Selectivity of commercial and novel mixed functionality cation exchange resins in mildly acidic sulfate and mixed sulfate–chloride solution

The equilibrium selectivity and operational capacity of two commercial (Lewatit MonoPlus TP 207 XL and TP 220) and four novel monosized macroporous ion exchange resins are characterized as a function of pH and chloride concentration in conditions relevant to nickel and cobalt recovery from laterite leach solution. The four novel functionalizations were mixtures of acetic acid, picolyl, and sulfonic acid. Resin with the acetic acid functionalization displayed higher operational capacity and lower selectivity for nickel and cobalt over other metals than those with picolyl functionalization. The presence of potassium chloride generally had either a negligible or positive effect on metal loading in the context of nickel laterite processing by decreasing loading of unwanted metals such as iron, aluminum, calcium and magnesium. Significant potassium loading was seen on resins involving the sulfonic acid group. In picolyl based resins the presence of chloride increased cobalt loading by a small amount. The magnitude of these effects varied significantly between resins. Of the novel resins, the functionalization combining acetic acid and picolyl seems the most promising as it displays a higher capacity than the bis-picolylamine resin and better selectivity for nickel and cobalt over other metals than the iminodiacetic acid resin.