重铬酸铵清洁生产新工艺

New clean process for ammonium dichromate production

将铬酸钠碳氨转化得到的NaNH4CrO4.2H2O复盐结晶,经低温热分解得到铬酸钠和重铬酸铵,以这2个产物为原料经重结晶可以制备重铬酸铵产品。测定了Na2CrO4-(NH4)2Cr2O7-H2O体系的溶解度和相图,并以此为依据对热分解产物的重结晶分离制备重铬酸铵过程进行分析。结果表明:铬酸钠和重铬酸铵混合物经高温(100℃)溶解-冷却(50℃)结晶可以制备得到高纯度的重铬酸铵产品,收率为76.8%,母液可以蒸氨制备重铬酸钠,氨可在工艺中循环。该工艺具有清洁、环保的特点。

A new clean process for production of ammonium dichromate was developed by recrystallizing the low-temperature thermal decomposition products of sodium chromate （Na2CrO4） and ammonium dichromate from a double salt crystal, NaNH4CrO4·2H20 obtained from the carbonation process of Na2CrO4 in ammonia solution.The solubility and phase diagram of Na2CrO4-（NH4）2Cr207-H20 system were determined.According to the solubility data and phase diagram, the recrystallizing separation process of thermal decomposition products to prepare ammonium dichromate was analyzed.Results showed that the high purity ammonium dichromate could be obtained by dissolving and cooling crystallizing the thermal decomposition pro- ducts at 100 ~C and 50 ~C, respectively, and the yield of ammonium dichromate was 76.8%.Through ammonia still process, the mother solution could be reused, and the ammonia could be recycled in the process.Therefore,the process was cleaner and more environmentally friendly.