基于微流体技术的微乳液膜萃取分离镍钴的机理研究

Nickel and cobalt are important strategic metals, and play an important role in the industry. Because of the very similar physical and chemical properties, these two metals are always the symbiotic and associated elements in the deposit, it has significant meaning to separate and recover nickel and cobalt from leachate. To overcome the problems existed in the conventional solvent extraction, the new processes of microemulsion extraction and separation of nickel and cobalt based on microfluidic technology are introduced in this research. It is concluded that the use of these processes has high extraction efficiency and rapid separation, it also advantageous to overcome the problems of liquid membrane rupture，swelling，entraining losses and emulsification caused by high shear forces by stirring. Meanwhile, it is conducive to increase the mass transfer coefficient and contacting area, and to achieve a uniform concentration. The project is focused on the stability of microemulsion system; investigating the distribution and extraction mechanism of nickel and cobalt on the condition of microfluidic conditions; revealing the influence of extractant concentration, saponification rate, balance of time and pH etc to microemulsion extraction of metal ions results; obtaining the extraction kinetics equation and interfacial diffusion reaction mechanism; eventually forming the new green processes of the extraction separation of nickel and cobalt. The project will enrich the theoretical system and basic research of extraction and separation of nickel and cobalt. All that will promote the development of microfluidic technology in the field of extraction and separation of nickel and cobalt.

镍、钴是重要的战略储备金属，在工业中占据重要地位。由于物理化学性质相似，在矿床中常共生、伴生，从溶液中进行分离回收具有十分重要的意义。针对目前工业上常规溶剂萃取分离镍钴中存在的问题，结合微乳液膜萃取的高效、快速分离的优点，同时克服高速剪切力下的破裂、溶胀、溶剂夹带损失及再乳化等问题，增大传质系数和传质接触面积，均化各处浓度，提出了微流体条件下的微乳液膜萃取分离镍钴的新技术。项目研究微乳体系的稳定性影响因素，探讨微流体条件下的镍钴分配规律和萃取机理，揭示萃取剂浓度、皂化率、平衡时间、平衡pH等对有机相微乳液膜负载金属离子能力的影响规律，得到萃取动力学方程及界面扩散反应机理，形成镍钴绿色萃取的新技术，丰富镍钴萃取分离的理论体系和基础研究，推动微流体技术在镍钴萃取分离中的发展。

微流体技术是重要的过程强化手段，是在微米尺度空间进行混合和发生化学反应。由于微通道的尺寸效应，克服了常规湿法冶金溶剂萃取中分子扩散距离长、传质阻力大、传质系数低导致的萃取效率低、反应级数多等问题。.本项目创新性地将微流体技术用于钴镍的溶剂萃取中，实现了钴从硫酸镍溶液中的分离净化，获得了最佳的操作参数及微流体萃取规律。主要的研究内容包括：（1）基于弱酸性P507萃取剂的皂化机理，制备了稳定透明的P507/煤油/NaOH微乳液膜体系，开展了皂化P507萃取钴镍相关机理的研究；（2）微芯片反应器内，单相液弹内循环对流传质及相邻液弹之间的分子扩散强化了不混溶两相间的传质。优化工艺参数条件下，10 s的接触时间内钴的单级萃取率可达到99.9%以上。但不同浓度镍离子的存在将明显降低目标金属钴的萃取率;（3）对微管式反应器内钴镍萃取分离进行了系统研究，考察了P507皂化率、浓度及两相接触时间对钴镍分离效果的影响，并与常规萃取结果进行了平行比较。结果表明，微流体条件下Co的单级萃取率均高于常规萃取，Co与Ni的分离系数得到显著提高，萃取级数得到降低。（4）基于水-油两相的流动模型，得到稳定弹状流条件下液-液两相比表面积及传质系数值，获得镍钴界面扩散反应相关机理。（5）负载有机相的多次循环再生规律研究中，钴的单级反萃率可达到99.84%，多次再生后的萃取剂与新鲜有机相具有很好的一致性。.总之，微流体萃取有利于克服液-液两相传质阻力，提高目标金属离子的选择性，获得更好的分离净化效果。本项目的成功实施为钴镍溶剂萃取分离提供了一种新的技术原型，进一步拓展了微流体技术的应用领域，具有广阔的应用前景。