摘要
采用两步脱氟和一步脱重金属与砷净化湿法磷酸 ,得到磷酸杂质含量为 :w(Pb) <0 0 0 1% ,w(F) <0 0 0 4% ,w(As) <0 0 0 0 2 % ,可作为食品添加剂使用。探讨了pH值、温度以及脱氟剂、脱重金属与脱砷剂用量等对净化效果的影响 ,得到第一步最佳净化工艺条件 :温度为 90～ 95℃ ,脱氟剂 (SiO2 )用量为磷酸中含F总质量的 12 0 % ;第二步最佳净化工艺条件 :pH值为3 0～ 3 2 ,温度为 10℃以下 ,脱氟剂 (SiO2 +Na2 CO3)组分SiO2 用量为第一步净化后磷酸中含F总质量的 2 5 0 % ,两组分的质量比m(SiO2 )∶m(Na2 CO3) =(5～ 10 )∶1,脱重金属与脱砷剂 (Na2 S)用量为磷酸中含重金属与砷总质量的 2 80 %。进一步净化磷酸制得了食品级磷酸氢钙。
Wet-way phosphoric acid is purified by two-step method. Impurity contents in the purified acid are fluorine content w(F) [less-than or equal to] 0.004%, heavy metal content w(Pb) [less-than or equal to] 0.001% and arsenic content w(As) [less-than or equal to] 0.0002%. It is suitable for food. Influences of pH value, temperature and amounts of defluorinating agent, demetalating-dearsenicating agent on the results of purification are investigated in detail. The optimal conditions for purification process are obtained. In the first step, the temperature is 90-95°C, amount of defluorinating agent (SiO2) is 120% of the mass of fluorine in phosphoric acid before purification. In the second step, the pH value is 3.0-3.2, the temperature is below 10°C, amount of defluorinating agent(SiO2 + Na2CO3) is 250% of mass of fluorine in phosphoric acid after the first step purification and mass ratio m(SiO2):m(Na2CO3) = (5-10):1, and amount of demetaling-dearsenicating agent(Na2S) is 280% of the total mass of heavy metal and arsenic in phosphoric acid. Furthermore, food grade calcium hydrogen phosphate is prepared is prepared.
出处
《精细化工》
EI
CAS
CSCD
北大核心
2001年第5期265-267,共3页
Fine Chemicals
关键词
湿法磷酸
两步法
净化
食品级磷酸氢钙
制备
wet way phosphoric acid
two step method
purification
food grade calcium hydrogen phosphate
