Kinetic Modeling and Binding Sites Analysis during Lead Biosorption by Rhodotorula glutinis

Abstract

The yeast Rhodotorula glutinis was examined for its ability to remove heavy metals from aqueous solution. Among the heavy metals tested, selectivity of lead ion was very high. 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. This result showed that the biosorption of Pb²⁺ by R. glutinis could be characterized as a monolayer, single site type phenomenon with no interaction between ions adsorbed in neighboring sites. The pseudo second-order equation was well fitted to the experimental data. The correlation coefficients for the linear plots of t/q against t for the second-order equation are 0.999 for all the initial concentrations of biosorbent for contact times of 180 min. The theoretical q_eq value was very close to the experimental q_eq value. The titration data shows that the cell surface of R. glutinis biomass has a variety of cation binding functional group such as carboxyl, phosphoryl, and amine functional groups.