A concise and mild green synthetic route of sodium chromate through ferrochrome electrochemical oxidation and in-situ purification

Abstract

Sodium chromate (Na2CrO4) is the main semi-finished product for manufacturing all other chromium compounds with wide industrial applications. Unfortunately, the traditional processes for producing Na2CrO4 generate amounts of solid and liquid waste that pose serious threats to the environment and human health. Here, a green and convenient synthesis process for Na2CrO4 was developed by electrochemical oxidation of high carbon ferrochromium in sodium hydroxide aqueous solution at room temperature and atmosphere pressure. Through electrochemical oxidation process, Na2CrO4 was obtained from electrolyte conveniently. Furthermore, the prepared Na2CrO4 electrolyte was purified efficiently in-situ to remove water-soluble carbon and iron compound through one pot hydrothermal progress at 260 ℃ for 6 h. After the hydrothermal progress the water-soluble carbon particles were oxidized to Na2CO3 by Na2CrO4 while some chromium (III) compound microspheres possessing hierarchical microstructure was obtained. In the meantime, iron compound was adsorbed on the surface of chromium (III) compound microspheres. And the removal rate of iron compound was more than 99.9 %. The main factors influencing the electrochemical oxidation process were investigated including sodium hydroxide concentrations, reaction temperatures and current intensities. The new process is a promising cleaner approach for chromium compound industrial productions which prevent chromium pollution from the source.