Boron adsorption using a new boron-selective hybrid gel and the commercial resin D564

A new hybrid gel with boron-selective functional groups is prepared with tetraethoxysilane (TEOS), (3-glycidoxypropyl)trimethoxysilane (GPTMS), and a new precursor (W) synthesized from GPTMS and N-methylglucamine (MG). We investigate the boron adsorption onto the hybrid gel and the commercial resin D564 in aqueous solution by varying the initial boron concentration, pH, ionic strength, and temperature. Adsorption of both the hybrid gel and the D564 can be described by the second-order kinetics and the hybrid gel shows the lower second-order rate constant and the initial adsorption rate than the commercial resin. A maximum boron adsorption occurs at pH 4-9, which can be explained by the adsorption suppression by H⁺ ions at low pH and the weakened complexation by electrostatic repulsion at high pH. Ionic strength of the solution affects both the adsorption kinetics and thermodynamics, and it has a more pronounced effect on the kinetics of the hybrid gel than the D564. For both the hybrid gel and the D564, adsorption was found to be a chemisorption, which may be more advantageous in removal of boron from water than physisorption due to a higher adsorption capacity and better selectivity. Compared with other boron-selective adsorbents, the boron-selective hybrid gel in this study is easy to prepare, and has a good mechanical strength and an adsorption capacity (1.15 mmol g^-1).