JP4553507B2 - Method for dehydrating aluminum hydroxide sludge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a method for dewatering aluminum sludge, and more specifically, industrially useful alumina gel is produced from alkaline and / or acidic waste liquid containing aluminum generated in the surface treatment process of aluminum material made of aluminum or aluminum alloy. In this case, the present invention relates to a dehydration method for efficiently dewatering the concentrated sludge of aluminum hydroxide generated by neutralizing the waste liquid.
[0002]
[Prior art]
Aluminum materials made of aluminum or aluminum alloys are used in various fields such as various materials such as ships, vehicles, machinery, and building materials such as sashes, as well as electrical products and office supplies. The material is subjected to various surface treatments such as etching with an alkaline solution and anodizing with an acidic solution for the purpose of cleaning the surface and imparting corrosion resistance and design.
[0003]
By the way, with regard to the treatment liquid used in such surface treatment, consumption of active ingredients in the treatment liquid and accumulation of aluminum from the aluminum material inevitably occur, and these consumption and accumulation exceed a certain limit. Then, it becomes a so-called etching treatment aging bath or an anodic oxidation aging bath and needs to be renewed, and these aging baths become an aluminum-containing waste liquid containing a large amount of aluminum.
[0004]
In recent years, these aging baths themselves have been devised in a way to regenerate them while making useful resources of aluminum, or have come to be used as industrial chemicals in other fields. The above problems have been overcome, and surface treatment that is more efficient than conventional methods has been performed.
[0005]
In addition, the aluminum material surface treatment is not limited to the aluminum-containing waste liquid consisting of an aging bath, but is scattered as a mist together with the gas generated during the surface treatment of the aluminum material, and is generated by being absorbed by the exhaust system. The so-called “waste liquid derived from mist” leaks as handling loss, and a large amount of “waste liquid derived from washing water” generated in the water washing step performed after each surface treatment.
[0006]
And the waste liquid derived from these mists and the waste liquid derived from washing water has a dilute concentration, and since it contains a wide variety of impurities, there is no effective utilization method, and the waste liquid is treated in a lump. ing.
[0007]
In this waste liquid treatment, usually, the waste liquid is first neutralized to pH 5-9, preferably pH 5.5-8.5, and the gelled aluminum hydroxide sludge generated at that time is separated and removed as much as possible. The neutral clarified liquid obtained is treated as waste water. Various studies are currently underway to make aluminum hydroxide sludge economically useful as a resource, but sometimes it is unavoidable to dispose of it at a high processing cost. Therefore, dehydration exists as a very important process for making aluminum hydroxide sludge a useful resource. This aluminum hydroxide sludge contains 70 to 80% of water, and a dehydration step is essential to improve aluminum purity by removing one-quarter to one-half sulfate radicals of aluminum. It is not allowed.
[0008]
As a flocculant used at the time of dehydration of aluminum hydroxide sludge, for example, JP-A-48-32800 describes an example of a product form of a nonionic polyacrylamide aqueous solution. In addition, for the coagulation and separation of waste water discharged from the aluminum processing step, Japanese Patent Application Laid-Open No. 9-3671 uses an anionic emulsion type polyacrylamide, and the same applies to the dehydration of the separated aluminum hydroxide sludge. It was common to use polyacrylamide. However, the aqueous solution when these polyacrylamide type flocculants are added has a high viscosity, poor dispersibility in aluminum hydroxide sludge, and after addition, the sludge becomes viscous, so a filter press commonly used as a dehydrator It cannot be said that the dehydration property is sufficient.
[0009]
[Problems to be solved by the invention]
Therefore, the object of the present invention is that when aluminum hydroxide sludge is dehydrated by a dehydrator, the dispersion system of the flocculant aqueous solution in the aluminum hydroxide sludge is good, and as a result, the moisture content of the sludge is sufficiently reduced, and the efficiency It is to develop a method of dehydrating well.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the following inventions have been achieved. That first aspect of the invention, an aluminum sludge in the water-soluble monomer mixture in an aqueous salt solution, with a dispersant presence consisting soluble polymer in salt solution, particle size 100 [mu] m produced by dispersion polymerization An aluminum hydroxide sludge dewatering method characterized in that an anionic or nonionic water-soluble polymer composed of the following fine particles is added and mixed, and then dehydrated by a dehydrator.
[0011]
The invention of claim 2 is characterized in that the anionic or nonionic water-soluble polymer is an anionic monomer represented by the following general formula (1): 0 to 50 mol%, acrylamide 50 to 100 mol%, and other copolymers. It consists of 0-20 mol% of possible nonionic monomers, The aluminum hydroxide sludge dehydration method of Claim 1 characterized by the above-mentioned.
[Chemical 1]
R ₁ is hydrogen, methyl group or carboxymethyl group, R ₂ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or C
[0012]
A third aspect of the present invention is the aluminum hydroxide sludge dewatering method according to the first or second aspect, wherein the dispersant comprising the polymer is an ionic polymer.
[0013]
Invention of Claim 4 is a dehydration method of the aluminum hydroxide sludge of Claim 3 whose ion equivalent of the said ionic polymer is 1.5-15 meq / g.
[0014]
The invention according to claim 5 is the method for dehydrating aluminum hydroxide sludge according to claim 1 or 2, wherein the molecular weight of the anionic or nonionic water-soluble polymer is 2 million to 20 million. .
[0015]
The invention of claim 6 is the aluminum hydroxide sludge dewatering method according to claim 1 or 2, wherein the salt constituting the aqueous salt solution contains at least one kind of polyvalent anionic salt.
[0016]
A seventh aspect of the present invention is a method for dehydrating aluminum hydroxide sludge according to any one of the first to fifth aspects , which is a filter press.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The anionic or nonionic water-soluble polymer used in the present invention is prepared by stirring a water-soluble monomer mixture in a salt aqueous solution in the presence of a dispersant composed of a polymer soluble in the salt aqueous solution. present as a dispersion consisting of particle size 100 [mu] m or less of fine particles produced by the dispersion polymerization method, after the aqueous solution was diluted in water and added to the aluminum hydroxide sludge. Among the water-soluble monomers used, examples of the anionic monomer include methacrylic acid, acrylic acid, maleic acid, and itaconic acid. A sulfonic acid group-containing monomer can also be used. Examples thereof include vinyl sulfonic acid, vinyl benzene sulfonic acid, acrylamide 2-methylpropane sulfonic acid, 2- (acryloyloxy) ethyl sulfonic acid, and the like.
[0018]
The water-soluble polymer comprising the polymer dispersion may be an acrylamide homopolymer that is a nonionic monomer, or a nonionic monomer or a copolymer with the anionic monomer. Examples of nonionic monomers include (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, and N-vinyl pyrrolidone. N-vinylformamide, N-vinylacetamide, and the like, and one or two or more of these anionic monomers or nonionic monomers can be copolymerized. Most preferred are acrylamide homopolymers in the case of nonionic water-soluble polymers, and acrylic acid or acrylamide 2-methylpropane sulfonic acid and acrylamide in the case of anionic water-soluble polymers.
[0019]
The proportion of the anionic water-soluble monomer in the water-soluble polymer is 0 to 70 mol%, acrylamide is 30 to 100 mol%, and the copolymerizable nonionic monomer is 0 to 20 mol%. . Preferably, the anionic water-soluble monomer is 0 to 40 mol%, the acrylamide is 60 to 100 mol%, and the copolymerizable nonionic monomer is 0 to 10 mol%.
[0020]
The molecular weight of the nonionic or anionic water-soluble polymer constituting the dispersion is 1 million to 20 million, and preferably 5 million to 15 million.
Below 1 million, the cohesive force is insufficient and the yield decreases, and above 20 million, the floc becomes enormous and the dehydrating property is returned and deteriorated. In addition, the solution viscosity becomes too high, dispersibility is deteriorated, and handling of the aqueous solution is also deteriorated.
[0021]
When the nonionic or anionic water-soluble polymer comprising the polymer dispersion used in the present invention is produced in a salt aqueous solution, a polymer dispersant that dissolves in the salt aqueous solution is used. As the nonionic polymer, a polymer having a weak hydrophobic group such as polyvinylpyrrolidone, a vinylpyrrolidone-based polymer, or polyvinyl alcohol is used.
These polymers have a molecular weight of 1,000 to 100,000, preferably 5,000 to 20,000. Further, the polymer that can be used more preferably is an ionic polymer, and anionic and cationic polymers can be used. As the anionic polymer, a homopolymer of an anionic monomer or a copolymer of an anionic monomer and a nonionic monomer can be used. Examples of nonionic monomers include acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, acrylonitrile, diacetone acrylamide, 2-hydroxyethyl (meth) acrylate And so on. The anionic monomer is acrylamide 2-methylpropane sulfonic acid, styrene sulfonic acid, (meth) acrylic acid, etc., but the most preferable combination is acrylamide 2-methylpropane sulfonic acid (salt) and methacrylic acid (salt). And a copolymer.
[0022]
In addition, as the cationic polymer, homopolymers such as (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, these cationic monomers and the above It is a copolymer with a nonionic monomer. Preferably used is a homopolymer of acryloyloxyethyltrimethylammonium chloride. The molecular weight of these ionic polymers is 10,000 to 1,000,000, preferably 50,000 to 500,000.
[0023]
Salts used at the time of polymerization are salts of alkali metal ions such as sodium and potassium, ammonium ions, halide ions, sulfate ions, nitrate ions, phosphate ions, etc., but salts with polyvalent anions. More preferred. The concentration of the salt solution is 5% by weight or more and the saturation concentration or less.
[0024]
In order to (co) polymerize a monomer (mixture) containing an anionic monomer, a radical polymerization initiator is used. As the initiator to be used, any of azo, peroxide and redox can be polymerized. Examples of oil-soluble azo initiators are 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate) and the like are dissolved in a water-miscible solvent and added. Examples of water-soluble azo initiators include 2,2′-azobis (amidinopropane) dichloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] And dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include ammonium peroxydisulfate or potassium in combination with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Examples of peroxides include ammonium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, and t-butylperoxy 2-ethylhexanoate. Can do. Most preferred of these initiators are redox systems, ammonium peroxodisulfate and sodium bisulfite.
[0025]
An anionic water-soluble polymer comprising a dispersion produced by the dispersion polymerization method used in the present invention is an anionic water-soluble polymer produced by an aqueous solution polymerization method, a water-in-oil emulsion polymerization method, or a water-in-oil dispersion polymerization method. Compared to molecules, the apparent viscosity when dissolved in water is very low. For example, in the case of a copolymer containing sodium acrylate and acrylamide in a molar ratio of 30/70, the viscosity of an aqueous solution having a molecular weight of about 13 million and 0.2% by weight is obtained by an aqueous solution polymerization method or a water-in-oil emulsion polymerization method. In the case of a polymer obtained by the water-in-oil dispersion polymerization method, it is 400 to 800 mPa · s, whereas an anionic water-soluble polymer comprising a dispersion produced by the dispersion polymerization method used in the present invention is 20 to 20 mPa · s. 100 mPa · s. This is also due to the influence of inorganic salts that coexist during polymerization. Another reason is that only 10 to 20 mol% of the monomeric acid used during polymerization is neutralized. However, even if these effects are subtracted, this alone cannot be explained.
This phenomenon is presumed to be caused by polymerizing while precipitating the polymer produced in the aqueous salt solution, but the detailed mechanism is unclear. Therefore, the low apparent viscosity means that the dispersibility in the sludge is so good that a sufficient coagulation effect can be exhibited and the amount of the anionic water-soluble polymer added can be reduced.
[0026]
The addition amount of the nonionic or anionic water-soluble polymer comprising the polymer dispersion of the present invention to the aluminum hydroxide sludge is 0.01% to 1% with respect to the water-containing aluminum hydroxide sludge, preferably Is 0.05% to 0.1%. The nonionic or anionic water-soluble polymer composed of the polymer dispersion used in the present invention has a low apparent viscosity of the aqueous solution, and thus is well dispersed in sludge. As a result, sludge is efficiently agglomerated, and the amount added can be reduced by 20% to 40%, and in some cases by about 50%, compared to conventional dehydrating agents. In addition, there is little "stickiness" of sludge after addition,
Dehydration efficiency is improved and the water content after dehydration is reduced.
[0027]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated in more detail with an Example and a comparative example, this invention is not restrict | limited to a following example, unless the summary is exceeded.
[0028]
(Synthesis Example-1)
In a four-neck 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, deionized water: 107.7 g, ammonium sulfate 26.8 g, sodium sulfate 17.9 g, 60% acrylic acid: 32.7 g 50% acrylamide: 90.3 g was added, and 16 mol% of acrylic acid was neutralized with 5.8 g of 30 wt% sodium hydroxide. Further, 15% by weight of methacrylic acid / acrylamide 2-methylpropanesulfonic acid = 3/7 (molar ratio, neutralizing 90 mol% of the acid) copolymer aqueous solution (solution viscosity 42, 600 mPa · s) 18.9 g was added. did. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. After 30 minutes from the introduction of nitrogen, 0.6 g of 0.1 wt% ammonium peroxonisulfate and 0.1 wt% aqueous solution of ammonium hydrogen sulfite were added in this order to initiate the polymerization. After 3 hours from the start of polymerization, the same amount of each initiator was added, and after 6 hours, 3.0 g was added, and the reaction was completed in 15 hours. Let this prototype be prototype-1. In the trial production-1, the molar ratio of acrylic acid to acrylamide was 30:70, and the viscosity was 400 mPa · s. As a result of microscopic observation, the particles were found to be 5 to 35 μm. Moreover, the weight average molecular weight was measured with the molecular weight measuring machine (Otsuka Electronics DLS-7000) by a static light scattering method. The results are shown in Table 1.
[0029]
(Synthesis Example-2)
An anionic water-soluble polymer dispersion having a molar ratio of acrylic acid to acrylamide of 10:90 was synthesized in the same manner as in Synthesis Example-1. The results are shown in Table 1.
[0030]
(Synthesis Example-3)
In a four-neck 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, deionized water: 220.4 g, ammonium sulfate 34.0 g, sodium sulfate 10.7 g, acrylamide 2-methylpropanesulfonic acid: 2.8 g, 60% acrylic acid: 9.9 g, 50% acrylamide: 182.2 g were added and 1.6 g of 25% by weight sodium hydroxide was 10 with respect to the equivalent value of acrylamide 2-methylpropanesulfonic acid and acrylic acid. % Neutralized. Further, 15% by weight of methacrylic acid / acrylamide 2-methylpropanesulfonic acid = 3/7 (molar ratio, neutralizing 90 mol% of the acid) copolymer aqueous solution (solution viscosity 42, 600 mPa · s) 18.9 g was added. did. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. using a constant temperature water bath. After 30 minutes from the introduction of nitrogen, 0.6 g of 0.1 wt% ammonium peroxonisulfate and 0.1 wt% aqueous solution of ammonium hydrogen sulfite were added in this order to initiate the polymerization. After 3 hours from the start of polymerization, the same amount of each initiator was added, and after 6 hours, 3.0 g was added, and the reaction was completed in 15 hours. Let this prototype be prototype-3. In this trial production-3, the molar ratio of acrylic acid / acrylamide 2-methylpropanesulfonic acid / acrylamide was 6: 1: 93, and the viscosity was 835 mPa · s. As a result of microscopic observation, the particles were found to be 5 to 20 μm. Moreover, the weight average molecular weight was measured with the molecular weight measuring machine (Otsuka Electronics DLS-7000) by a static light scattering method. The results are shown in Table 1.
[0031]
(Synthesis Example 4)
A deionized water: 181.8 g, ammonium sulfate 64.0 g, 50% acrylamide: 120.0 g were added to a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, and a polymer dispersant Dimethyldiallylammonium chloride polymer 15.0 (20 wt% solution, 2250 mPa · s) g and acryloyloxyethyltrimethylammonium chloride polymer 15.0 (20 wt% solution, 9750 mPa · s) g were added as (Each monomer is 5% by weight). Further, 0.3 g of sodium fluoride (50 ppm relative to the monomer) was added as a polymerization degree modifier. Thereafter, heating is performed from the outside with a water bath, the temperature in the reaction vessel is adjusted to 35 ° C., and nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. After 30 minutes, 0.9 g of a 1% by weight solution of 2,2-azobisamidinopropane dihydrochloride (150 ppm monomer) was added to initiate the polymerization. The reaction was continued at 35 ° C., and after 7 hours, 0.6 g of the initiator solution was added, and the reaction was completed in 15 hours. This dispersion is referred to as trial production-4. The viscosity of the dispersion liquid of this trial production-4 was 230 mPa · s. As a result of microscopic observation, the particles were found to be 5 to 35 μm. Moreover, the weight average molecular weight was measured with the molecular weight measuring device (DLS-7000 by Otsuka Electronics) by a static light scattering method. The results are shown in Table 1.
[0032]
Examples 1 to 4
A dehydration test was conducted assuming a filter press using aluminum hydroxide sludge generated as a result of neutralizing the aluminum agent surface treatment waste liquid and performing a coagulation sedimentation operation. This sludge had a pH of 7.06, an aluminum content of 18200 mg / L, and a sulfate radical of 8210 mg / L. Sample 200 mL of sludge into a poly beaker, add 20 ppm or 40 ppm of the water-soluble anionic or non-ionic polymer of Prototype-1 to Prototype-4 in Table 1 to the liquid volume, transfer to the beaker, and stir. After 10 times, the beaker was transferred, stirred 10 times, filtered through a filter cloth for filter press (similar to an on-site dehydrator), and naturally filtered for 5 minutes. Thereafter, the sludge on the filter cloth was dehydrated at a press pressure of 2.5 kg / m 2 for 2 minutes and dried at 105 ° C. for 20 hours, whereby the moisture content of the cake was measured. Moreover, the filter cloth peelability at the time of dehydration was checked visually. The results are shown in Table 2.
[0033]
[Comparative Examples 1-3]
By the same operation as in Examples 1 to 4, powder product anionic (ss-120, manufactured by Hymo Co., Ltd., polymer flocculant, sodium acrylate / acrylamide = 20/80 copolymer, molecular weight: 12 million) (Comparative- 1) and nonionic water-soluble polymer (ss-200, manufactured by Hymo Co., Ltd., polymer flocculant, acrylamide polymer, molecular weight: 12 million), (Comparison-2) emulsion type anionic water-soluble polymer (V- 320, manufactured by Hymo Co., Ltd., a polymer flocculant, sodium acrylate / acrylamide = 20/80 copolymer, molecular weight: 12 million) (Comparative-3), a comparative test was performed. The results are shown in Table 2.
[0034]
[Table 1]
AAC; acrylic acid, AMPS; acrylamide 2-methylpropanesulfonic acid, AAM; acrylamide,
Dispersion viscosity: mPa · s, molecular weight; unit is 10,000
[Table 2]
Sludge moisture content: mass%, dehydrating agent added to the liquid; mass%
Removability of filter cloth; indicates good in order of ○>△> ×

Claims (7)

Aluminum hydroxide sludge, the water-soluble monomer mixture in an aqueous salt solution, with a dispersant presence consisting soluble polymer in salt solution, consisting of particle size 100 [mu] m or less of fine particles produced by dispersion polymerization A method of dehydrating aluminum hydroxide sludge, comprising adding and mixing an anionic or nonionic water-soluble polymer and then dehydrating with a dehydrator. Anionic or nonionic water-soluble polymer is an anionic monomer represented by the following general formula (1) 0 to 50 mol%, acrylamide 50 to 100 mol%, and other copolymerizable nonionic monomers The method for dehydrating aluminum hydroxide sludge according to claim 1, comprising 0 to 20 mol% of the body.
R ₁ is hydrogen, methyl group or carboxymethyl group, R ₂ is hydrogen or carboxyl group, A is SO ₃ , C ₆ H ₄ SO ₃ , CONHC (CH ₃ ) ₂ CH ₂ SO ₃ or COO, Y is hydrogen or positive ion  The method for dewatering aluminum hydroxide sludge according to claim 1 or 2, wherein the dispersant comprising the polymer is an ionic polymer. The method for dewatering aluminum hydroxide sludge according to claim 3 , wherein the ion equivalent of the ionic polymer is 1.5 to 15 meq / g.  The method of dehydrating aluminum hydroxide sludge according to claim 1 or 2, wherein the molecular weight of the anionic or nonionic water-soluble polymer is 2 million to 20 million.  The method for dewatering aluminum hydroxide sludge according to claim 1 or 2, wherein the salt constituting the aqueous salt solution contains at least one kind of polyvalent anionic salt. 6. The method for dehydrating aluminum hydroxide sludge according to claim 1 , wherein the dehydrator is a filter press.