铬酸钠溶液中微量铝硅杂质的脱除

采用铝硅含量分别为189.65和51.08 mg/L的铬酸钠配制溶液，通过常压和高压反应脱除杂质微量铝硅. 常压下加入偏铝酸钠调节体系铝硅元素比为6，无需CaO添加剂，60℃下反应40 min，几乎可完全脱除杂质硅；在高压釜中通过调节CO2压力为0.4 MPa，60℃下反应20 min，几乎能完全脱除杂质铝. 化学纯铬酸钠脱除铝硅杂质后能达到分析纯级别. 高压釜内脱铝的同时铬酸钠发生碳化反应，溶液pH值随反应进行逐渐降低，趋于稳定，显示碳化反应近于平衡.

Removal of Trace Al and Si Impurities in Sodium Chromate Solution

By using simulated sodium chromate solution containing trace Al and Si impurities at 51.08 and 189.65 mg/L respectively, their removal was carried out with the reactions at atmospheric and high pressures. Under atmospheric pressure, when the elemental ratio of Al to Si in the solution with addition of NaAl(OH)4 was 6, and reaction time 40 min at 60℃, Si could be removed completely without addition of CaO. When CO2 pressure was 0.4 MPa in an autoclave, and reaction time 20 min at 60℃, Al could be removed completely. Chemically pure sodium chromate could reach the level of analytical purity after removal of Al and Si impurities. During dealumination in the autoclave, the carbonation reaction of sodium chromate also proceeded, pH value was gradually reduced with the reaction, and approached to stable state, showing that the carbonation reaction approached equilibrium.