Method for treating hexavalent chromium in solid wastes

Abstract

A method for treating hexavalent chromium in solid wastes comprises the following steps: mixing a heavy metal stabilizer with pulverized or powdery solid wastes, adding water, stirring uniformly, standing and solidifying to form a solidified material, wherein the heavy metal stabilizer is a hydrodithiocarboxylate compound as shown in formula I; maintaining the formed solidified material for more than 1 day under natural conditions; and detecting leaching toxicity of the maintained solidified material. The hexavalent chromium is reduced into trivalent chromium under mild conditions, metal chelating is carried out to generate stable heavy metal chelate, a large number of acid and alkali do not need to be consumed additionally, the chemical feeding amount is small, resources and energy are saved, and secondary pollution is avoided; a solidifying and stabilizing effect can be achieved without additionally adding a solidifying agent, the cost is reduced, and capacity increasing is avoided;and the leaching toxicity Cr6+ of the stabilized solid wastes is lower than the national standard limit value, and thus, the method is suitable for being popularized and used.

Description

technical field [0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method for treating hexavalent chromium in solid waste. Background technique [0002] With the development of economy and social progress, various environmental pollution problems have become prominent in people's daily life, especially heavy metal pollution, which has become the most serious problem in my country's environmental pollution control, and the pollution disposal demand of heavy metals in solid waste is particularly urgent. [0003] Heavy metal chromium mainly comes from chromium ore processing, electroplating, chemical industry, leather making, textile, printing and dyeing and other industries. Among them, hexavalent chromium has high water solubility and toxicity, and is considered to be a carcinogenic, teratogenic and mutagenic substance. It is not easy to be biodegraded and difficult to handle. It is a ubiquitous pollutant. [0004] At...

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Problems solved by technology

[0005] The high-temperature reduction method (dry method) mainly uses reducing substances to reduce hexavalent chromium to trivalent chromium at high temperature, but there are problems such as high processing cost, small processing amount, and incomplete processing.

[0006] The wet reduction method (wet method) mainly focuses on the chemical treatment method, that is, the use of reducing substances in the liquid medium to convert hexavalent chromium into trivalent chromium and fix it, such as ferrous sulfate reduction method and sulfite reduction method , barium salt method, etc., and then developed the ferrite method, ion exchange method, electrolysis method, etc., but due to the poor treatment effect of these methods, it is difficult to meet the standards or due to high cost, economically unfeasible and other reasons, to a large extent limit its practical application

[0007] The solidification / stabilization method is to pulverize the solid waste containing hexavalent chromium, add a reducing stabilizer such as ferrous sulfate or inorganic acid according to a certain proportion after pulverization, reduce the hexavalent chromium to trivalent chromium, and then add an appropriate amount of solidification Such as cement, etc., add water and stir, solidify and condense, seal the chromium-containing compound in the solidified body substrate, it is difficult to dissolve again, and achieve the purpose of solidification stabilization and harmlessness, but this method needs to add a large amount of curing agent, causing increase problems such as capacity and cost increase

[0008] In addition, the conventional method for treating hexavalent chromium is to add a reducing agent under acidic conditions to reduce the highly toxic hexavalent chromium to less toxic trivalent chromium, and then add alkaline substances to form chromium hydroxide precipitates. However, this The method requires high treatment conditions, consumes a large amount of acid and alkali, and the dosage of reducing agent is far greater than the theoretical value, which is easy to cause waste of reducing agent and secondary pollution.

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