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Abstract: The effects of pH, initial Eu(III) concentration, ionic strength and fulvic acid (FA) on the adsorption of Eu(III) on TiO2 are investigated by using batch techniques. The results indicate that the presence of FA strongly enhances the adsorption of Eu(III) on TiO2 at low pH values. Besides, the adsorption of Eu(III) on TiO2 is significantly dependent on pH values and independent of ionic strength. The adsorption of Eu(III) on TiO2 is attributed to inner-sphere surface complexation. The diffuse layer model (DLM) is applied to simulate the adsorption data, and fits the experimental data well with the aid of FITEQL 3.2. X-ray photoelectron spectroscopy (XPS) is performed to study the species of Eu(III) adsorbed on the surfaces of TiO2/FA–TiO2 hybrids at a molecular level, which suggest that FA act as “bridge” between Eu(III) and TiO2 particles to enhance the ability to adsorb Eu(III) in solution. [Copyright &y& Elsevier]

Abstract: The mutual effects of Cu(II) and phosphate on their interaction with γ-Al2O3 are investigated by using batch experiments combined with density functional theory (DFT) calculations. The results of batch experiments show that coexisting phosphate promotes the retention of Cu(II) on γ-Al2O3, whereas phosphate retention is not affected by coexisting Cu(II) at low initial phosphate concentrations (≤3.6mg P/L). Cu-phosphate aqueous complexes control Cu(II) retention through the formation of type B ternary surface complexes (where phosphate bridges γ-Al2O3 and Cu(II)) at pH 5.5. This deduction is further supported by the results of DFT calculations. More specifically, the DFT calculation results indicate that the type B ternary surface complexes prefer to form outer-sphere or monodentate inner-sphere binding mode under our experimental conditions. The enhancement of phosphate retention on γ-Al2O3 in the presence of Cu(II) at high initial phosphate concentrations (>3.6mg P/L) may be attributed to the formation of 1:2 Cu(II)-phosphate species and/or surface precipitates. Understanding the mutual effects of phosphate and Cu(II) on their mobility and transport in mineral/water environments is more realistic to design effective remediation strategies for reducing their negative impacts on aquatic/terrestrial environments. [Copyright &y& Elsevier]