| Three-dimensional silver-loaded titanium dioxide composites (3D-TiO2-Ag)which had a highly selective adsorption characteristic for the removal of iodide ions inall types of water were prepared by hydrolysis-Ultraviolet photolysis method. Andoptimization of the preparation conditions, the adsorption properties of materialscharacterization, adsorption experiments and adsorption mechanism were researchedcomprehensively.Firstly, the prepared samples were characterized by SEM, EDS, BET, Raman,XRD and XPS potential to investigate morphology, microstructure, elementalcomposition and the valence change. The SEM results show that the3D-TiO2materialhad performance including thorn-like surface structure spherical and microspheresconsisting of rutile. Analysis and calculation results of BET indicated specific surfacearea of3D-TiO2-Ag increasesd from147.6m2/g to153.7m2/g, pore size and porevolume decreased from2.451nm and0.109cm3/g to1.687nm and0.088cm3/g,respectively. EDS, Raman, XRD and XPS results demonstrated that Ag and Ag2Ocoexsited on the surface of the composites uniformly, and Ag was dominated.Secondly, adsorption experiment results suggested that the composites reached toequilibrium adsorption at300min and equilibrium adsorption capacity was207mg/g,which used Freundlich formula combining with second-order equation indicatingmainly existing chemisorption process. The results of adsorption thermal kineticsexperiments had an excellent relevance with Langmuir model, the theoreticalcalculation results demonstrated that the maximum adsorption capacity of thecomposites could reach to212.77mg/g. The composites had good behavior inalkaline environment and the adsorption capacity was the best in pH=6~8; theisoelectric point of the compoites was8.22pH, this provided a theoretical explanation.The effect of coexisting anions (F-, Cl-, NO3-, SO42-and CO32-), the environment ofsimulated seawater and analog Salt Lak were investigated and the results show thatadsorption capacity of composites still maintain150mg/g more than, indicating thatthe composites had a huge potential for removal and extraction application of iodineion in all kinds of complex water environment. Finally, microcosmic adsorption mechanism was analysised by FT-IR, Raman，XPS，XRD and Zeta potential. The result indicated that H2O and O2in the air whichcan capture the electrons and holes generated by the surface of the composites in thelight were easily adsorbed on surface of3D-TiO2-Ag, then forming O2-and OH ionpossess a strong oxidizability and adsorptivity which play a major role in theadsorption process. Iodine elements in solution were reacted with silver elements onthe composite surface generating AgIn(n≥1) compounds. |
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