大孔树脂对镍钴萃取废水中有机物的吸附性能

Adsorption properties of macroporous resin for organic pollutants in nickel-cobalt solvent extraction wastewater

镍钴溶剂萃取废水属于含高盐、高有机物废水,有机物不仅造成化学需氧量(COD)超标、还会引起蒸发结晶过程起泡、结晶困难和产生废盐等问题,严重制约废水近零排放。本研究通过对比四种典型大孔树脂的微观结构以及对镍钴溶剂萃取废水中有机物的吸附性能,探究了大孔树脂的结构与吸附性能之间的关系。研究发现,具有合理孔径分布和较大比表面积的ORZ-A2型树脂的吸附容量最优,单级静态吸附总有机碳(TOC)去除率为70.79%,总磷(TP)去除率为83.11%。通过GC-MS表征吸附前后镍钴溶剂萃取废水中的有机物组成,发现废水中有机物成分主要是以2-乙基己酸为代表的有机磷萃取剂及其水解产物和衍生物。四种大孔树脂对有机磷酸萃取剂和2-乙基己酸吸附效果较好,但吸附出水中有机物主要为戊酸,以戊酸为代表的水溶性小分子有机物可能是影响TOC去除效果进一步提升的关键。通过吸附动力学分析表明,大孔树脂对有机物的吸附动力学符合准二级动力学模型。热力学参数的计算结果表明树脂对有机物的吸附是自发的、放热的物理吸附过程。本工作为指导大孔树脂吸附镍钴溶剂萃取废水中有机物技术的工业化应用提供了理论依据。

Nickel-cobalt solvent extraction wastewater contains high salt and high organic pollutants,organic pollutants not only caused chemical oxygen demand(COD)to exceed the emission standard of pollutants,but also caused enormous problems such as generating a lot of foam,emerging difficulty in crystallization and producing waste crystalline salt in the evaporative crystallization process of wastewater,which seriously restricts the near-zero discharge of nickel-cobalt solvent extraction wastewater.In this study,the relationship between the structure and adsorption performance of macroporous resins(MARs)was explored by comparing the microstructure of four typical MARS and their adsorption capacity for organic pollutants in the nickel-cobalt solvent extraction wastewater.The study found that ORZ-A2 had the best adsorption capacity of organic pollutants and the single-stage static adsorption removal rate of total organic carbon(TOC)and total phosphorus(TP)were 70.79%and 83.11%respectively,which might be attributed to the reasonable pore size distribution and large specific surface area.Further,GC-MS was used to characterize the composition of organic pollutants of raw wastewater and adsorbed wastewater by MARs.It was found that the organic pollutants in nickel-cobalt solvent extraction wastewater were mainly organophosphorus extractants,their hydrolysates and derivatives represented by 2-ethylhexanoic acid.The four types of MARs had good adsorption effects on organophosphorus extractant and 2-ethylhexanoic acid,however,the organic pollutant in the adsorbed wastewater was mainly valeric acid,which indicated that the water-soluble small molecular organic pollutants represented by valeric acid might be the key to further enhance the removal rate of TOC.Subsequently,the kinetics study found that organic pollutants uptake onto four MARs followed the pseudo-second order model.The calculation results of thermodynamic parameters indicated that the adsorption of organic pollutants on MARs was a spontaneous,and exothermic physical adsorption process.This work provides a theoretical basis for guiding the industrial application of MARs adsorption technology for organic pollutants in nickel-cobalt solvent extraction wastewater.