萃取法制取磷酸二氢钠的试验研究

Study on preparation of sodium dihydrogen phosphate by extraction method

中国磷酸钠盐的生产一般是以工业磷酸和碳酸钠或氢氧化钠为原料,生产成本较高。开发了一种以湿法磷酸、氯化钠为原料,采用连续萃取法制取工业级磷酸二氢钠的方法,并进行了连续化的模式试验研究。结果表明:在控制溶配液中磷酸与氯化钠物质的量比为1.1,溶配液(五氧化二磷质量分数为14.45%)与萃取剂的体积比为1:7,萃取温度为40～50℃,磷酸二氢钠料液的pH为4.2～4.5,盐洗液的pH为5.0～6.5,氯化铵液的pH为8.0～9.0的工艺条件下,试验得到的磷酸二氢钠产品质量可达到工业级磷酸二氢钠(HG/T2767—1996)指标要求。阐述了试验的基本原理、连续萃取法的工艺条件、产品质量和消耗,提出了直接采用湿法磷酸、氯化钠为原料生产工业磷酸钠盐的可行性。

Generally,production of sodium salts of phosphate in China was based on industrial phosphoric acid and sodium carbonate or sodium hydroxide as raw materials,however,production cost was relatively high.A new technology of preparing industrial grade sodium dihydrogen phosphate with wet-process phosphoric acid and sodium chloride by continuous extraction method was developed and continuous experimental study was carried out.Results indicated that the quality of sodium dihydrogen phosphate product could reach index requirements of industrial-grade sodium dihydrogen phosphate （HG/T 2767—1996） when amount-of-substance ratio of H3PO4 to NaCl was 1.1 in solution,volume ratio of the solution （mass fraction of P2O5 is 14.45%） to extracting agent was 1∶7,extraction temperature was 40～50 ℃,pH of sodium dihydrogen phosphate solution was 4.2～4.5,pH of salt washing solution was 5.0～6.5,and pH of ammonium chloride solution was 8.0～9.0.In addition,principles of experiment,process conditions of continuous extraction method,and product quality and consumption were expatiated,and feasibility of direct production of industrial grade sodium salts of phosphate with wet-process phosphoric acid and sodium chloride was put forward.