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

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, pH(6), 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 (r(2) = 0.98 for optimal condition), corresponding to a 0.023 min(-1) rate constant. Both HO center dot and SO4 center dot- radicals generated from the rGO-Co3O4/PS system were primarily species that degraded TC in solutions.

Automated summary

In this study, rGO, Co3O4, and rGO-Co3O4 composites were successfully synthesized and evaluated for their catalytic activity in degrading TC in aqueous solutions. The rGO-Co3O4 composite exhibited significantly enhanced efficiency compared to pure Co3O4, showing potential as a recyclable catalyst system. The degradation process primarily followed pseudo-first order kinetics and was influenced by various factors such as pH, TC concentration, catalyst dosage, and PS concentration. HO dot and SO4 dot- radicals generated from the rGO-Co3O4/PS system were key species in degrading TC in solutions.