萃取法制备工业级磷酸二氢铵-萃取剂的反萃取研究

本课题以高效的2-乙基己基磷酸(D2EHPA)为萃取剂,采用溶剂萃取法来提取MAP溶液中的Mg2++杂质,从而实现生产高品质MAP的目的；但是实现其产业化的难点之一,就是反萃取剂的选择,而在选择反萃取剂时关键是实现络合物D2EHPA-Fe3+的有效分离,因为络合物D2EHPA-Fe3+是非常稳定的,而且Fe3+的富集能使萃取剂老化.因此,选择有效的反萃取剂来实现D2EHPA的循环回收利用是非常有必要的.以H2SO4+添加剂A为反萃取剂,通过考察反萃取剂浓度,相比,反应温度,反应时间,搅拌速度等对反萃取Fe3+反萃取率的影响,求得最佳工艺条件为H2SO4浓度:4mol· L-1,反应温度45℃,相比为1∶1,搅拌速度550r· min-1,搅拌时间0.5h.

Study on the stripping of the extractant from the production of industrial-grade ammonium dihydrogen phosphate solution by solvent extraction

In this paper, the effective D2EHPA is empolyed as extractant. Based on the extractant of D2EHPA, The abilities to extract Mg^2＋ from ammonium dihydrogen phosphate solution with the separation methods of extraction, emulisification extraction, saponified D2EHPA, and predispersed solvent extraction have been studied. And superior grade NH4H2PO4（MAP） can be obtained by two levels of extraction under optimal condition. However one of difficulties to realize industrialization is the choice of strippant. The key for selection of strippant is to realize the complex D2EHPA-Fe^3＋ effective separation, because complex D2EHPA-Fe^3＋ is very stable, moreover concentration of Fe^3＋ can cause the extractant aging. Therefore the choice of the effective strippant to realize the extractant D2EHPA recycling use is necessary. In the stripping of Mg^2＋/Fe^3＋ in the organic phase, H2SO^4＋ additive A is used to strip Fe^3＋. to study the stripping extraction ratio and advantages of the strippant H2SO4 in the removal of Fe^3＋, various parameters： concentraction of H2SO4, reaction temperature, phase mass ratio, stirring speed, stirring time are studied and optimized. The optimized parameters affecting the process are as follows： The concentraction of H2SO4： 4mol·L^-1; the reaction temperature： 45℃; the phase volume ratio： 1：1; stirring speed： 550r·min^-1, stirring time： 0.5h.