Kinetic modelling of the uranium biosorption by Deinococcus radiodurans biofilm

Increasing number of reports on uranium contamination in groundwater bodies is a growing concern. Deinococcus radiodurans biofilm-based U(VI) bioremediation has great potential to provide solution. This study focuses on the kinetic modelling of uranium biosorption by D. radiodurans biofilm biomass and identification of the functional groups involved in the sequestration process. The effect of temperature, pH and amount of biofilm dry mass were studied using two uranyl ion concentrations (100 and 1000 mg/L). D. radiodurans dry biomass showed good affinity for uranyl ion adsorption. The kinetic experiments revealed that the biosorption process was spontaneous and exothermic in nature. The modelling of kinetic adsorption data revealed that U(VI) sorption by D. radiodurans biofilm biomass follows a pseudosecond-order reaction. Mechanism of U(VI) sorption was suggested to follow an intra-particle diffusion model, which includes covalent bonding between U(VI) and functional groups present on the surface of biofilm biomass, and diffusional barrier acts as a rate limiting step. External mass transfer was the rate-limiting step as evident from Boyd and Elovich plot. Chemical modifications in surface functional groups of biofilm biomass, confirmed the involvement of carboxyl, phosphate, and hydroxyl groups in uranium binding as a significant loss in U(VI) sorption capacity was recorded in these chemically modified biomasses. XRD data indicated the formation of metal deposits, predominantly as uranyl phosphates. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study focuses on the kinetic modeling of uranium biosorption by Deinococcus radiodurans biofilm biomass, indicating the process is spontaneous and exothermic. The sorption of U(VI) by D. radiodurans biofilm biomass is suggested to follow a pseudosecond-order reaction. Chemical modifications in surface functional groups of the biofilm biomass significantly impact uranium binding capacity.