WO2002036497A1 - Method of treating aqueous compositions - Google Patents
Method of treating aqueous compositions Download PDFInfo
- Publication number
- WO2002036497A1 WO2002036497A1 PCT/GB2001/004613 GB0104613W WO0236497A1 WO 2002036497 A1 WO2002036497 A1 WO 2002036497A1 GB 0104613 W GB0104613 W GB 0104613W WO 0236497 A1 WO0236497 A1 WO 0236497A1
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- WIPO (PCT)
- Prior art keywords
- aqueous composition
- hydrotalcite
- smectite clay
- clay
- reaction mixture
- Prior art date
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
- B01J20/08—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04 comprising aluminium oxide or hydroxide; comprising bauxite
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
- B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
- B01J20/10—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising silica or silicate
- B01J20/12—Naturally occurring clays or bleaching earth
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
- C02F1/281—Treatment of water, waste water, or sewage by sorption using inorganic sorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2220/00—Aspects relating to sorbent materials
- B01J2220/40—Aspects relating to the composition of sorbent or filter aid materials
- B01J2220/42—Materials comprising a mixture of inorganic materials
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/28—Treatment of water, waste water, or sewage by sorption
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/30—Organic compounds
- C02F2101/36—Organic compounds containing halogen
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/22—Nature of the water, waste water, sewage or sludge to be treated from the processing of animals, e.g. poultry, fish, or parts thereof
- C02F2103/24—Nature of the water, waste water, sewage or sludge to be treated from the processing of animals, e.g. poultry, fish, or parts thereof from tanneries
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
- C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/30—Nature of the water, waste water, sewage or sludge to be treated from the textile industry
Definitions
- This invention relates to a method of treating aqueous compositions and, in particular, to a method in which a combination of a smectite clay and a hydrotalcite-like material is used to treat the aqueous composition.
- European Patent Application EP 0 531 432 discloses a process in which reactive dyes are removed from an aqueous wash medium using an absorbent, which is preferably a hydrotalcite-like material.
- PCT Application WO 92/11932 discloses composite materials which are intended for use as absorbents and comprise a hydrotalcite-like material deposited on a matrix. This matrix may be a clay material.
- European Patent Application 0 541 358 proposes the use of hydrotalcite-like materials for the removal of organo-toxins from water. A method for treating a liquid medium to remove contaminants is described in European Patent Application EP 0 566 260.
- the sorbing agent used to treat the liquid is a freshly-prepared or at least partly undried hydrotalcite- like material or a reaction mixture capable of forming in situ a hydrotalcite-like material.
- a process for removing residual dyes from effluents is disclosed in PCT Application WO 95/17350.
- the pH of the effluent to be treated is firstly adjusted to between 4 and 5.5, a hydrotalcite-like material is added and the pH of the effluent is raised to above 7.
- aqueous compositions which is more effective than those known until now. It is desirable to improve the known treatment methods.
- a desirable treatment is one which is at least as effective in removing contaminants, such as colours, as conventional methods using hydrotalcite-like materials are, but which also produces a treated aqueous composition with a lower Chemical Oxygen Demand (COD) than has previously been possible with conventional methods using such material.
- COD Chemical Oxygen Demand
- a method of treating an aqueous composition comprises mixing said aqueous composition with a smectite clay at a pH below 9 and with a hydrotalcite-like material or a reaction mixture capable of forming a hydrotalcite-like material and subsequently separating the treated aqueous composition from solid materials therein.
- a smectite clay and a reaction mixture capable of forming a hydrotalcite-like material are mixed with the aqueous composition at a pH below 9, the pH of the mixture is raised to a value above 10 and the solid material present in the treated aqueous composition is separated from the liquid material therein.
- hydrotalcite-like material is meant material having the formula M k+m N n+P (OH) 2 A/ ' . xH 2 O where
- M is any 1 + or 2+ cation or combination thereof
- N is any 3+ or 4+ cation or combination thereof
- k is the sum of the individual mole fractions of the 1+ cations
- m is the sum of the individual mole fractions of the 2+ cations
- n is the sum of the individual mole fractions of the 3+ cations
- p is the sum of the individual mole fractions of the 4+ cations, either, but not both, of k and m or n and p can be zero
- k + m + n + p 1
- Examples of the cations M in the above formula are Li + , Mg 2+ , Zn 2+ , Fe 2+ , Cu 2+ , Sn 2+ , Ca 2+ and Sr 2+ .
- Suitable N cations include Al 3+ , Fe 3+ , Ti 4+ and Sn 4+ .
- Preferred divalent cations are Zn 2+ , Cu 2+ or g 2+ or a combination of these ions or a combination with other divalent cations.
- the anion A y" may be an inorganic or organic anion.
- Preferred inorganic anions A y" are Cl " , N0 3 " , S0 4 2" , C0 3 2" and OH ' .
- Examples of organic anions are carboxylate ions such as citrate and stearate.
- hydrotalcite-like materials has a molar ratio of magnesium : aluminium of from 3 : 1 to 8 : 1 and contains C0 3 2" anions.
- hydrotalcite-like materials useful in the method of this invention are:
- the smectite clay can be any suitable clay having the smectite structure.
- Particularly suitable clays include montmorillonite and hectorite clays.
- montmorillonite and hectorite clays One class of naturally-occurring montmorillonite clays is known as the bentonite clays and these have been found to be especially suitable for use in this invention.
- Different forms of bentonite clays are known in which the inherent negative charge of the clay matrix is balanced by different cations.
- the naturally-occurring forms wherein the cation is predominantly either sodium or calcium (hereinafter called sodium-form and calcium-form respectively) are suitable, as is the material produced by treating calcium-form bentonite with a compound of sodium.
- bentonite clay Surprisingly, an acid activated form of bentonite clay has also been found to be suitable.
- a preferred bentonite clay is calcium-form bentonite clay which has been treated with sodium carbonate and which is sold under the trade name "Brebent" by Laporte pic.
- a polymeric flocculant is also mixed with the aqueous composition.
- a polymeric flocculant is used, the rate at which solid material settles from the treated composition is increased and the volume of the settled floe is substantially reduced in comparison with conventional treatment with hydrotalcite-like materials.
- Polymeric flocculants include nonionic polymeric flocculants and anionic or cationic polyelectrolytes.
- Preferred polymeric flocculants are acrylic polymers, particularly nonionic, anionic or cationic polyacrylamides such as those sold under the trade names Magnafloc 1011 , Zetag 7652 and Magnafloc 351 , by Ciba Specialty Chemicals.
- an aqueous composition is treated initially at a pH below 9 by mixing with a smectite clay.
- the pH of the aqueous composition is in the range 4 to 9, and, more preferably, in the range 5 to 8.
- appropriate adjustment can be made by addition of acid or alkali.
- the amount of smectite clay used will depend, to some extent, on the amount of contaminant which is to be removed from the aqueous composition by the treatment.
- a concentration of smectite clay greater than 0.25 g per litre of aqueous composition will generally be necessary. Since the smectite clay needs to be removed when the aqueous composition has been treated, it is usually not efficient to use more than about 1 g smectite clay per litre of aqueous composition. Frequently, the amount of smectite clay will not exceed 0.5 g per litre of aqueous composition. However, the nature and amount of any contaminant to be removed from the aqueous composition may necessitate the use of amounts of smectite clay outside these limits.
- the amount of smectite clay will be from 0.1 g per litre to 1.0 g per litre of aqueous composition when the initial COD of the composition is in the range 200 to 2000 mg oxygen per litre.
- an appropriate adjustment in the amount of smectite clay used can easily be calculated by a person skilled in the art.
- a slurry of the smectite clay in water before the smectite clay is mixed with the aqueous composition This aids in swelling the smectite clay.
- the slurry contains from 1 to 5 per cent by weight of smectite clay.
- the slurry is left to stand with stirring for a period of 30 to 180 minutes, during which time the smectite clay swells, before the slurry is mixed with the aqueous composition.
- a reaction mixture capable of forming a hydrotalcite-like material is also mixed with the aqueous composition in the preferred method of the invention.
- This reaction mixture may be added at the same time as the smectite clay or at a later stage.
- the components of the reaction mixture may be admixed prior to their addition to the aqueous composition but, if so, it is preferable to admix the components immediately before addition, for example by admixing and immediately adding the reaction mixture to the aqueous composition.
- the components of the reaction mixture can be added to the aqueous composition at the same time as the smectite clay.
- a dry mix of smectite clay and solid reaction mixture components may be added to the aqueous composition.
- the smectite clay and reaction mixture when the smectite clay and reaction mixture are added to the aqueous composition together, the smectite clay is preferably slurried with water, as described hereinbefore and the reaction mixture is added to the slurry after the smectite day has been allowed to swell.
- the pH of this slurry of swelled smectite clay and reaction mixture is adjusted to a pH value at which the hydrotalcite-like material is formed before the mixture is added to the aqueous composition.
- a further aspect of this invention is a composition comprising a solid particulate mixture of a smectite clay and a reaction mixture capable of forming a hydrotalcite-like material.
- this composition will comprise smectite clay and reaction mixture in a ratio of from 2 to 20 parts, preferably from 4 to 15 parts, of smectite clay by weight to one part by weight total metals (sum of N and M as defined in the formula given hereinbefore).
- the smectite clay is a bentonite clay.
- this slurry may contain from 1 to 15 per cent by weight smectite clay.
- Preferred reaction mixture components include soluble organic salts, nitrates, chlorides, and sulphates of the metals designated M or N in the above description of hydrotalcite- like materials.
- the hydrotalcite-like material When the hydrotalcite-like material is formed in situ, it is preferable to ensure that it is not formed in the initial treatment step of the method. This is generally achieved by maintaining a pH value for the aqueous composition below that at which the hydrotalcite- like material is formed.
- the appropriate pH value will depend on the reaction mixture components, but a pH below 9 frequently provides appropriate conditions.
- the contaminants in the aqueous composition are allowed to interact with the smectite clay before generation of the hydrotalcite-like material is induced, i.e., the pH of the aqueous composition is maintained, for a period, at a value where hydrotalcite-like materials are not produced or addition of the reaction components is delayed until the smectite clay has been allowed to interact with the aqueous composition.
- the smectite clay is allowed to interact with the contaminants for at least 5 minutes before generation of the hydrotalcite-like material is induced. There is no preferred upper limit on this time allowed for interaction but there is generally no perceived benefit for interaction times longer than 20 minutes and a time of not more than 10 minutes is frequently suitable.
- smectite clay and preformed hydrotalcite-like material are separately added to the aqueous composition, the mixture of smectite clay and aqueous composition being allowed to interact for a period of time before the hydrotalcite-like material is added.
- the amount of hydrotalcite-like material or reaction mixture capable of forming hydrotalcite-like material depends upon the amount of contaminant in the aqueous composition. Typically, the amount added is at least 30 mg of total metals (M and N in the formula given hereinbefore) used to form the hydrotalcite-like materials per litre of aqueous composition. Frequently, at least 45 mg of total metals per litre of aqueous composition is used and, often, little benefit is obtained from more than 100 mg of total metals per litre of aqueous composition. Normally, the actual amount will be adjusted to suit the amount of contaminant present in the aqueous composition.
- the amount of total metals (N + M) used is in the range 30 mg to 60 mg per litre of aqueous composition where the initial COD of the aqueous composition is in the range 200 to 2000 mg oxygen per litre.
- the amount of total metals used can easily be calculated by a person skilled in the art.
- the smectite clay is allowed to interact with the aqueous composition before generation of the hydrotalcite-like material.
- an appropriate method of generating the hydrotalcite-like material is to adjust the pH of the aqueous composition to an alkaline pH. The pH necessary to form the hydrotalcite-like material depends upon the reaction mixture, particularly the specific metals used.
- a Zn/AI hydrotalcite-like material is to be generated, formation can be induced at a pH of 7 or above, whereas a Mg/AI hydrotalcite-like material is more efficiently precipitated at a pH above 9, even more efficiently above 10 and a convenient operating pH for good flocculation is above 11.
- the reaction mixture is added at the same time as the smectite clay and the clay is allowed a period to interact with the aqueous composition, then it is necessary to ensure that the pH of the aqueous composition during this period is below the value at which the chosen hydrotalcite-like material is precipitated.
- the relative amounts of the metal compounds used in the reaction mixture are chosen according to the desired composition of the hydrotalcite-like material which is selected for use in any specific method, the ratio being controlled according to the possible ratios of metals in the formula for hydrotalcite-like materials given hereinbefore.
- Metal cation M is generally present in greater amounts than the metal of higher valency, N.
- Ratios of M : N preferably vary from 2 :1 to 10 : 1 , and a particularly preferred range of hydrotalcite-like materials for treating effluents is where M is magnesium and N is aluminium, and where the molar ratio of magnesium : aluminium ranges from 3 : 1 to 8 : 1 , with an especially preferred magnesium : aluminium ratio in the range 4 : 1 to 6 : 1.
- a polymeric flocculant When a polymeric flocculant is used in the process of the invention, it is preferably added after the pH of the aqueous composition has been adjusted to above 10, preferably above 11. Addition at this point has been found to result in a particularly rapid settlement of the solids and to lead to a densely packed precipitate.
- the amount of polymeric flocculant used is generally in the range from 1 mg to 8 mg per litre for aqueous compositions where the initial COD of the aqueous composition is in the range 200 to 2000 mg oxygen per litre. For initial COD values outside these, an appropriate adjustment in the amount of polymeric flocculant used can easily be calculated by a person skilled in the art.
- the method of the invention can be carried out at any convenient temperature but higher temperatures tend to lead to a more effective lowering of the COD of the aqueous composition.
- the aqueous composition is at a temperature above 40° C, but, generally, not above 60° C, at least when it is mixed with the smectite clay.
- the method of the invention can be used to treat a variety of aqueous compositions such as potable water and influent or effluent water from an industrial plant, for example in the textile, paper, leather and food and drink (e.g. brewing) industries.
- aqueous compositions such as potable water and influent or effluent water from an industrial plant, for example in the textile, paper, leather and food and drink (e.g. brewing) industries.
- aqueous compositions can be treated by methods embodying the invention.
- Effluents i) Dyestuffs/colorants: mainly in the textile industry but also printing inks, paper industry, leather industry and in the colour-producing industry etc.
- Mothproofing agents applied to woollen carpet yarn to protect finished carpets, iii) Pesticides in raw wool scouring liquors; sheep dip pesticides are washed out of wool during scouring and are discharged to sewers and ultimately rivers.
- AOX Absorbable organo halogens
- Potable Water i) Removal of humic substances, and other natural organic matter (NOM). ii) Removal of Pesticides/herbicides. iii) Removal of phosphate and/or nitrate.
- Methods for embodying the invention can also find use in allowing sorption of desired materials from aqueous compositions containing them.
- reaction mixture capable of forming a hydrotalcite-like material in situ is particularly preferred for the removal of dyestuffs and organotoxins.
- the method of the invention may be operated batchwise or as a continuous process.
- the method of the invention is capable of reducing the COD of an aqueous effluent to a level which is considered desirable according to current standards for discharge to the environment but has generally not been achievable using conventional methods employing hydrotalcite-like materials.
- the method is also capable of removing sufficient colour and COD to allow the treated water to be re-used.
- the precipitates or flocs formed using the method generally settle quickly and have a relatively low volume. The benefits of rapid settling and small floe volume are particularly apparent when a polymeric flocculant is used in the method.
- the effluent was at 40° C, the COD was 731 mg oxygen per litre and the absorbance in a 2.5 cm cell at the wavelength of maximum absorbance was 0.96. Subsequent absorbance measurements on treated effluent were carried out at the same wavelength.
- Suspension A 2.48 g of Suspension A was added to 500 mis of the effluent and the pH adjusted to 8 by the addition of dilute sulphuric acid. The mixture was stirred for 20 minutes after which time the pH was then taken to 11.2 by the addition of sodium hydroxide. Stirring was continued for 5 minutes and 4 ppm polymeric flocculant (Magnafloc 1011 ) added. A dense floe was produced and removed by gravity settlement. The supernatant liquid was filtered through a 0.45 ⁇ m filter prior to the measurement of absorbance and COD. This was called Treatment A.
- Treatment A Using the treatment technique described in Example 1 as Treatment A, several treatments were carried out at different dosages (expressed as g per 500 ml of effluent) of Suspension A in an effluent from a similar dyeing factory. The results are shown in Table 2 below.
- Suspension H an exact repeat preparation of Suspension A was carried out, in this case referred to as Suspension H.
- 2.48 g of Suspension H was added to 500 mis of the effluent and the pH adjusted to 8 by the addition of dilute sulphuric acid. The mixture was stirred for 20 minutes after which time the pH was taken to 11.2 by the addition of sodium hydroxide. Stirring was continued for 5 minutes and 4 ppm polymeric flocculant (Magnafloc 1011) added. A further 2 minutes stirring were allowed. A dense floe was produced and allowed to settle. The majority of the clear supernatant liquid was decanted off into a clean glass beaker whilst the remaining liquid and sludge were transferred to a glass, 250 cm 3 measuring cylinder.
- the sludge was allowed to settle for 30 minutes before the volume of sludge was recorded.
- the sludge volume will be referred to below as y and is in cm 3 .
- the entire contents of the measuring cylinder and beaker of retained supernatant liquid were filtered through a pre-dried and weighed filter paper using a standard Buchner apparatus. Any residual solids on the glassware were rinsed off and through the filter.
- the filter cake formed was washed with 2 sequential 10 ml aliquots of boiling deionised water to wash out any soluble impurities.
- the cake sample and filter paper were then dried until a constant weight was achieved prior to re- weighing. With the filter paper weight already known, the weight of dry solids was readily calculable.
- the weight of solids will be referred to below as z and is in grams. This was called Treatment H.
- Suspension J 12.5 g of Suspension J were then added to 500 ml of effluent followed by a subsequent addition of 1.0 g of Suspension I.
- the scheme of Treatment H was followed. This to be called Treatment J.
- Treatment J Repeat procedures for Treatments H to J were carried out on plain water (uncontaminated) for comparison purposes. Samples from all six treatments were then characterised in terms of % dry solids in the sludge using the techniques described above. The dry solids concentration of the sludge was calculated by dividing z by y and multiplying by 100 and these figures are given in Table 3 below.
- Example 1 Using the treatment technique described in Example 1 as Treatment A, several treatments were carried out using different polymeric flocculants in the final part of the treatment (all at a dosage rate of 4 ppm on weight of effluent) on the effluent used in Example 1. Results are given in Table 4 below.
- Treatment A was carried out using a variety of different clays and compared with Treatment C on the same effluent. Results are given in Table 5 below.
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Abstract
A method of treating an aqueous composition comprises mixing said aqueous composition with a smectite clay at a pH below (9) and awith a hydrotalcite-like material or a reaction mixture capable of forming a hydrotalcite-like material and subsequently separating the treated aqueous composition from solid materials therein. Preferably, a polymeric flocculant is also added to the aqueous composition, especially after the pH of the aqueous composition has been adjusted to a value above (11).
Description
METHOD OF TREATING AQUEOUS COMPOSITIONS
This invention relates to a method of treating aqueous compositions and, in particular, to a method in which a combination of a smectite clay and a hydrotalcite-like material is used to treat the aqueous composition.
The use of hydrotalcite-like materials for sorption of contaminants in aqueous compositions is known. European Patent Application EP 0 531 432 discloses a process in which reactive dyes are removed from an aqueous wash medium using an absorbent, which is preferably a hydrotalcite-like material. PCT Application WO 92/11932 discloses composite materials which are intended for use as absorbents and comprise a hydrotalcite-like material deposited on a matrix. This matrix may be a clay material. European Patent Application 0 541 358 proposes the use of hydrotalcite-like materials for the removal of organo-toxins from water. A method for treating a liquid medium to remove contaminants is described in European Patent Application EP 0 566 260. The sorbing agent used to treat the liquid is a freshly-prepared or at least partly undried hydrotalcite- like material or a reaction mixture capable of forming in situ a hydrotalcite-like material. A process for removing residual dyes from effluents is disclosed in PCT Application WO 95/17350. The pH of the effluent to be treated is firstly adjusted to between 4 and 5.5, a hydrotalcite-like material is added and the pH of the effluent is raised to above 7.
Despite these useful processes for treating aqueous compositions, there exists a need for a method of treatment of aqueous compositions which is more effective than those known until now. It is desirable to improve the known treatment methods. In particular a desirable treatment is one which is at least as effective in removing contaminants, such as colours, as conventional methods using hydrotalcite-like materials are, but which also produces a treated aqueous composition with a lower Chemical Oxygen Demand (COD) than has previously been possible with conventional methods using such material.
It has now been surprisingly found that the use of a combination of a particular clay and hydrotalcite-like material leads to a treated aqueous composition with a lower COD than has been achieved conventionally with hydrotalcite-like materials.
Consequently, according to the invention, a method of treating an aqueous composition comprises mixing said aqueous composition with a smectite clay at a pH below 9 and with a hydrotalcite-like material or a reaction mixture capable of forming a hydrotalcite-like material and subsequently separating the treated aqueous composition from solid materials therein.
In a particularly preferred process according to the invention, a smectite clay and a reaction mixture capable of forming a hydrotalcite-like material are mixed with the aqueous composition at a pH below 9, the pH of the mixture is raised to a value above 10 and the solid material present in the treated aqueous composition is separated from the liquid material therein.
An essential component of the method according to the invention is a hydrotalcite-like material or a reaction mixture capable of forming a hydrotalcite-like material. By hydrotalcite-like material is meant material having the formula Mk+m Nn+P (OH)2 A/'. xH2O where
M is any 1 + or 2+ cation or combination thereof,
N is any 3+ or 4+ cation or combination thereof, k is the sum of the individual mole fractions of the 1+ cations, m is the sum of the individual mole fractions of the 2+ cations, n is the sum of the individual mole fractions of the 3+ cations, p is the sum of the individual mole fractions of the 4+ cations, either, but not both, of k and m or n and p can be zero, k + m + n + p = 1 , Az y" is any ion of charge y" and mole fraction z, or a combination of anions of similar or differing y", k + 2m + 3n + 4p - 2 - zy = 0, and x can range from 1 to 100.
Examples of the cations M in the above formula are Li+, Mg2+, Zn2+, Fe2+, Cu2+, Sn2+, Ca2+ and Sr2+. Suitable N cations include Al3+, Fe3+, Ti4+ and Sn4+. Preferred divalent cations are Zn2+, Cu2+ or g2+ or a combination of these ions or a combination with other divalent cations. The anion Ay" may be an inorganic or organic anion. Preferred inorganic anions Ay" are Cl", N03 ", S04 2", C03 2" and OH'. Examples of organic anions are carboxylate ions such as citrate and stearate.
An especially preferred range of hydrotalcite-like materials has a molar ratio of magnesium : aluminium of from 3 : 1 to 8 : 1 and contains C03 2" anions. Examples of hydrotalcite-like materials useful in the method of this invention are:
Mg6 AI2 (OH)16 (C03). xH20 Zn16 AI2(OH)36 (CI)2. xH20
Mg6AI2 (OH)16 (N03)2. xH20
Cu16AI2 (OH)36 (CI)2. xH20
This formula includes hydrotalcite itself, of the formula: Mg6AI2 (OH)16 (C03). 4H20
Preparation of hydrotalcite-like compounds is known and has been described in a number of publications including papers by Walter T Reichle in Solid State Ionics, 22 (1986), pages 135-141 , entitled "Synthesis of Anionic Clay Minerals (Mixed Metal Hydroxides, Hydrotalcite)" and Chemtech (January 1986) pages 58 to 63, entitled "Anionic Clay Minerals".
The smectite clay can be any suitable clay having the smectite structure. Particularly suitable clays include montmorillonite and hectorite clays. One class of naturally-occurring montmorillonite clays is known as the bentonite clays and these have been found to be especially suitable for use in this invention. Different forms of bentonite clays are known in which the inherent negative charge of the clay matrix is balanced by different cations. The naturally-occurring forms wherein the cation is predominantly either sodium or calcium (hereinafter called sodium-form and calcium-form respectively) are suitable, as is the material produced by treating calcium-form bentonite with a compound of sodium. Surprisingly, an acid activated form of bentonite clay has also been found to be suitable. A preferred bentonite clay is calcium-form bentonite clay which has been treated with sodium carbonate and which is sold under the trade name "Brebent" by Laporte pic.
In a particularly preferred process, a polymeric flocculant is also mixed with the aqueous composition. When a polymeric flocculant is used, the rate at which solid material settles from the treated composition is increased and the volume of the settled floe is substantially reduced in comparison with conventional treatment with hydrotalcite-like materials. Polymeric flocculants include nonionic polymeric flocculants and anionic or cationic polyelectrolytes. Preferred polymeric flocculants are acrylic polymers, particularly nonionic, anionic or cationic polyacrylamides such as those sold under the trade names Magnafloc 1011 , Zetag 7652 and Magnafloc 351 , by Ciba Specialty Chemicals.
In the method according to the invention, an aqueous composition is treated initially at a pH below 9 by mixing with a smectite clay. Preferably, the pH of the aqueous composition is in the range 4 to 9, and, more preferably, in the range 5 to 8. Where the aqueous composition to be treated has a pH value outside the range chosen for initial treatment, appropriate adjustment can be made by addition of acid or alkali. The amount of smectite clay used will depend, to some extent, on the amount of contaminant which is to be removed from the aqueous composition by the treatment. However, for typical aqueous compositions for which the method of the invention is applicable, a concentration of
smectite clay greater than 0.25 g per litre of aqueous composition will generally be necessary. Since the smectite clay needs to be removed when the aqueous composition has been treated, it is usually not efficient to use more than about 1 g smectite clay per litre of aqueous composition. Frequently, the amount of smectite clay will not exceed 0.5 g per litre of aqueous composition. However, the nature and amount of any contaminant to be removed from the aqueous composition may necessitate the use of amounts of smectite clay outside these limits. Generally the amount of smectite clay will be from 0.1 g per litre to 1.0 g per litre of aqueous composition when the initial COD of the composition is in the range 200 to 2000 mg oxygen per litre. For initial COD values outside these, an appropriate adjustment in the amount of smectite clay used can easily be calculated by a person skilled in the art.
it is preferable to produce a slurry of the smectite clay in water before the smectite clay is mixed with the aqueous composition. This aids in swelling the smectite clay. Typically, the slurry contains from 1 to 5 per cent by weight of smectite clay. Generally, the slurry is left to stand with stirring for a period of 30 to 180 minutes, during which time the smectite clay swells, before the slurry is mixed with the aqueous composition.
A reaction mixture capable of forming a hydrotalcite-like material is also mixed with the aqueous composition in the preferred method of the invention. This reaction mixture may be added at the same time as the smectite clay or at a later stage. When the components of the reaction mixture are added separately from the smectite clay, they may be admixed prior to their addition to the aqueous composition but, if so, it is preferable to admix the components immediately before addition, for example by admixing and immediately adding the reaction mixture to the aqueous composition. Alternatively, the components of the reaction mixture can be added to the aqueous composition at the same time as the smectite clay. For example, a dry mix of smectite clay and solid reaction mixture components may be added to the aqueous composition. In a further alternative method, when the smectite clay and reaction mixture are added to the aqueous composition together, the smectite clay is preferably slurried with water, as described hereinbefore and the reaction mixture is added to the slurry after the smectite day has been allowed to swell. In some treatment processes, such as the treatment of potable water, the pH of this slurry of swelled smectite clay and reaction mixture is adjusted to a pH value at which the hydrotalcite-like material is formed before the mixture is added to the aqueous composition. This method avoids the need to adjust the pH value of the aqueous composition where such adjustment is undesirable.
The use of a solid mixture of smectite clay and reaction mixture capable of forming a hydrotalcite-like material, which is added to the aqueous composition to be treated either as a dry powder or, preferably, in the form of a slurry, is a particularly desirable way to carry out the method of the invention. Consequently, a further aspect of this invention is a composition comprising a solid particulate mixture of a smectite clay and a reaction mixture capable of forming a hydrotalcite-like material. Normally this composition will comprise smectite clay and reaction mixture in a ratio of from 2 to 20 parts, preferably from 4 to 15 parts, of smectite clay by weight to one part by weight total metals (sum of N and M as defined in the formula given hereinbefore). In a preferred form of this solid mixture, the smectite clay is a bentonite clay. When this solid mixture is prepared as a slurry before addition to the aqueous composition, this slurry may contain from 1 to 15 per cent by weight smectite clay.
Preferred reaction mixture components include soluble organic salts, nitrates, chlorides, and sulphates of the metals designated M or N in the above description of hydrotalcite- like materials.
When the hydrotalcite-like material is formed in situ, it is preferable to ensure that it is not formed in the initial treatment step of the method. This is generally achieved by maintaining a pH value for the aqueous composition below that at which the hydrotalcite- like material is formed. The appropriate pH value will depend on the reaction mixture components, but a pH below 9 frequently provides appropriate conditions. Preferably, the contaminants in the aqueous composition are allowed to interact with the smectite clay before generation of the hydrotalcite-like material is induced, i.e., the pH of the aqueous composition is maintained, for a period, at a value where hydrotalcite-like materials are not produced or addition of the reaction components is delayed until the smectite clay has been allowed to interact with the aqueous composition. Preferably, the smectite clay is allowed to interact with the contaminants for at least 5 minutes before generation of the hydrotalcite-like material is induced. There is no preferred upper limit on this time allowed for interaction but there is generally no perceived benefit for interaction times longer than 20 minutes and a time of not more than 10 minutes is frequently suitable. Alternatively, smectite clay and preformed hydrotalcite-like material are separately added to the aqueous composition, the mixture of smectite clay and aqueous composition being allowed to interact for a period of time before the hydrotalcite-like material is added.
The amount of hydrotalcite-like material or reaction mixture capable of forming hydrotalcite-like material depends upon the amount of contaminant in the aqueous composition. Typically, the amount added is at least 30 mg of total metals (M and N in the
formula given hereinbefore) used to form the hydrotalcite-like materials per litre of aqueous composition. Frequently, at least 45 mg of total metals per litre of aqueous composition is used and, often, little benefit is obtained from more than 100 mg of total metals per litre of aqueous composition. Normally, the actual amount will be adjusted to suit the amount of contaminant present in the aqueous composition. Preferably, the amount of total metals (N + M) used is in the range 30 mg to 60 mg per litre of aqueous composition where the initial COD of the aqueous composition is in the range 200 to 2000 mg oxygen per litre. For initial COD values outside these, an appropriate adjustment in the amount of total metals used can easily be calculated by a person skilled in the art.
In the preferred method according to the invention, the smectite clay is allowed to interact with the aqueous composition before generation of the hydrotalcite-like material. Where the reaction mixture capable of forming a hydrotalcite-like material is mixed with the aqueous composition at the same time or approximately the same time as the smectite clay, then an appropriate method of generating the hydrotalcite-like material is to adjust the pH of the aqueous composition to an alkaline pH. The pH necessary to form the hydrotalcite-like material depends upon the reaction mixture, particularly the specific metals used. For example, if a Zn/AI hydrotalcite-like material is to be generated, formation can be induced at a pH of 7 or above, whereas a Mg/AI hydrotalcite-like material is more efficiently precipitated at a pH above 9, even more efficiently above 10 and a convenient operating pH for good flocculation is above 11. Where the reaction mixture is added at the same time as the smectite clay and the clay is allowed a period to interact with the aqueous composition, then it is necessary to ensure that the pH of the aqueous composition during this period is below the value at which the chosen hydrotalcite-like material is precipitated.
The relative amounts of the metal compounds used in the reaction mixture are chosen according to the desired composition of the hydrotalcite-like material which is selected for use in any specific method, the ratio being controlled according to the possible ratios of metals in the formula for hydrotalcite-like materials given hereinbefore. Metal cation M is generally present in greater amounts than the metal of higher valency, N. Ratios of M : N preferably vary from 2 :1 to 10 : 1 , and a particularly preferred range of hydrotalcite-like materials for treating effluents is where M is magnesium and N is aluminium, and where the molar ratio of magnesium : aluminium ranges from 3 : 1 to 8 : 1 , with an especially preferred magnesium : aluminium ratio in the range 4 : 1 to 6 : 1.
When a polymeric flocculant is used in the process of the invention, it is preferably added after the pH of the aqueous composition has been adjusted to above 10, preferably
above 11. Addition at this point has been found to result in a particularly rapid settlement of the solids and to lead to a densely packed precipitate. The amount of polymeric flocculant used is generally in the range from 1 mg to 8 mg per litre for aqueous compositions where the initial COD of the aqueous composition is in the range 200 to 2000 mg oxygen per litre. For initial COD values outside these, an appropriate adjustment in the amount of polymeric flocculant used can easily be calculated by a person skilled in the art.
It is necessary to separate the treated aqueous composition from the derived floe and this may be accomplished by any of a variety of solid-liquid separation techniques such as centrifugation, settlement (a preferred example of which is a lamellar plate separator), use of hydro-cyclone, filtration (e.g. band, belt, bag, filter press, candle or cross-flow membrane filtration) or dissolved air flotation.
The method of the invention can be carried out at any convenient temperature but higher temperatures tend to lead to a more effective lowering of the COD of the aqueous composition. Preferably, the aqueous composition is at a temperature above 40° C, but, generally, not above 60° C, at least when it is mixed with the smectite clay.
The method of the invention can be used to treat a variety of aqueous compositions such as potable water and influent or effluent water from an industrial plant, for example in the textile, paper, leather and food and drink (e.g. brewing) industries.
For example it will allow removal of dyestuff materials and organic materials contributing to COD from waste water, allowing the water to be re-used in a dyeing factory, as well as allowing removal of humic materials from influent water.
In particular, the following aqueous compositions can be treated by methods embodying the invention. Effluents i) Dyestuffs/colorants: mainly in the textile industry but also printing inks, paper industry, leather industry and in the colour-producing industry etc. ii) Mothproofing agents applied to woollen carpet yarn to protect finished carpets, iii) Pesticides in raw wool scouring liquors; sheep dip pesticides are washed out of wool during scouring and are discharged to sewers and ultimately rivers. iv) Absorbable organo halogens (AOX); products of chlorination of wool to produce machine washable wool and also found if cotton or wood pulp is bleached with hypochlorite.
Removal of above is often by "end-of-pipe" treatment in batchwise or continuous water treatment equipment.
Influents/Potable Water
Influent:
Removal of humic substances for textile and papermaking processes and in the food and drink industry but also pre-treatment of water prior to ultrafil -ration or reverse osmosis in the pharmaceutical and electronics industries.
Potable Water: i) Removal of humic substances, and other natural organic matter (NOM). ii) Removal of Pesticides/herbicides. iii) Removal of phosphate and/or nitrate.
Methods for embodying the invention can also find use in allowing sorption of desired materials from aqueous compositions containing them.
The use of a reaction mixture capable of forming a hydrotalcite-like material in situ is particularly preferred for the removal of dyestuffs and organotoxins.
The method of the invention may be operated batchwise or as a continuous process.
The invention is illustrated by the following, non-limiting examples. As demonstrated in these examples, the method of the invention is capable of reducing the COD of an aqueous effluent to a level which is considered desirable according to current standards for discharge to the environment but has generally not been achievable using conventional methods employing hydrotalcite-like materials. The method is also capable of removing sufficient colour and COD to allow the treated water to be re-used. The precipitates or flocs formed using the method generally settle quickly and have a relatively low volume. The benefits of rapid settling and small floe volume are particularly apparent when a polymeric flocculant is used in the method.
EXAMPLES
Example 1
57 g of sodium treated calcium-form bentonite (Brebent supplied by Laporte pic) was mixed with 28 g magnesium sulphate (calcined kieserite) and 15 g aluminium sulphate
hexadecahydrate. 35.8 g of the derived solid mixture was then taken and made up to 200 g with water. The pH of the resultant suspension (Suspension A) was 4.2. An effluent was taken from a dyeing factory dyeing cotton and polyester with reactive and disperse dyes and printing cotton and cotton/polyester with reactive dyes and pigments. The effluent was at 40° C, the COD was 731 mg oxygen per litre and the absorbance in a 2.5 cm cell at the wavelength of maximum absorbance was 0.96. Subsequent absorbance measurements on treated effluent were carried out at the same wavelength.
Absorbance was measured in a Hach DR/2000 spectrophotometer (available from Hach, Chaussee de Namur 1 , B5150 Floriffoux (Namur), Belgium) in the range 400-700 nm. COD was measured by digestion in COD (0-1500 range) phials from Hach in a Hach COD reactor at 150° C for 120 minutes, followed by analysis and interpretation at 620 nm in the same spectrophotometer.
2.48 g of Suspension A was added to 500 mis of the effluent and the pH adjusted to 8 by the addition of dilute sulphuric acid. The mixture was stirred for 20 minutes after which time the pH was then taken to 11.2 by the addition of sodium hydroxide. Stirring was continued for 5 minutes and 4 ppm polymeric flocculant (Magnafloc 1011 ) added. A dense floe was produced and removed by gravity settlement. The supernatant liquid was filtered through a 0.45 μm filter prior to the measurement of absorbance and COD. This was called Treatment A.
For comparison purposes two further treatments were carried out on the same effluent. In the first, 10 g Brebent was made up to 250 g with water to give a 4% bentonite suspension (Suspension B). 12.5 g of Suspension B were then added to 500 ml of effluent and the scheme of Treatment A followed. This was called Treatment B. In the second treatment, 9.89 g magnesium sulphate (calcined kieserite) and 5.19 g aluminium sulphate hexadecahydrate were made up to 200 g with water to produce Solution C. 2.48 g of Solution C was then added to 500 mis of the effluent and the scheme of Treatment A followed. Samples from all three treatments were then characterised in terms of absorbance and COD using the techniques described above. Results are given in Table 1.
TABLE 1
Note: An Absorbance of 0.009 or less indicates that the aqueous composition is virtually colourless to the eye, whereas those having an Absorbance of 0.01 and above are noticeably coloured.
Example 2
Using the treatment technique described in Example 1 as Treatment A, several treatments were carried out at different dosages (expressed as g per 500 ml of effluent) of Suspension A in an effluent from a similar dyeing factory. The results are shown in Table 2 below.
TABLE 2
Example 3
Three treatments were carried out looking at the effect of alternative materials, compared to bentonite, on sludge (the separated floe from supernatant) solids concentration on the same effluent used in Example 2. In each case, the sum of N plus M added to the effluent is the same although other material quantities vary.
In this example an exact repeat preparation of Suspension A was carried out, in this case referred to as Suspension H. 2.48 g of Suspension H was added to 500 mis of the effluent and the pH adjusted to 8 by the addition of dilute sulphuric acid. The mixture was stirred for 20 minutes after which time the pH was taken to 11.2 by the addition of sodium hydroxide. Stirring was continued for 5 minutes and 4 ppm polymeric flocculant
(Magnafloc 1011) added. A further 2 minutes stirring were allowed. A dense floe was produced and allowed to settle. The majority of the clear supernatant liquid was decanted off into a clean glass beaker whilst the remaining liquid and sludge were transferred to a glass, 250 cm3 measuring cylinder. The sludge was allowed to settle for 30 minutes before the volume of sludge was recorded. The sludge volume will be referred to below as y and is in cm3. After this measurement, the entire contents of the measuring cylinder and beaker of retained supernatant liquid were filtered through a pre-dried and weighed filter paper using a standard Buchner apparatus. Any residual solids on the glassware were rinsed off and through the filter. The filter cake formed was washed with 2 sequential 10 ml aliquots of boiling deionised water to wash out any soluble impurities. The cake sample and filter paper were then dried until a constant weight was achieved prior to re- weighing. With the filter paper weight already known, the weight of dry solids was readily calculable. The weight of solids will be referred to below as z and is in grams. This was called Treatment H.
For comparison purposes two further treatments were carried out on the same effluent. In the first 28.3 g magnesium sulphate (calcined kieserite) was mixed with 14.9 g aluminium sulphate hexadecahydrate and 6.9 g silica. 43.4 g of the derived solid mixture was then taken and made up to 200 g with water to give a 3% silica suspension (Suspension I). 1.0 g of Suspension I was then added to 500 ml of effluent and the scheme of Treatment H followed. This was called Treatment I. In the second treatment, 8.0 g Brebent was made up to 200 g with water to give a 4% bentonite suspension (Suspension J). 12.5 g of Suspension J were then added to 500 ml of effluent followed by a subsequent addition of 1.0 g of Suspension I. The scheme of Treatment H was followed. This to be called Treatment J. Repeat procedures for Treatments H to J were carried out on plain water (uncontaminated) for comparison purposes. Samples from all six treatments were then characterised in terms of % dry solids in the sludge using the techniques described above. The dry solids concentration of the sludge was calculated by dividing z by y and multiplying by 100 and these figures are given in Table 3 below.
TABLE 3
Using the treatment technique described in Example 1 as Treatment A, several treatments were carried out using different polymeric flocculants in the final part of the treatment (all at a dosage rate of 4 ppm on weight of effluent) on the effluent used in Example 1. Results are given in Table 4 below.
TABLE 4
Example 5
Using a fresh industrial effluent similar to that used in Example 1 but from a different factory, Treatment A was carried out using a variety of different clays and compared with Treatment C on the same effluent. Results are given in Table 5 below.
TABLE 5
Claims
1. A method of treating an aqueous composition comprising mixing said aqueous composition with a smectite clay at a pH below 9 and with a hydrotalcite-like material or a reaction mixture capable of forming a hydrotalcite-like material and subsequently separating the treated aqueous composition from solid materials therein.
2. A method according to claim 1 characterised in that the smectite clay and reaction mixture capable of forming a hydrotalcite-like material are mixed with the aqueous composition at a pH below 9, the pH of the mixture is raised to a value above 10 and the solid material present in the treated aqueous composition is separated from the liquid material therein.
3. A method according to claim 1 or 2 characterised in that the hydrotalcite-like material contains carbonate ions and magnesium and aluminium species in a molar ratio of Mg : Al in the range 3 : 1 to 8 : 1.
4. A method according to any one of the preceding claims characterised in that the smectite clay is a montmorillonite clay or a hectorite clay.
5. A method according to claim 4 characterised in that the montmorillonite clay is a calcium-form bentonite clay or a sodium-treated calcium-form bentonite clay.
6. A method according to any one of the preceding claims further characterised in that a polymeric flocculant is added to the aqueous composition.
7. A method according claim 6 characterised in that the polymeric flocculant is a nonionic, anionic or cationic polyacrylamide.
8. A method according to any one of the preceding claims characterised in that the smectite clay is mixed with the aqueous composition at a pH in the range 5 to 8.
9. A method according to any one of the preceding claims characterised in that the smectite clay is added in an amount of greater than 0.25 g per litre of aqueous composition.
10. A method according to any one of the preceding claims characterised in that a slurry of the smectite clay in water is produced before the smectite clay is mixed with the aqueous composition.
11. A method according to claim 10 characterised in that the slurry of smectite clay contains from 1 to 5 per cent by weight of smectite clay.
12. A method according to claim 10 characterised in that the slurry of smectite clay contains a reaction mixture capable of forming hydrotalcite-like materials and from 1 to 15 per cent by weight of smectite clay.
13. A method according to any one of claims 10 to 12 characterised in that the slurry of smectite clay is allowed to stand with stirring for 30 to 180 minutes before it is mixed with the aqueous composition. '
14. A method according to any one of the preceding claims characterised in that a reaction mixture capable of forming hydrotalcite-like materials is used and components of the reaction mixture are soluble organic salts, nitrates, chlorides or sulphates.
15. A method according to any one of the preceding claims characterised in that the smectite clay is allowed to interact with contaminants in the aqueous composition for a period before the hydrotalcite-like material is added to or formed in the aqueous composition.
16. A method according to claim 15 characterised in that the smectite clay is allowed to react with contaminants in the aqueous composition for a period of at least 5 minutes before the hydrotalcite-like material is added to or formed in the aqueous composition.
17. A method according to any one of the preceding claims characterised in that the amount of hydrotalcite-like material added to or formed in the aqueous composition is in the range 30 to 100 mg, calculated as total metals in the hydrotalcite-like material, per litre of aqueous composition.
18. A method according to any one of claims 2 to 17 characterised in that the pH of the aqueous composition is raised to above 11 after the smectite clay has been allowed to interact with the aqueous composition.
19. A method according to claim 18 characterised in that a polymeric flocculant is added to the aqueous composition after the pH has been adjusted to above 11.
20. A method according to any one of claims 6 to 19 characterised in that polymeric flocculant is added to the aqueous composition in an amount in the range 1 to 8 mg of polymeric flocculant per litre of aqueous composition.
21. A method according to any one of the preceding claims characterised in that the temperature of the aqueous composition is at least 40° C when it is mixed with the smectite clay.
22. A composition comprising a solid particulate mixture of a smectite clay and a reaction mixture capable of forming a hydrotalcite-like material.
23. A composition according to claim 22 characterised in that the smectite clay is a bentonite clay.
24. A composition according to claim 22 or 23 characterised in that the mixture comprises from 2 to 20 parts by weight of smectite clay to one part by weight of total metals in the reaction mixture capable of forming hydrotalcite-like material.
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AU2001294062A AU2001294062A1 (en) | 2000-11-02 | 2001-10-16 | Method of treating aqueous compositions |
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GB0026784A GB0026784D0 (en) | 2000-11-02 | 2000-11-02 | Method of treating aqueous compositions |
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Cited By (6)
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EP1533275A1 (en) | 2003-11-20 | 2005-05-25 | S.A. Minera Catalano-Aragonesa | Ecological composition for treating and purifying waste water |
CN100349652C (en) * | 2005-09-05 | 2007-11-21 | 暨南大学 | Bentonite base composite material for water treatment and its preparation method |
EP2007686A1 (en) * | 2006-04-06 | 2008-12-31 | Commonwealth Scientific & Industrial Research Organisation ( C.S.I.R.O. ) | Remediation of groundwater |
EP2881369A1 (en) * | 2013-12-04 | 2015-06-10 | Zhang, Zhuangdou | Tannery process with effluent recycling |
CN109293004A (en) * | 2018-10-31 | 2019-02-01 | 张家界贵友环保材料科技有限公司 | A kind of purifying agent and preparation method thereof |
US10260115B2 (en) | 2014-03-20 | 2019-04-16 | Zhuangdou Zhang | Leather production using waste liquids |
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WO1992018238A1 (en) * | 1991-04-16 | 1992-10-29 | The Dow Chemical Company | Adducts of clay and activated mixed metal oxides |
EP0626346A1 (en) * | 1993-05-27 | 1994-11-30 | PELT & HOOYKAAS B.V. | Method for capturing ecologically harmful substances from material polluted with such substances |
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EP0832849A1 (en) * | 1996-09-25 | 1998-04-01 | Eastman Kodak Company | Method for eliminating heavy metals from a photographic effluent |
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-
2001
- 2001-10-16 AU AU2001294062A patent/AU2001294062A1/en not_active Abandoned
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JPS61133190A (en) * | 1984-10-24 | 1986-06-20 | Kurita Water Ind Ltd | Method for removing silica |
WO1992018238A1 (en) * | 1991-04-16 | 1992-10-29 | The Dow Chemical Company | Adducts of clay and activated mixed metal oxides |
EP0626346A1 (en) * | 1993-05-27 | 1994-11-30 | PELT & HOOYKAAS B.V. | Method for capturing ecologically harmful substances from material polluted with such substances |
FR2740361A1 (en) * | 1995-10-31 | 1997-04-30 | Rhone Poulenc Chimie | HEAVY METAL REMOVAL AGENT COMPRISING A SULFUR COMPOUND |
EP0832849A1 (en) * | 1996-09-25 | 1998-04-01 | Eastman Kodak Company | Method for eliminating heavy metals from a photographic effluent |
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Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
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EP1533275A1 (en) | 2003-11-20 | 2005-05-25 | S.A. Minera Catalano-Aragonesa | Ecological composition for treating and purifying waste water |
CN100349652C (en) * | 2005-09-05 | 2007-11-21 | 暨南大学 | Bentonite base composite material for water treatment and its preparation method |
EP2007686A1 (en) * | 2006-04-06 | 2008-12-31 | Commonwealth Scientific & Industrial Research Organisation ( C.S.I.R.O. ) | Remediation of groundwater |
EP2007686A4 (en) * | 2006-04-06 | 2013-10-30 | Commw Scient Ind Res Org | Remediation of groundwater |
US9133041B2 (en) | 2006-04-06 | 2015-09-15 | Commonwealth Scientific And Industrial Research Organisation | Remediation of groundwater |
EP2881369A1 (en) * | 2013-12-04 | 2015-06-10 | Zhang, Zhuangdou | Tannery process with effluent recycling |
US9776887B2 (en) | 2013-12-04 | 2017-10-03 | Zhuangdou Zhang | Tannery process with effluent recycling |
US10501336B2 (en) | 2013-12-04 | 2019-12-10 | Zhuangdou Zhang | Tannery process with effluent recycling |
US11040890B2 (en) | 2013-12-04 | 2021-06-22 | Zhuangdou Zhang | Tannery process with effluent recycling |
US10260115B2 (en) | 2014-03-20 | 2019-04-16 | Zhuangdou Zhang | Leather production using waste liquids |
CN109293004A (en) * | 2018-10-31 | 2019-02-01 | 张家界贵友环保材料科技有限公司 | A kind of purifying agent and preparation method thereof |
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GB0026784D0 (en) | 2000-12-20 |
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