铬酸钾电解-结晶制备重铬酸钾的工艺

利用阳离子膜，以K2CrO4电解结晶制备K2Cr2O7，考察了电流密度、温度、阴极液KOH浓度、阳极液K2CrO4浓度等因素对转化率、电流效率和直流能耗的影响；研究了K2Cr2O7不同浓度、不同转化率下的结晶纯度和收率及搅拌速率、降温速率和晶种加入量等对晶体粒度分布和形貌的影响. 结果表明，最佳电解工艺条件为：电流密度0.2 A/cm2，电解温度80℃，阴极液KOH浓度50 g/L，阳极液K2CrO4浓度400 g/L. K2Cr2O7转化率大于90%时，结晶纯度不低于99.8%. 优化的结晶条件为：溶液初始K2Cr2O7浓度500 g/L，搅拌速率300 r/min，降温速率0.5℃/min，不添加晶种. 所得产品符合GB 28657-2012要求.

Preparation of Potassium Dichromate by Potassium Chromate Electrolytic and Crystallization

The cationic membrane electrolysis of potassium chromate and potassium dichromate crystallization were studied. The effects of current density, temperature, KOH concentration and K2CrO4 concentration on electrolytic process were investigated. The purity and yield were studied under different concentrations and conversions of potassium dichromate solution. The effects of stirring rate, cooling rate and seeds adding on the particle size distribution and crystal morphology were researched. The results showed that, the optimum condition was current density of 0.25 A/cm2, electrolysis temperature of 80℃, KOH of 50 g/L and K2CrO4 of 400 g/L. The purity of crystal is not less than 99.8% when the conversion rate of K2Cr2O7 more than 90%. The optimize conditions of crystallization process were K2Cr2O7 initial concentration of 500 g/L, stirring speed of 300 r/min, cooling rate of 0.5℃/min, no seed adding. Product was completely in conformity to GB 28657-2012.