Effect of pH on the Catalytic Degradation of Rhodamine B by Synthesized CDs/g-C₃N₄/Cu _x O Composites.

ABSTRACT: The narrow pH range of Fenton oxidation restricts its applicability in water pollution treatment. In this work, a CDs/g-C₃N₄/Cu _x O composite was synthesized via a stepwise thermal polymerization method using melamine, citric acid, and Cu₂O. Adding H₂O₂ to form a heterogeneous Fenton system can degrade Rhodamine B (Rh B) under dark conditions. The synthesized composite was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption/desorption isotherms. The results showed that CDs, Cu₂O, and CuO were successfully loaded on the surface of g-C₃N₄. By evaluating the catalytic activity on Rh B degradation in the presence of H₂O₂, the optimal contents of citric acid and Cu₂O were 3 and 2.8%, respectively. In contrast to a typical Fenton reaction, which is favored in acidic conditions, the catalytic degradation of Rh B showed a strong pH-dependent relation when the pH is raised from 3 to 11, with the removal from 45 to 96%. Moreover, the recyclability of the composite was evaluated by the removal ratio of Rhodamine B (Rh B) after each cycle. Interestingly, recyclability is also favored in alkaline conditions and shows the best performance at pH 10, with the removal ratio of Rh B kept at 95% even after eight cycles. Through free radical trapping experiments and electron spin resonance (ESR) analysis, the hydroxyl radical (^•OH) and the superoxide radical (^•O₂ ^-) were identified as the main reactive species. Overall, a mechanism is proposed, explaining that the higher catalytic performance in the basic solution is due to the dominating surface reaction and favored in alkaline conditions.

SUBMITTER: Guo Y 

PROVIDER: S-EPMC8014920 | biostudies-literature | 2021 Mar

REPOSITORIES: biostudies-literature