Characterization of Pb2+ biosorption from aqueous solution by Rhodotorula glutinis

The yeast Rhodotorula glutinis was examined for its ability to remove Pb2+ from aqueous solution. Within 10 min of contact, Pb2+ sorption reached nearly 80% of the total Pb2+ sorption. The optimum initial pH value for removal of Pb2+ was 4.5-5.0. The percentage sorption increased steeply with the biomass concentration up to 2 g/l and thereafter remained more or less constant. Temperature in the range 15-45degreesC did not show any significant difference in Pb-2+ sorption by R. glutinis. The light metal ions such as Na+, K+, Ca2+, and Mg2+ did not significantly interfere with the binding. The Langmuir sorption model provided a good fit throughout the concentration range. The maximum Pb2+ sorption capacity q(max) and Langmuir constant b were 73.5 mg/g of biomass and 0.02 l/mg, respectively. The mechanism of Pb2+ removal by R. glutinis involved biosorption by direct biosorptive interaction with the biomass through ion exchange and precipitation by phosphate released from the biomass.