用N_(235)-TBP混合体系从硫酸盐溶液中协同萃取除铁

Removal of Fe(Ⅲ) from sulphate solutions by synergistic extraction using N_(235)-TBP mixed solvent systems

研究了采用N235-TBP协同萃取体系从硫酸盐溶液中萃取除铁,考察了萃取体系、N235浓度和料液初始pH值对Fe(Ⅲ)萃取的影响以及相比(Vorg/Vaq)、H2SO4浓度和平衡pH值对Fe(Ⅲ)反萃的影响。结果表明:N235和TBP对硫酸盐溶液中的Fe(Ⅲ)具有协同萃取效应;加入TBP能有效地抑制载铁有机相的分层,提高Fe(Ⅲ)的反萃率;料液初始pH值及N235浓度对Fe(Ⅲ)的萃取率影响显著,萃铁曲线的最高点随着N235浓度的增大向低pH值方向移动;以含30%N235和10%TBP(体积分数)的有机相作萃取剂,在相比(Vorg/Vaq)为2∶1的条件下,含铁12.73 g/L的合成料液经过3级错流萃取,萃余液中含铁低于0.15 g/L,铁的总萃取率接近99%;以0.4 mol/L的H2SO4为反萃剂,控制反萃液平衡pH小于0.8,铁的单级反萃率大于96%;含铁7.05 g/L的有机相在相比为1∶1时,经过2级错流反萃,铁基本上被反萃完全,贫有机相不经处理可以循环使用。

The removal of iron （ Ⅲ） from sulphate solutions was investigated by solvent extraction using a mixed solvent system consisting of tertiary amine （N235） and tributyl phosphate （TBP）. The effect of extraction systems, concentration of N235 and initial pH on the extraction of iron（ Ⅲ ）, as well as the effect of volume ratio of organic to aqueous（Vorg/Vaq）, concentration of sulfuric acid and equilibrium pH on the stripping of iron（ Ⅲ ） in loaded organic phase were studied. The results demonstrate that the N235-TBP system has a synergistic effect on the extraction of iron（ Ⅲ） ; By adding TBP in N235 , the demixing of loaded organic phase can be prevented and the stripping ratio of iron （Ⅲ ） increases. Initial pH and concentration of N235 have remarkable influences on iron （Ⅲ ） extraction, the maximum on the extraction curve moves towards the direction of low pH with increasing concentration of N235. At Vorg ： Vaq of 2 ： 1, the concentration of iron（Ⅲ） in raffinate is less than 0.15 g/L after a three-stage cross-flow extraction with a organic phase consisting of 30%N235 and 10%TBP and a total extraction ratio of nearly 99% is achieved for a feed solution containing 12.73 g/L Fe（ Ⅲ ）. Furthermore, the stripping results indicate that with a dilute sulphuric acid （0. 4 mol/L）, iron stripping ratio can reach 96% controlling equillium pH less than 0. 8. At Vorg ： Vaq of 1 ： 1, iron（ Ⅲ ） in loaded organic phase containing 7. 05 g/L Fe（ Ⅲ ） can be easily and completely stripped by a dilute sulphuric acid （0.4 mol/L） after a two-stage cross-flow stripping.