工业级磷酸二氢钾除砷制备食品级聚偏磷酸钾

Production of food grade potassium polymetaphosphate from industrial potassium dihydrogen phosphate by trace arsenic removal

介绍了以工业级磷酸二氢钾为原料,通过去除微量的砷杂质制备食品级磷酸二氢钾,再经过脱水聚合制备聚偏磷酸钾的方法。其中微量砷离子脱除是重要的一步。除砷方法是将工业级磷酸二氢钾加热至熔融状态,利用氢卤酸与砷离子反应生成低沸点的卤化砷,并在高温下气化分离出去,以达到脱除微量砷的目的,得到食品级磷酸二氢钾。考察了反应时间、搅拌转速、卤化氢用量对除砷效果的影响,当磷酸二氢钾与氢卤酸物质的量比低于16.7、搅拌转速大于250 r/min、反应时间在45 min以上时,可以使工业级磷酸二氢钾中的砷含量达到食品级磷酸二氢钾的要求。采用化学分析以及X射线衍射(XRD)、红外光谱(IR)、拉曼光谱(Raman)等表征手段,综合分析了聚偏磷酸钾实验样品的黏度、分子组成等,并与商业样品相比较,结果表明二者性质一致,并达到了国家标准的要求。

A preparation method for food grade potassium polymetaphosphate with industrial grade potassium dihydrogen phosphate as raw material,by removing trace arsenic to food grade potassium dihydrogen phosphate and by subsequent dehydration polymerization was introduced.It was of great importance that the trace arsenic removal in all the steps.During the removal,potassium dihydrogen phosphate was heated to a molten state at first,hydrogen halogen acid and arsenic ion had a reaction between each other so as to obtain low boiling point arsonium halide.Food grade potassium dihydrogen phosphate would be obtained after gasification separation at high temperature.The influences of reaction time,stirring speed and the amount of hydrogen halide on the removal effect were investigated.When the amount of substance ratio of potassium dihydrogen phosphate to halogen acid was lower than 16.7,the stirring speed was higher than 250 r/min,and reaction time was above45 min,the arsenic content in industrial potassium dihydrogen phosphate could reache the standard of food grade.The structure and viscosity etc.of potassium polymetaphosphate samples were characterized by XRD,IR and Raman.Compared with the commercial samples,they were consistent in nature and met the requirements of the national standard.