Synergistic effect for the degradation of tetracycline by rGO-Co3O4 assisted persulfate activation

Abstract

In this work, reduced graphene oxide (rGO), Co3O4, and rGO–Co3O4 composites were successfully synthesized while their catalytic activity was evaluated regarding the degradation of tetracycline (TC) by persulfate (S2O82−) activation process in aqueous solutions. Surface morphologies, composition, and structure of the as produced materials were investigated with the aid of different techniques such as XRD, SEM, EDX, FT-IR, and BET analysis. The catalytic activity of rGO–Co3O4 composite was evaluated regarding TC degradation by K2S2O8 (PS). The results revealed that pure Co3O4, rGO, and rGO–Co3O4 were successfully synthesized. Co3O4 sample presented spinel structure, with an average diameter of 26.7 nm while C/O ratio in rGO sample was about 3.2. rGO–Co3O4 composite significantly enhanced the removal of TC with a typical efficiency of over twofold compared to sole Co3O4.About 96% of TC (5 mg/L) were decomposed by rGO–Co3O4/PS catalytic system after 60 min at room temperature. The catalytic performance of rGO–Co3O4/PS system was affected by pH of solutions, TC initial concentration, catalyst dosage, and PS concentration. The rGO–Co3O4/PS system degraded the most TC in aqueous solutions at the following condition: rGO = 200 mg/L, pH6, TC = 5 mg/L, and PS = 0.3 mM; it was shown to be a perspective recyclable potential with a TC removal efficiency of more than 84% after three reuse cycles.TC degradation process fitted the pseudo-first order kinetics the most (r2 = 0.98 for optimal condition), corresponding to a 0.023 min−1 rate constant. Both HO• and SO4•- radicals generated from the rGO–Co3O4/PS system were primarily species that degraded TC in solutions.