真空浓缩冷却结晶法减少弗洛斯坦镀锡液中的亚铁离子

Decrease of ferrous ions in Ferrostan tinning bath by vacuum concentration and cooling crystallization

采用真空浓缩冷却结晶法去除镀锡液中的Fe2＋，考察了镀锡液初始Fe2＋含量、体积浓缩程度、冷却结晶温度和时间对Fe2＋去除率和sn2＋损失率的影响。结果表明，初始Fe2＋含量越高，浓缩程度越大，冷却结晶时间越长、冷却结晶温度越低，Fe2＋的去除率就越高，并且相应的sn2＋损失率都远低于Fe2＋去除率。真空浓缩的最佳工艺条件为：真空度0．097～0．098MPa，温度50℃，体积浓缩程度60％。冷却结晶的最优工艺条件为：温度5℃，时间2h。Fe2＋含量为13．44g/L、Sn2＋含量为30．30g／L的镀锡液在该条件下处理后，Fe2＋的去除率达79．73％，Sn2＋损失率为39．48％。将该处理液按正常sn2’含量（25～30gm）稀释后，Fe2＋含量为4．462g/L，满足镀锡液中Fe2＋含量应低于7g／L的要求。

Fe2＋ ions were removed from a tinning bath by vacuum concentration and cooling crystallization. The effects of initial Fe2＋ content in the tinning bath, concentration degree of volume, as well as temperature and time of cooling crystallization on the removal ofFe〉 and loss of Sn2＋ were studied. The results showed that the removal ofFe〉 is increased by increasing initial Fe2＋ content or concentration degree, prolonging cooling crystallization time, and lowering cooling crystallization temperature, much higher than the loss of Sn2＋. The optimal process conditions are temperature 50 ℃, pressure 0.097-0.098 MPa, and concentration degree of volume 60% for vacuum concentration, temperature 5 ℃ and time 2 h for cooling crystallization. For the tinning bath containing 13.44 g/L Fe〉 and 30.30 g/L Sn2＋, the removal rate of Fe2＋ is up to 79.73% and the loss rate of Sn2＋ is 39.48% after treatment under the given conditions. The Fe2＋ content in treated solution is 4.46 g/L after dilution in accordance with the normal Sn2＋ content （25-30 g/L）, meeting the requirement of Fe2＋ content, i.e. 〈7 g/L, in common tinning bath.