title: Uranium removal by novel graphene oxide-immobilized Saccharomyces cerevisiae gel beads.
abstract: To evaluate its ability to absorb dissolved uranium (VI), the waste biomass of Saccharomyces cerevisiae was immobilized using different agents, including Ca-alginate (Ca-SA), Ca-alginate with graphene oxide (GO), polyvinyl alcohol (PVA, 5% or 10%, w/v)-SA-GO in CaCl2-boric acid solution. The experimental results showed that graphene oxide at 0.01% (w/v) could enhance the performance of the immobilized cells. The yeast gel beads prepared with 5% PVA-1% SA-2% yeast-0.01% GO-2% CaCl2-saturated boric acid (4#) generally showed the better physical-chemical properties such as higher tolerance to the unfavorable environmental conditions. Moreover, the 4# gel beads exhibited more stable capacity for U(VI) sorption and desorption at various conditions, such as pH in the range of 3-9. A pseudo second-order kinetic model could describe the kinetics of U(VI) sorption onto the 4# gel beads (R2= 0.96). The Langmuir, Freundlich, Tempkin and Sips models could be used to describe U(VI) sorption by the 4# gel beads, with the R2being 0.90, 0.83, 0.96, 0.97, respectively. The Sips maximum capacity of 4# gel beads was 24.4 mg U/g dry weight. The desorption efficiency of U(VI) adsorbed onto the 4# gel beads was 91%, 73% and 40% by 0.1 M HNO3, 0.1 M HCl and 0.1 M NaOH, respectively. However, the 4# gel beads exhibited lower U(VI) sorption capacity than the raw yeast cell (Sips maximum capacity of 35.6 mg U/g). The immobilized Saccharomyces cerevisiae using SA, PVA and/or GO showed obvious changes in the molecular vibration of functional groups such as carboxyl, amide and hydroxyl groups compared with the raw yeast cells, according to FTIR analysis. The SEM-EDX analysis showed that U(VI) was adsorbed unevenly on the cellular surface. Carboxyl and hydroxyl groups may be involved in U(VI) binding by yeast cells.
authors.affiliation: Collaborative Innovation Center for Advanced Nuclear Energy Technology, INET, Tsinghua University, Beijing, 100084, PR China.
authors.forename: Can
authors.initials: C
authors.lastname: Chen
authors.affiliation: Collaborative Innovation Center for Advanced Nuclear Energy Technology, INET, Tsinghua University, Beijing, 100084, PR China; Beijing Key Laboratory of Radioactive Waste Treatment, Tsinghua University, Beijing, 100084, PR China. Electronic address: wangjl@tsinghua.edu.cn.
authors.forename: Jianlong
authors.initials: J
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D000464:Alginates; D020723:Glucuronic Acid; D006108:Graphite / Q000737:chemistry*; D006603:Hexuronic Acids; D008956:Models, Chemical; D011142:Polyvinyl Alcohol; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D014501:Uranium / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000464:Alginates; D006603:Hexuronic Acids; D014501:Uranium; D006108:Graphite; D020723:Glucuronic Acid; D011142:Polyvinyl Alcohol
keywords: Alginate; Graphene oxide; Immobilization; Polyvinyl alcohol (PVA); Saccharomyces cerevisiae; Uranium