WO1996034684A1

WO1996034684A1 - Elimination of waste materials in paper production

Info

Publication number: WO1996034684A1
Application number: PCT/AU1996/000261
Authority: WO
Inventors: Gunter Heinzel; Rosenia Baumann
Original assignee: Mosaic Tile And Pottery Co. Pty. Ltd.
Priority date: 1995-05-02
Filing date: 1996-05-02
Publication date: 1996-11-07
Also published as: DE59607558D1; BR9606382A; FI965239A0; NO965624L; DE19515932A1; CA2193839A1; NO965624D0; DE19515932C2; EP0741113B1; JPH10502871A; AU5490796A; FI965239A; ATE204834T1; EP0741113A1

Abstract

The invention is directed to an agent to remove contaminants from water used in the production of paper and related products, of the general formula: (ZO)nAln(OH)n-mClm (or of closely related empirical formula), which, optionally, has been further coated with a polymer, wherein Z is derived from an aluminosilicate material. The agent is prepared by activating the aluminosilicate material by treating with acid or by subjecting the material to ammonium ion exchange and then heating the thus activated material in the presence of a cationic agent, followed by coating with a polymer. The preferred aluminosilicate is a zeolite-containing mineral of a clinoptilolite structure and the preferred cationic agent is selected from polyaluminiumchloride, epichlorohydrin (or a polymer derivative thereof) or dicyanodiamide. The preferred coating polymer is polyacrylamide. Use of the agent leads to production increase, reduction of sludge generation, reduction of contaminant load, reduction in chemical oxygen demand and a cost saving.

Description

TITLE; ELIMINATION OF WASTE MATERIALS IN PAPER PRODUCTION

FIELD OF THE INVENTION

THIS INVENTION relates to the elimination of waste materials and other pollutants from water. In particular, it is directed to the production and use of compounds which efficiently clarify or otherwise remove these waste materials and other pollutants during the manufacture o_f paper, cardboard and similar products.

BACKGROUND OF THE INVENTION

Up until approximately the early 1970's, cellulose and wood pulp were used almost exclusively for the manufacture of paper and related products. These were clean, primary raw materials without significant contaminants. Increasingly however, "new" paper has been manufactured by combining these raw materials with "recycled" paper, that is, paper which has been previously manufactured, used and then returned to the manufacturing industry to be used again in the preparation of fresh paper.

With the use of this recycled paper, comes the introduction of significant contaminants into the paper manufacturing process. Typical contaminants are resins, starch, binders, adhesives/gums/glues and other compounds - usually synthetic - introduced in the manufacturing process to provide specific qualities or properties to the original paper such as brightness and strength.

Further, it is a requirement of most Government Authorities today that polluted water and other waste material generated by industry are adequately treated before their disposal. It is of particular concern to ensure that these industrial by-products are disposed of carefully without undue harm to the environment. This has lead to the development of "closed" systems whereby the water that is required in the manufacture of paper and related products is continuously circulated within the manufacturing plant until it is essentially all consumed resulting in only minimal discharge of "waste" water to the outside environment. In fact, it is not uncommon to manufacture "new" paper from 100% recycled paper in a totally closed system.

However, such processes face a number of problems, including (a) sedimentation within the system leading to the shutting down of the process while cleansing is undertaken; and (b) as the "pollutants" and the agents to remove them are incorporated as a component of the final paper product, they can have an adverse effect on the final paper quality, particularly with respect to moisture content, unwanted staining and lower than desired strength - these latter problems are further amplified by the inclusion of auxiliary agents to bring the final paper quality back to the desired level but which, in turn, effectively add to the quantity of "contaminants" present in the manufacturing process.

One such quality is the sizing of paper, that is, the degree to which the paper will repel water. Sizing is expressed as how much water paper or cardboard can absorb per minute over a specific area and is known as the COBB value.

The principle of sizing is that anionic adhesive agents added to the paper pulp are flocculated and then undergo ion exchange by the addition of suitable cationic additives. They are then able to be absorbed onto the paper fibre. However, anionic contaminants lead to fluctuations of the COBB value in the fibre product and if too much sizing agent is added, strong foaming occurs, leading to problems in the production of the final paper product.

The presence of contaminants causes other problems, for example, variations in weight and moisture content of the final paper product and adverse effects on the chemical oxygen demand, the biological oxygen demand and the quantity of halogenated hydrocarbons.

With a relatively high biological oxygen demand, a satisfactory procedure for removing the thus present bacteria and other microorganisms from the circulating water and/or their incorporation into the final paper product has not yet been satisfactorily resolved.

It is a complex task to handle and utilise these contaminants because they have quite different properties, particulate sizes and reactivities; they may appear in solution, in colloid form, as a suspension or dispersion; in small or large particulate size.

Conventional products that have been used in an attempt to alleviate the afore-mentioned problems include microtalcum, cationised microtalcum, altonite/bentonite, cationic polymers and polyaluminiumchloride.

Microtalcum, due to its large surface area, has the ability to absorb small, sticky particles. However, a great disadvantage is that relatively large quantities of microtalcum (up to 1.5%) must be employed which is detrimental to the strength of the final paper and it does not remove colloidal or anionic contaminants. In an attempt to increase the usefulness of microtalcum by giving it the property of being able to remove anionic contaminants, cationised microtalcum was developed. As microtalcum is essentially chemically inert, this could only be achieved by coating the microtalcum with a cationic substance, for example, polydadmac. However, this coating was readily washed off by the water of the paper making process and thus it only removed minimal anionic contaminants before reverting to microtalcum with its attendant disadvantages referred to above.

Altonite and bentonite are insert silicate minerals and function similarly to microtalcum. However, they display no significant higher absorption capacity for contaminants then that by microtalcum and are more expensive to purchase.

Strongly cationised polymers, developed in the mid 1980's- mid 1990's, have been partially successful in that they remove anionic contaminants. However, the resultant composites have proved virtually impossible to remove from the system effectively. They are also expensive to manufacture and require high application rates and have thus provided uneconomical.

Polyaluminiumchloride (PAC) has been used successfully in the treatment of effluent and similar waste water and is a favoured coagulant in sedimentation tanks.

Much research has been undertaken to improve to efficiency of this agent. For example, in a method described in Japanese Unexamined Patent Publication No. 60-209214 (Application No. 59-65078, filed April 3, 1984) it is blended with finely divided aluminosilicate-containing minerals to provide a means for improving the time taken for sedimentation to be effected. In Japanese Unexamined Patent Publication No. 3-056104 (Application No. 1-192232, filed July 25, 1989), separate quantities of an aluminosilicate mineral, particularly one containing a zeolite, are individually treated with (1) sulfuric acid to give a product "a", (2) with hydrochloric acid followed by polyaluminiumchloride to give a product "b", and (3) with sodium hydroxide to give a product "c". The products a, b and c are then blended together in a 1:1:1 ratio to give a mixture which is then used to clarify polluted water.

While these improved processes may be successful, and PAC offers many properties which appear suited to the removal of contaminants from water, PAC has a major disadvantage if it is to be used in the paper industry, namely, its acidity (pH range approximately 1 to 3). As it is acidic, PAC cannot be used wherein a contaminant is a carbonate, for example, calcium carbonate, as it reacts with carbonates at a pH of <6.3 to produce a gas which is detrimental in the production of paper leading to significant contamination of the final product.

There thus remains a need for an economical material which can remove contaminants during the manufacture of paper or related products (in a closed system, if necessary), and which can be incorporated into the final product without detrimental effect on the required properties of that product.

It is thus an object of the present invention to eliminate, or at least ameliorate, one or more of the above problems and to provide an agent for use in the removal of contaminants from water used in the production of paper and related products which is economical to produce, effective in the removal of more than one type of contaminant and which can be incorporated into the final product without detrimental effect on the required properties of that product.

SUMMARY OF THE INVENTION

It has now been established that compounds similar to those described in International Patent Application No. PCT/AU95/00122, the entire content of which is incorporated herein by reference, with or without further modification, can be used to meet this objective.

Therefore, according to a first aspect of the present invention, there is provided an agent for use in the removal of contaminants from water used in the production of paper and related products, said agent comprising a compound of the general formula:

(Z0)_nAl_n(0H)_n__mCl_m

or a compound of closely related empirical formula, which, optionally, has been further coated with a polymer, wherein Z is derived from an aluminosilicate material.

As a second aspect of the present invention there is provided a method for the preparation of a compound of the general formula:

(Z0)_nAl_n(0H)_n__mCl_m

or a compound of closely related empirical formula, wherein Z is derived from an aluminosilicate material,

said method comprising:

1) activating said material; 2) heating the thus activated material in the presence of a cationic agent; and

3) optionally, coating the resultant product with a polymer.

A third aspect of the present invention is a method of removing contaminants from water used in the production of paper and related products, said method comprising treating the water with a compound having the following general formula:

(Z0)_nAl_n(0H)_n__mCl_m

or a¹ compound of closely related empirical formula, which, optionally, has been further coated with a polymer, wherein Z is derived from an aluminosilicate material.

As a fourth aspect of the present invention, there is provided a method of manufacturing paper and related products, wherein contaminants from water used in the production of the paper and related products have been removed by a compound as hereinbefore described and incorporated into the final paper or related product.

The aluminosilicate can be a natural or synthetic material.

Preferably, the material is a zeolite-containing mineral.

Preferably, the zeolite content of the mineral is at least 40% by weight.

Preferably, the Si:Al ratio of the zeolite is greater than 3. More preferably, the quartz content of the zeolite is not more than 5% by weight, preferably not more than 1% .

Most preferably, the zeolite is of a clinoptilolite structure.

Most preferably, the mineral is finely divided to a particle size ranging between 0.1 and 30 μm.

Preferably the zeolite-containing mineral is activated by treating with acid or by subjecting said mineral to ammonium ion exchange.

More preferably, the zeolite-containing mineral is activated by treatment with hydrochloric acid. i

Preferably, the cationic agent is selected from an alumino compound, epichlorohydrin or a derivative thereof, or dicyanodiamide.

Preferably, the alumino compound is a polyaluminium salt.

More preferably, the polyaluminium salt is polyaluminiumchloride.

Preferably, the ratio of mineral : alumino compound is in the range of 1:0.1 to 1:5 by weight.

More preferably, the ratio of mineral : alumino compound is in the range of 1:1 to 1:2 by weight.

Most preferably, the ratio is 1:1 by weight.

Preferably, the activated mineral and the alumino compound are heated together at a temperature which is in the range 100 - 600°C. More preferably, the heating is undertaken at about 300°C.

Preferably, the epichlorohydrin derivatives are polymers of epichlorohydrin which, optionally, have been further mixed with an acid, preferably, melamine acid.

Preferably the coating polymer is an amide.

More preferably, the amide is a polyamide.

Most preferably, the polyamide is polyacrylamide.

Preferably, the product of the invention is granulated to a particle size of 0.25 - 100 μm.

Mixtures of agents prepared by the present invention can also be used, i.e., mixtures selected from a first agent incorporating polyaluminiumchloride as the cationic agent; a second agent incorporating dicyanodiamide as the cationic agent; a third agent incorporating epichlorohydrin as the cationic agent; and a fourth agent incorporating polyaluminiumchloride as the cationic agent and then subsequently coated with a cationic polymer.

DESCRIPTION OF THE INVENTION

GENERAL EXAMPLE

A naturally occurring, acid-resistant, thermostable, zeolite-containing mineral is first finely divided by any convenient means and then activated by washing with hydrochloric acid. An aqueous polyaluminiumchloride solution is then added and the mixture is heated between 150 and 250^CC with simultaneous evaporation of water. The product is then cooled relatively rapidly by passing through a spray tower. The product formed preferably has a water content of less than 10 percent by weight, more preferably less than 5 percent by weight.

More details on the preparation of such composites can be found in the aforementioned International Patent Application No. PCT/AU95/00122.

The thus - prepared composites are then coated with the required polymer by any conventional means known in the art. For example, by dipping in, or spraying on, a solution of the polymer and then drying to produce the coated composite.

Although not wishing to be bound by theory, the reaction is believed to be a dehydroxylisation between the protonated zeolite and the hydroxyl groups of the partially hydrolized cationic agent, for example, polyaluminium chloride.

In more detail, activating by washing with hydrochloric acid forms a protonated zeolite and a metal salt. For example:

(Z0)_nAl(0Na) + HC1 → (Z0)_nA10H + NaCl

Upon treatment with polyaluminiumchloride, a composite is formed in a number of ways. For example:

(1) (Z0)_nA10H + Al_n(0H)_mCl_3n__m - (Z0)_nA10Al_n(0H)_m_₁Cl_3n__m

+ H₂0

(2) (Z0)_nA10H + Al_n(0H)_mCl_3n__m → (Z0)_nA10Al(0H)_mCl_3n__(m+1) + HC1 The product of the present invention is thus believed to be approximately of the general formula (ZO)_nAl_n(OH)_n__m(Cl)_m, wherein m is greater than 0. However, it is difficult to provide an exact empirical formula because the product of the invention can exist in various forms. Three examples of these forms are given below:

z - 0 Z - 0 0 - z

\ \ \

Al - OH Al - OH Al - Cl

/ / / / / z - 0 Z - 0 z - 0

\ \ \

Al - OH Al - OH Al - Cl

V / / zz - - o0 Z - 0 z - 0

\ \ \

Al - OH Al - Cl Al - OH

/ / / z - 0 Z - 0 Z - 0

\ \

Al - Cl Al - OH

/ /

SPECIFIC EXAMPLES

The procedure described above in the General Example was undertaken with a number of zeolite-containing minerals from various sources, particularly from China, Hungary and Bulgaria, to produce a number of composites hereinafter designated as ZEOPAC VP1, ZEOPAC 1, ZEOPAC 2, ZEOPAC 3 and ZEOPAC 4. WET STRENGTH

Tests were carried out to determine the wet strength of paper prepared from bleached spruce/pine wood pulp which had been deliberately contaminated by the additional of ground wood pulp filtrate (an anionic contaminant) at concentrations of 0, 2 and 4 μ mol/g of fibre. ZEOPAC VP1 was selected as the composite of the invention and was used at 0, 1 and 2 percent concentration. The wet strength agent was MARVESIN T35AS - a polyamide-amine- epichlorohydrin resin - at concentrations of 2, 4 and 6 percent. The test matrix were thus as follows in Table 1.1.

The resultant wet strength percentages are presented in Table 1.2.

These results are also illustrated graphically in Figures 1.1, 1.2 and 1.3.

The wet strength increased almost linearly with the increase in quantity of the wet strength agent, and the anionic contaminants, not surprisingly, diminish the effect of the wet strength agent. However, by the addition of ZEOPAC VP1, this reduction in wet strength can be curbed, and the composite of the invention is thus compensating for the disadvantageous effect of the contaminant present.

DRY CONTENT, pH and CATIONIC CHARGE

The dry content was determined after drying composites of the invention for three hours at 80°C at 1 atmosphere. The pH was measured immediately after production of a 4% ZEOPAC aqueous suspension and 30 minutes thereafter. The cationic charge was determined, by polyelectrolytetitration ( PET ) .

The appropriate parameters are given in Table 2.1.

The cationic surface charge in ascending order is ZEOPAC 4, ZEOPAC 1, ZEOPAC 2, ZEOPAC 3.

Sieve filtrates from paper production were analyzed for dissolved electrolytes with and without ZEOPAC 1 to ZEOPAC 4. The results of the PET and the conductivity measurements are presented in Table 2.2.

ZEOPAC 1, ZEOPAC 2 and ZEOPAC 3 have a similar effect on the decrease of titratable anions in the filtrates, with ZEOPAC 4 exhibiting a slightly weaker effect.

CONCENTRATION OF ZEOPAC

ZEOPAC 1 was selected to determine the influence of ZEOPAC dose rates. The results are presented in Table 3 and depicted in Figure 2.

GUMMING TESTS

A commercial gum (Keysize S30C) (7%) and aluminium sulphate (4%) were added to the aforementioned pulp and the effect of ZEOPAC 1 at 0,1 and 2% concentrations was determined. The results are presented in Table 4 and illustrated in Figures 3 and 4.

As the concentration of anionic contaminants increases, the performance of the sizing agent decreases. However, upon the addition of ZEOPAC 1, the performance of the sizing agent is restored as reflected in the better COBB values. It should be noted that these improvements are reflected not only on the sieve side but also on the upper side of the paper page. The chemical oxygen deficiency (CSB) also decreases upon the addition of ZEOPAC 1.

EFFECTIVE DOSE OF ZEOPAC 1 IN PRESENCE OF A FLOCKING AGENT

The effect on anionic charge when using ZEOPAC 1, with or without the presence of a flocking agent, was tested at 0, 0.8, 1.6 and 3.8% concentration of ZEOPAC 1. The results are presented in Table 5 and illustrated in Figure 5.

As can be seen, the anionic charge level is lower in the presence of ZEOPAC 1.

PLANT TRIAL 1 - PAPER PRODUCTION

The effect of composites of the present invention on the product of "fresh" paper from 100% "recycled" paper was determined. The results of introducing 1% ZEOPAC are presented in Table 6.

PLANT TRIAL 2 - PRODUCTION OF WATER-PROOF CREPE

Hygiene papers were prepared from 100% recycled paper. The effect of introducing 0.3% ZEOPAC in the process is presented in Table 7.

As ZEOPAC is introduced into the production, the quantity of wet strength agent required is reduced by approximately 20% but the wet breaking strength is maintained. There is also a significant financial saving on the cost of production. PLANT TRIAL 3 - PRODUCTION OF CARDBOARD CARTONS

The results are presented in Table 8. The introduction of ZEOPAC saw a reduction in gumming contaminants, a reduction in the amount of sizing agent required, but maintaining the COBB value. Once again, a significant cost saving in production was evident.

PLANT TRIAL 4 - NEWSPAPER PRINT

Similar to Plant Trial 3 described above, the effect of ZEOPAC in the production of newspaper print from 100% recycled paper was determined. The results are presented in Table 9.

The COBB value can be maintained at lower concentrations of sizing and gumming agents.

EXAMPLE 1

Table 10 presents the results whereby 10 or 15 kilograms of ZEOPAC were added per tonne of a fibrous suspension containing de-inked waste paper. The pulp concentration was 1% by weight. A 2% solution of cationic size was added at 70 kg per tonne of pulp, followed by a 10% solution of aluminium sulphate at 30 kg per tonne of pulp. Paper sheets of weight 75g/m^ were prepared. The effect of the size on the paper was determined by measuring its COBB value. The anionic charge of the paper suspension was determined by PET using a Streaming Current Detector (SCD).

EXAMPLE 2

Table 11 presents the results whereby 10 kilograms of ZEOPAC were added per tonne of a fibrous suspension containing de-inked waste paper. The pulp concentration was 1% by weight. A 1% solution of polyamide-polyamine- epichlorohydrin was added at 60kg per tonne of pulp. Sheets of paper of weight 75g/m² were prepared and their wet strength determined. The chemical oxygen demand of the white water was determined by the method of Dr Lange.

EXAMPLE 3

Table 12 presents the results whereby 2.5, 5, 10 or 15 kilograms of ZEOPAC were added per tonne to a fibre suspension pulp containing coated waste paper. The pulp concentration was 0.2% by weight. After 10 minutes mixing, the suspension was drained. The anionic charge of the white water was determined by PET with a SCD.

EXAMPLE 4

Table 13 presents the results of adding 10 kilograms of ZEOPAC or talcum per tonne of waste paper pulp (comprising 70% newspaper and 30% magazines). The concentration of the suspension was 15% by weight. After the addition, sodium hydroxide solution (50%) was added at 11kg per tonne, followed by sodium silicate at 20kg per tonne. A fatty acid (4kg per tonne) and hydrogen peroxide (12kg per tonne of a 15% solution) were then added. After 15 minutes mixing, the suspension was diluted to 1% and the suspension held in a de-inking flotation cell for 10 minutes at 35°C. Sheets of paper with a weight of 70g/m² were prepared from this de-inked material and tested for whiteness, ash content and presence of undesired flecks. The anionic charge of the white water was also determined by PET with a SCD. EXAMPLE 5

Figures 6 and 7 illustrate the significant effect ZEOPAC has on the anionic contaminant levels of ground wood pulp filtrate and "recycled" paper filtrate respectively, when compared to currently available zeolites 1,2, 3 and 4.

Table 1 . 1

(Test No)

Wet Strength Agent %

Anionic Contaminant 2 4 6

0 μmol/g fibre (1) (4) (7)

1 2 0

2 μmol/g fibre (2) (5) (8)

2 0 1

4 μmol/g fibre (3) (6) (9)

0 1 2

Table 1.2

Test No Wet Strength %

WS1 12.7

WS2 12.6

WS3 6.5

WS4 16.2

WS5 12.5

WS6 14.2

WS7 18.9

WS8 19.4

WS9 19.0

Table 2. 1

Test Dry pH Value Cationic Content % Charge

Immediate After 30 mmol/g min

ZEOPAC 1 97 4.2 4.2 1.76

ZEOPAC 2 97 4.0 3.9 2.19

ZEOPAC 3 96 3.8 3.8 2.49

ZEOPAC 4 98 4.2 4.1 0.47 Table 2. 2

Dose Anionic Charge Conductivity μ mol/g fibre mS/cm

0% 6.1 5.04

1% ZEOPAC 1 3.9 4.92

1% ZEOPAC 2 4.0 4.89

1% ZEOPAC 3 3.8 4.92

1% ZEOPAC 4 4.6 4.89

Table 3

Dose Anionic Charge (% ZEOPAC) μ mol/g fibre

0 6.1

0.5 5

1 3.9

2 3.1

Table 4

Cobb_βo, g/m² Anionic CSB Conduct¬ Charge ivity

% ZEOPAC 1 Cobb - Cobb - μ mol/g mg/1 mS/cm

Sieve Upper

Side Side

0 50 40 3.0 2240 4.40

1 43 32 2.1 2080 4.31

2 42 31 1.8 2000 4.31

Table 5

Table 6

Parameter Standard With 1% With 1% Production ZEOPAC ZEOPAC VP 1

Submitted : 100% recycled paper

Yield : Approximately 85% (Approx. 15% rejected)

PM Rate : 220 m min

Steam Pressure : 2.2 bar

Production in m² per 24 hrs : 725475

Production 23.577 24.666 26.117 Tonnes 24 hrs

Surface 32.5 34 36 Weight g/m²

Moisture % 6.5 6.0 5.0

Total 46.0 52.0 60.0 Retention %

Ash 27.0 31.5 40.0 Rentention %

Dry Content 37 41 43 Sludge %

Sludge Tonnes 5.0 3.1 2.3 24 hrs

CSB 1 mg It 3,050 2,600 2,400

Yield % 63.0 66.2 70.8

Due to the large surface area of the composites of the present invention, together with its cationic charge, anionic contaminants can be bound to the composite. With the high retention rate possible, the contaminants are removed to become incorporated into the paper product.

Further, due to the cationic charge, the composites of the invention are not simply loosely attached to the cellulose fibre of the paper, but a hydrogen bond is formed to the cellulose fibre. In effect, the composites which are thus used as a filler in paper production are firmly embedded in the fibre structure thereof thus significantly reducing dust formation.

The composites also exhibit a high bacteriostatic effect as the protein shell of any microorganism is dissolved on contact. Once again, the composites with its bacterial contaminants are incorporated into the final paper product.

As the composites and the contaminants function as a filler in the paper production, the quantity of additional fillers required is thus reduced with a concomitant reduction in the paper manufacturing costs.

Contaminants which affect the COBB value are also removed, and thus reduce the quantities of sizing agents required.

Thus, by using the present invention to remove contaminants, it achieves simultaneously a retention increase, an increase of the dry content of the paper prior to drying, the removal of solid substances from the water, the reduction of dissolved colloidal contaminants as well as a reduction in the number of microorganisms and other contaminants likely to be present in any waste water to be discharged from the manufacturing plant. In summary, the use of composites of the present invention is both ecologically and economically recommended as it leads to production increase, reduction of sludge generation, reduction of contaminant load, reduction in chemical oxygen deficiency and a cost saving.

It will be appreciated that the above examples are illustrative only of the present invention and that modification and alterations can be made thereto without departing from the inventive concept as defined in the following claims.

Claims

CLAIMS :

1. An agent for use in the removal of contaminants from water in the production of paper and related products, said agent comprising a compound of the general formula:

(ZO)_nAl_n(OH)_n__mCl_m

2. An agent as defined in Claim 1, wherein the material is a zeolite-containing mineral.

3. An agent as defined in Claim 2, wherein the zeolite content of the mineral is at least 40% by weight.

4. An agent as defined in Claim 2 or Claim 3, wherein the Si:Al ratio of the zeolite is greater than 3.

5. An agent as defined in Claim 4 wherein the quartz contact of the zeolite is not more than 5% by weight, preferably not more than 1%.

6. An agent as defined in Claim 5, wherein the zeolite is of a clinoptilolite structure.

7. An agent as defined in any one of Claims 1 to 6, wherein the coating polymer is an amide.

8. A method as defined in Claim 7, wherein the amide is a polyamide.

9. A method as defined in Claim 8, wherein the polyamide is polyacrylamide.

10. A method for the preparation of a compound of the general formula:

(Z0)_nAl_n(0H)_n__mCl_m

or a compound of closely related empirical formula, wherein z is derived from an aluminosilicate material, said method comprising:

1) activating said material; and

2) heating the thus activated material in the presence of a cationic agent; and

3) optionally, coating the resultant product with a polymer.

11. A method as defined in Claim 10, wherein the mineral is activated by treating with acid or by subjecting the mineral to ammonium ion exchange.

12. A method as defined in Claim 11, wherein the mineral is activated by treatment with hydrochloric acid.

13. A method as defined in any one of Claims 10 to 12, wherein the cationic agent is selected from an alumino compound, epichlorohydrin or a derivative thereof, or dicyanodiamide.

14. A method as defined in Claim 13, wherein the alumino compound is a polyaluminium salt.

15. A method as defined in Claim 14, wherein the polyaluminium salt is polyaluminiumchloride.

16. A method as defined in any one of Claims 13 to 15, wherein the ratio of mineral:alumino compound is in the range of 1:1 to 1:2 by weight.

17. A method as defined in Claim 16, wherein the ratio is 1:1.

18. A method as defined in any one of Claims 13 to 17, wherein the activated mineral and the alumino compound are heated together at a temperature which is in the range of 100 to 600°C.

19. A method as defined in Claim 18, wherein the temperature is 300°C.

20. A method as defined in Claim 13, wherein the epichlorohydrin derivative is a polymer of epichlorohydrin.

21. A method as defined in Claim 20, wherein the polymer is further mixed with an acid.

22. A method as defined in Claim 21, wherein the acid is melamine acid.

23. An agent as defined in any one of Claims 1 to 9, when prepared by a method as defined in any one of Claims 10 to 23.

24. A method of removing contaminants from water used in the production of paper and related products, said method comprising treating the water with a compound of the general formula:

(ZO)_nAl_n(OH)_n__mCl_m

or a component of closely related empirical formula, with, optionally, has been further coated with a polymer, wherein Z is derived from an aluminosilicate material.

25. Paper or related product having incorporated therein an agent as defined in any one of Claims 1 to 9.

26. Paper or related product having incorporated therein an agent as defined in any one of Claims 1 to 9, together with contaminants removed by said agent.