Improved process for wet detoxification of hexavalent chromium-containing waste residues or hexavalent chromium contaminated soil

A technology of polluting soil and hexavalent chromium, which is applied in the field of pollution control, can solve problems such as difficult stirring, unfavorable reduction of hexavalent chromium, thickening of slurry, etc., to reduce calcium sulfate precipitation, promote full contact, and reduce aging time Effect

Pending Publication Date: 2019-08-16
BEIJING GEOENVIRON ENG & TECH
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  • Abstract
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  • Application Information

AI Technical Summary

Problems solved by technology

[0006] 2. Add sulfuric acid for acidification treatment. Since most of the chromium slag has a high calcium content, when sulfuric acid is added, the sulfate radical and calcium form calcium sulfate. Because the amount of water added to the slurry is small, the concentration of calcium sulfate in the slurry is too high to easily form calcium sulfate Precipitation (the solubility of calcium sulfate is about 2g / L), causing the slurry to become thick and difficult to stir;
[0008] 4. Mature the reducing agent and the acidified hexavalent chromium slurry in the stirring tank. If the curing time is not long enough, it will be unfavorable for the reduction of hexavalent chromium. If the curing time is too long, on the one hand, the energy consumption will be high, and on the other hand, the Reduced efficiency of wet detoxification systems

Method used

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  • Improved process for wet detoxification of hexavalent chromium-containing waste residues or hexavalent chromium contaminated soil

Examples

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Effect test

Embodiment 1

[0057] The mixture of chromium slag and soil at the original site of a chromium salt production enterprise in Baiyin, Gansu Province, the content of hexavalent chromium is 2000-3000mg / kg.

[0058] S1, put the slag mixture that has been screened and ground into a ball mill for wet grinding, so that it can pass through a 100-mesh sieve;

[0059] S2, first pump the sulfuric acid (10% solution)-acetic acid (5% solution) mixed solution with a volume ratio of 1:1 into the acidification reaction tank, then gradually pump the slurry through the 100 mesh sieve into the acidification reaction tank and acidification reaction tank The solution is mixed and stirred to keep the pH of the slurry in the range of 5-6, and aged for 6 hours;

[0060] S3, gradually pump the slurry after the acidification into the reduction reaction tank and stir and mix it with the reducing agent. The pumping time is 2 hours. The ratio of the aqueous solution of the reducing agent in the reduction reaction tank i...

Embodiment 2

[0065] The mixture of chromium slag and soil at the original site of a chromium salt production enterprise in Zhangye, Gansu has a hexavalent chromium content of 4000-5000mg / kg.

[0066] S1, put the slag mixture that has been screened and ground into a ball mill for wet grinding, so that it can pass through a 150-mesh sieve;

[0067] S2. Pump the sulfuric acid (20% solution)-acetic acid (10% solution) mixture with a volume ratio of 3:1 into the acidification reaction tank, and then gradually pump the slurry passing through the 150 mesh sieve into the acidification reaction tank to mix with the acid solution Stir to keep the pH of the slurry in the range of 5-6, and age for 6 hours;

[0068] S3, gradually pump the slurry after the acidification into the reduction reaction tank and stir and mix it with the reducing agent. The pumping time is 2 hours. The ratio of the aqueous solution of the reducing agent in the reduction reaction tank is as follows: the molar ratio of ferrous s...

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Abstract

The invention discloses an improved process for wet detoxification of hexavalent chromium-containing waste residues or hexavalent chromium contaminated soil. The process comprises the following steps:a) carrying out wet grinding treatment on hexavalent chromium-containing waste residues or hexavalent chromium contaminated soil to obtain residue slurry; b) conveying the residue slurry into a sulfuric acid-acetic acid mixed solution for acidification treatment to obtain slurry; c) conveying the slurry into a reducing agent solution for a reduction reaction to convert hexavalent chromium in theslurry into trivalent chromium; and d) carrying out solid-liquid separation on the trivalent chromium slurry after the reduction reaction, recycling the separated filtrate for acidification treatment,and carrying out external maintenance treatment on the separated filter cake. Acetic acid is added to reduce generation of calcium sulfate precipitates in the wet detoxification process, so that hexavalent chromium pollutant particles are prevented from being wrapped by the calcium sulfate precipitates, and dissolution of hexavalent chromium in the acid leaching stage is improved. According to the method, the acidified slurry is gradually added into the reducing agent solution, so that the hexavalent chromium pollutant particles are promoted to be in full contact with the reducing agent, anda microenvironment beneficial to reduction reaction is held on a reaction interface.

Description

technical field [0001] The invention relates to the technical field of pollution control, in particular to an improved process for wet detoxification of hexavalent chromium-containing waste residue or hexavalent chromium-contaminated soil to realize harmless treatment of hexavalent chromium-containing pollutants. Background technique [0002] At present, the waste slag containing hexavalent chromium has been harmlessly treated, but because most of the chromium slag stockpiles have been stored for a long time and there is a lack of measures to prevent the spread of hexavalent chromium, the soil in the chromium slag storage area has also been seriously polluted, and some The waste residue containing hexavalent chromium is mixed with the polluted soil. The harmless treatment of hexavalent chromium-containing waste residue and hexavalent chromium-contaminated soil in the site is an important part of the comprehensive treatment of hexavalent chromium-contaminated sites. [0003]...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B09C1/08
CPCB09C1/08
Inventor 李淑彩方华祥李来顺吕正勇闾文景宋登慧苗竹朱湖地
Owner BEIJING GEOENVIRON ENG & TECH
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