Resorcinol formaldehyde xerogels are modified by mercaptopropyl-trimethoxysilane during the sol-gel process used to produce the xerogel. The chemical modification is confirmed by Fourier-transform infrared spectroscopy. The xerogel is then used to adsorb mercury ions from aqueous solutions. The effects of the molar ratios of the precursors as well as the catalyst and the modifier are studied on the textural properties of the xerogel and the adsorption efficiency. It is shown that the chemical modification of the resorcinol formaldehyde xerogels creates the chemical sites on the structure of the xerogel to adsorb more mercury ions and increase the adsorption efficiency. At the same time, chemical modification decreases the xerogel surface area which results in a reduction of the mercury adsorption. Therefore, there exists an optimum value for the chemical modification of the xerogel to achieve the highest adsorption efficiency. Adsorption kinetics as well as equilibrium isotherm of xerogels were examined using pseudo-first- and second-order kinetic equations, and Freundlich and Langmuir isotherm models. The adsorption kinetics was found to follow the pseudo-second-order kinetic equations. The experimental data was also fitted into the Longmuir model more precisely comparing the Freundlich model. Finally, a series of mercury adsorption-desorption tests proved that the optimized mercapto-modified resorcinol formaldehyde xerogel was an efficient reusable adsorbent for mercury ions. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42543.
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