Split regeneration of chelating resins for the selective recovery of nickel and copper

Abstract

The management of spent acids containing heavy metals has been traditionally carried out by neutralization-precipitation technologies that often fail to provide the required selectivity for metal recovery. This work proposed a split elution process using H2SO4 and NH4OH solutions to regenerate bispicolylamine-based chelating resins (Puromet™ MTS9600) employed in a previous work to separate nickel and copper from spent sulfuric acid effluents. Operation variables namely S/L ratio, concentration of the regeneration agents and process configuration were analysed to select the best conditions to optimize the metal unloading and their selective recovery in independent solutions. It was found that 43% of nickel was eluted from the resin by H2SO4 2.0 M and recovered with purities of 98% while 47% of copper was desorbed with NH4OH 2.0 M and recovered with purities of 97%. The long-term assessment evidenced that copper removal and metal recovery were not affected after 10 adsorption-regeneration cycles, while the nickel adsorption efficacy decreased about 10%.