Adsorption of antimony(III) from aqueous solution by mercapto-functionalized silica-supported organic–inorganic hybrid sorbent: Mechanism insights

Adsorption of Sb(III) ions onto mercapto-functionalized silica-supported organic–inorganic hybrid sorbent from aqueous solutions was studied by a batch technique. The mercapto-functionalized hybrid sorbent was prepared via sol–gel method and characterized by Fourier transform infrared spectra and scanning electron microscopy coupled to an energy dispersive spectrometer. The effects of parameters (such as pH, contact time, initial concentration and temperature) on the adsorption of Sb(III) onto mercapto-functionalized hybrid sorbent were investigated. Mercapto-functionalized hybrid sorbent had a tendency toward higher adsorption affinity for Sb(III) compared with the Sb(V), a fast adsorption equilibrium time within 20 min, and a wide pH range (3–8) for Sb(III) adsorption. The Langmuir, Freundlich and Dubbin–Radushkevich isotherm models were applied to describe the equilibrium data of Sb(III) adsorption. The analysis of adsorption isotherms indicated that Langmuir model described well the equilibrium data of Sb(III) adsorption. The capacity of mercapto-functionalized hybrid sorbent for Sb(III) was found to be 108.8 mg g−1. The analysis of the kinetic data by the pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetic models revealed that pseudo-second-order model gave the best fit for Sb(III) adsorption. Thermodynamic parameters demonstrated that adsorption of Sb(III) ions onto mercapto-functionalized hybrid sorbent was an endothermic, spontaneous and thermodynamically feasible process. As the results indicated, mercapto-functionalized hybrid sorbent has a suitable potential for the removal of Sb(III) ions in practical process.