Removal of platinum group metals from dilute process streams: Identification of influential factors using DOE approach

• Five different platinum group metals (PGMs) from dilute stream have been investigated.
• The effects of pH, initial metal ion concentration, temperature and biomass dosage on PGMs removal were assessed using the design of experiment approach.
• Design of experiment (DOE) approach was able to determine statistically significant and insignificant factors.
• Link observed between initial metal ion concentration and solution pH.
• The biomass was successfully used for five adsorption desorption cycles.

The removal of platinum group metals (PGMs) from dilute streams is essential due to their economic value and the increasing need to recycle process water. This study presents the removal of Pd(II), Ir(III), Pt(II), Rh(III) and Au(III), from synthetic multicomponent aqueous solution using untreated, NaOH treated and ethanol treated Saccharomyces cerevisiae waste biomass obtained as a byproduct of brewery fermentation industry. A two-level four factor full-factorial experimental design and analysis was successfully employed for the test work. The effects of pH, initial metal ion concentration, temperature and biomass dosage on PGMs removal were assessed using the design of experiment (DOE) approach. Solution pH and initial metal concentration were found to be statistically significant for the adsorption of PGMs tested. Ethanol treated biomass gave the highest adsorption uptake for all the PGMs tested. The sorption uptake is in the order of Au > Pd > Pt > Ir > Rh. Desorption was carried out using acidified 0.1 M thiourea and the biosorbent was successfully regenerated and reused up to five cycles.