preparation processes, the effluents of which may be difficult to purify due to the presence of traces of carotene; mining; industrial and power generation; and sewage treatment.

Coagulants characteristically dissociate into strongly charged ions and the charge density of the coagulant is a significant factor in determining the efficiency of coagulation and particle removal; the higher the charge density, the better the coagulation and the more particles that can be removed. It is known from US 4,566, 986, that aqueous polyaluminium chloride solutions are useful agents in water treatment applications.

In the paper manufacturing process, as well as needing coagulants, it is also important to maximise the retention of the filler and pulp fines (micro-and nanoparticles), usually by the addition of a high molecular weight soluble polymer, for example, a derivative of polyacrylamide in a typical amount of from 0. 1 to 0.75 kg per tonne of paper produced. The polyacrylamide used may be cationic or anionic in nature and, in general, it has been found that the higher the molecular weight of the polymer material, the greater the retention. However, there is a compromise; as molecular weight of the polyacrylamide increases, the paper sheet formation and water drainage characteristics deteriorate. Water is removed from the furnish slurry when this is passed from the head box of a paper machine on to the moving wire belt on which paper sheet forms. Initially, water simply drains through the wire belt but as the belt progresses away from the head box, the furnish slurry, from which the paper is forming, is subjected to additional drainage techniques such as vacuum assisted drainage. After this, the paper now has sufficient structural integrity to be removed from the wire belt and passed over heated rollers that lower the moisture content even further to produce the finished product. The more moisture that drains off on the initial section, namely the wire belt, the less is the cost of subsequent drying operations, therefore, it is advantageous to find ways to promote the early removal of water.

It is known that the presence of suitable drainage aids in the furnish slurry can be of assistance and low to intermediate molecular weight cationic polymers such as based on polyacrylamide, polyethyleneimine, polymers produced from dimethylamine and epichlorohydrin and polydiallyldimethyl ammonium chloride are examples of drainage aids currently in use. Alternatively, cationic inorganic polymers such as basic aluminium chloride solutions, otherwise known as polyaluminium chloride, have also been used as very effective drainage aids. In particular, highly basic aluminium chloride compositions are preferred, such as those described in Patent Application GB99296337.8.

U. S. Pat. No. 4,753, 710 teaches a paper manufacturing process in which a high molecular weight cationic polymer is added to a paper furnish followed by high shear and then subsequently adding bentonite to improve retention, drainage, drying and formation. Also, F167736 and W086/05826 discuss the use of cationic polymeric materials with colloidal silica.

Similarly, U. S. Pat. No. 5,071, 512 teaches the addition of hectorite clay and a cationic starch to the furnish to improve the retention of filler material and the quality of the paper. U. S Pat. No. 5,178, 730 describes a process in which a cationic polymer and natural hectorite to the furnish prior to the head box.

All of the prior art micro particle retention aid processes mentioned above rely on an agent based on silica to provide the enhanced process improvement; the present invention uses a different system.

We have discovered new aluminium chloride and/or basic aluminium chloride containing compositions that are not only very useful for coagulation and floc formation in the removal of anionic trash from the process liquids and effluents of industrial processes, but are also extremely effective when used in paper manufacture as micro-and nano-particle retention aids and for enhancing drainage and sheet formation. Moreover, we have found that the compositions of the present invention are also useful to condition waste sludge (industrial or sewage) to reduce costs by improving the dewatering efficiency. In particular, we have discovered that a mixture of basic aluminium chloride and/or aluminium chloride in combination with one or more zirconium-containing compounds, produces a synergistic enhancement of these process steps over the use of basic aluminium chloride and/or aluminium chloride without a zirconium-containing compound.

Accordingly, the present invention provides compositions comprising an aqueous solution of aluminium chloride and/ or basic aluminium chloride, a zirconium-containing compound or compounds and, optionally, a boron compound or compounds.

The aluminium chloride used to make the compositions of the present invention may be derived directly from synthetic raw materials such as, for example from anhydrous aluminium chloride or from a mixture of alumina trihydrate and hydrochloric acid or may be a by-product of another industrial process. The aluminium chloride has a concentration of at least 5%, particularly preferably at least 8% and preferably up to 25% or more, particularly preferably up to 20%, calculated as Aids.

If the concentration of the aluminium chloride solution as supplied is towards the lower end of, or below, the range stated above its aluminium content may be augmented by the addition of further aluminium compounds or aluminium metal together with an addition of HC1 if required to ensure the conversion of the same to the chloride. The pH of the solution of aluminium chloride is preferably from 0.5 to 1.5. It is preferred to add the carbonate compounds and/or other basic compounds to the acidic solution of the aluminium chloride, to maintain the resulting mixture with stirring or other means of agitation for the desired reaction period to allow the carbonate compounds to be sufficiently consumed having regard to any decrease in the reaction rate with decreasing concentration of reactants. If a carbonate other than magnesium carbonate is to be used it is found that this may materially reduce the reactivity of the magnesium carbonate, even to the extent that it is difficult to achieve the consumption of the last 5 of 10% by weight thereof, unless the magnesium carbonate is added to the aluminium chloride first and allowed to react, at least to a major extent, for example to more than 75%, preferably to more than 90% by weight, before the other carbonate is added.

International Patent Publication WO 99/35090 describes a process for the production of polyaluminium chloride (basic aluminium chloride) coagulants by the inclusion of one or more magnesium and/or calcium carbonate-containing materials in the aluminium chloride solution. The cationic charge density was found to be considerably augmented when a suitable quantity of the carbonate material had been added. It is envisaged herein that this charge augmentation process may be modified by the use of other soluble carbonates, such as alkali metal or ammonium carbonates, and/or by the use of other basic materials for example alkali metal oxides and, also, that the process may be used to upgrade existing polyaluminium chloride coagulant solutions by the suitable addition of magnesium carbonate and/or calcium carbonate-containing materials, or of other basic materials.

In the practice of the above charge-augmentation process magnesium carbonate may be used alone or may be used in conjunction with up to a major proportion of calcium carbonate, or suitable sources, for example mineral sources thereof. For example, calcium carbonate or a suitable source thereof may be in combination with only 0.1% or 0. 2% of magnesium carbonate or a suitable source thereof. Any relative proportions of magnesium to calcium carbonate between these extremes may be used for example at least 20%, very suitably at least 30%, of the total quantity of these carbonates, of magnesium carbonate. Preferably, the content of impurities in the magnesium carbonate is less than 20%, particularly preferably less than 10% by weight. The quantity of the carbonate material is preferably at least sufficient, in theory, to react with the aluminium chloride. More suitably, the carbonate material is in at least 5% excess, preferably at least 20% excess, and possibly up to 100% excess or more as required at the reaction conditions used to achieve complete conversion of the aluminium chloride. Preferably a proportion of the calcium carbonate, if used, is replaced by sodium carbonate. This also helps to reduce sludge formation during the use of the coagulant, as a result of the precipitation of calcium compounds. If a content of sodium is required in the coagulant composition this may preferably be provided by an addition of soda ash or other sodium source or sodium carbonate material.

The charge-augmentation process is preferably conducted by maintaining contact between the aluminium chloride and the carbonate compound or compounds at a temperature less than 60 C for a duration of more than 4 hours so as to encourage a slow rate of carbonate decomposition. The

temperature may very suitably be at least 10 C and/or less than 50oC. The duration of the contact may, very suitably, be more than 8 hours and/or up to 36 hours although the effect anticipated may be attained in a lesser time than that, for example in no more that 24 hours. Where the aluminium chloride is sufficiently pure for use to produce a specific coagulant, a temperature of up to the boiling temperature at the prevailing pressure, and a correspondingly shorter time of contact, may suitably be used. If a content of sulphate is required in the coagulant according to the invention a proportion of sulphuric acid and/or one or more sulphates may be added to the reaction mixture or to the coagulant product. On completion of the reaction to the desired extent the resulting solution may be filtered or otherwise separated from any residue and forms the product of the invention.

The charge-augmentation process described above is particularly suitable for the conversion of aluminium chloride contaminated with organic impurities into a coagulant. Aluminium chloride is used on a large scale as a catalyst for organic transformations. For example, it is used as a catalyst in the alkylation of aromatic or aliphatic compounds by means of the Friedel-Krafts reaction. After use for this purpose the aluminium chloride may be contaminated with compounds such as, for example, benzene, chloropropanol, alkyl substituted dioxolanes, dioxanes or methylene chloride, up to individual concentrations which may vary from as little as 4 micrograms/litre to as much as 200 micrograms/litre aluminium chloride solution or even up to a level as high as 1% by weight, in the case of methylene chloride.

Commonly, the total organic carbon content of used catalytic aluminium chloride solutions may be over 100, often over 200 milligrams/litre. Such contaminated aluminium chloride solutions are usually deep yellow in colour. It may be undesirable to use a coagulating agent containing organic or aromatic impurities for particular clarification applications, depending on the nature of the impurities, and for this reason organics-contaminated aluminium chloride may be considered to be unsuitable for use as a raw material for the production of coagulants.

The zirconium-containing compound or compounds used to make the compositions of the present invention may be selected from one or more of the compounds indicated below: Zirconia (zirconium oxide, ZrO, zirconium sol (hydrated zirconium oxide) and zirconium salts such as zirconium chloride, zirconyl chloride (zirconium oxychloride), zirconium nitrate, zirconium sulphate, zirconium acetate, and zirconium carbonate. Zirconia is the active agent when the compositions are used to aid fine particle retention and water drainage, and can be generated as the pH is raised (for example by metal carbonates) from zirconium salts such as those listed above.

Preferably the zirconia is used in sol form as zirconium sol. The zirconium sol and the aluminium chloride and/or basic aluminium chloride can then either be added separately to the process liquid or furnish slurry, or the zirconium sol can be combined with aluminium chloride and/or basic aluminium chloride before addition to the process liquid or furnish slurry.

The zirconium sol may be produced by any known method.

For example, US 3,423, 193 discloses dissolving boric acid or a salt thereof in an aqueous solution of zirconyl chloride (zirconium oxychloride). Zirconyl chloride is tetravalent at low pH values and exists as the common cation, ZrO2+. The resulting solution is then treated with one or more alkaline compounds such hydroxides or carbonates to produce zirconium sol as a finely divided precipitate.

The compositions of the present invention may be produced by mixing aluminium chloride and/or basic aluminium chloride with the zirconium sol in a molar ratio of Al : Zr of 0. 1 to 50, preferably 1 to 15.

Medium to high molecular weight cationic charged polymers may be used in conjunction with the compositions of present invention and are typically those having a molecular weight as characterised by intrinsic viscosity in the range of 5 to 25 dl/g and having a charge density of from 0.01 to 5 equivalents of cationic nitrogen per kg as measured by polyelectrolyte titration (0.1% to 50% mole substitution). Such polymers include addition to the quaternised Mannich polyacrylamides, polymers such as tertiary amine Mannich polyacrylamides, quaternised and unquaternised copolymers of dimethylamino ethyl (meth) acrylate and acrylamide, polyethylene imines, polyamine epichlorohydrin polymers and homo-and co-polymers (with acrylamide) of diallyldimethylammonium chloride.

A boron compound or compounds may optionally be present in the compositions of the present invention and these will stabilise the basic aluminium chloride in a similar way to their use in the production of highly basic aluminium chlorides described in GB Patent Application 99296337.8.

When a boron compound is present, the molar ratio of the boron to zirconium (B: Zr) in the compositions of the present invention can be from 0.01 to 1. 5 but is preferably from 0.1 to 0.5.

When the compositions of the present invention are used in paper manufacture as drainage aids and fine particle retention aids, a typical dose rate is 0.25-4kg per tonne of dry paper. It is also preferable that the composition of the invention comprises one or more polyacrylamides (preferably cationic) in amounts of from 0.1 to 0.75kg per tonne of dry paper. This dose rate is lower than the amount of polyacrylamide typically used in paper manufacture. It is also advantageous if the composition of the present invention contains a charge bearing starch at a dose rate of from 0.5 to 5 kg per tonne of dry paper. This can be in the presence or absence of a polyacrylamide. Suitable starches are selected from one or more of a cationic starch having a degree of substitution above 0.03 (0.15 equivalents of nitrogen per kg of starch) and an amphoteric starch. Particularly useful starches are potato starch, waxy maize starch, corn starch, wheat starch and rice starch.

We have also discovered an efficient process for making the compositions of the present invention which involves forming zirconium sol in situ in the presence of aluminium chloride and/or basic aluminium chloride. This advantageously forms the compositions of the present invention directly, avoiding the need for separate steps to form the zirconium sol and then mixing this with aluminium chloride and/or basic aluminium chloride. The reaction mixture from the process of the invention can be used, without purification, as a coagulant in water treatment, as a fines material retention aid and a water drainage aid in paper manufacture and to condition waste sludge.

Accordingly, the present invention provides a process for the preparation of a composition according to the invention comprising the steps of: i) dissolving a zirconium-containing compound in an aqueous solution of aluminium chloride and/or basic aluminium chloride, optionally in the presence of a boron compound or compounds; and, optionally, ii) adding an alkaline agent thereto.

When the zirconium-containing compound used in the process of the invention is zirconium carbonate, it can either be used as the only basification agent, or in conjunction with another base, for example a basic carbonate.

Further, when the zirconium-containing compound is zirconium carbonate, step i) is preferably carried out at a temperature between 5 and 75OC.

Typically, when present, the alkaline agent is magnesium carbonate, calcium carbonate, sodium hydroxide or dolomite, and has the effect to assist in basifying the solution, increasing its cationic charge and producing the zirconia sol in situ.

When a boron compound is present, the molar ratio of the boron to zirconium (B: Zr) used in the process of the invention can be from 0. 01 to 1.5 but is preferably from 0.1 to 0.5.

The present invention will now be described with reference to the following Examples.

Example 1-Preparation of Acidic Zirconium Sol (Prior art method) Preparation of an acidic boratozirconium chloride sol using the method described in US 3,423, 193: lg Boric acid was dissolved in 100g of an aqueous solution of zirconyl chloride (20% Zur02). The ratio of B: Zr in this mixture was 0.1. The resulting mixture gave boratozirconium chloride as an acidic viscous sol solution.

Example 2-Preparation of Basic Zirconium Sol (Prior art method) The acidic boratozirconium sol prepared as in Example 1 was converted to a basic boratozirconium sol by reacting the acidic sol with 5g of dolomite.

Example 3-Process of the Present Invention Preparation of Sample A (10% basicity) Zirconium sol was produced in-situ with an aqueous aluminium chloride solution (basicity 10%). First, lg boric acid was dissolved in 80g of an aqueous solution of aluminium chloride (10% A1203) and to the resulting mixture was added 20g of an aqueous solution of zirconyl chloride (20% Zur02).

The charge density of the final composition was +480 ueq/kg.

In all cases described herein, charge density was measured following standard techniques using a Mutec streaming current detector by a titrimetric method.

Example 4- (Process of the present invention) Preparation of Sample B (65% basicity) To the final composition obtained using the process of Example 3 above was added 5g of powdered dolomite. This was allowed to dissolve in the final composition from Example 3 at a temperature of between 5 and 75OC, and gave a mixture with 65% basicity and a significantly higher cationic charge density of +1153 ueq/kg Example 5- (Process of the Present Invention) Preparation of Sample C (85% basicity) The zirconium sol can also be produced in-situ in a similar manner to that of Examples 3 or 4 using aluminium chlorohydrate in place of aluminium chloride. lg boric acid was dissolved in 80g of an aqueous solution of aluminium chlorohydrate (23% A1203) and to the resulting mixture was added 20g of an aqueous solution of

zirconyl chloride (20% Zur02). The charge density of the resulting product was +1836 ueq/kg Example 6- (Process of the Present Invention) Preparation of Sample F (10% basicity) Sample F was prepared using the process of Example 3 except that less zirconyl chloride was used; the weight ratio of polyaluminium chloride: zirconyl chloride for Sample F was 5: 1. The charge density of the resulting composition was 318 ueq/kg Example 7- (method of the Present Invention) Preparation of Sample I 5.4g (40% Zur02) Zirconium carbonate was dissolved in lOg of water acidified with 3.2g hydrochloric acid (20%). To the resulting solution was added 90.4g of an aqueous solution of aluminium chloride (10% A1203), and lg boric acid, and then 5g of powdered dolomite. The final composition had a charge density of 641 ueq/kg.

Evaluation of the Efficacy of Samples A to I in Water Treatment and Paper Manufacturing Applications Summary of the composition of Samples A to I Sample A* = Low basicity (10%) aluminium/zirconyl chloride solution (4 : 1 weight basis) Sample B* = Medium basicity (65%) aluminium/zirconyl chloride solution (4: 1 weight basis) Sample C* = High basicity (83%) aluminium/zirconyl chloride solution (4: 1 weight basis) Sample D = Zirconyl chloride solution Sample E = Low basicity aluminium chloride solution Sample F* = Low basicity (10%) aluminium/zirconyl chloride solution (5: 1 weight basis) Sample G = Medium basicity (65%) aluminium chloride solution Sample H = High basicity (83%) aluminium chloride solution Sample I* = Medium basicity aluminium/zirconyl chloride solution prepared from zirconium carbonate and dolomite.

The Samples marked * are according to the present invention.

Tests A) Efficacy of Compositions of the Invention in Water Treatment Applications The following model experiment was devised to demonstrate the synergy between cationic aluminium and zirconium chlorides using humic acid dissolved in water as an example of an anionic substrate.

The efficacy of aluminium chloride/basic aluminium chloride and zirconium-containing compositions as coagulants in water treatment applications was evaluated at pH 7.0 using a Standard Jar Tester.

8 Jars were filled with a synthetic effluent which simulated the typical effluent from a water treatment works. The synthetic effluent in each jar comprised 500

ml of water and 10ml humic sodium salt solution (1000ppm). Samples A, B, C and F of the present invention, prepared above, were then added to one of each of 4 of the jars at a rate of 500ppm. To one of each of the remaining 4 jars was added 500ppm zirconyl chloride (Sample D), 500ppm of aluminium chloride (10% basicity) (Sample E), 500ppm of aluminium chloride (65% basicity) (Sample G) and 500ppm of aluminium chlorohydrate (Sample H).

Results The clarifier and filtered analysis for the synthetic effluent in each of the jars post treatment with the coagulant (Samples A to H) was then determined by measuring turbidity (Ntu) and colour (Hazen), using standard techniques. The results obtained are summarised below in Table 1.

Table 1

A B C D E F G H Coagulant Sample Coagulant Sample Clarifier Turbidity 0.29 0. 32 0.30 2.20 1.40 0.85 0.61 0.96 Analysis (Ntu) Colour 7.5 7.6 8.1 26. 4 27.2 17.7 9.3 15.9 (Hazen) Filtered Turbidity 0. 02 0. 02 0. 03 0.12 0.21 0.12 0. 07 0. 08 Analysis (Ntu) Colour 3. 3 3. 5 5.7 8. 4 9. 1 6.3 4.5 5.1 (Hazen) These results are also presented in graph form in Figures 1 and 2; Figure 1 is a plot of the filtered turbidity (Ntu) and clarifier turbidity (Ntu) for each of the Samples A-H, and Figure 2 is a plot of the filtered colour (Hazen) and the clarified colour (Hazen) for each of the Samples A-H.

Conclusions The above results demonstrate that zirconyl chloride is not effective as a coagulant when used alone (Sample D), and that coagulation activity and the ability to produce structured floes of basic aluminium chloride (polyaluminium chloride) is substantially improved when used in conjunction with zirconyl chloride. It was also observed that Sample B produced more structured floes than Samples A and F, and smaller floes than Sample G.

Smaller structured floes are considered to be more desirable firstly, because they remove more impurities due to their high charge density and secondly, they will neutralise the anionic trash found in many mixtures like paper pulps.

B) Efficacy of Compositions of the Invention as Water drainage and Fine Particle Retention Aids in Paper Manufacture A pulp furnish (Pulp 1) was selected for evaluation which had a significant anionic charge from pulp fibres (1: 4 softwood: birch), broke (recovered pulp fibres which can contain surface applied chemicals which are returned to the paper-making process and contain substances (usually anionic) which can impair process efficiency) and calcium carbonate filler (23% addition).

Micro particle retention aids, Samples B, D, G and I, and a bentonite control sample were added to the furnish at a fixed rate of 1.13 kg/tonne dry paper with a cationic polyacrylamide (PAM) at doses of 0.32 and 0.63 kg/tonne based on dry paper.

Standard Britt Jar analysis (the Dynamic Drainage Test) was used to determine fines retention. Drainage rates, that is, the time taken to drain a set volume, were also determined using Buchner filtration and a turbidimeter was used to determine the clarity of the filtrates using usual method known in the art.

Results The results in Tables 2,3 and 4 below show that Samples B and I (Al/Zr combinations) are clearly superior to Samples D (Zr alone) and G (Aluminium alone) and to bentonite in all key performance tests, that is, drainage rate, fines retention and filtrate turbidity.

Table 2 Drainage Rate for Pulp No. 1

SAMPLE DRAINAGE RATE (g/s) DRAINAGE RATE (g/s) (Sample Dose rate 1.13 Kg/t (Sample Dose rate 1.13 Kg/t pd Dose rate 0.32 Kg/t) PAM1 Dose rate 0.63 Kg/t) G6. 0139. 235 B 8.478 14. 711 D 5. 414 8. 698 I 11.678 16. 1 Control2 5. 027 6. 746 1 PAM = polyacrylamide 2 Control = bentonite Table 3 % Fines Retention for Pulp No. 1

SAMPLE % FINES RETENTION % FINES RETENTION (Sample Dose rate 1.13 Kg/t (Sample Dose rate 1.13 Kg/t PAM1 Dose rate 0. 32 Kg/t) PAM1 Dose rate 0. 63 Kg/t) G 89. 395. 5 B 91 99. 99 D 85. 2 97. 3 I 97.4 99. 9 Control2 68.4 79. 5 1 PAM = polyacrylamide 2 Control = bentonite Table 4 Turbidity for Pulp No. 1

SAMPLE TURBIDITY (Ntu) TURBIDITY (Ntu) (Sample Dose rate 1.13 Kg/t (Sample Dose rate 1.13 Kg/t PAte Dose rate 0. 32 Kg/t) PAW- Dose rate 0. 63 (gut) G 42 11 B 30 10.2 D 66 21 I 11 7 Control2 53 22 1 PAM = polyacrylamide 2 Control = bentonite The results are also presented in graph form in Figures 3,4 and 5, where Figure 3 is a bar graph of drainage rate for each Sample; Figure 4 is a bar graph of % fines retention for each Sample and Figure 5 is a bar graph of turbidity for each Sample.

Conclusions Superior drainage rates achieved using compositions according to the present invention (Samples G, B, D, and I) suggest that improvements in sheet formation would improve paper strength.

The tests also suggest that lower polyacrylamide doses are also possible compared to the competitive bentonite micro particle system which would reduce treatment cost and aid improved drainage rates.

C) Efficacy of Compositions of the Invention in Paper Manufacture Using a Cationic Polyacrylamide (C-PAM), an Anionic Polyacrylamide (A-PAM) and Reversing the Order of Addition A second series of tests was carried out on a different pulp furnish (Pulp No. 2) to determine the effect of using 0. 32Kg/tonne of dry paper of a cationic polyacrylamide (C-PAM), and of using 0. 32Kg/tonne of dry paper of an anionic polyacrylamide (A-PAM). As a control comparison, micro particle retention systems based on commercially used bentonite and hectorite clays were tested.

The'normal'order of addition of PAM and clay to the pulp furnish in commercial paper manufacture is clay first, then PAM. If this order is reversed, significant reduction in efficiency results. A third series of tests was carried out which reversed the order of addition, that is, PAM first then clay and PAM first then the zirconium compositions of the invention, to see if this had any effect on efficiency.

Results The results, given in Tables 5,6 and 7 below, demonstrate the synergy between aluminium and zirconium ions and, in particular, the fact that increasing the level of zirconium ions improves the drainage rate.

As mentioned above, the order of addition can significantly impair the efficiency of both of the claybased micro particle systems but, as the results show, had minimal effect when Samples G, B and I of the present invention were used. Also, all of Samples G, B and I can be used with either cationic or anionic polymers.

Table 5 Drainage Rate for Pulp No. 2

SAMPLE DRAINAGE RATE No PAM C-PAM A-PAM Reversed Polymer (0. 32Kg/ (0. 32Kg7 Addition Tonne) Tonne) G 1. 74 10. 24 9.8 Not tested B 1. 71 13.22 11.2 11.76 I 1. 12 10.05 10.2 10.92 Control3 2. 51 10.16 8.41 7. 47 Control4 1.76 11.26 10. 61 5. 05 3 Control = bentonite 4 Control = hectorite Table 6 % Fines Retention for Pulp No. 2

SAMPLE % FINES RETENTION No PAM C-PAM A-PAM Reversed Polymer (0. 32Kg/ (0. 32Kg/ Addition Tonne) Tonne) G 86.1 96. 9 97.6 Not tested B 84. 8 97.4 97. 1 94.3 I 82. 2 98.2 96.8 96.9 Control3 83. 4 97.8 96. 1 93 Control4| 83.5 96.8 96.7 91.3 3 Control = bentonite 4 Control = hectorite Table 7 Turbidity for Pulp No. 2

SAMPLE TURBIDITY No PAM C-PAM A-PAM Reversed Polymer (0.32Kg/ (0. 32Kg/ Addition Tonne) Tonne) G 178 21 20 Not tested B 212 18 31 28 I 13.2 Control3 73 13 13.6 20 Control 117 1 18. 1 18 65 3 Control = bentonite 4 Control = hectorite A further experiment was also conducted to determine the percentage of fines retained from the process waters after one pass through the mesh. The results are presented in Table 8.

Table 8 First Pass Retention for Pulp No. 2

SAMPLE FIRST PASS RETENTION No PAM C-PAM A-PAM Reversed Polymer (0. 32Kg/ (0. 32Kg/ Addition Tonne) Tonne) G 90.6 98 98.3 Not tested B 90.1 98.2 98.1 96.2 I 88.6 98.2 97.9 97.8 Control 89. 1 97.8 97.5 95.3 Controls 89. 3 96.8 97.8 94.4 3 Control = bentonite 4 Control = hectorite All of the above results are presented in graph form in Figures 6, 7,8 and 9, where Figure 6 is a bar graph of drainage rate for each Sample with either C-PAM or A-PAM, and with reverse addition; Figure 7 is a bar graph of % fines retention for each Sample with either C-PAM or A PAM, and with reverse addition; Figure 8 is a bar graph of turbidity for each Sample with either C-PAM or A-PAM, and with reverse addition and Figure 9 is a bar graph of first pass retention for each Sample with either C-PAM or A-PAM, and with reverse addition.

Conclusions Overall it is evident that order of addition of components does not affect performance efficiency of products of the invention unlike that for anionic micro particles based on clay products. This suggests that the compositions of the present invention provide a more robust process that is easier to control.

The negatively charged micro particles tend to work more efficiently with cationic polyacrylamide additions.

It was also noted that that zirconium products containing

4% Zur02 (sample B) had a better drainage rate than product containing 2% Zur02 (Sample I) but with fines retention the situation was reversed. It is likely, therefore, that products according to the present invention can be formulated and tailored to suit individual mill requirements.

D) Efficacy of Compositions of the Invention in Paper Manufacture under Shear Rates of 500 and 1000 rpm A third series of tests on a further pulp furnish (pulp No. 3) was conducted to investigate the effect of shear rate on products made using the present invention and to compare this with the effect of shear rate on competitive bentonite and hectorite micro particle systems. PAM was added to the pulp furnish at 0.32Kg/tonne of dry paper and the Samples and Controls were added at 1. 13Kg/tonne of dry paper.

Results Standard Britt Jar analysis using standard techniques was used to measure the effect of shear rate carried out at 500 and 1000 rpm.

Again, products made using the present invention were more resistant to the effects of shear rate in terms of drainage rate and fines retention. The results obtained are summarised in Tables 9 and 10 below.

Table 9 Drainage Rate for Pulp No. 3

SAMPLE DRAINAGE RATE DRAINAGE RATE (Shear speed 500 rpm) (Shear speed 1000 rpm) B 9. 67 7. 82 I 10.74 7. 9 Control5 9.54 7. 47 Control6 8.37 6. 38 5 Control = bentonite 6 Control = hectorite Table 10 % Fines Retention for Pulp No. 3

SAMPLE RETENTION (Shear rpm) B 97 94.3 I 92.5 94.3 Control5 92.4 86.2 Control6 94.3 92.3

5 Control = bentonite 6 Control = hectorite These results are also presented in graph form in Figures 10 and 11, where Figure 10 is a bar graph of drainage rate for each Sample at shear speeds of 500 and 1000 rpm; and Figure 11 is a bar graph of % fines retention for each Sample at shear speeds of 500 and 1000 rpm Conclusions As machine rates increase, the rate of shear on the pulp fibres can impair mill efficiency. Strong resistance to shear effects with the samples of the present invention compared to competitive (bentonite and hectorite) systems was confirmed.

Claims (11)

1. Claims: 1. A composition comprising an aqueous solution of aluminium chloride and/or basic aluminium chloride, a zirconium-containing compound or compounds and, optionally, a boron compound or compounds.
2. 2. A composition according to claim 1 wherein the zirconium-containing compound or compounds is selected from one or more of Zirconia, zirconium sol, and zirconium salts such as zirconium chloride, zirconium oxychloride, zirconium acetate, zirconium nitrate, zirconium sulphate and zirconium carbonate.
3. 3. A composition according to claim 1 or 2 wherein the molar ratio of aluminium to zirconium in the composition is 0.1 to 50.
4. 4. A composition according to any of claims 1,2 and 3 further comprising one or both of the following: i) one or more polyacrylamides ; and ii) one or more charge-bearing starches.
5. 5. A composition according to any preceding claim wherein, when a boron compound or compounds is present, the molar ratio of boron to zirconium is 0.01-1. 5.
6. 6. A process for the preparation of a composition according to any of the preceding claims comprising the steps of: i) dissolving a zirconium-containing compound in an aqueous solution of aluminium chloride and/or basic aluminium chloride, optionally in the presence of a boron compound or compounds; and, optionally, ii) adding an alkaline agent thereto.
7. 7. A coagulant for use in water treatment applications comprising a composition according to any of claims 1-3 and 5, and optionally containing one or more polyacrylamides.
8. 8. A micro-and nano-particle retention aid for use in paper manufacture comprising a composition according to any of claims 1-5.
9. 9. A water drainage aid for use in paper manufacture comprising a composition according to any of claims 1-5.
10. 10. A sludge conditioning aid for use in dewatering industrial or sewage sludges comprising a composition according to any of claims 1-3 and 5.
11. 11. A composition, process, coagulant, micro particle retention aid or water drainage aid substantially as described in any one of Examples 3 to 7 herein.