氨-硫酸铵溶液中萃取分离锌镉

Extraction and separation of zinc and cadmium from ammoniacal/ammonium sulfate solutions

研究Mextral54-100(HA)和Mextral54-100+TRPO(HA+TRPO)两种萃取体系从氨-硫酸铵溶液中萃取分离锌镉的性能,确定出锌镉分离的最佳工艺。结果表明:HA+TRPO萃取体系在初始pH为7.2时对锌具有较高的选择性萃取能力,而不同pH条件下两种萃取体系对镉的萃取能力均很低。因此,宜采用HA+TRPO体系在初始pH为7.2条件下萃取锌,镉不被萃取而留在溶液中,实现锌与镉的分离。对于锌的萃取,采用0.4 mol/L HA+0.05 mol/L TRPO的协同萃取体系,在温度为25℃,初始pH为7.2,O/A相比为1:1的条件下,经2级萃取,锌萃取率为99.2%,镉的萃取率小于5%;对负载锌有机相,在温度为25℃,相比为2:1,硫酸浓度为0.1 mol/L的条件下,经2级反萃,锌反萃率为99.9%。萃余液中的镉可通过化学沉淀法将其沉淀回收。通过选择合适的萃取体系和萃取条件,获得了氨-硫酸铵溶液中萃取分离锌和镉的最佳工艺流程和技术参数。

The performances of extraction systems, Mextral54-100（HA） and Mextral54-100＋TRPO（HA＋TRPO）, on extraction and separation of zinc and cadmium from ammoniacal/ammonium sulfate solutions were investigated, and the optimal process of zinc-cadmium separation was determined. The results show that high selective extractability of zinc is achieved with HA＋TRPO extraction system at initial pH 7.2, while low extractabilities of cadmium are achieved with both extraction systems at different pH values. Therefore, it is supposed to extract zinc with HA＋TRPO system at initial pH 7.2, and cadmium is left in the solution as it can not be extracted, which achieves the separation of zinc and cadmium. For extraction of zinc, the extraction ratio of zinc reaches 99.2% with two extraction stages under the conditions of 0.4 mol/L HA＋0.05 mol/L TRPO synergistic extraction system, 25 ℃, initial pH 7.2, and phase ratio（O/A） 1：1, while the extraction ratio of cadmium is less than 5%. For loaded organic phase containing zinc, the stripping ratio of zinc is 99.9% with two stripping stages. The cadmium consisting in extraction raffinate can be recycled by chemical precipitation method. In this work, by means of selecting the appropriate extraction system and extraction conditions, the best technical process and parameters for extraction and separation of zinc and cadmium from ammoniacal/ammonium sulfate solutions are acquired.