Method for continuously preparing sodium dichromate by ionic membrane electrolysis

Abstract

The invention relates to a method for continuously preparing sodium dichromate by an ionic membrane electrolysis. The method comprises the following steps of: firstly, neutralizing industrial alkaline sodium chromate solution, removing impurities, and collecting filtrate serving as feed solution of electrolysis process; secondly, introducing the filtrate into an anode chamber in a one-membrane two-chamber ionic membrane electrolyzer, and introducing sodium hydroxide solution into a cathode chamber, wherein anions and cations migrate to the anode and the cathode respectively under the action of an electric field, sodium dichromate acidizing fluid is obtained in the anode chamber, high-concentration sodium hydroxide solution is obtained in the cathode chamber, and hydrogen and oxygen are produced on a positive electrode and a negative electrode respectively; and finally, performing evaporation concentration and natural cooling crystallization on the sodium dichromate acidizing fluid to separate out dehydrate sodium dichromate products. The method has the advantages of short process, low cost, high purity of the obtained sodium dichromate products, near 100 percent of raw material utilization rate, and high economic value of byproducts.

Description

Technical field [0001] The invention belongs to the technical field of inorganic salt materials, and relates to a method for preparing sodium dichromate, in particular to a method for continuously preparing sodium dichromate by ion-exchange membrane electrolysis. Background technique [0002] my country is a big country in the production and consumption of chromium salts. The domestic production of chromium salts is increasing year by year. At present, the annual output of chromium salts has exceeded 300,000 tons, accounting for more than a quarter of the total output of chromium salts in the world. The hexavalent chromium in the three waste emissions from the chromium salt production process has strong oxidizing properties, which will cause corrosion and damage to organisms, and make organisms prone to poisoning. Therefore, the chromium salt industry has long been listed as the top polluting industry. The environmental protection problem of chromium salt production is still a wo...

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Problems solved by technology

[0003] The traditional chromium salt production method has many shortcomings such as large chromium-containing waste residue, waste water, and waste gas discharge, low conversion rate of main metal chromium, and serious equipment corrosion.

Sodium dichromate is prepared by sulfuric acid acidification in my country and abroad, and the limitations of this technology have become increasingly obvious: the operating environment is harsh, the application of chromium-containing Glauber's salt is difficult, and the production efficiency is low.

This situation not only hinders the sustainable development of the chromium salt industry, but also is not conducive to the overall development of the national economy. It is urgent to develop new production technologies to produce high-quality chromium salt products to meet market demand.

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