Wet detoxification and bioremediation combined method for chromium slag and chromium-contaminated soil

Abstract

The invention discloses a wet detoxification and bioremediation combined method for chromium slag and chromium-contaminated soil, wherein the method comprises the steps: pretreating waste slag containing hexavalent chromium or chromium-contaminated soil, removing large-particle materials, and conveying to a slurry stirring tank to obtain chromium-containing slurry; conveying the slurry to a wet detoxification acidification reduction tank, adding concentrated sulfuric acid, organic acid, hydroxy carboxylate and ferrous sulfate, carrying out acidification reduction reaction, dissolving out hexavalent chromium, and reducing hexavalent chromium into trivalent chromium; and then enabling the slurry to enter a reduction and stabilization tank, adding a reduction and stabilization agent for further reduction and stabilization reaction, and fully reacting hexavalent chromium to generate a stable trivalent chromium complex; then carrying out solid-liquid separation on the slurry, wherein filtrate flows into a wet detoxification reaction tank for recycling; and further carrying out biological reduction stabilizing treatment on dewatered cement cake, so as to ensure the long-term stability of the treated material.

Description

technical field [0001] The invention belongs to the field of pollutant treatment, in particular to a method for wet detoxification combined with bioremediation of chromium slag and chromium-contaminated soil. Background technique [0002] During the production of chromium salts using the traditional calcium roasting process, a large amount of chromium slag will be produced, which contains high-concentration and highly mobile carcinogen hexavalent chromium. And because the control measures are not in place, the chromium slag is stored in disorder and without anti-seepage. After several landfills and coverings, the mixed pollution of chromium slag and the storage area and surrounding soil is extremely serious, which intensifies the migration and diffusion of chromium pollution. Increased the difficulty of chromium pollution control. [0003] The wet detoxification process is a commonly used harmless treatment process for chromium slag. The wet detoxification process includes ...

AI Technical Summary

Problems solved by technology

In the acidification stage, a large amount of sulfate ions tend to form calcium sulfate precipitates and wrap on the surface of chromium slag, hindering the dissolution of hexavalent chromium

And a large amount of sulfate can easily lead to soil salinization (alkali), which will cause soil compaction, deterioration of physical and chemical properties, and increase of groundwater salinity

[0006] 2. After a large amount of concentrated sulfuric acid is added, there will be escape phenomenon, resulting in too high concentration of acid mist in the workshop, affecting the health of operators

[0007] 3. In the neutralization reaction stage, if it is necessary to increase the pH to form Cr(OH)3 precipitates, a large amount of lime milk (8% to 20% of the mass of chromium slag) needs to be added, and the dosage is large, and the lime neutralization reaction increases. The capacity is relatively large, which is not conducive to subsequent backfilling

[0008] 4. The reaction time is long, usually between 6 and 12 hours, resulting in a large equipment footprint, high investment costs, and low engineering efficiency

[0009] 5. The traditional wet detoxification process is only aimed at the reduction and fixation of heavy metal element chromium, while chromium slag and chromium-contaminated soil are usually accompanied by other heavy metal elements such as zinc, nickel, arsenic, mercury, etc. It is necessary to comprehensively consider the remediation of heavy metal pollution

[0010] 6. The chromium slag is landfilled directly after wet detoxification, which cannot maintain a long-term reducing atmosphere and long-term stability. After a certain period of time, there are a lot of signs of "returning to yellow"

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