Uranium biosorption mechanism model of protonated Saccharomyces cerevisiae.

Further understanding absorption uranium mechanism of the regenerational biosorbent is very interesting in application of the biosorbent. The regeneration adsorbent of Saccharomyces cerevisiae biomass was made by hydrochloric acid. Using it to absorb uranium at low constant pH(2.50), accompanied with proton releasing the ratio almost 1:2 which is to be analyzed in this paper. The type and amount of functional groups in the biomass such as carboxyl, amino, phosphoryl were determined by Potentiometric titrations and FTIR analysis. Chemical modification showed that the contribution of functional groups to uranium adsorption was carboxyl, phosphoryl and amino in turn. Analysis of SEM-EDX and staining microscopy showed that uranium on the surface of cells did not exist in the form of precipitation at lower pH 2.98, but at higher pH 4.52. The effects of phosphorus release and pH on uranium species was analyzed by MINTEQ software 3.0. Based on the above boundary conditions of the model construction, a multi-site of functional groups model equation of ion exchange absorption mechanism was built in which the final uranium ion concentration and pH as functions. It could well describe the exchange equilibrium of proton with uranium ion at pH2.50 to pH4.00.