Cube-shaped Cobalt-doped zinc oxide nanoparticles with increased visible-light-driven photocatalytic activity achieved by green co-precipitation synthesis

Abstract

From the perspective of environmental protection, the highly efficient degradation of antibiotics and organic dyes in wastewater needs to be tackled as soon as possible. In this study, an ecofriendly and green cube-shaped cobalt-doped zinc oxide nanoparticles (Co–ZnO NPs) photocatalyst using Pterocladia Capillacea (P. Capillacea) water extract loaded with 5, 10, and 15% cobalt ions were formed via co-precipitation process to degrade antibiotics. The prepared Co–ZnO NPs were tested as a photocatalyst for the photodegradation of ciprofloxacin (CIPF) in the presence of a visible LED-light source. Co–ZnO NPs have been obtained through the co-precipitation method in the presence of P. Capillacea extract as a green capping agent and reducing agent, for the first time. Several characterization techniques including FTIR, XRD, BET, XPS, TEM, EDX, SEM, TGA and DRS UV–Vis spectroscopy were applied to study the prepared Co–ZnO NPs. XRD results suggested that the average size of these NPs ranged between 42.82 and 46.02 nm with a hexagonal wurtzite structure. Tauc plot shows that the optical energy bandgap of ZnO NPs (3.19 eV) gradually decreases to 2.92 eV by Co doping. Examinations showed that 5% Co–ZnO NPs was the highest efficient catalyst for the CIPF photodegradation when compared with ZnO NPs and other 10 and 15% Co–ZnO NPs. A 10 mg/L solution of CIPF was photo-degraded (100%) within the first 15 min irradiation. The kinetics showed that the first-order model is suitable for displaying the rate of reaction and amount of CIPF elimination with R2 = 0.952. Moreover, central composite design optimization of the 5% Co-doped ZnO NPs was also investigated.

A critical mini-review on doping and heterojunction formation in ZnO-based catalysts

“…11,12 Doped ZnO shows reduced PL intensity compared to host ZnO, indicating diminished electron and hole recombination due to interactions between the host sp and dopant d states. 13,14 The reduction in intensity of the DRS-UV-vis spectra for doped ZnO is linked to extended visible light absorption. XPS also reveals a lower binding energy shi for doped ZnO than the ZnO host.…”

“…3 ). 47 Using a green approach, Meky et al 14 synthesized cubic-shaped Co–ZnO NPs. The optical analysis using UV-vis DRS revealed three unique light absorption bands in the visible region due to Co 2+ d–d transitions.…”

Photocatalytic Degradation of Methylene Blue from Aqueous Solutions by Using Nano-ZnO/Kaolin-Clay-Based Nanocomposite

“…In the case of the 10-ppm solution, the MB dye was degraded by almost 96% in 120 min, while when the concentration of MB in the solution was 25 and 50 ppm, the % degradation of dye was about 58% and 23%, respectively. Yadav et al, 2022 also removed MB from liquid media by using surfacemodified ferrospheres recovered from coal fly ash [74]. Gnanamoorthy et al also performed photocatalytic degradation of MB by using CuNiO 2 and their rGO nanocomposite and obtained efficient results [49].…”