A novel Al0-CNTs-Fe3O4 for the removal of low concentration sulfamethoxazole from aqueous solution by a couple of adsorption and degradation processes

A novel composite (Al-0-CNTs-Fe3O4), synthesized through sintering and co-precipitation, was used to remove low concentration sulfamethoxazole (SMZ) in wastewater with a two-step process (adsorption followed by oxidation). Briefly, SMZ was firstly adsorbed on the surface of Al-0-CNTs-Fe3O4 at initial pH of 3 (the adsorption process), then the adsorbed SMZ was degraded by the Al-0-CNTs-Fe3O4/O-2 system with 3 g/L Al-0-CNTs-Fe3O4 and initial pH of 1.5 (the degradation process). With the two-step process, 99.6% of the SMZ was degraded within 10 min while only 68.5% degraded with the one-step process (simultaneous adsorption and degradation). The Langmuir model and pseudo-second-order kinetic model could describe well the adsorption behavior of SMZ on Al-0-CNTs-Fe3O4. The maximum adsorption capacity (Q(max)) calculated from the Langmuir isotherm model and the adsorption rate constant (K-2) calculated from the pseudo-second-order kinetic model were 17.497 mg/g and 0.192 g/(mg min) (T = 298 K, pH = 3.0), respectively. Moreover, the saturated Al-0-CNTs-Fe3O4 was easily separated from the aqueous solution due to its saturation magnetization (Ms) value of 35.14 emu/g, which was convenient for the subsequent degradation process. Possible mechanisms of the adsorption and degradation of SMZ by Al-0-CNTs-Fe3O4 were also proposed.