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...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.展开更多
An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated b...An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated by XRD and TEM. The tribological properties of γ-AIOOH nanoparticles with the average diameter of 15 nm as additives in liquid paraffin were investigated by a four-ball tester, and the worn surfaces were analyzed by SEM and EDS. Results show that the average size of synthesized γ-AIOOH nanoparticles increases with the increase of the pH value and temperature of the reactant. The γ-AIOOH nanoparticles as additives could exhibit good tribological properties due to their covering effect, which prevents the direct contact of asperities and reduces the adhesion. As the real area of contact decreases with the decrease of applied load, the optimum concentration varies from 0.4 % to 0.1% when the applied load decreases from 294 N to 200 N.展开更多
基金supported by the National Science Foundation, Grant No. CHE0714183supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886+1 种基金supported by the U.S. DOE under Contract No. DE-AC02-06CH11357Additional support was provided by the National Research Foundation of Korea grant funded by the Korean government (MSIP) (No. 2014R1A2A2A01007294)
文摘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Sponsored by the Excellent Young Scholars Research Fund of Beijing Institute of Technology(2006Y0411)
文摘An experiment procedure was presented for the synthesis of γ-AIOOH nanoparticles by a dehydration process which employed the solution of H202 as dehydrator. The phase and morphology of the product were investigated by XRD and TEM. The tribological properties of γ-AIOOH nanoparticles with the average diameter of 15 nm as additives in liquid paraffin were investigated by a four-ball tester, and the worn surfaces were analyzed by SEM and EDS. Results show that the average size of synthesized γ-AIOOH nanoparticles increases with the increase of the pH value and temperature of the reactant. The γ-AIOOH nanoparticles as additives could exhibit good tribological properties due to their covering effect, which prevents the direct contact of asperities and reduces the adhesion. As the real area of contact decreases with the decrease of applied load, the optimum concentration varies from 0.4 % to 0.1% when the applied load decreases from 294 N to 200 N.
