High-efficient separation mechanism of Co/Mo/V system by ethanolamine-induced phosphonic acid extractants

Abstract

Conventional phosphonic acid extractants such as bis (2-ethylhexyl) phosphate (P204) have only been used for cobalt extraction and perform poor separation efficiency. In this work, we propose a route to synergistically extract and separate Co, Mo, and V from spent hydrogenation catalysts by utilizing the modulating effect of ethanolamine (MEA) on phosphonic acid-based extractants, which eliminates the need for saponification and acidification of the extractants. The extraction mechanism of V, Co and Mo have been explained detailedly. By performing quantum chemical calculations on the surface properties of various amines, their metal extraction effects were predicted and validated using machine learning, laying the foundation for the design of synergistic extractants. The Co/Mo/V selective separation process was finally built with the aim of extracting cobalt first in the form of Co(RNH₂)₂A₂. At a P204 concentration of 25 %, MEA addition of 5 %, stirring time of 10 min, stirring rate of 400 rpm, the combined recoveries of the three metals Co, V and Mo reached 94.56 %, 85.60 % and 88.81 %, the separation factors β_Co/Mo and β_Co/V could be increased up to 44748.77 and 1174.04, respectively. It was also demonstrated that the extractant was also suitable for the selective extraction of Ni²⁺. This work provided fundamental research for the development of high-performance extraction systems.