摘要
以粗钼酸钠溶液为原料,采用净化—双极膜电渗析—结晶法制备高纯钼酸产品.考察了净化过程离子交换关键参数对钙、镁等离子吸附容量的影响;双极膜电渗析过程中钼酸钠溶液中初始钼浓度、电流密度等对电耗的影响;结晶时间对钼酸纯度的影响.结果表明:粗钼酸钠溶液经离子交换达到Ca、Mg离子浓度均<0.3 mg/L的最佳作业参数为吸附前钼酸钠溶液pH值9～10、吸附溶液流速8～16 m/h.双极膜电渗析较优工艺参数为:盐室钼酸钠溶液Mo浓度80～100 g/L、电流密度300～400 A/m2、Mo的收率大于99.97%、K残留浓度为3.7 mg/L、Na残留浓度86.4 mg/L;电流效率平均约67.8%,直流电耗为925 kWh/T[Mo].钼酸溶液蒸发180 min所得钼酸产品的粒径大小更加均匀,纯度高,溶解性等符合催化剂行业原料标准.
Abstract
High-purity molybdate products were prepared from crude sodium molybdate solution by purification-bipo-lar membrane electrodialysis-crystallization method.The effects of key parameters of ion exchange on the adsorption capacity of calcium and magnesium ions in the purification process,the effects of initial molybdenum concentration and current density in sodium molybdate solution on power consumption in the process of bipolar membrane electro-dialysis,and the effects of crystallization time on the purity of molybdic acid were investigated.The results showed that the optimum operating parameters for crude sodium molybdate solution to reach the concentration of Ca and Mg ions both<0.3 mg/L by ion exchange were pH 9～10 of sodium molybdate solution before adsorption,and the flow rate of adsorption solution was 8～16 m/h.The more optimum process parameters for bipolar membrane electrodial-ysis were Mo concentration of sodium molybdate solution in the salt chamber was 80～100 g/L,the current density was 300～400 A/m2,and the Mo yield was greater than 99.97%,K residual concentration was 3.7 mg/L,and Na residual concentration was86.4 mg/L;the average current efficiency was about 67.8%,and the DC power con-sumption was 925 kWh/T[Mo].The molybdic acid product obtained by evaporating the molybdic acid solution for 180 min had a more uniform particle size,high purity,and solubility,etc.,in accordance with the standards for raw materials in the catalyst industry.
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