Comparative study of chelating ion exchange resins for metal recovery from bioleaching of nickel laterite ores

Heterotrophic fungi and their metabolic products have been used in extracting nickel and cobalt from low grade nickel lateritic ores. This study compared the potential of two commercial chelating resins based on iminodiacetate and aminophosphonate functional groups (Purolite S930 and S950) in recovering nickel and cobalt from pregnant bioleaching solutions. The sorption characteristics of these resins were examined using various metal concentrations (from 15 to 2000 mg/L), chelating agents including citric, dl-malic and lactic acids, and solution pH. The solution pH was varied by preparing metal solutions using 0.01 and 0.1 M of organic acids. Metals were recovered from loaded resins using 2 M HNO3. To interpret the sorption behavior of the resins, the adsorption data were fitted to the Freundlich and Langmuir models. The results showed both nickel and cobalt organic complexes adsorptions were in a good agreement with the two empirical models suggesting that the adsorption mechanisms follow a combination of monolayer and multilayer. The adsorption performance of the aminophosphonate based resin (Purolite S950) was found to exceed that of the Purolite S930. Favourable adsorptions of nickel and cobalt complexes were achieved in weakly acidic solution. Purolite S950 also showed higher selectivity toward nickel and cobalt complexes compared to Purolite S930. The desorption efficiencies from Purolite S950 were about 90% for nickel and from 82% to 98% for cobalt.