Method for removing hexavalent chromium from polluted soil

Abstract

The invention discloses a method for removing hexavalent chromium from polluted soil. The method comprises the following steps: washing polluted soil in water, stirring, adding ferrous salt to reduce hexavalent chromium into trivalent chromium, and adding an alkaline conditioning agent while the addition of the ferrous salt in order to make the trivalent chromium form chromium hydroxide precipitate, wherein a weight ratio of soil to water to the ferrous salt to the alkaline conditioning agent is 100:300-2400:10-20:1-5, and the stirring reaction time is 10-60min. The method can effectively reduce the content of hexavalent chromium in soil.

Description

technical field [0001] The invention relates to a method for removing hexavalent chromium pollution in soil, belonging to the fields of chemistry and environmental treatment. Background technique [0002] In the past few decades, with the continuous development of industry, soil pollution has become more and more serious. Among them, the pollution of heavy metal chromium has attracted much attention. Hexavalent chromium is the main environmental pollution toxin and has strong oxidative properties. Intestinal ulcers, and even induce cancer. As one of the heavy metal ions, because it cannot be degraded by microorganisms, it accumulates in the soil for a long time and can be bio-accumulated, eventually causing it to seriously endanger human health through the food chain. Therefore, the remediation of heavy metal-contaminated soil is extremely important. How to remove hexavalent chromium pollution in soil has always been the foreword and hot spot in the field of environmental c...

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Problems solved by technology

[0004] Patent CN102500612A uses Na 2 EDTA solution washes heavy metal-contaminated soil to effectively remove effective cadmium and lead in the soil; patent CN102247980A uses a mixture of citric acid and pyrolusite as a leaching agent for chromium-contaminated soil, and the weight percentages of citric acid and pyrolusite are 95-99% respectively and 1-5%; CN103521513A uses reducing agent iron powder or sodium metabisulfite to reduce hexavalent chromium to trivalent chromium, but the problem with this method is that although the trivalent chromium can be precipitated by solid alkali at last, this method needs to adopt a specific design equipment, and still can not realize the separation of metal chromium from the solid phase soil to the liquid phase; similarly, CN102228901A also utilizes ferrous iron salt solution to add chromium-contaminated soil to reduce hexavalent chromium to trivalent chromium, and then lime The solution is injected into the soil to convert trivalent chromium into chromium hydroxide precipitation. The problem with this method is that the chromium still stays in the soil and cannot effectively remove secondary pollution.

[0005] More importantly, the applicant has carefully studied the effect of the reduction precipitation method in the prior art for removing hexavalent chromium pollution in soil, and found that it cannot remove hexavalent chromium in the soil due to the problem of dosage and reagent addition sequence. levels are reduced to acceptable levels

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