Chromic salt production and extracting and reducing method of hexavalent chromium from chromic slag left behind society

Abstract

The invention discloses a method for extracting and reducing sexivalent chrome in chromium residue which is produced in chromate production and remained in the society. The method of the invention adopts a porous slot to load chromium residue (needing no grinding disposal); the sexivalent chrome liquor in the chrome residue is extracted under the conditions of pressurizing high-temperature saturation, high-pressure and vacuum by adding water in an autoclave; acid water is then added in the autoclave to dip and dissolve calcium chromate in the chrome residue, which is then converted into sexivalent chrome solution; the sexivalent chrome liquor is then extracted under the conditions of high pressure and vacuum; reduction reagent (ferrous sulfate) is added in the autoclave to reduce the sexivalent chrome residual in the chrome residue and converts the sexivalent chrome residue into trivalent chromium which is then fixed in the chrome residue; the gained sexivalent chrome can be used for preparing chrome products; the disposed non-toxic chrome residue can be used for auxiliary materials of cement and concrete, brick aggregate used for building and natural filling and disposal.

Description

A method for extracting and reducing hexavalent chromium in chromium salt production and chromium residue left over from society technical field The invention relates to a method for extracting and reducing hexavalent chromium in chromium salt production and chromium slag left over from society. Background technique The production of chromium salt is based on chromite, limestone and soda ash as raw materials. After calcination, trivalent chromium is oxidized to hexavalent chromium, and then hexavalent chromium is leached with water to make sodium dichromate (called chromium salt). The discharged residue called chrome residue. Chromium slag generally contains 1% to 2% of sodium chromate and calcium chromate (hexavalent chromium), and the hexavalent chromium in it will be leached out when exposed to water, polluting water and soil, and endangering life. Therefore, chromium slag is classified as hazardous waste by the national environmental protection department, and the nat...

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Problems solved by technology

(3) Calcium chromate in the chromium slag is soaked and dissolved in acid water and converted into an aqueous solution of hexavalent chromium, and the chromium slag is fully soaked through high temperature and high pressure, so that the acid-soluble hexavalent chromium in the chromium slag is fully extracted, and the crystalline chromium in the chromium slag is solved. Secondary pollution caused by calcium acid;

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