Biosorption of Eu(III) and U(VI) on Bacillus subtilis: Macroscopic and modeling investigation

The biosorption of Eu(III) and U(VI) on Bacillus subtilis (B. subtilis) as a function of reaction time, pH, ionic strength, temperature was investigated by macroscopic and modeling techniques. The macroscopic experiments indicated that the biosorption kinetics and isotherms of Eu(III) and U(VI) on B. subtilis can be satisfactorily fitted by pseudo-second-order kinetic model and Langmuir model, respectively. No effect of ionic strength revealed that the inner-sphere surface complexation dominated the biosorption of Eu(III) and U(VI) onto B. subtilis. The maximum sorption capacity of B. subtilis calculated from Langmuir model at pH 4.5 and 298 K was 58.80 and 90.91 mg/g for Eu(III) and U(VI), respectively. According to the surface complexation modeling, the biosorption of Eu(III) and U(VI) on B. subtilis can be simulated by diffuse layer modeling with three inner-sphere surface complexation sites such as phosphoryl, carboxyl and hydroxyl groups. The findings presented herein suggested that B. subtilis is a promising bio-adsorbent for the preconcentration and retardation of radionuclides in the environmental remediation strategy such as permeable reactive barrier.