JP2011074350A - Heavy metal-treating agent and method for treating heavy metal-contaminated material by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the potential of a conventional heavy metal-treating agent is not sufficient in treating a heavy metal-contaminated material contaminated with a harmful anionic kind and cationic kind, and handling is difficult and generating harmful gas, or the like. <P>SOLUTION: The heavy metal-treating agent composed of a carbodithioic acid salt of piperazine and a dialkali metal sulfide, which is free from generation of the harmful gas and capable of treating the heavy metal-contaminated material contaminated with the harmful anionic kind and cationic kind, with one agent. The preferable carbodithioic acid salt of piperazine is piperazine-N,N'-biscarbodithioic acid potassium and/or piperazine-N,N'-biscarbodithioic acid sodium, and the preferable dialkali metal sulfide is disodium sulfide and/or dipotassium sulfide. The carbodithioic acid salt of an amine having at least a carbodithioic acid group bonding to a primary amino group is preferable. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to heavy metal pollutants, for example, incinerated ash and fly ash discharged from garbage incinerators, soil contaminated with heavy metals, sludge generated after wastewater treatment, lead contained in wastewater discharged from factories, cadmium, etc. , Mercury, zinc, arsenic, selenium, hexavalent chromium and other harmful heavy metals that can be fixed easily, efficiently and stably with a single agent, and a method for treating heavy metal contaminants is there.

  Fly ash discharged from municipal waste incineration plants and the like has a high heavy metal content and needs to be treated to suppress elution of heavy metals. As one of such treatment methods, there is a drug treatment method, and a method of insolubilizing heavy metals by adding a heavy metal treatment agent such as a chelate-based drug is used.

  As chelating agents, carbodithioates of amine derivatives are mainly used. In particular, piperazine carbodithioate is widely used as a heavy metal treating agent because it generates less harmful gases such as hydrogen sulfide and carbon disulfide than other amine derivatives (see, for example, Patent Document 1).

  However, arsenic, selenium, hexavalent chromium and the like contained in heavy metal contaminants exist in the form of anionic species, and it has been difficult to treat with chelating agents such as carbodithioates of amine derivatives.

  A method for treating heavy metal contaminants with iron sulfide has been known (for example, Patent Documents 2 and 3). However, these methods may not be effective for anionic species such as arsenic and hexavalent chromium, and may be insufficient or re-eluted for cationic species such as lead, cadmium, mercury, and zinc. was there. Further, since it is in the form of powder or slurry, there is a problem in handling.

  Moreover, the method of processing a heavy metal contaminant using a water-soluble iron salt is known (for example, patent document 4, 5). However, in these methods, there is a problem that the apparatus is corroded because there is no immobilization effect on cationic species such as lead, cadmium, mercury, and zinc and the acidity is further strong. In addition, when used in combination with amine carbodithioate to immobilize cationic species, the problem is that amine carbodithioate decomposes and generates harmful gases such as carbon disulfide and hydrogen sulfide. was there.

  In addition, there has been proposed a method in which a sulfur compound is mixed with an amine dithiocarbamate having four or more functional groups (dithiocarboxy groups) in one molecule (see Patent Document 6). However, there is no disclosure of a method for suppressing harmful gases generated from sulfur compounds.

Japanese Patent No. 3391173 JP 2002-326819 A JP 2006-160542 A Japanese Patent Laid-Open No. 3-254889 JP 2004-17025 A JP 2006-299004 A

  The present invention relates to heavy metal pollutants containing heavy metal pollutants, anionic species and cationic species heavy metals, and harmful anions such as arsenic, selenium and hexavalent chromium and harmful cations such as lead, cadmium and mercury in one agent. An object of the present invention is to provide a heavy metal treatment agent capable of treating seeds simultaneously and a treatment method using the same.

  In the present invention, as a result of intensive studies to solve the above-mentioned problems, heavy metal treatment agents containing piperazine carbodithioate and dialkali metal sulfides generate harmful gases such as carbon disulfide and hydrogen sulfide. It can be significantly reduced, and without the use of other drugs, harmful anionic species such as hexavalent chromium, selenium and arsenic in heavy metal pollutants and harmful cationic species such as lead, cadmium, mercury and zinc can be used in one agent. The present inventors have found that it is possible to process simultaneously and highly efficiently, and have completed the present invention.

  Hereinafter, the heavy metal treating agent and the heavy metal contaminant treatment method of the present invention will be described in detail.

  The heavy metal treating agent of the present invention comprises a piperazine carbodithioate and a dialkali metal sulfide. By using piperazine carbodithioate and dialkali metal sulfide, which generate extremely noxious gases among amine carbodithioates, hexavalent in heavy metal pollutants in one agent without increasing the generation of harmful gases. It is possible to simultaneously treat harmful anionic species such as chromium, selenium and arsenic and harmful cationic species such as lead, cadmium, mercury and zinc.

  It is known that a dialkali metal sulfide alone generates hydrogen sulfide by reacting with carbon dioxide gas or oxygen in the air. In the method of the present invention, generation of hydrogen sulfide and carbon disulfide from a dialkali metal sulfide can be suppressed by using a dialkali metal sulfide and a carbodithioate of piperazine.

  On the other hand, when an amine carbodithioate other than the piperazine carbodithioate is used, harmful gas generation such as carbon disulfide and hydrogen sulfide is remarkably generated, and the heavy metal treatment capacity may be insufficient.

  In sulfides and sulfur compounds other than dialkali metal sulfides, harmful gases such as carbon disulfide and hydrogen sulfide from the chemicals are remarkably generated. However, disulfide dialkali metal salts do not have such problems.

  Examples of the piperazine carbodithioate used in the heavy metal treating agent of the present invention include piperazine-N-carbodithioate, piperazine-N, N′-biscarbodithioate, or a mixture thereof. In particular, piperazine-N, N'-biscarbodithioate or a compound with a high ratio thereof is desirable. As these salts, alkali metal salts, alkaline earth metal salts, and ammonium salts are used, and sodium salts and potassium salts are preferable from the viewpoint of thermal stability and solubility.

  The amount of piperazine carbodithioate in the heavy metal treating agent of the present invention varies depending on the content and form of harmful cation species in the heavy metal contaminant, and thus cannot be determined unconditionally. A range of 20% by weight, in particular 20-40% by weight is preferred. If the content of the piperazine carbodithioate is too low, the ability to treat harmful cation species will be reduced, and if it is too high, the viscosity may be improved and the low-temperature properties may be reduced.

  Examples of the dialkali metal sulfide used in the heavy metal treating agent of the present invention include dilithium sulfide, disodium sulfide, dipotassium sulfide, etc., but when the heavy metal treating agent is used as an aqueous solution, it is mixed with carbodithioate of piperazine. Disodium sulfide and dipotassium sulfide, which have high solubility at the time, are inexpensive and easily available, are preferred.

  Since the amount of the dialkali metal sulfide in the heavy metal treating agent of the present invention varies depending on the content and form of harmful anion species in the heavy metal pollutant, it cannot be generally determined. 0.1 to 10% by weight, particularly 0.5 to 5% by weight is preferred. When the content of the dialkali metal sulfide is too small, the processing capacity of harmful anion species is decreased, and when it is excessive, the viscosity may be improved and the low-temperature physical properties may be decreased.

  The heavy metal treating agent of the present invention preferably further contains a carbodithioate of an amine having a carbodithioic acid group bonded to at least a primary amino group. The amine carbodithioate having a carbodithioic acid group bonded to a primary amino group reduces hexavalent chromium by its reducing action and promotes insolubilization.

  The carbodithioate of an amine having a carbodithioic acid group bonded to at least a primary amino group is not particularly limited, but alkylamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine are preferred as the amine to be used. .

  Since the content of carbodithioate of amine having a carbodithioic acid group bonded to at least a primary amino group varies depending on the content and form of harmful anion species in heavy metal contaminants, it cannot be generally determined. In this case, 0.1 to 10% by weight, particularly 0.5 to 5% by weight is preferable. When the content is too small, the processing capacity of harmful anion species is decreased, and when the content is too large, viscosity may be improved, low-temperature physical properties and the like may be decreased.

  The heavy metal treating agent of the present invention may contain other components as long as the effects of the present invention are not hindered. Examples of other components include water, organic solvents, amines, and alkali hydroxides.

  The method for treating heavy metal contaminants using the heavy metal treating agent of the present invention is not particularly limited, and the heavy metal treating agent of the present invention and heavy metal contaminants may be mixed.

  The amount of the heavy metal treating agent of the present invention varies depending on the state of heavy metal contaminants, the content of heavy metals and the form of heavy metals, but is usually used in the range of 0.01 to 30% by weight with respect to fly ash. Moreover, in order to make a process easy, you may add 1-50 weight% humidified water with respect to a processed material at the time of kneading | mixing.

  Although the heavy metal contaminant in this invention will not be specifically limited if it is a substance containing a heavy metal, Fly ash, soil, sludge, drainage, etc. are illustrated.

  Examples of harmful heavy metals in these heavy metal pollutants include substances containing any of lead, cadmium, mercury, zinc, arsenic, selenium, and hexavalent chromium.

  In the heavy metal treating agent of the present invention, it is possible to safely treat heavy metal pollutants including anionic species such as arsenic, selenium, hexavalent chromium and cationic species such as lead, cadmium, mercury, zinc, etc. in one agent, and at the time of storage, There is very little generation of harmful gas during use, and it can be used safely.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Gas generation test)
Example 1
Piperazine-N, N′-biscarbodithioate is added to 87.5 g of 40 wt% aqueous solution of potassium by weight, disodium sulfide nonahydrate 7.5 g and pure water 5.0 g are added, and piperazine-N, N′-biscarbohydrate is added. Potassium dithioate was 35% by weight and disodium sulfide was 2.4% by weight (sulfur concentration derived from disodium sulfide = 1.0% by weight). 20 g of this aqueous solution was collected in a 1 L Tedlar bag, charged with 1 L of air, and then heated at 65 ° C. for 1 hour. Carbon disulfide and hydrogen sulfide in the head space after heating were measured using a detector tube (No. 13 and No. 4LL manufactured by GASTEC). The results are shown in Table 1. Both carbon disulfide and hydrogen sulfide were below the control concentration (1 ppm).

Comparative Example 1
The same operation as in Example 1 was carried out except that disodium sulfide nonahydrate was changed to 1.7 g of sodium hydrogen sulfide (sulfur concentration derived from sodium hydrogen sulfide = 1.0 wt%) and 10.8 g of pure water. . The results are shown in Table 1. Hydrogen sulfide was below the control concentration, but carbon disulfide was above the control concentration.

Comparative Example 2
The same operation as in Example 1 was conducted except that disodium sulfide · 9 hydrate was changed to 5.4 g of disodium tetrasulfide (sulfur concentration derived from disodium tetrasulfide = 1.0% by weight) and 7.1 g of pure water. went. The results are shown in Table 1. Both carbon disulfide and hydrogen sulfide exceeded the control concentration.

Comparative Example 3
The same operation as in Example 1 was performed except that disodium sulfide · 9 hydrate was changed to 7.7 g of sodium thiosulfate · pentahydrate (sulfur concentration = 1.0% by weight) and 4.8 g of pure. The results are shown in Table 1. Hydrogen sulfide was below the control concentration, but carbon disulfide was above the control concentration.

Comparative Example 4
The same operation as in Example 1 was conducted except that potassium piperazine-N, N′-biscarbodithioate was replaced by sodium tetraethylenepentamine-N1, N2, N3, N4, N5-pentacarbodithioate. The results are shown in Table 1.

  Carbon disulfide when tetraethylenepentamine-N1, N2, N3, N4, N5-pentacarbodithioate sodium having 5 functional groups (dithiocarboxy group) in one molecule and disodium sulfide are used in combination. And the amount of hydrogen sulfide generated increased.

(Processing capacity test)
Example 2
50 parts by weight of fly ash (Pb content = 3100 ppm, Cu content = 5700 ppm, Cr (VI) content = 52 ppm) 4.5 parts by weight of the heavy metal treating agent of Example 1 (9.0 weights with respect to fly ash) %) And 10 parts by weight of humidified water (20% by weight with respect to fly ash) were added and kneaded. The results are shown in Table 2.

Example 3
Piperazine-N, N′-biscarbodithioic acid potassium 35% by weight, disodium sulfide 0.96% by weight (sulfur concentration derived from disodium sulfide = 0.4% by weight), and tetraethylenepentamine-N1, A heavy metal treating agent containing 1% by weight of sodium N2, N3, N4, N5-pentacarbodithioate was added to 4.5 parts by weight of fly ash as in Example 2 (9.0% by weight with respect to fly ash). %) And 10 parts by weight of humidified water (20% by weight based on fly ash) were added and kneaded, and then the Environment Agency Notification No. 13 test was conducted to measure the heavy metal concentration in the eluate. The results are shown in Table 2.

Comparative Example 5
The same operation as in Example 2 was carried out except that the heavy metal treating agent was a piperazine-N, N′-biscarbodithioate potassium 40 wt% aqueous solution. The results are shown in Table 2. Lead was below the reference value, but hexavalent chromium was not below the reference value (1.5 mg / L).

The present invention can be used as a treatment agent for heavy metal pollutants, for example, incineration ash and fly ash discharged from garbage incineration plants, soil contaminated with heavy metals, sludge generated after wastewater treatment, wastewater discharged from factories, etc. it can.

Claims (8)

  A heavy metal treating agent comprising a carbodithioate of piperazine and a dialkali metal sulfide.   The heavy metal treating agent according to claim 1, wherein the piperazine carbodithioate is piperazine-N, N'-biscarbodithioate potassium and / or piperazine-N, N'-biscarbodithioate.   The heavy metal treating agent according to claim 1 or 2, wherein the dialkali metal sulfide is disodium sulfide and / or dipotassium sulfide.   The heavy metal treating agent according to any one of claims 1 to 3, further comprising a carbodithioate of an amine having a carbodithioic acid group bonded to at least a primary amino group.   The heavy metal treating agent according to claim 4, wherein the amine of the carbodithioate of an amine having a carbodithioic acid group bonded to at least a primary amino group is any one of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. .   A method for treating a heavy metal pollutant, comprising mixing the heavy metal treating agent according to any one of claims 1 to 5 with a heavy metal pollutant.   The method for treating a heavy metal pollutant according to claim 6, wherein the heavy metal pollutant is fly ash, soil, sludge, or waste water.   The method for treating a heavy metal pollutant according to claim 6 or 7, wherein the heavy metal pollutant contains any of lead, cadmium, mercury, zinc, hexavalent chromium, arsenic, and selenium.