Method for producing chromium oxide green with low soluble chromium and zero hexavalent chromium

Abstract

The invention discloses a method for producing chromium oxide green with low soluble chromium and zero hexavalent chromium, which comprises the following steps of S1, producing chromium oxide green byadopting a chromic anhydride thermal decomposition method: directly putting chromic anhydride into a rotary kiln, and performing high-temperature thermal decomposition at the temperature of 1100 DEGC to produce chromium oxide green, S2, conducting thermal treatment: directly mixing urea into the chromium oxide green produced in the step S1 at the material temperature of 350-460 DEG C at the tailof a rotary kiln for reaction, S3, putting the chromium oxide green product treated by the thermal method in the step S2 into a washing slurrying tank, and adding an organic reducing agent and the chromium oxide green product into the washing slurrying tank for mixing reaction, and after the reaction is finished, adding caustic soda until the pH value of the material is 7-7.5, and S4, sequentially filtering, drying and crushing the material finally obtained in the step S3, and producing to obtain the final chromium oxide green product. The hexavalent chromium content of the product produced by the method can be reduced to below 1ppm, the soluble chromium content is reduced to below 20ppm, and the international and domestic low soluble chromium and zero hexavalent chromium chromium chromium oxide green product standards are met.

Description

technical field [0001] The invention relates to the technical field of metallurgy and chemical industry, in particular to a production method of chromium oxide green which is green and environment-friendly and can realize low soluble chromium and zero hexavalent chromium. Background technique [0002] With the increasing awareness of environmental protection in the current society, chromium-based products need to develop green environmental protection products with zero hexavalent chromium and low soluble chromium. The chromium oxide green produced by the traditional chromic anhydride thermal decomposition method puts chromic anhydride into the rotary kiln and thermally decomposes it at a temperature of 1050-1350°C to form chromium trioxide. However, because chromic anhydride itself is a hexavalent chromium salt product, some Complete hexavalent chromium is not decomposed, so the hexavalent chromium produced is generally between 200-1000ppm, and the soluble chromium is highe...

AI Technical Summary

Problems solved by technology

However, it is found in the actual production process that the above-mentioned method can generally treat hexavalent chromium to below 10ppm, and there are still difficulties in further processing to reduce hexavalent chromium, but the biggest problem is that the chromium sulfate generated after the reduction of hexavalent chromium by sulfur in thiourea is Soluble trivalent chromium salt, soluble chromium is still greater than 100ppm, which cannot meet the standard requirements of chromium oxide green products with low soluble chromium

[0004] CN108793252A (public date: 2018.11.13) discloses a method for reducing hexavalent chromium in chromium oxide green, and records a method for reducing hexavalent chromium in the product through thermal decomposition using reducing agents such as ammonium salt, ammonia water, alcohol and aldehyde , which has basically the same principle as CN103253709A, through thermal treatment to achieve the purpose of reducing hexavalent chromium in the product, but can not achieve the effect of completely reducing the soluble chromium in the product to below 20ppm