JPH0474073B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention is a detoxifying treatment agent for industrial waste containing hazardous heavy metals. Collection of hazardous heavy metals in wastewater or industrial waste characterized by containing humic acid as a stabilizer in a dialkyldithiocarbamate represented by (R is an alkyl group and M is Na or NH ₄ ) This is related to drugs. When added to industrial waste containing hazardous heavy metals, such as factory wastewater containing heavy metals or contaminated soil containing heavy metals, it reacts with the heavy metals to produce insoluble substances, rendering the industrial waste harmless. It is used in such pollution fields. (Prior art) Conventionally, methods such as neutralization with alkaline agents, coagulation, and precipitation, electrolytic methods, ion exchange methods, and cement fixation methods have been used to treat this type of industrial waste. Ta. (Problem to be solved) Conventional methods such as neutralization, coagulation, and precipitation using alkaline agents do not have a perfect treatment effect, and in particular complex compounds containing copper ammonium complex salts cannot be treated with this method. Ta. The ion exchange method requires another processing device for regeneration, and has the drawback of increasing equipment costs except for metal reuse methods. Consolidation with cement is cost-effective for highly concentrated hazardous wastes, but consolidating general waste with concrete requires a large amount of cement, and the amount of material to be treated after consolidation increases. However, there were disadvantages such as the cost and location of dumping. (Specific means for solving the problem) The present invention is a detoxifying treatment agent for wastewater or industrial waste containing harmful heavy metals. Collection of hazardous heavy metals in wastewater or industrial waste characterized by containing humic acid as a stabilizer in a dialkyldithiocarbamate represented by (R is an alkyl group and M is Na or NH ₄ ) Related to drugs. When a conventional dialkyldithiocarbamate is used alone, two molecules of the treatment agent itself combine with each other due to natural air oxidation to form a thulum-based compound, which loses its binding strength with heavy metal ions. In the present invention, by mixing humic acid with dialkyldithiocarbamate, 2 moles of sialkyldithiocarbamate does not become a thulum-based compound, stably retains its own chemical composition even in natural conditions, and can be used in wastewater or industrial applications. It is unique in that it combines with hazardous heavy metals in waste to produce insoluble substances, making it completely harmless. Furthermore, this humic acid itself reacts with heavy metals to produce a chelate with strong binding strength, and when used in combination with a dialkyldithiocarbamate, the effects are mutually enhanced and the performance as a processing agent is improved. When the waste is contaminated water, by adding the product of the present invention, toxic metals react and change into insoluble substances, which are separated and removed, thereby completely rendering the water harmless. When the waste is contaminated soil, after kneading the product of the present invention, it is solidified using a suitable solidifying agent such as cement to prevent harmful metals from re-eluting, making it possible to completely render it harmless. In the present invention, in the case of contaminated water, the required amount of treatment agent is
Although it varies depending on the content of hazardous metals in the waste, the minimum amount necessary for detoxification is generally 2 of the hazardous metals contained in the amount of dialkyldithiocarbamate.
It is necessary to add more than twice the molar amount. If the amount is less than this, harmful metals may remain in the water in the form of ions, and especially for zinc ions, 3 times the molar amount was optimal. In the case of contaminated soil, it is possible to completely sequester the toxic metal ions contained in the waste by adding the present invention in a molar amount more than twice that of the toxic metals and cement in an amount of 12% or more based on the weight of the contaminated soil. done. The reaction mechanism by which the product of the present invention is effective is thought to be that M ions in the dialkyldithiocarbamate stably replace harmful heavy metal ions in the presence of humic acid. This reaction showed different conditions depending on the pH range, and the reaction was effective at a pH of 6 or higher, and residual metal ions could be completely removed. Representative substances of dialkyldithiocarbamates include sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, sodium dipropyldithiocarbamate, and sodium dibutyldithiocarbamate. Humic acids include soil humic acid and coal humic acid, both of which can be used. These have ion-exchange properties and exhibit colloidal properties, and this property is presumed to be effective in collecting heavy metals, and because they have polyvalent phenol groups and carboxyl groups, It is presumed that this prevents deterioration of the bonding strength of dithiocarbamic acid compounds with heavy metals due to natural oxidation in the air. The product of the present invention also has reducing power, which is about 10 times or more compared to ferrous sulfate and the like. Therefore, it has a very effective effect on waste containing hexavalent chromium and the like. In other words, it has the power to reduce harmful hexavalent chromium to trivalent chromium, and this means that when the waste is contaminated water, the hexavalent chromium ions first turn into trivalent chromium ions in an aqueous solution, and then the present invention It is thought to combine with other substances to form an insoluble substance. If the waste is contaminated soil, the hexavalent chromium in the contaminated soil is reduced to trivalent chromium and then consolidated with cement, making it a harmless treated product that does not contain hexavalent chromium. (Example 1) Humic acid used as an experimental material was obtained by removing accompanying substances in humic substances with an organic solvent and extracting with dilute alkali.
Adjusted concentrations of copper, zinc, lead, cadmium, and hexavalent chromium were used. The pH was unified to 7.5. Two experimental methods were used for comparison: adding sodium dimethyldithiocarbamate to a certain amount of waste liquid, and adding the product of the present invention mixed with humic acid. The reaction product produced by the addition was removed using qualitative filter paper No. 2, the pH of the filtrate was adjusted to 7.5, and the amount of residual metal ions (mg/) was measured using an atomic absorption spectrometer. (1) Comparative Example: Table 1 shows the results when sodium dimethyldithiocarbamate was treated alone. However, the ion amount is in units of mg/.

【table】

[Table] (2) Comparative example: In the case of single treatment with humic acid, the treatment results are shown in Table 2. The amount of humic acid added is the number of grams per 1 part of waste water.

[Table] (3) Example of the present invention: 0 to 10 humic acid added to 2 moles of sodium dimethyldithiocarbamate (DDTC)
% addition is shown in Table 3. However, the case where the amount of humic acid added is 0 is a comparative example.

【table】

[Table] (Example 2) The experimental materials were the same as in Example 1, except that sodium dimethyldithioorbamate was added 3 moles per mole of harmful metal ions contained in the waste, and 3 moles of sodium dimethyldithioorbamate were added.
A 10% mixture of humic acid was added as a treatment agent based on mole/mol. As a comparative example, the PH value is 2~
5. Table 4 shows the results when the pH value changed from 6 to 11 as an example of the present invention.

[Table] However, the unit of ion amount is ppm. (Example 3) 1 kg of contaminated soil containing 3000 ppm each of copper, zinc, lead, cadmium, and hexavalent chromium as toxic metals was taken, and a mixture of sodium dimethyldithiocarbamate and humic acid was used as a treatment agent for each toxic metal. Cement was added in an amount of 2 to 3 times the molar amount, and 5 to 16% of cement was added to the weight of the contaminated soil, and the mixture was thoroughly kneaded. The comparative example has a small amount of cement added, and the example of the present invention has an added amount of 12 to 14% or more. As an experimental method, the solidified processed material was left to stand for 24 hours, and the amount of toxic metal ions re-eluted was measured using the Environment Agency Notification No. 13, ``Method for Assaying Hazardous Substances Contained in Industrial Waste.'' The results are shown in Tables 5 and 6.

【table】

【table】

[Table] (Effects of the invention) In a comparative example in which dialkyl carbamate and humic acid were used alone as a scavenger for harmful heavy metals as in Example 1, the scavenging effects were as shown in Tables 1 and 2. has not improved much. On the other hand, as shown in Table 3 of the invention examples, when the dialkyldithiocarbamate of the invention mixed with humic acid is used, it is possible to treat the treatment solution until residual heavy metal ions are not detected. It becomes possible,
This is an epoch-making achievement as it has not been possible to completely treat residual heavy metal ions in the past. It is also effective to mix about 8% or more of humic acid with sodium dimethyldithiocarbamate (a solution of about twice the molar amount or more). For the product of the present invention to work effectively, the PH value is preferably 6 or more, and this is shown in Experimental Example 2. If the target is contaminated soil, as in Example 3, in addition to the product of the present invention containing dialkyldithiocarbamate in a molar amount or more twice that of toxic metals, add cement in an amount of approximately 14% or more based on the weight of the contaminated soil. Then it works.

Claims (1)

[Claims] 1. As a detoxification treatment agent for wastewater or industrial waste containing hazardous heavy metals. (wherein R is an alkyl group and M is Na or NH ₄ ) A hazardous heavy metal collector in wastewater or industrial waste characterized by containing humic acid as a stabilizer in a dialkyldithiocarbamate. .