基于镍钴同时萃取的协萃过程界面微观作用与结构调控研究

In our previous studies, both nickel and cobalt can be highly selectively extracted from an acidic polymetallic aqueous solution using a new synergistic mixture containing dinonylnaphthalene sulphonic acid (DNNSA) and pyridinecarboxylate ester. However, there exists a problem that the phase separation rate of the solvent extraction became too slow at high metal loading of the loaded organic phase, which limits the large-scale industrial application of the new synergistic mixture.. In order to solve this problem, several intensive observations will be done in this project as follows:. Simulated sulfate acid leaching solution of low-grade nickel laterite ore is regarded as a typical research object, and on the basis of our previous studies, the effects of the extraction conditions on the phase separation characteristics and macroscopic interfacial characters for the synergistic solvent extraction of nickel(II) or cobalt(II) will be investigated. Using the combination of empirical thermodynamics and kinetics methods, modern characterization methods, quantum chemical theoretical calculation and molecular dynamics simulation, microscopic structure changes of organic phases before and after the synergistic solvent extraction will be studied, and the interfacial structure changes and phase separation behaviors during the synergistic solvent extraction will be also investigted at atomic and molecular levels. After that, the relationship between the changes of the interfacial structures and the phase separation characteristics during the synergistic solvent extraction will be revealed from macroscopic and microscopic perspectives, and an interfacial structure control method will be formed. After repeated theoretical prediction and experimental confirmation, a new kind of synergistic mixture containing DNNSA, pyridinecarboxylate ester and other additives will be obtained with improved phase separation rate at high metal loading of the organic phase, and this improved phase separation rate can meet the industrial design requirements of the mixer-settler for the industrial solvent extraction process. The research results from this project could be provided as a theoretical support for the promotion of the industrial application of the new synergistic mixture containing DNNSA and pyridinecarboxylate ester in near future.

前期研发的二壬基萘磺酸(DNNSA)和吡啶羧酸酯所组成新型协萃体系，可从多金属酸性溶液中高选择性地同时萃取镍钴。但有机相金属负载量高时存在萃取分相速度过慢的问题，从而制约了其工业应用。.本项目拟针对此问题，以低品位红土镍矿模拟硫酸浸出液为研究对象，在前期基础上，研究萃取条件对Ni(II)或Co(II)萃取分相性能及界面宏观性质的影响，采用经典热力学与动力学、现代表征技术与量子化学理论计算及分子动力学模拟相结合的研究方法，研究萃取前后有机相微观结构变化，基于原子分子水平研究界面结构变化与分相行为，从宏观与微观角度阐明协萃过程界面结构变化与萃取分相能力的对应关系，形成可显著提高萃取分相速度的界面结构调控方法，经理论预测与实验验证，使最终所获得的新型协萃体系，其有机相金属负载量高时的萃取分相速度满足工业设计要求。以上研究，将为推进DNNSA与吡啶羧酸酯所组成新型协萃体系的工业应用，提供理论支撑。

本项目针对可从多金属酸性溶液中同时萃取镍钴的二壬基萘磺酸(HDNNS)/4-吡啶羧酸异辛酯（4PC）协萃体系存在萃取分相速度过慢的问题，研究萃取条件对Ni(II)或Co(II)或铜(II)萃取分相性能及界面宏观性质的影响，采用经典热力学与动力学 、现代表征技术与量子化学理论计算相结合的研究方法，研究萃取前后有机相微观结构变化，基于原子分子水平研究界面结构变化与分相行为，从宏观与微观角度阐明协萃过程界面结构变化与萃取分相能力的对应关系。研究结果表明，（1）HDNNS/4PC协萃体系的铜萃取过程中，负载有机相的铜负载量大小并不影响萃取分相性能；随着负载有机相的镍或钴负载量增大，影响萃取分相性能越来越差。HDNNS/4PC协萃体系与铜或镍钴形成的萃合物结构差异，从而导致铜负载有机相与镍或钴负载有机相的水增容能力有差异，这是导致铜镍钴萃取分相能力差异的主要原因。（2）对于镍钴负载有机相，提出了改善萃取分相性能的调控方法：1）降低负载有机相对水的增容能力可减少负载有机相反相胶束尺寸，从而降低负载有机相粘度，可显著提高萃取分相能力；2）4PC的碳链长度并不影响萃取分相性能，而萘磺酸的萘环上长碳链的数目是影响协萃体系负载有机相萃取分相性能的决定性因素。.在此基础上，我们合成了长碳链三烷基萘磺酸新型萃取剂，与4PC所组成的新型协萃体系，研究了其萃取选择性，测定了反相胶束的形状和尺寸。结果表明，与DNNSA/4PC协萃体系相比，长碳链三烷基萘磺酸/4PC新型协萃体系，并不影响铜镍钴与钙镁铁等杂质金属的选择性，却显著提高了镍钴的分相能力。