JPH09268279A - Metal scavenger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it easy to form precipitation of metals in a metal scavenger solution and to solve the problems that pumps and piping for feeding chemicals such as a solution of a metal scavenger tend to be clogged in the process where a metal scavenger solution is added to waste water containing metals and to solid waste material to collect the metals. SOLUTION: This metal scavenger comprises a metal-complex forming agent which reacts with metals to form water-insoluble metal complexes but is itself soluble or dispersible in water, an another water-soluble and metal complex- forming agent which bonds to hardness components to from water-soluble metal complex or is prepared by dissolving a metal complex-forming agent which forms water-insoluble metal complexes and another metal complex-forming agent which forms water-soluble metal complexes.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a metal scavenger.

[0002]

2. Description of the Related Art Metals contained in industrial wastewater, especially mercury,
Heavy metals harmful to the human body, such as cadmium, zinc, lead, copper and chromium, may pollute rivers and the sea and cause serious environmental problems. Heavy metals contained in slag discharged from mines, incinerated ash from garbage incinerators, used sludge from wastewater treatment plants, contaminated soil such as factory sites, etc. are also eluted into rivers and the sea. It may cause the next pollution. Therefore, when treating wastewater such as factory wastewater containing heavy metals and solid waste such as slag, incineration ash, sludge, and soil,
Especially strict regulations are set.

[0003]

Various methods have been proposed so far for treating wastewater, solid waste, and the like, but in recent years, a metal scavenger capable of forming an insoluble metal complex with a metal. A method in which metal in waste water or solid waste is collected and treated as an insoluble complex is widely used. As a method for treating wastewater using a metal scavenger, an aqueous solution of the metal scavenger is added to the wastewater to be treated, and the metal scavenger collects insoluble flocs generated by collecting the metal in the wastewater. After removing the precipitate, it is common to discharge the wastewater into a river or the like. In the case of treating solid waste, after adding an aqueous solution of a metal scavenger to the solid waste and kneading, the metal in the solid waste is collected by the metal scavenger to insolubilize it. Generally, the final disposal method is solid waste.

When an aqueous solution of the metal scavenger is added to waste water or solid waste for treatment, a chemical injection pump is used to add the aqueous solution of the metal scavenger. A precipitate is likely to be generated in the aqueous solution, and there is a risk that the chemical injection pump and the pipe used for adding the aqueous metal scavenger solution to wastewater, solid waste, and the like may be clogged.

The present inventors investigated the tendency of the precipitates in the metal scavenger aqueous solution to be easily formed, and found that the longer the period from the preparation of the metal scavenger aqueous solution to the use was, It was found that the amount of precipitate produced tended to increase. It was also found that the ease with which precipitates are formed depends on the type and concentration of the metal scavenger. According to the research conducted by the present inventors, since the metal scavenger aqueous solution is generally alkaline, carbon dioxide in the air is easily absorbed in the aqueous solution, and as a result, the hardness components such as calcium and magnesium existing in the aqueous solution are It was suspected that the formation of insoluble carbonate by reacting with carbon dioxide might be the cause of precipitation.

The present invention has been made in order to solve the above-mentioned problems, and does not cause problems such as clogging of chemical pumps and pipes due to the precipitate formed in the prepared aqueous solution of the metal collector. The purpose is to provide a collecting agent.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] That is, the metal scavenger of the present invention binds to a metal to form an insoluble metal complex, and is itself a water-soluble or water-dispersible insoluble metal complex-forming agent. , A water-soluble metal complex-forming agent that forms a water-soluble metal complex by combining with a hardness component. Further, the metal scavenger of the present invention binds to a metal to form an insoluble metal complex. However, the metal scavenger itself has a water-soluble or water-dispersible insoluble metal complex-forming agent and a water-soluble agent by binding with a hardness component. And a water-soluble metal complex-forming agent which forms the metal complex of 1. are dissolved in an aqueous solvent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An insoluble metal complex-forming agent, which is one of the components of the metal scavenger of the present invention, is water-soluble or water-dispersible by itself, but is insoluble when it collects a metal. Is a compound that forms. As the insoluble metal complex-forming agent, an ordinary metal scavenger which has been conventionally used for wastewater treatment or solid waste treatment can be used. Examples thereof include an alkali metal salt of dimethyldithiocarbamic acid, an alkaline earth metal salt, an ammonium salt, or a compound having a functional group at the nitrogen atom of amine or imine (hereinafter, simply referred to as amines). As the functional group bonded to the nitrogen atom of amines, dithio acid,
Examples thereof include alkali metal salts, alkaline earth metal salts, ammonium salts and the like of alkylene phosphoric acid, alkylene carboxylic acid and the like, and two or more different functional groups may be bonded. Examples of the above-mentioned alkali metal include lithium, sodium and potassium, and examples of the alkaline earth metal include calcium and magnesium.

Examples of amines in compounds having a functional group bonded to the nitrogen atom of amines include ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, dibutylene. Triamine, triethylenetetramine, tripropylenetetramine, tributylenetetramine, tetraethylenepentamine, tetrapropylenepentamine, tetrabutylenepentamine, pentaethylenehexamine, iminobispropylamine, monomethylaminopropylamine, methyliminobispropylamine, 1 Aliphatic amines such as 1,3-diaminopropane and 1,4-diaminobutane; phenylenediamine, o-, m-, p-xylenediamine, 3,5-diaminoc Aromatic amines such as Robenzen; 1,3-bis cycloalkane amine such as (aminomethyl) cyclohexane; polyethyleneimine, polypropyleneimine, poly-2-methyl ethyleneimine, poly -
2-ethylethyleneimine, poly-3-methylpropyleneimine, poly-3-ethylpropyleneimine, poly-
Polymers of cyclic imines such as 2-methylpropyleneimine and poly-2-ethylpropyleneimine, polymers of unsaturated amines such as polyvinylamine and polyallylamine; unsaturated amines such as vinylamine and allylamine, and dimethylacrylamide, styrene, Examples thereof include copolymers with other monomers having a copolymerizable unsaturated bond, such as methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, styrene sulfonic acid, and salts thereof. When using a polymer of cyclic imine, a polymer of unsaturated amine, or a copolymer thereof, those having an average molecular weight of 300 to 2,000,000 are preferable, and those having an average molecular weight of 1,000 to 500,000 are more preferable.

In addition to the above amines, an alkyl group, a β-hydroxyalkyl group, an acyl group, an alkylphenyl group,
Those having an alkyl-substituted hydroxyalkyl group introduced as an N-substituent can also be used. Further, polycondensed amines obtained by polycondensing the above amines with epihalohydrin can also be used. Examples of the epihalohydrin include epichlorohydrin, epibromhydrin, epiiodohydrin, bromomethyloxirane, chloromethyloxirane, iodomethyloxirane, and the like.

The compound having the above-mentioned functionality bonded to the nitrogen atom of amines can be obtained by a known method. For example, a compound having a dithioate as a functional group at the nitrogen atom of amines can be prepared by reacting polyamines with carbon disulfide in the presence of an alkali such as an alkali metal hydroxide or an alkaline earth metal hydroxide. can get.

Further, a xanthogenic acid compound can also be used as an insoluble metal complex-forming agent. The xanthogenic acid compound can be obtained by reacting an alkali compound of a hydroxy compound with carbon disulfide. As the hydroxy compound, taobato monohydric alcohol, polyhydric alcohol, cellulose, starch, polyvinyl alcohol, polyvinyl alcohol and copolymerization of ethylene, propylene, styrene, acrylic acid, methacrylic acid, allylamine, vinylamine, vinyl acetate, etc. Examples thereof include coalesce, chitin, chitosan, and the like, and those into which an alkyl group, β-hydroxyalkyl group, acyl group, alkylphenyl group, alkyl-substituted hydroxyalkyl group, or the like is introduced as a substituent.

Examples of the monohydric alcohol include methyl alcohol, ethyl alcohol, butyl alcohol,
Propyl alcohol, isopropyl alcohol, amyl alcohol, hexyl alcohol, octyl alcohol, nonyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, aliphatic saturated alcohols such as behenyl alcohol, allyl alcohol, crotyl alcohol, propargyl alcohol, etc. Aliphatic unsaturated alcohols, alicyclic alcohols such as cyclopentanol and cyclohexanol, aromatic alcohols such as Benjuru Alcohol, cinnamyl alcohol, and heterocyclic alcohols such as furfuryl alcohol are included.

Examples of the polyhydric alcohol include ethylene glycol, 1,2-propanediol, 1,3-
Propanediol, 1,4-butanediol, 1,6-
Hexanediol, 1,5-pentanediol, diethylene glycol, triethylene glycol, diethylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, polyethylene glycol,
Glycerin, pentaglycerin, sorbitan, mannitan, trait, erythritol, pentaerythritol,
Examples include arabite, rebit, xylit, lamb knit, sorbit, mannite, idit, talit, galactit, arit, alrit and the like.

Further, a hydroxy compound, a product obtained by treating the above hydroxy compound with nitric acid or the like, a product obtained by partially reducing a carbonyl group, or a polyalkylene polyamine which is reacted with an epoxy compound such as an alkylene oxide to introduce a hydroxyl group. Those obtained by reacting the above hydroxy compound with an epoxy compound can also be used.

The water-soluble metal complex-forming agent, which is another component of the metal scavenger of the present invention, is a compound that forms a water-soluble complex with hardness components such as calcium and magnesium. As the water-soluble metal complex forming agent, a general sequestering agent can be used, and examples thereof include EDTA (ethylenediaminetetraacetic acid), NTA (nitrotriacetic acid), HEDTA (hydroxyethylethylenediaminetriacetic acid), DTPA.
(Diethylenetriaminepentaacetic acid), TTAH (triethylenetriaminehexaacetic acid), HIDA (hydroxyethyliminodiacetic acid), DHEG (dihydroxyethylglycine), polycarboxylic acids (polyacrylic acid, polymethacrylic acid and these and other vinyl monomers. And copolymers), polystyrene sulfonic acids (polystyrene sulfonic acid and copolymers of styrene sulfonic acid and styrene, etc.), HEDP (1-hydroxyethylidene-1,1)
-Phosphoric acids such as diphosphonic acid) and aminophosphoric acids such as ATMP (aminotrimethylenephosphonic acid). These water-soluble metal complex-forming agents may be appropriately combined with the insoluble metal complex-forming agent, but when the pH of the aqueous solution of the metal-scavenger is 9 or more, precipitation does not occur in the aqueous solution of the metal-scavenger. For this purpose, it is preferable to use polycarboxylic acids, polystyrene sulfonic acids, phosphoric acids, aminophosphoric acids as the water-soluble metal complex forming agent.

The metal scavenger of the present invention comprises the above-mentioned insoluble metal complex-forming agent and the water-soluble metal complex-forming agent. The content of the water-soluble metal complex-forming agent in the mixture of both is 0.01-5. %, Preferably 0.0
It is preferably 1 to 3% by weight. The metal scavenger of the present invention containing the insoluble metal complex-forming agent and the water-soluble metal complex-forming agent can be dissolved in an aqueous solvent and used as an aqueous solution. The aqueous solution has a metal scavenger concentration of 0.1.
It is preferable to adjust it to be about 40.

The aqueous solution of the metal scavenger of the present invention may be prepared by dissolving a mixture of the insoluble metal complex-forming agent and the water-soluble metal complex-forming agent described above in an aqueous solvent. Even if the water-soluble metal complex-forming agent is dissolved in the aqueous solution to prepare the water-soluble metal complex-forming agent, the water-soluble metal complex-forming agent is dissolved in the aqueous solution to prepare the insoluble metal complex-forming agent. Alternatively, it may be prepared by mixing an aqueous solution in which an insoluble metal complex-forming agent is dissolved and an aqueous solution in which a water-soluble metal complex-forming agent is dissolved. Even when the insoluble metal complex-forming agent and the water-soluble metal complex-forming agent are separately dissolved in an aqueous solvent, the content ratio of the water-soluble metal complex-forming agent to the total amount of the insoluble metal complex-forming agent and the water-soluble metal complex-forming agent Is preferably 0.01 to 5% by weight.

The metal scavenger of the present invention is generated during waste incineration in a wastewater discharged from a factory, a waste treatment plant, a waste incineration plant, a thermal power plant, or a waste incineration plant. Fly ash (depending on the dust collection method, MC
There are ash, EP ash, cyclone ash, scrubber ash, bag filter ash, etc. ) And incineration ash such as residual ash, slag discharged from mines, sludge in wastewater treatment plants, etc., or metals contained in solid waste such as contaminated soil such as factory sites. .

When the metal scavenger of the present invention is used for treating waste water, solid waste, waste gas, etc., sodium hydrogen sulfide, sodium monosulfide, sodium disulfide, sodium trisulfide, sodium tetrasulfide, sodium pentasulfide. And the like, and one or more of sodium sulfides, trimercaptotriazine or salts thereof and the like can be used in combination.

As a method for treating wastewater with the metal scavenger of the present invention, an aqueous solution of the scavenger of the present invention is added to the wastewater, and the insoluble metal complex-forming agent in the metal scavenger of the present invention is added to the wastewater. It is possible to employ a method in which the metal is collected and the flocs produced are precipitated and filtered to be separated from the wastewater. The wastewater after the flocs are separated and removed can be discharged to rivers. When treating the wastewater with the metal collecting agent of the present invention, it is preferable to adjust the pH of the wastewater to about 3 to 12 in order to enhance the metal collecting effect. To adjust the pH of the wastewater,
Acids such as hydrochloric acid, sulfuric acid and nitric acid, and alkalis such as sodium hydroxide and potassium hydroxide are used.

As a method for treating solid waste, the metal scavenger aqueous solution of the present invention is sprayed on the surface of the solid waste, and the metal scavenger is permeated into the solid waste, or the metal scavenger of the present invention is used. A method in which an aqueous solution is added to solid waste and kneading is adopted. The metal in the solid waste is collected by the insoluble metal complex-forming agent in the metal collector of the present invention to form an insoluble metal complex, and the insoluble metal complex is difficult to elute from the solid waste. , The solid waste after treatment can be safely disposed of for final disposal. When treating solid waste, it is preferable to use an acidic substance or an alkaline substance together, if necessary. Further, as a method of treating waste gas, a method of introducing an aqueous solution of the metal scavenger of the present invention into the waste gas or introducing an aqueous solution of the metal scavenger of the present invention together with an acidic gas adsorbent is adopted.

The metal scavenger of the present invention is particularly excellent in the scavenging performance of mercury, cadmium, zinc, copper, chromium, arsenic, gold, silver, platinum, vanadium, thallium and the like, and the metal scavenger of the present invention. The collecting agent is suitable for treating waste water, waste gas, and solid waste containing them.

[0025]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 1 part by weight of a metal scavenger containing 99% by weight of sodium dimethyldithiocarbamate as an insoluble metal complex-forming agent and 1% by weight of EDTA (2Na salt) as a water-soluble metal complex-forming agent was mixed with industrial water (calcium). 33 mg / l) 10
It was dissolved in 0 part by weight to prepare a solution having a pH of 8.4.
After leaving this aqueous solution at room temperature for 48 hours, the state of the aqueous solution was observed. The results are shown in Table 1. The aqueous solution of the metal scavenger after standing at room temperature showed the same metal scavenging performance as the case of using only sodium dimethyldithiocarbamate.

[0027]

[Table 1]

* 1 Observing the state of the metal scavenger aqueous solution after standing, ◯ ... no precipitate was observed. Δ: A slight precipitate is observed. X: A large amount of precipitate is observed. Was evaluated.

Comparative Example 1 1 part by weight of sodium dimethyldithiocarbamate was dissolved in 100 parts by weight of industrial water as in Example 1 to adjust the pH.
= 8.4 aqueous solution was prepared. This aqueous solution was allowed to stand at room temperature for 48 hours in the same manner as in Example 1, and then the state of the aqueous solution was observed. The results are shown in Table 1.

Example 2 2 parts by weight of a metal scavenger containing 99.9% by weight of sodium diethyldithiocarbamate as an insoluble metal complex-forming agent and 0.1% by weight of sodium polyacrylate as a water-soluble metal complex-forming agent, Plant water (calcium 66
The solution was dissolved in 100 parts by weight (containing mg / l) to prepare an aqueous solution having a pH of 9.4. After leaving this aqueous solution at room temperature for 24 hours, the state of the aqueous solution was observed. The results are shown in Table 1.
Further, the aqueous solution of the metal-collecting agent after standing showed the same metal-collecting performance as the case of using only sodium diethyldithiocarbamate.

Example 3 Compound 99. In which a sodium dithioate group was introduced into the nitrogen atom of diethylenetriamine as an insoluble metal complex-forming agent.
2 parts by weight of a metal scavenger containing 99% by weight and 0.01% by weight of a sodium salt of HEDP as a water-soluble metal complex-forming agent were dissolved in 100 parts by weight of water (containing 50 mg / l of calcium) to obtain a pH = An aqueous solution of 10.4 was prepared. After leaving this aqueous solution for 12 hours at room temperature, the state of the aqueous solution was observed. The results are shown in Table 1. The aqueous solution of the metal scavenger after standing showed a metal scavenging performance equivalent to that of a compound containing no sodium salt of HEDP but having a sodium dithioate group introduced into the nitrogen atom of diethylenetriamine.

Comparative Example 2 2 parts by weight of the same insoluble metal complex-forming agent as used in Example 3 was dissolved in 100 parts by weight of water as in Example 3 to obtain p.
An aqueous solution of H = 10.5 was prepared. After leaving this aqueous solution for 12 hours at room temperature, the state of the aqueous solution was observed. The results are shown in Table 1.

Example 4 4 parts by weight of a metal scavenger containing 98% by weight of sodium ethyl xanthate as an insoluble metal complex-forming agent and 2% by weight of sodium polystyrene sulfonate as a water-soluble metal complex-forming agent was mixed with industrial water (calcium 24mg / l included)
It was dissolved in 100 parts by weight to prepare an aqueous solution having a pH of 9.6. After leaving this aqueous solution at room temperature for 24 hours, the state of the aqueous solution was observed. The results are shown in Table 1. The aqueous solution of the metal scavenger after standing showed a metal scavenging performance equivalent to that of the case where only sodium ethyl xanthate was used.

Comparative Example 3 4 parts by weight of sodium ethyl xanthate were added to Example 4
PH = 9. By dissolving in 100 parts by weight of industrial water similar to the above.
An aqueous solution of 5 was prepared. After leaving this aqueous solution at room temperature for 24 hours, the state of the aqueous solution was observed. The results are shown in Table 1.

[0035]

INDUSTRIAL APPLICABILITY The metal scavenger of the present invention contains a water-soluble metal complex-forming agent that forms a water-soluble metal complex in combination with a hardness component together with an insoluble metal complex-forming agent. No precipitate is generated in the solution, there is no risk of clogging of chemical pumps and pipes for adding the metal scavenger solution to wastewater or solid waste, etc. There is an effect that it can be greatly improved.

Claims (2)

[Claims] 1. An insoluble metal complex is formed by combining with a metal, and an insoluble metal complex forming agent having water solubility or water dispersibility by itself and a hardness component are combined to form a water soluble metal complex. And a water-soluble metal complex-forming agent that 2. An insoluble metal complex is formed by combining with a metal, and an insoluble metal complex forming agent having water solubility or water dispersibility by itself and a hardness component are combined with each other to form a water soluble metal complex. And a water-soluble metal complex-forming agent that is dissolved in an aqueous solvent.