Facile Synthesis of CuO Nanosheets and Efficient Degradation of Rhodamine B in a Copper Oxide/Ascorbic Acid/Hydrogen Peroxide System: Kinetics, Fate of Ascorbic Acid, and Mechanism

Abstract

CuO nanosheet was successfully prepared via a simple, green hydrothermal method. The resulted product was characterized by various technologies. CuO combined with trace ascorbic acid exhibited excellent Fenton-like catalytic activity for Rhodamine B degradation. 80 % of RhB degradation occurred in the first 10 min and ascorbic acid was transformed to dehydroascorbic acid at this stage. When the RhB degradation reaction ended, the mineralization of ascorbic acid commenced and finally the ascorbic acid was mineralized to CO 2 and H 2 O. The role of ascorbic acid was to accelerate the two cycles (�Cu II !�Cu III !�Cu II and �Cu I !�Cu II !�Cu I ) on the surface of CuO particles, which results in the continuous generation of abundant free radicals and rapid degradation of pollutants. The rapid degradation kinetics can be described by Behnajady-Modirshahla-Ghanbery equation. The rate constant of HO * generation was 3.7 × 10 À 2 s À 1 and the most utilization efficiency of H 2 O 2 reached 75 %. The CuO/ascorbic acid catalyst has environmentally friendly features, thereby highlighting its practical utility for wastewater treatment.

Ascorbic Acid-Enhanced CuO/Percarbonate Oxidation: Insights Into the pH-Dependent Mechanism

“…Regarding the O 1s XPS spectrum of fresh CuO, three characteristic peaks located at 529.9, 531.5, and 532.1 eV, , corresponding to the lattice oxygen (O L , 26.70%), adsorbed oxygen, and surface hydroxyl species (O S , 52.75%), respectively (Figure c). As for reacted CuO, the proportion of O L reduced to 19.92% at pH 7.0, whereas it increased to 52.75 and 36.90% at pH 3.0 and 9.0, respectively.…”

“…As suggested by prior studies, the mechanisms of Cu-catalyzed AOPs remain controversial, and different oxidation pathways have been proposed, which mainly include free radical ( • OH, sulfate radical (SO 4 •– ), superoxide radical (O 2 •– )), nonradical (Cu­(III), surface-activated persulfate (i.e., peroxymonosulfate (PMS) and peroxydisulfate (PDS)), and singlet oxygen ( 1 O 2 )) pathways. − In addition, the reactive oxygen species (ROS) involved in Cu-based AOPs were found to be pH-dependent . For example, Wei et al proposed that surface-associated Cu­(III) played an important role in 4-chlorophenol (4-CP) in the CuO/PMS process in the pH range of 3.0–10.0 .…”

Mesoporous CuO Prepared in a Natural Deep Eutectic Solvent Medium for Effective Photodegradation of Rhodamine B

“…Cupric oxide (CuO), a p -type semiconductor, with a narrow band gap of about 1.7 eV has been widely used as a photocatalyst in the degradation of organic pollutants, because of its low cost and high efficiency in absorbing sunlight [ 1 , 2 ]. Generally, CuO particles with various structures are synthesized via solvothermal [ 1 , 3 ], ultrasound-assisted [ 4 , 5 ], and microwave assisted [ 6 , 7 ] methods. For example, Sun et al prepared sheet-like CuO using a solvothermal method (reaction time, 12 h; reaction temperature, 80 °C) and the synthesized sheet-like CuO NPs could efficiently activate peroxydisulfate to degrade bisphenol A [ 1 ].…”

“…Recently, CuO NPs were also applied as catalysts for the degradation of RhB [ 7 , 8 ]. Xiao et al developed a Fenton-like catalyst by combining CuO with ascorbic acid (Vc) to activate H 2 O 2 and degrade RhB.…”

“…Xiao et al developed a Fenton-like catalyst by combining CuO with ascorbic acid (Vc) to activate H 2 O 2 and degrade RhB. The removal efficiency of RhB reached 76% [ 7 ]. Liu and co-workers prepared oxygen vacancy-rich CuO NPs to construct a CuO/PMS system for the degradation of RhB.…”