Combined adsorption and catalytic ozonation for removal of sulfamethoxazole using Fe2O3/CeO2 loaded activated carbon

Treatment of sulfamethoxazole (SMX) in terms of total organic carbon (TOC) by combined adsorption and catalytic ozonation by commercial activated carbon (PAC) and Fe2O3/CeO2 loaded activated carbon (MOPAC) has been investigated. Adsorbent dosage of 2g/L, initial pH similar to 6.5 and contact time = 50 min were found optimum for adsorption studies. Among various models, experimental data was well fitted by pseudo second-order model while Langmuir isotherm model represented equilibrium adsorption of SMX on both adsorbents. Adsorption of SMX was influenced by surface and intraparticle diffusion. The change in enthalpy (Delta H degrees) and entropy (Delta S degrees) for adsorption of SMX onto PAC and MOPAC were estimated as 105 kJ/mol and 396 J/mol K; and 21 kJ/mol and 131 J/mol K, respectively. The values of Delta G degrees decreased slightly as a function of temperature that showed spontaneity of adsorption process. According to ozonation study, the removal of SMX was higher in MOPAC/O-3 combination compared to PAC/O-3 combination for low pH values. However, the effect of catalyst type was minimal at pH values of 7.5. Similarly, mechanism study suggested the enhancement in removal of SMX in the presence of MOPAC/O-3 combination. Ozone consumption experiments also confirmed better consumption of ozone gas in case of MOPAC/O-3 combination. (C) 2011 Elsevier B.V. All rights reserved.