Metal biosorption in single- and multi-metal solutions by biosorbents: Indicators of efficacy in natural wastewater

Metal biosorption by a mixed-microbial biosorbent of Stenotrophomonas maltophilia (bacterium) and Saccharicola bicolor (fungus) was compared against their respective single biosorbents to determine their efficacies in removing Pb, Cu, Zn, and Cd in single- and multi-metal solutions. The multi-metal solutions mimic natural wastewater which may interact differently between metal ions-biosorbent, as well as between the metal ions. The results revealed that application of S. maltophilia (single, Sm) was the most effective, followed by mixed-biosorbent (MB), then S. bicolor (single, Sb); occurring in both single- and multi-metal solutions. The biosorbents preferred Cu > Pb > Cd > Zn in both metal-solutions, with Sm demonstrating superior biosorption for all metals compared to other biosorbents. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) analysis detected different functional group profiles present on mixed biosorbent compared to the respective single forms, which may have influenced metal biosorption. All biosorbents adsorbed most of the metals via a rate-limiting step indicated by compliance to pseudo-second order kinetic. The biosorbent Sm was identified to having the most potential for further development as useful biosorbent for application in natural wastewater.