In the hydrometallurgical processing of nickel laterite ore a significant amount of dissolved nickel and cobalt can be lost to tailings slurry. Chelating ion exchange resin can be used to scavenge this otherwise lost metal value through resin-in-pulp contact with tailings. This thesis explores various chemical aspects of resin scavenging as applied to hydrometallurgical processing of nickel laterite ore.
The effect of resin functionalization on resin selectivity and capacity was investigated through characterization of several commercial and novel resin functional groups under conditions relevant to nickel laterite leaching. The affinity of each resin for nickel and cobalt relative to important impurity elements such as iron, aluminium, manganese, magnesium, copper, potassium, sodium and calcium was studied in weakly acidic sulphate and sulphatechloride media. The novel functional group that combined acetic acid and picolyl was identified as a promising candidate for application to base metal processing.
During resin scavenging significant amounts of unwanted impurity metals such as iron, aluminium and manganese can be loaded by the resin along with the desired nickel and cobalt. These impurities must be managed in order to integrate recovered metal value with existing refinery flow sheets. The selective elution of nickel and cobalt from mixed metal loaded resins with ammoniacal eluent was investigated. It was found that nickel and cobalt could be selectively eluted from iminodiacetic acid functionalized resin with solutions of aqueous ammonia, ammonium sulphate and magnesium sulphate. In this process, magnesium was found to displace nickel and cobalt from the loaded resin while leaving the majority of impurity elements behind. It was found that bis-picolylamine functionalized resin could be eluted using solutions of aqueous ammonia. This method led to very high selectivity of nickel and cobalt over impurity elements. The kinetics and extent of these reactions were measured as a function of eluent and resin composition. In both cases, the resultant eluate was high in nickel and cobalt with very low concentrations of impurities, making it appropriate for downstream integration in existing nickel/cobalt refineries. Strategies for integrating ammoniacal metal bearing eluate with the ammonia chemistry of commercial metal refineries were explored.
The application of selective elution strategies and novel synthetic ion exchange resins to acid mine drainage remediation was investigated. In both acid mine drainage remediation and tailings scavenging recovery of metal value and production of stable waste appropriate for long term storage is desired. Acid mine drainage has the additional challenge of containing toxic, low-value metals such as cadmium, mercury and chromium.