Metals uptake by live yeast and heat-modified yeast residue
This study evaluated the biosorption of Cd2+, Cr3+, Pb2+ and Cu2+ at pHs 3, 4, 5 and 6 for Saccharomyces cerevisiae both alive and biologically inactivated by different heating procedures (oven, autoclave or spray dry technique originated from alcohol industry). The material inactivated by autoclave (IA, at 120°C, 30 min) had the best performance for metals uptake: 1.88 ± 0.07 (Cu2+), 2.22 ± 0.02 (Cr3+) and 1.57 ± 0.08 g kg-1 (Pb2+). For Cd2+; while the material inactivated by spray dry (RY) presented the higher sorption capacity, 2.30 ± 0.08 g kg-1. The sorption studies showed that the biosorbent materials presented different sorption capacities and an ideal sorption pH. The sorption sites were investigated by potentiometric titration and FT-IR and showed that different heating processes used to inactivate biological samples produce materials with different characteristics and with a diverse sorption capacity due to modification of the available sorption sites. This suggests that inactivation by heating can be an alternative to improve the performance of biosorbents. The main sorption sites for each material were phenolic for live yeast (LY) and carboxylic for yeast inactivated by heating in an autoclave (IA).