The role of chitin in uranium adsorption by R. arrhizus.

ABSTRACT

In order to further refine and support the uranium biosorption mechanism hypothesis proposed for Rhizopus arrhizus, uranium competitive equilibrium uptake isotherms by chitin were determined at two different solution pH levels and in the presence of different concentrations of competing ions, namely, Cu(2+), Zn(2+), and Fe(2+). The co-ion effect became more poronounced as the co-ion concentration in solution and pH increased. Obtained equilibrium data are in agreement with uranium biosorption data reported earlier. Infrared, mass, and electron paramagnetic resonance (EPR) spectra of chitin before and after uranium uptake in the presence of the competing ions Cu(2+), Zn(2+), and Fe(2+) were recorded. The combination of the spectral data and the information from equilibrium studies supported the hypothesis advanced earlier on the mechanism of uranium uptake by R.arrhizus. In addition, the data suggested the participation of a free radical in uranium coordination by the cell wall chitin. The mechanism of reduction of the uranium uptake capacity of the biomass in the presence of competing ions was also elucidated further.