Uranium sorption by Pseudomonas biomass immobilized in radiation polymerized polyacrylamide bio-beads

A Pseudomonas strain identified as a potent biosorbent of uranium (U) and thorium was immobilized in radiation-induced polyacrylamide matrix for its application in radionuclide containing wastewater treatment. The immobilized biomass exhibited a high U sorption of 202 mg g(-1) dry wt. with its optimum at pH 5.0. A good fit of experimental data to the Freundlich model suggested multilayered uranium binding with an affinity distribution among biomass metal binding sites. Scanning electron microscopy revealed a highly porous nature of the radiation-polymerized beads with bacterial cells mostly entrapped on pore walls. Energy dispersive X-ray analysis (EDXA) coupled with SEM ascertained the accumulation of uranium by the immobilized biomass without any physical damage to the cells. A significant (90%) part of biosorbed uranium was recovered using sodium bicarbonate with the immobilized biomass maintaining their U resorption capacity for multiple sorption-desorption cycles. Uranium loading and elution behavior of immobilized biomass evaluated within a continuous up-flow packed bed columnar reactor showed its effectiveness in removing uranium from low concentration (50 mg U L-1) followed by its recovery resulting in a 4-5-fold waste volume reduction. The data suggested the suitability of radiation polymerization in obtaining bacterial beads for metal removal and also the potential of Pseudomonas biomass in treatment of radionuclide containing waste streams.