A strategy for deep removal of Cu from Ni anolyte based on the ion-exchange method

Abstract

The sulfide precipitation method has been one of the major strategies used for the removal of Cu from the Ni anolyte. However, the high cost and short shelf-life of the Cu removal agents have consistently posed problems in the practical industrial use of the Ni anolyte purification process. In the present study, a new method for removing Cu from Ni anolyte based on ion exchange is proposed to address the drawbacks of the current sulfide precipitation method. Through isothermal adsorption curve analysis, thermodynamic studies, kinetic studies and cross-sectional SEM-EDS analyses, it was found that the selectivity difference of D850 resin to Cu2+ and Ni2+ is dependent on iminodiacetic acid forming a triple bond with Cu2+ while forming a double bond with Ni2+ in the removal of Cu from a Ni anolyte. The resin dynamic adsorption experiments showed that the fixed-bed ion exchange process is quite similar to the cascade solvent extraction process. The investigations into resin regeneration found that the desorption of Cu2+ and Ni2+ was adequately completed for static desorption when the desorbent concentration was than more 1 mol/L for 60 min. The experiments on D850 resin desorption showed that the desorption equilibrium time, desorbent concentration, and desorption temperature were key factors affecting the desorption of Cu2+ and Ni2+. The dynamic desorption process revealed that a high concentration of hydrochloric acid and a high flow rate could accelerate the desorption process, concentrating the outflow peak and facilitating the collection of Cu2+ and Ni2+. This Cu removal method based on resin ion exchange utilizes the different characteristics of iminodiacetic acid adsorbing Cu and Ni to achieve efficient Cu removal from the Ni anolyte and its recycling. This method is superior to the current method due to its high selectivity, fast adsorption, high desorption rate, and high Cu–Ni ratio of the desorption solution.