JP2002331204A - Dehydration method of aluminum hydroxide sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient dehydration method with in which the dispersion property of an aqueous aggregation solution to aluminum hydroxide sludge is good and as a result, a moisture content of the sludge is sufficiently reduced when the aluminum hydroxide sludge is hydrated by a dehydrating machine. SOLUTION: The purpose of the invention is achieved in the following process: An anionic or non-ionic water-soluble powdery polymer with a particle diameter of 100 mμ or less is prepared by dispersion polymerization in which mixed water-soluble monomers are polymerized in an aqueous salt solution in the presence of a dispersion agent comprising a polymer soluble to the aqueous salt solution. The obtained polymer is added to aluminum oxide sludge and mixed. The resultant slurry is dehydrated with a dehydrator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dewatering aluminum sludge and, more particularly, to an industrial method for converting an alkaline and / or acidic waste liquid containing aluminum generated in a surface treatment step of an aluminum material made of aluminum or an aluminum alloy. When producing useful alumina gel,
The present invention relates to a dehydration method for efficiently dehydrating concentrated sludge of aluminum hydroxide generated by neutralizing the waste liquid.

[0002]

2. Description of the Related Art Aluminum materials made of aluminum or aluminum alloys are used in various fields such as construction materials such as various parts such as ships, vehicles and machines, sashes, electric products, office supplies, and the like. At this time, the aluminum material is subjected to various surface treatments such as an etching treatment with an alkali solution and an anodic oxidation treatment with an acidic solution for the purpose of cleaning the surface, imparting corrosion resistance and designability, and the like.

[0003] In the treatment liquid used in such a surface treatment, consumption of an effective component in the treatment liquid and accumulation of aluminum derived from an aluminum material inevitably occur. When the limit is exceeded,
A so-called etching aging bath or an anodic oxidation aging bath requires renewal, and these aging baths become aluminum-containing waste liquids containing a large amount of aluminum.

In recent years, these aging baths themselves have been devised by a method of regenerating the aging bath while making it a useful resource, or have been used as industrial chemicals in other fields. The problem in the treatment of the waste liquid has been overcome, and the surface treatment has been performed more efficiently than in the past.

[0005] In the surface treatment of aluminum material, not only the aluminum-containing waste liquid consisting of an aging bath, but also scattered as a mist together with the gas generated during the surface treatment of the aluminum material, and may be absorbed by the exhaust system. In addition, so-called "waste liquid derived from mist" which leaks as other handling loss is generated, and a large amount of "waste liquid derived from cleaning water" generated in a washing step performed after each surface treatment is generated.

[0006] The waste liquid derived from the mist and the like and the waste liquid derived from the washing water have a low concentration, and
Since it contains various impurities, there is no effective use method, and the waste liquid is collectively treated.

In this waste liquid treatment, the waste liquid is usually first neutralized to pH 5 to 9, preferably 5.5 to 8.5, and the gelled aluminum hydroxide sludge generated at that time is removed as much as possible. It is separated and removed, and the resulting neutral clarified liquid is treated as waste water. At present, various studies have been made on the use of aluminum hydroxide sludge as an economically useful resource, but sometimes waste treatment is inevitably carried out at a high processing cost. Therefore, dewatering is a very important step in turning aluminum hydroxide sludge into a useful resource. This aluminum hydroxide sludge contains 70 to 80% of water, and a dehydration step is indispensable for removing a quarter to a half of sulfates of aluminum and improving aluminum purity. It is something that can not be done.

As a flocculant used for dehydrating aluminum hydroxide sludge, for example, JP-A-48-32800
In the publication, an example of a product form of a nonionic aqueous solution of polyacrylamide is described. For coagulation and separation of waste water discharged from an aluminum processing step, see Japanese Patent Application Laid-Open No. 9-6767.
In JP-A No. 1, it was common to use an anionic emulsion-type polyacrylamide, and further use the same polyacrylamide for dehydration of separated aluminum hydroxide sludge. However, the aqueous solution when these polyacrylamide-based flocculants are added has high viscosity and poor dispersibility in aluminum hydroxide sludge, and after addition, the sludge becomes viscous. The dehydration property in is not sufficient.

[0009]

Accordingly, an object of the present invention is to provide a method for dispersing an aqueous solution of a coagulant into aluminum hydroxide sludge when the aluminum hydroxide sludge is dewatered by a dehydrator. An object of the present invention is to develop a method for efficiently dehydrating the water content, which is sufficiently reduced.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the following inventions have been reached. That is, the invention of claim 1 is a method of preparing a 100 m particle system produced by a dispersion polymerization method in a salt solution of a water-soluble monomer mixture in aluminum sludge in the presence of a dispersant comprising a polymer soluble in the salt solution.
A method for dehydrating aluminum hydroxide sludge, comprising adding and mixing an anionic or nonionic water-soluble polymer composed of fine particles having a particle size of μ or less, followed by dehydration with a dehydrator.

According to a second aspect of the present invention, an anionic or nonionic water-soluble polymer comprises 0 to 50 mol% of an anionic monomer represented by the following general formula (1) and acrylamide 5:
The method for dehydrating aluminum hydroxide sludge according to claim 1, comprising 0 to 100 mol% and 0 to 20 mol% of another copolymerizable nonionic monomer.

Embedded image R1 is hydrogen, methyl or carboxymethyl, R2
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation

The invention according to claim 3 is the method for dehydrating aluminum hydroxide sludge according to claim 1 or 2, wherein the dispersant comprising the polymer is an ionic polymer.

[0013] The invention of claim 4 is the method for dehydrating aluminum hydroxide sludge according to claim 4, wherein the ionic equivalent of the ionic polymer is 1.5 to 15 meq / g.

According to a fifth aspect of the present invention, the anionic or nonionic water-soluble polymer has a molecular weight of 2,000,000 to 200,000.
The method for dehydrating aluminum hydroxide sludge according to claim 1 or 2, wherein the amount is 100,000.

The invention according to claim 6 is the method for dehydrating 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. It is.

The invention according to claim 7 is the method for dewatering aluminum hydroxide sludge according to any one of claims 1 to 5, wherein the method is a filter press.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The anionic or nonionic water-soluble polymer used in the present invention is prepared by mixing a water-soluble monomer mixture in a salt aqueous solution with a dispersant comprising a polymer soluble in the salt aqueous solution. Under agitation, it is present as a dispersion comprising fine particles having a particle size of 100 μm or less produced by a dispersion polymerization method with stirring, diluted with water to form an aqueous solution, and then added to aluminum hydroxide sludge. Among the water-soluble monomers used, anionic monomers include methacrylic acid, acrylic acid, maleic acid and itaconic acid. Further, a sulfonic acid group-containing monomer can also be used. For example, vinyl sulfonic acid, vinyl benzene sulfonic acid, acrylamide 2-methylpropane sulfonic acid, 2- (acryloyloxy) ethyl sulfonic acid and the like can be mentioned.

The water-soluble polymer comprising the polymer dispersion is a non-ionic monomer such as acrylamide homopolymer, a non-ionic monomer or a copolymer with the anionic monomer. But it is good. Examples of nonionic monomers include (meth) acrylamide, N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone , N-vinylformamide, N-vinylacetamide, etc., and copolymerization with one or more of these anionic monomers or nonionic monomers is possible. Most preferably, in the case of a nonionic water-soluble polymer, acrylamide homopolymer,
In the case of an anionic water-soluble polymer, acrylic acid or acrylamide 2-methylpropanesulfonic acid and acrylamide are used.

The proportion of the anionic water-soluble monomer in the water-soluble polymer is 0 to 70 mol%, and acrylamide is 3%.
0 to 100 mol%, the copolymerizable nonionic monomer is 0%
~ 20 mol%. Also preferably, the anionic water-soluble monomer is 0 to 40 mol%, and the acrylamide is 60 to 10 mol%.
0 mol%, and the copolymerizable nonionic monomer is 0 to 10 mol%.

The molecular weight of the nonionic or anionic water-soluble polymer constituting the dispersion is from 1,000,000 to 20
Million, preferably 5,000,000 to 15,000,000. If it is less than 1,000,000, the cohesive strength is insufficient and the yield rate decreases,
If it is more than 20 million, the floc becomes huge and dehydration property returns to deteriorate. In addition, the solution viscosity becomes too high, dispersibility deteriorates, and handling of the aqueous solution also deteriorates.

When the nonionic or anionic water-soluble polymer comprising the polymer dispersion used in the present invention is produced in an aqueous salt solution, a polymer dispersant that is soluble in the aqueous salt 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.
The molecular weight of these polymers is from 1,000 to 100,000, preferably from 5,000 to 20,000. Further, polymers that can be used more preferably are ionic polymers, 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, diacetoneacrylamide, 2-hydroxyethyl (meth) acryle And so on. Anionic monomers include acrylamide 2-methylpropanesulfonic acid, styrenesulfonic acid, (meth)
Acrylic acid and the like, the most preferred combination is
It is a copolymer of acrylamide 2-methylpropanesulfonic acid (salt) and methacrylic acid (salt).

Examples of the cationic polymer include homopolymers such as (meth) acryloyloxyethyltrimethylammonium chloride, dimethyldiallylammonium chloride and (meth) acryloylaminopropyltrimethylammonium chloride; And a non-ionic monomer. Preferably used are homopolymers of acryloyloxyethyltrimethylammonium chloride. The molecular weight of these ionic polymers is 10,000 to 1,000,000, preferably 50,000 to 500,000.

The salts used at the time of polymerization include salts of alkali metal ions such as sodium and potassium or ammonium ions with halide ions, sulfate ions, nitrate ions and phosphate ions. Are more preferred. The concentration of the salt solution is not less than 5% by weight and not more than the saturation concentration.

In order to (co) polymerize a monomer (mixture) containing an anionic monomer, a radical polymerization initiator is used. As the initiator to be used, it is possible to polymerize any of an azo type, a peroxide type and a redox type. Examples of the oil-soluble azo initiator include 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 the water-soluble azo initiator include 2,2′-
Azobis (amidinopropane) dichloride, 2,
2'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dichloride, 4,4'-azobis (4-cyanovaleric acid) and the like. Examples of the redox system include a combination of ammonium or potassium peroxydisulfate with sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, or the like. Further, examples of peroxides include ammonium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate, and the like. Can be. Most preferred of these initiators are the redox systems, ammonium peroxodisulfate and sodium bisulfite.

The anionic water-soluble polymer comprising a dispersion produced by the dispersion polymerization method used in the present invention was produced by an aqueous solution polymerization method, a water-in-oil emulsion polymerization method, or a water-in-oil dispersion polymerization method. The apparent viscosity when dissolved in water is very low as compared with the anionic polymer. For example, in the case of a copolymer containing sodium acrylate and acrylamide at a molar ratio of 30/70, the viscosity of an aqueous solution having a molecular weight of about 13,000,000 and 0.2% by weight is determined by an aqueous solution polymerization method and a water-in-oil emulsion polymerization method. In the polymer produced by the water-in-oil dispersion polymerization method, the pressure is 400 to 800 mPa · s, whereas the anionic water-soluble polymer composed of the dispersion liquid produced by the dispersion polymerization method used in the present invention is 20 to 20 mPa · s. 100mPa ・
s. This is affected by inorganic salts coexisting during polymerization. Further, 10 to 20 of the monomers used during the polymerization are used.
One factor is that it only neutralizes mole%. However, these effects alone cannot be explained. It is presumed that this phenomenon is caused by polymerization while precipitating the polymer formed in the aqueous salt solution, but the detailed mechanism has not been elucidated. Therefore, lower apparent viscosity means better dispersibility in sludge, more sufficient coagulation effect, and a reduced amount of anionic water-soluble polymer.

The amount of the nonionic or anionic water-soluble polymer comprising the polymer dispersion of the present invention added to aluminum hydroxide sludge is 0.01% to 1% based on the water-containing aluminum hydroxide sludge. And preferably 0.05% to 0.1%. The nonionic or anionic water-soluble polymer composed of the polymer dispersion used in the present invention has good dispersion in sludge because the apparent viscosity of the aqueous solution is low. As a result, sludge aggregates efficiently,
The addition amount can be reduced by 20 to 40%, and in some cases, about 50% as compared with the conventional dehydrating agent. In addition, the “slime” of the sludge after addition is small, the dewatering efficiency is improved, and the water content after dewatering is reduced.

[0027]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples unless it exceeds the gist thereof.

(Synthesis Example 1) In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 107.7 g of deionized water, 26.8 g of ammonium sulfate, and 17.9 g of sodium sulfate. , 60% acrylic acid: 32.7 g, 50% acrylamide: 90.
3 g were added and 16 mol% of acrylic acid was neutralized with 5.8 g of 30% by weight sodium hydroxide. 15% by weight of methacrylic acid / acrylamide 2-methylpropanesulfonic acid = 3/7 (molar ratio, neutralizes 90 mol% of the acid)
Copolymer aqueous solution (solution viscosity 42, 600 mPa · s) 1
8.9 g were added. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. by a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.6 g of a 0.1% by weight aqueous solution of 0.1% by weight of ammonium peroxodisulfate and ammonium hydrogen sulfite were added in this order to initiate polymerization. Three hours after the start of the polymerization, the same amount of each of the initiators was added, and after 6 hours, 3.0 g of each of the initiators was added. This prototype is referred to as prototype-1. The molar ratio of acrylic acid to acrylamide of this prototype 1 was 3
0:70 and the viscosity was 400 mPa · s. As a result of microscopic observation, it was found that the particles had a size of 5 to 35 μm. Further, the weight average molecular weight was measured by a molecular weight measuring device (DLS-7000 manufactured by Otsuka Electronics Co., Ltd.) by a static light scattering method. Table 1 shows the results.

(Synthesis Example 2) By the same operation as in Synthesis Example-1, the molar ratio of acrylic acid to acrylamide was 10: 9.
An anionic water-soluble polymer dispersion consisting of 0 was synthesized.
Table 1 shows the results.

(Synthesis Example-3) In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen inlet tube, 220.4 g of deionized water, 34.0 g of ammonium sulfate, and 10.7 g of sodium sulfate. Acrylamide 2-methylpropanesulfonic acid: 2.8 g, 6
0% acrylic acid: 9.9 g, 50% acrylamide: 1
82.2 g were added and 25% by weight of sodium hydroxide 1.
6 g neutralized 10% of the equivalent value of acrylamide 2-methylpropanesulfonic acid and acrylic acid. Also, 15% by weight of methacrylic acid / acrylamide 2-methylpropanesulfonic acid = 3/7 (molar ratio, neutralizes 90 mol% of acid) copolymer aqueous solution (solution viscosity 42, 600 mP
a.s) 18.9 g were added. Thereafter, nitrogen is introduced from a nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 30 ° C. by a constant temperature water bath. Thirty minutes after the introduction of nitrogen, 0.6 g of a 0.1% by weight aqueous solution of 0.1% by weight of ammonium peroxodisulfate and ammonium hydrogen sulfite were added in this order to initiate polymerization. Three hours after the start of the polymerization, the same amount of each of the initiators was added, and after 6 hours, 3.0 g of each of the initiators was added. Prototype-3
And Acrylic acid / acrylamide 2 of this prototype-3
The molar ratio of -methylpropanesulfonic acid / acrylamide was 6: 1: 93, and the viscosity was 835 mPa · s. As a result of microscopic observation, it was found that the particles had a size of 5 to 20 μm. Further, the weight average molecular weight was measured by a molecular weight measuring device (DLS-7000 manufactured by Otsuka Electronics Co., Ltd.) by a static light scattering method. Table 1 shows the results.

(Synthesis Example 4) In a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 181.8 g of deionized water, 64.0 g of ammonium sulfate, and 120% of acrylamide. Dimethyldiallylammonium chloride polymer 15.0 (20% by weight solution, 2250 m 2) as a polymer dispersant.
Pa.s) g and 15.0 g of a acryloyloxyethyltrimethylammonium chloride polymer (20% by weight solution, 9750 mPa.s) were added (each 5% by weight to the monomer). Also, 0.3 g of sodium fluoride (50 ppm with respect to monomer) was added as a polymerization degree regulator. Thereafter, the mixture is heated 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 pipe while stirring to remove dissolved oxygen. After 30 minutes, 2, 2
1% by weight of azobisamidinopropane dihydrochloride
0.9 g (150 ppm based on the monomer) of the solution was added to initiate 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 Prototype-4. The dispersion viscosity of this prototype-4 was 230 mPa · s. As a result of microscopic observation, it was found that the particles had a size of 5 to 35 μm. Also,
Molecular weight measuring device by static light scattering method (Otsuka Electronics DLS-
7000). Table 1 shows the results.

[0032]

Examples 1 to 4 A dehydration test assuming a filter press was carried out using aluminum hydroxide sludge produced as a result of neutralizing a waste liquid of a surface treatment of an aluminum agent and performing coagulation and sedimentation. This sludge had a pH of 7.06, an aluminum content of 18,200 mg / L, and a sulfate group of 8210 mg / L. 200 mL of sludge is collected in a polybeaker,
20 ppm or 40 ppm of the water-soluble anionic or nonionic polymer of Prototype-1 to Prototype-4 in Table 1 with respect to the liquid amount.
ppm, added to the beaker, and stirred 10 times.
After the beaker was transferred and stirred 10 times, the mixture was filtered with a filter press filter cloth (similar to an in-situ dehydrator).
The mixture was naturally filtered for 5 minutes. Thereafter, the sludge on the filter cloth was dewatered for 2 minutes at a pressing pressure of 2.5 kg / m 2,
The cake moisture content was measured by drying for an hour. In addition, the releasability of the filter cloth during dehydration was visually checked. Table 2 shows the results.

[0033]

Comparative Examples 1 to 3 The same procedure as in Examples 1 to 4 was carried out to obtain anionic powder (ss-120, manufactured by Hymo Co., Ltd., polymer flocculant, sodium acrylate / acrylamide = 20 /
80 copolymer, molecular weight: 12 million) (comparative-1) and a nonionic water-soluble polymer (ss-200, manufactured by Hymo Co., Ltd.)
Polymer flocculant, acrylamide polymer, molecular weight: 120
(0000,000), (Comparative-2) Emulsion type anionic water-soluble polymer (V-320, manufactured by Hymo Co., Ltd., polymer flocculant, sodium acrylate / acrylamide = 20/80 copolymer, molecular weight: 12,000,000) ( A comparative test was performed using Comparative-3). Table 2 shows the results.

[0034]

[Table 1] AAC; acrylic acid, AMPS; acrylamide 2-methylpropanesulfonic acid, AAM; acrylamide,
Dispersion viscosity; mPa · s, molecular weight; unit is 10,000

[0035]

[Table 2] Sludge water content; mass%, amount of dehydrating agent added to the liquid; mass% Filter cloth releasability;

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08F 2/20 C08F 2/20 2/24 2/24 Z 20/56 20/56 F-term (Reference) 4D015 BA05 BA19 BB05 CA20 DB07 DB30 DC02 DC06 DC08 EA39 4D059 AA30 BE16 BE58 BE59 DB24 4G076 AA10 AB27 BA15 BA42 BA50 BC02 BC07 BE11 4J011 JA06 JA14 JB08 JB14 JB26 KA15 KA16 KA29 KB08 KB14 KB29 AM08 AL08A08A08A04 AM21R AN04R AP01Q AQ08R BA13R BA14R BA56Q CA01 CA04 CA05 DA01 DA28 DA38 EA09 JA18

Claims (7)

[Claims] 1. A particle system produced by a dispersion polymerization method in which a water-soluble monomer mixture is added to an aluminum hydroxide sludge in a salt aqueous solution in the presence of a dispersant comprising a polymer soluble in the salt aqueous solution, and having a particle size of 100 mμ or less. A method for dehydrating aluminum hydroxide sludge, comprising adding and mixing an anionic or nonionic water-soluble polymer composed of fine particles of the above, followed by dehydration with a dehydrator. 2. An anionic or nonionic water-soluble polymer comprising 0 to 50 mol% of an anionic monomer represented by the following general formula (1) and 50 to 100 mol% of acrylamide.
And 0 to 20 mol% of other copolymerizable nonionic monomers
The method for dehydrating aluminum hydroxide sludge according to claim 1, comprising: Embedded image R1 is hydrogen, methyl or carboxymethyl, R2
Is hydrogen or carboxyl group, A is SO3, C6H4S
O3, CONHC (CH3) 2CH2SO3 or C
OO and Y are hydrogen or cation 3. The method for dewatering aluminum hydroxide sludge according to claim 1, wherein the polymer dispersant is an ionic polymer. 4. An ion equivalent of the ionic polymer,
The method for dehydrating aluminum hydroxide sludge according to claim 4, wherein the amount is 1.5 to 15 meq / g. 5. The method for dewatering aluminum hydroxide sludge according to claim 1, wherein the molecular weight of the anionic or nonionic water-soluble polymer is 2,000,000 to 20,000,000. 6. The method for dehydrating aluminum hydroxide sludge according to claim 1, wherein the salt constituting the salt aqueous solution contains at least one kind of polyvalent anionic salt. 7. The method for dehydrating aluminum hydroxide sludge according to claim 1, wherein the dehydrator is a filter press.