Preparation Of Chelating Resin/SBA-15 Composite Materials For Adsorption Of As(Ⅴ) Species

Mesoporous silica materials have showed great potential in separation, catalysis, and adsorption fields. Pristine mesoporous silica materials possess relatively inert surface and cannot adsorb heavy metals efficiently without organo-functionalization. Nowadays, organo-functionalization of mesoporous silica materials is generally based on organosiloxane processes. Commercially available organosiloxanes are limited and some are very expensive, which would limit the application range of organo-functionalized mesoporous silica materials. Owning to their easy synthetic procedure, low cost, and good chemical stability, chelating resins have widely been used in adsorption of heavy metals. However, chelating resins have low surface areas, leading to the presence of inaccessible adsorption active sites. That chelating resins are incorporated into mesoporous silicas avoids the use of organosiloxanes, eliminating the limitation involving in the application range of organo-functionalized mesoporous silicas. Moreover, skeleton effect of mesoporous silicas increases surface area of chelating resins, which could lead to elevated adsorption capacity.In this dissertation, a series of chelating resin/SBA-15 composite materials were synthesized via a co-condensation method by using melamine, thiourea, formaldehyde, and tetraethyl orthosilicate（TEOS） as starting materials, P123(EO₂₀-PO₇₀-EO₂₀) as template. The effects of pre-polymerization time of the chelating resin precursors and pre-hydrolysis time of TEOS on the resultant composite materials were investigated systematically. It was found that the change of the above two synthesis parameters could affect textural properties of the composite materials and that all the resultant composite materials had high incorporation efficiency of the organic moieties.The obtained composite materials were used to adsorb aqueous As（Ⅴ） species. The effects of pH value, adsorption time, and ionic strength on the adsorption performance were investigated systematically in order to optimize adsorption parameters. The adsorption kinetics/thermodynamics results indicated that the composite materials follow pseudo second order model and Langmuir adsorption model. Arrhenius formula fitting showed the adsorption activation energy（Ea） was equal to 12.13 kJ/mol, implying that the adsorption can occur easily.Finally, the adsorption mechanism of the chelating resin/SBA-15 composite materials was further studied by means of X-ray photoelectron spectroscopy（XPS） and X-ray absorption near edge structure（XANES）. The obtained results indicated that As（Ⅴ） species were partially reduced on the composite materials.