Removal of iron from cobalt sulfate solutions by ion exchange with Diphonix resin and enhancement of iron elution with titanium(III)

Diphonix resin was used to remove ferric iron from a cobalt sulfate solution. In the pH range of 0.5 to 2.5, the solution pH greatly affected the loading of cobalt while the loading behaviour of iron was little changed. Lower pH values and higher resin concentrations led to a higher separation factor between iron and cobalt. Iron was not eluted at all at low acid concentrations while 96% of cobalt was eluted with 30 g/L sulfuric acid. Addition of Ti(III) to the sulfuric acid eluant greatly enhanced the elution of iron even at low acid concentrations. Elution of iron with an eluant containing 4 g/L Ti(III) and 300 g/L sulfuric acid led to complete elution of iron at room temperature. It was found that the enhancement of iron elution with Ti(III) is due to the combined effects of reduction of Fe(III) and competitive adsorption of Ti(III) and Ti(IV) ions.