草酸强化三价铁离子的反萃性能  

Intensification of the stripping characteristics of iron(Ⅲ) using oxalic acid

作　　者：袁飞刚 YUAN Feigang(School of Metallurgy and Environment,Central South University,Changsha 410083,Hunan,China;Key Laboratory of Hunan Province for Metallurgy and Material Processing of Rare Metals,Changsha 410083,Hunan,China)

机构地区：[1]中南大学冶金与环境学院 [2]稀有金属冶金与材料制备湖南省重点实验室

出　　处：《化工进展》2019年第10期4437-4443,共7页Chemical Industry and Engineering Progress

基　　金：国家重点研发计划（2018YFC1901603）

摘　　要：二(2-乙基己基)磷酸(P204)常作为溶液净化除铁的萃取剂,P204-磺化煤油体系中Fe^3+与有机相形成络合能力较强的萃合物,使得Fe^3+反萃比较困难,需采用较高浓度的酸作为反萃剂,但高浓度的酸会破坏有机分子的结构,影响萃取剂循环利用。针对P204-磺化煤油负铁有机相反萃困难的问题,提出利用草酸为反萃剂对负载1g/L铁的P204-磺化煤油有机相的反萃行为进行研究,考察了反萃转速、草酸浓度、反萃温度、反萃时间和相比对Fe^3+反萃率的影响。结果表明:以反萃转速200r/min,草酸0.4mol/L,反萃时间10min,反萃温度40℃,反萃相比1∶1,采用二级逆流萃取方式,铁的反萃率可以达到99%以上;Fe^3+反萃过程是吸热反应,其反应的焓变为81.58kJ/mol,反萃过程符合准一级反应动力学方程,对应活化能为49.5kJ/mol。进一步研究了反萃后P204-磺化煤油有机相对Fe3+的萃取性能。结果表明:经5次草酸反萃后的P204-磺化煤油有机相萃铁性能几乎不变,对比于高浓度的酸反萃,草酸反萃简化了反萃流程,降低了萃取剂的消耗。Di-2-ethylhexyl phosphoric acid(D2EHPA)was used as extractant for deironing from solutions.The difficulty in stripping of Fe^3+from D2EHPA-kerosene phase was due to the strong complexation ability between Fe^3+and D2EHPA.The frequently-used method to strip Fe^3+from an organic solvent was the use of high concentrated acidic solutions.However,the use of a concentrated acidic solution would destroy the organic molecules and influence the cycling utilization of extractant.In this study,a process employing oxalic acid to increase the efficiency of Fe^3+stripping of Fe^3+-D2EHPA complexes from D2EHPA-kerosene phase has been developed.The process has been studied to optimize various process variables such as shaking speed,oxalic acid concentration,temperature,equilibration time and phase ratio for effective separation of Fe^3+.The results showed that approximate 99%of Fe^3+can be stripped from D2EHPA-kerosene phase loaded with 1g/L of Fe^3+after a two stage counter-current contact under the optimum conditions,where 0.4mol/L of oxalic acid was used to strip(Ⅲ)iron from Fe^3+-D2EHPA complexes for 10min at 40℃with a 1∶1 volumeric phase ratio(O/A,volume of Fe^3+-loaded D2EHPA-kerosene phase-0.4mol/L of oxalic acid aqueous solution).According to the results,the stripping of Fe^3+is an endothermic reaction with the enthalpy change of 81.58kJ/mol.In addition,the reaction was found to follow pseudo first order kinetics with the activation energy of 49.5kJ/mol.The stripping method was further tested to remove Fe^3+from D2EHPA-kerosene phase after being used for the extraction of Fe^3+from Fe2(SO4)3 aqueous solution.The results showed the extraction rate of Fe^3+remains unchanged after D2EHPA-kerosene phase being recycled for five times using 0.4mol/L of oxalic acid stripping solution,which is far more effective than high concentrated acidic solutions employed in the previous reports.The proposed stripping process could further simplify the stripping operation and reduce the extractant loss.

关 键 词：铁 二(2-乙基己基)磷酸 溶剂萃取 反萃 草酸 焓 反应动力学 

分 类 号：O614.81[理学—无机化学]