RGO/persulfate metal-free catalytic system for the degradation of tetracycline: effect of reaction parameters

Abstract

Reduced graphite oxide (rGO) was synthesized from graphene oxide (GO) by reduction process with the aid of ascorbic acid. GO was synthesized from graphite precursor by modified Hummers method. The prepared materials were characterized in terms of surface morphology, structure, functional group, and elemental compositions by different methods such as SEM/EDS, XRD, FT-IR, Raman, and BET. rGO/K2S2O8 system was used to study the impact of different reaction parameters on the degradation of tetracycline in water. The results showed that GO and rGO materials were successfully synthesized, with high purity. The prepared rGO promoted the degradation of tetracycline by sulphate radicals generated from K2S2O8 with an efficiency of two-fold higher than sole K2S2O8. More than 95% of 5 mg l−1 tetracycline were removed by rGO/K2S2O8 system after 40 min of reaction. The catalytic performance of rGO/K2S2O system in the degradation of tetracycline was dependent on pH of the solution, catalyst loading, tetracycline initial concentration, and persulfate concentration. The optimal conditions for the degradation of tetracycline in water were at pH10, with 5 mg l−1 tetracycline initial concentration, 20 mg l−1 of rGO, and 0.2 mM persulfate added. The catalytic performance of the system showed relatively stable, with about 75% tetracycline in solution were removed after 3 cycles. The degradation of tetracycline by rGO/K2S2O8 system followed the pseudo-first order kinetics, with a typical coefficient of determination above 0.95 for all experimental conditions.