Contributions of adsorption, bioreduction and desorption to uranium immobilization by extracellular polymeric substances  

作　　者：Chen Zhou Ermias Gebrekrstos Tesfamariam Youneng Tang Ang Li 

机构地区：[1]Biodesign Swette Center for Environmental Biotechnology,Arizona State University,Tempe,AZ 85281,USA [2]Department of Civil and Environmental Engineering,FAMU-FSU College of Engineering,Florida State University,Tallahassee,FL 32310,USA [3]State Key Laboratory of Urban Water Resource and Environment,School of Environment,Harbin Institute of Technology,Harbin 150090,China

出　　处：《Frontiers of Environmental Science & Engineering》2023年第9期125-135,共11页环境科学与工程前沿（英文）

摘　　要：Hexavalent uranium(U(VI))can be immobilized by various microbes.The role of extracellular polymeric substances(EPS)in U(VI)immobilization has not been quantified.This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI)immobilization:adsorption,bioreduction and desorption.Loosely associated EPS was extracted from a pure bacterial strain,Klebsiella sp.J1,and then exposed to H_(2) and O_(2)(no bioreduction control)to immobilize U(VI)in batch experiments.U(VI)immobilization was faster when exposed to H_(2) than O_(2) and stabilized at 94%for H_(2) and 85%for O_(2),respectively.The non-equilibrium data from the H_(2) experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption(ka=2.87×10^(−3) g EPS·(mg U)^(−1)·min^(−1)),first-order bioreduction(kb=0.112 min−1)and first-order desorption(kd=7.00×10^(−3) min^(−1))and fitted the experimental data with R^(2) of 0.999.While adsorption was dominant in the first minute of the experiments with H_(2),bioreduction was dominant from the second minute to the 50th min.After 50 min,adsorption was negligible,and bioreduction was balanced by desorption.This work also provides the first set of equilibrium data for U(VI)adsorption by EPS alone.The equilibrium experiments with O_(2) were well simulated by both the Langmuir isotherm and the Freundlich isotherm,suggesting multiple mechanisms involved in the interactions between U(VI)and EPS.The thermodynamic study indicated that the adsorption of U(VI)onto EPS was endothermic,spontaneous and favorable at higher temperatures.

关 键 词：ADSORPTION BIOREDUCTION DESORPTION Kinetics ISOTHERM URANIUM 

分 类 号：X703[环境科学与工程—环境工程]