Publications (3)6.32 Total impact
Article: Behavior and mechanism of Ni(II) uptake on MnO2 by a combination of macroscopic and EXAFS investigation[show abstract] [hide abstract]
ABSTRACT: The effects of pH, ionic strength, competing ions and initial metal concentrations on the uptake behavior and mechanism of radioactive Ni(II) onto MnO2 was investigated using a combination of classical macroscopic methods and the extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The results indicated that the uptake of Ni(II) on MnO2 is obviously dependent on pH but independent of ionic strength, which suggested that the uptake of Ni(II) onto MnO2 is attributed to an inner-sphere surface complex rather than an outer-sphere surface complex. EXAFS analysis shows that the hydrated Ni(II) is adsorbed through six-fold coordination with an average Ni–O interatomic distance of 2.04±0.01Å. It can be inferred from the EXAFS analysis that the inner-sphere surface complex of Ni(II) onto MnO2 is involved in both edge-sharing and corner-sharing linkages. Both the macroscopic uptake data and the molecular level evidence of Ni(II) surface speciation at the MnO2-water interfaces should be factored into better prediction of the bioavailability and mobility of Ni(II) in soil and water environment. KeywordsNi(II)–MnO2 –Uptake–Surface complex–EXAFSJournal of Radioanalytical and Nuclear Chemistry 04/2012; 289(1):129-135. · 1.52 Impact Factor
Article: Macroscopic and microscopic investigation of Ni(II) sequestration on diatomite by batch, XPS, and EXAFS techniques.[show abstract] [hide abstract]
ABSTRACT: Sequestration of Ni(II) on diatomite as a function of time, pH, and temperature was investigated by batch, XPS, and EXAFS techniques. The ionic strength-dependent sorption at pH < 7.0 was consistent with outer-sphere surface complexation, while the ionic strength-independent sorption at pH = 7.0-8.6 was indicative of inner-sphere surface complexation. EXAFS results indicated that the adsorbed Ni(II) consisted of ∼6 O at R(Ni-O) ≈ 2.05 Å. EXAFS analysis from the second shell suggested that three phenomena occurred at the diatomite/water interface: (1) outer-sphere and/or inner-sphere complexation; (2) dissolution of Si which is the rate limiting step during Ni uptake; and (3) extensive growth of surface (co)precipitates. Under acidic conditions, outer-sphere complexation is the main mechanism controlling Ni uptake, which is in good agreement with the macroscopic results. At contact time of 1 h or 1 day or pH = 7.0-8.0, surface coprecipitates occur concurrently with inner-sphere complexes on diatomite surface, whereas at contact time of 1 month or pH = 10.0, surface (co)precipitates dominate Ni uptake. Furthermore, surface loading increases with temperature increasing, and surface coprecipitates become the dominant mechanism at elevated temperature. The results are important to understand Ni interaction with minerals at the solid-water interface, which is helpful to evaluate the mobility of Ni(II) in the natural environment.Environmental Science & Technology 08/2011; 45(18):7718-26. · 4.80 Impact Factor
Article: Influence of solution chemistry on the removal of Ni (II) from aqueous solution to titanate nanotubes[show abstract] [hide abstract]
ABSTRACT: a b s t r a c t In this work, adsorption of Ni(II) from aqueous solution to titanate nanotubes (TNTs) as a function of various water quality parameters was investigated under ambient conditions. The results indicated that the adsorption of Ni(II) to TNTs was strongly dependent on pH and ionic strength. A positive effect of humic acid (HA)/fulvic acid (FA) on Ni(II) adsorption was found at pH < 6.0, whereas a negative effect was observed at pH > 6.0. At low pH, the adsorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na + /H + on TNT surfaces, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH. The TNTs are suitable material for the preconcentration of Ni(II) from large volumes of aqueous solutions.Chemical Engineering Journal. 01/2011; 168:178-182.