JPH0221311B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a method for treating incinerator dust ash, etc. When various types of waste such as municipal garbage, industrial waste, and even sludge are incinerated, incinerator dust ash, which is scattered from the incinerator and captured by an electrostatic precipitator, and remains in the incinerator. Incineration ash is generated secondary. If these incinerator dust ash, etc. are disposed of in a landfill, etc., harmful heavy metals such as Cd, Pb, Hg, Cr ⁶⁺ , etc. that may be contained in the incinerator dust ash, etc. will be eluted. There is a risk of causing serious secondary pollution. The present invention involves mixing an aqueous solution or aqueous dispersion of a specific soluble sulfide with an acidic aqueous solution under predetermined conditions in the incinerator ash, etc. to remove harmful substances contained in the incinerator ash, etc. The present invention relates to a treatment method for rendering harmless. <Prior art and its problems> Conventionally, a treatment method has generally been used in which incinerator dust ash is mixed with cement or asphalt, or silicic acid is added thereto and sintered. However, these conventional methods have the basic flaw that they do not sufficiently prevent the elution of harmful heavy metals as mentioned above, and the amount of waste disposed of in landfills has increased due to the need to mix large amounts of cement, asphalt, etc. There are also problems in that it is uneconomical because silicic acids are mixed and sintered at high temperatures. By the way, the present applicant has already proposed a method of adding and kneading soluble sulfide to steelmaking dust, a method of adding and kneading an alkaline substance together with this, and a method of curing these after addition and kneading, as methods for treating steelmaking dust. (Japanese Patent Application Laid-Open No. 118304, 1972). However, when this conventional method is used to treat incinerator dust ash, etc., although it is reasonably effective, the method of adding and kneading only soluble sulfides almost completely prevents the elution of harmful heavy metals as mentioned above. It cannot be prevented, and the method of adding and kneading the soluble sulfide and alkaline substance results in a pH of 10 to 11 or higher, so the adverse effects of the PH are significant.
Furthermore, there is a problem in that the method of cultivating the food requires more effort. <Problems to be Solved by the Invention and Means for Solving the Problems> The present invention solves the conventional problems as described above, and almost completely prevents the elution of harmful heavy metals as described above in a simple and economical manner. The present invention provides a method for processing incinerator dust ash, etc., which can Therefore, the present invention provides incinerator dust collection ash, etc. with Na ₂ S _n , K _{2 So} , CaS _p ,
(NH ₄ ) ₂ S _q , NaHS, KHS, Ca(HS) ₂ or (NH ₄ )HS [However, m, n, p, q are all 1
an aqueous solution or dispersion of an alkaline soluble sulfide having a reducing function selected from [an integer of ~5];
The present invention relates to a method for treating incinerator dust ash, etc., which is characterized by adjusting the pH to 8.0 to 9.5 by adding and kneading with an acidic aqueous solution. The soluble sulfides used in the present invention are mono- or polysulfides or hydrogen sulfides of alkali metals, alkaline earth metals or ammonium, which are alkaline and have a reducing function and are in the categories mentioned above. When an aqueous solution or aqueous dispersion of soluble sulfide from incinerator dust ash is added and kneaded, the following formula (when CaS ₄ is used as the soluble sulfide): CaS ₄ +O ₂ +H ₂ O→CaS ₂ O ₃ +H ₂ S + S The H ₂ S generated as a result of the reaction removes heavy metals (M = Cd, Pb,
Hg, etc.) becomes a metal sulfide (MS) and stabilizes as shown in the following formula: H ₂ S + M ²⁺ →MS↓+2H ⁺ , and hexavalent chromium becomes stable as shown in the following formula: CrO ₄ ^2- +4H ₂ S→Cr ³⁺ +4H ₂ O+4S CrO ₄ ^2- +4CaS ₂ O ₃ →Cr ³⁺ +4CaSO ₄ +4S is reduced to trivalent chromium, and the trivalent chromium is converted to hydroxide due to the alkalinity of this system. It is thought that this will stabilize the temperature. In the present invention, an aqueous solution or aqueous dispersion of a soluble sulfide and an acidic aqueous solution are added and kneaded to incinerator dust collection ash, etc., and the pH is adjusted to 8.0 to 9.5. Simply adding and kneading an aqueous solution or aqueous dispersion of soluble sulfide to incinerator dust ash, etc. can prevent the elution of heavy metals to some extent, but adding and kneading an acidic aqueous solution together with this can prevent the pH from 8.0 to 9.5. When adjusted to , it is possible to almost completely prevent the elution of heavy metals. As such an acidic aqueous solution, it is advantageous to use a steel pickling waste solution containing divalent iron ions in order to simultaneously treat the waste solution itself. Examples will be given below to make the structure and effects of the present invention more specific, but the present invention is not limited to these Examples. <Example> Incinerator dust collection ash having the composition shown in Table 1 was treated, and an aqueous solution of a soluble sulfide and an acidic aqueous solution as shown in Table 2 were added and kneaded to 100 g of the incinerator dust collection ash. After that, PH, Cd, Pb, Cr ⁶⁺ and T−
The amount of Hg (total mercury) eluted was measured. The results are shown in Table 2. In addition, as an aqueous solution of soluble sulfide, 27.5 of CaS ₄
A wt% aqueous solution was used. In addition, as the acidic aqueous solution, we used hydrochloric acid waste solution after steel pickling, which contains 24% by weight of FeCl ₂ and 3% by weight of free HCl.
I used 10ml. The amount of elution was measured in accordance with the Environment Agency Notification No. 13 (revised March 14, 1980, No. 4).

【table】

[Table] <Effects of the Invention> As is clear from the results in Table 2, the present invention described above has the ability to prevent the elution of harmful heavy metals from incinerator dust ash, etc. by simple and economical means. The effect is that it can be almost completely prevented.

Claims (1)

[Claims] 1. Na ₂ S _n , K ₂ S _o , CaS _p , etc. in incinerator dust ash, etc.
(NH ₄ ) ₂ S _q , NaHS, KHS, Ca(HS) ₂ or (NH ₄ )HS [However, m, n, p, q are all 1
an aqueous solution or dispersion of an alkaline soluble sulfide having a reducing function selected from [an integer of ~5];
A method for treating incinerator dust ash, etc., which comprises adding and kneading an acidic aqueous solution to adjust the pH to 8.0 to 9.5. 2. The method for treating incinerator dust ash, etc. according to claim 1, wherein the acidic aqueous solution is a steel pickling waste liquid.