Purification of a dilute platinum group metals process stream using waste yeast biomass immobilized on plaster of Paris

Abstract

The removal of platinum group metals (PGMs) from a dilute industrial process stream using a packed bed column of ethanol-Treated waste yeast biomass immobilized on plaster of Paris (POP) was investigated. The study also included the removal of base metals and other trace elements in dilute solution. The effects of feed flow rate and bed depth on the breakthrough characteristics of the adsorption system were determined. The results showed that removal was favoured by lower flow rates and higher bed depths. An increase in the bed depth with a decrease in flow rate increased the volume of effluent that could be treated effectively before breakthrough. The breakthrough curves for most of the elements do not resemble an ideal breakthrough curve, due to the complexity of the solution. The normalized concentration for most of the metals in solution remained high, even in the early stages of treatment when the sorbent material was most pristine. Generally, the affinity of the sorbent for the elements considered followed the order Pd2+> SO42->Te2+>Pt2+>Ir3+>Ni2+>Cl->.Ru3+>Se2+> Na+. The data from the column studies was fitted to Adam-Bohart and Thomas models. The Adam-Bohart model showed a superior prediction of the experimental data. COD analysis of the effluent was also carried out at different time intervals. The measured COD decreased from 200 mg/l to less than 68 mg/l after 30 minutes, which corresponds to the removal efficiency of about 66%.