| Abstract
| - SBA-15 mesoporous silicates with surface functional groups were synthesized by cohydrolysis of tetraethoxyorthosilicate and ethyl-, carboxylate-, and ethylenediaminetriacetic acid-functionalized organosilanes(ETES, CTES, EDATAS, respectively) using the nonionic surfactant poly(ethylene oxide)−poly(propyleneoxide)−poly(ethylene oxide) triblock copolymer (PEO20PPO70PEO20, Pluronic P123). X-ray diffraction revealedthat silicates synthesized with up to 5% (wt/wt total silica) of added functionalized silane yielded orderedmesoporous materials with P6mm hexagonal symmetry. Further increasing the amount of added functionalizedsilanes to 20% resulted in a significant decrease in the structural ordering of the resulting silicate. Surfaceareas, pore volumes, and pore diameters were determined from nitrogen gas adsorption/desorption isotherms.Pore size contraction was observed as the wt % of added ETES was increased but not for the silicates formedwith added CTES or EDATAS, with the exception of the silicate formed using 20% added EDATAS. Inclusionof 1,3,5-trimethylbenzene (TMB) during synthesis resulted in silicates with larger pore sizes but a loss ofstructural order. Appreciable adsorption of copper ions from solution was observed only for the EDATAS-functionalized silicates. X-ray photoelectron spectroscopy of Cu2+-bound EDATAS-functionalized silicatesrevealed an Cu/N ratio of 0.15, smaller than expected for 1:1 stoichiometry of copper ions andetylenediaminetriacetic acid groups. Adsorption isotherms for Cu2+ binding to EDATAS-functionalized silicateswere fit to a double-component Langmuir equation. Binding constants, but not capacity, were dependent onthe amount of added EDATAS used in the synthesis and were several orders of magnitude smaller than thatreported for structurally similar nonimmobilized HEDTA.
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