Method for efficiently removing nitrate radical impurities in cobalt sulfate solution

Abstract

The invention provides a method for efficiently removing nitrate radical impurities in a cobalt sulfate solution. The method comprises the steps of firstly, adjusting the pH value of a crude cobalt sulfate solution to be lower than or equal to 2.5 with dilute sulphuric acid; then adding a formaldehyde solution with the concentration being 40% and the mass of nitrate radicals being 0.4-0.5 time to the cobalt sulfate solution; conducting a reaction at the temperature of 75-85 DEG C; then removing formaldehyde left by the reaction with hydrogen peroxide with the concentration being 30% and the formaldehyde amount being 1.4-1.5 times; then conducting filtration, concentration, cooling and crystallization, so that high-purity cobalt sulfate heptahydrate is obtained. The impurity removal method is easy and convenient to operate, short in production procedure, mild in technological condition and easy to control; no other impurity is generated in the reaction process except a target product, gas and water; the nitrate radical impurities can be effectively removed; the content of the nitrate radical impurities in an obtained cobalt sulfate hexahydrate product can reach 0.02% or below; the method meets the using requirements of such industries as electronic information, batteries, catalysis and analytical tests.

Description

technical field [0001] The invention relates to a method for removing impurities, in particular to a method for removing nitrate impurities in a metal salt solution, and more particularly to a method for efficiently removing nitrate impurities in a cobalt sulfate solution. Background technique [0002] Cobalt sulfate heptahydrate is a rose-red monoclinic crystal, which turns into a red powder after dehydration, soluble in water and methanol, slightly soluble in ethanol. In the past, cobalt sulfate was mainly used in ceramic glazes and paint driers, as well as in electroplating, alkaline batteries, production of cobalt-containing pigments and other cobalt products, catalysts, analytical reagents, tire adhesives and lithopone additives, etc.; In recent years, cobalt sulfate has been widely used as a raw material for secondary battery cathode materials, and has broad market prospects. However, the existence of nitrate in cobalt sulfate has a great impact on its performance. In ...

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Problems solved by technology

[0004] For the impurity removal of cobalt sulfate products, how to remove the metal impurities in the cobalt sulfate solution is more studied at present, such as the Chinese patent with the patent number ZL201110101859 and the name "Preparation Method of Cobalt Sulfate", which introduces the removal of cobalt leaching solution. Miscellaneous method, this method is to use oxidation precipitation to remove impurity elements such as manganese, iron, arsenic in the cobalt sulfate leaching solution, and then remove impurity elements such as calcium and magnesium through fluoridation precipitation, this patent can only remove metal impurities, how to remove nitrate Impurities are not mentioned; the patent No. is ZL201280059603, and the Chinese patent titled "Manufacturing Method of Cobalt Sulfate" introduces a method for obtaining a high-concentration cobalt sulfate solution through solvent extraction using an acidic organic extractant, but this method is only Removal of metal impurities such as calcium, magnesium, sodium, etc., does not remove nitrate

For how to remove the nitrate impurities in the cobalt sulfate solution, the current method is generally to adopt crystallization and recrystallization to keep the nitrate in the crystallization mother liquor, but the nitrate content in the product after the mother liquor is applied mechanically for many times is relatively high, which cannot be reached at all. Requirements for the use of electronic information, batteries, catalysis, analysis and testing industries