摘要
Sorption of tungstate on boehmite（γ-Al OOH）is increased by co-sorption with Co^（2＋）over the near-neutral p H range.Batch uptake experiments show up to a 3-fold increase in tungstate uptake over the range WO4^（2-）=50–1000μmol/L compared to boehmite not treated with Co^（2＋）.Desorption experiments reveal a corresponding decrease in sorption reversibility for tungstate co-sorbed with Co^（2＋）.Reaction of boehmite with Co^（2＋）results in the formation of Co Al layered double hydroxide（LDH）,as confirmed by X-ray diffraction and X-ray absorption spectroscopy.Tungsten L3-edge X-ray absorption near edge structure（XANES）reveals that W（VI）is octahedrally coordinated in all sorption samples,with polymeric tungstate species forming at higher tungstate concentrations.X-ray diffraction and X-ray absorption spectroscopy indicate that the mechanism for enhancement of tungstate uptake is the formation of surface complexes on boehmite at low tungstate concentrations,while exchange into the Co Al LDH becomes important at higher tungstate concentrations.The results provide a basis for developing strategies to enhance tungstate sorption and to limit its environmental mobility at near-neutral pH conditions.
Sorption of tungstate on boehmite（γ-Al OOH）is increased by co-sorption with Co^（2＋）over the near-neutral p H range.Batch uptake experiments show up to a 3-fold increase in tungstate uptake over the range WO4^（2-）=50–1000μmol/L compared to boehmite not treated with Co^（2＋）.Desorption experiments reveal a corresponding decrease in sorption reversibility for tungstate co-sorbed with Co^（2＋）.Reaction of boehmite with Co^（2＋）results in the formation of Co Al layered double hydroxide（LDH）,as confirmed by X-ray diffraction and X-ray absorption spectroscopy.Tungsten L3-edge X-ray absorption near edge structure（XANES）reveals that W（VI）is octahedrally coordinated in all sorption samples,with polymeric tungstate species forming at higher tungstate concentrations.X-ray diffraction and X-ray absorption spectroscopy indicate that the mechanism for enhancement of tungstate uptake is the formation of surface complexes on boehmite at low tungstate concentrations,while exchange into the Co Al LDH becomes important at higher tungstate concentrations.The results provide a basis for developing strategies to enhance tungstate sorption and to limit its environmental mobility at near-neutral pH conditions.
基金
supported by the National Science Foundation, Grant No. CHE0714183
supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886
supported by the U.S. DOE under Contract No. DE-AC02-06CH11357
Additional support was provided by the National Research Foundation of Korea grant funded by the Korean government (MSIP) (No. 2014R1A2A2A01007294)
