Adsorption of Hydroquinone in Aqueous Solution by Granulated Activated Carbon

This paper reports the adsorptive removal of hydroquinone (HQ) from aqueous solution by granulated activated carbon (GAC). Physicochemical properties including surface area and surface texture of the GAC, before and after HQ adsorption onto GAC, were analysed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The adsorption follows pseudo-second-order kinetics. An intraparticle diffusion study reveals that the pore diffusion is not the only rate-limiting step. The effective diffusion coefficient of HQ was of the order of 3: 19 x 10(-10) m(2)/s. Equilibrium isotherm data were generated for HQ solutions over an initial concentration range of 0.18-9.08 mmol/L for the GAC dosage of 10 g/L at temperatures of 288, 303, and 318 K. Equilibrium data were well represented by the Temkin isotherm model. An increase in the temperature increases adsorption. The entropy change (Delta S-0), heat of adsorption (Delta H-0), and Gibb's free energy (Delta G(0)) were determined. Elution of HQ from the loaded HQ showed that the thermal desorption may be a better option over that of solvent desorption. GAC worked well for at least five adsorption-desorption cycles, with continuous decrease in adsorption efficiency after each thermal desorption. Owing to its heating value, spent-GAC can be used as cofuel in the boiler-furnace. DOI: 10.1061/(ASCE)EE.1943-7870.0000443. (C) 2011 American Society of Civil Engineers.