Facile approach for synthesis of stable, efficient, and recyclable ZnO through pulsed sonication and its application for degradation of recalcitrant azo dyes in wastewater

Abstract

In the present study, the ultrasound in pulsed mode was used as a part of an advanced oxidation method. The influence of the pulsed ultrasound mode for the preparation of the zinc oxide (ZnO) wurtzite nanoparticle was investigated. The catalysts synthesized were analysed using SEM, TEM, EDAX, BET surface area, XRD, and DRS to study their morphological and structural characterizations. The ZnO nanoparticles exhibited a highly hexagonal structure from pulsed sonication synthesis route. The efficiency of the decolourization of the reactive red 4 (RR4) dye was studied under different operation parameters such as dye concentration, initial solution pH, oxidant (e.g., H2O2) concentration, and catalyst loading. The hybrid combined process of pulsed sonolysis, pH (4.0), H2O2 (17.64 mmol), and catalyst (0.35 g/L) achieved 97% degradation and 87.5% chemical oxygen demand removal in about 20 min of reaction time. The cyclic degradation studies of RR4 removal with 0.35 g/L of ZnO showed the reusability of catalyst up to the fifth removal cycle with negligible loss in the catalytic performance. GC–MS study, used for the detection of the RR4 intermediates, revealed the oxidation–reduction reaction by the reactive radicals proceeded via the reductive cleavage of the azo bonds. The studied process, based on the pulsed ultrasound, is found to be effective for the degradation of RR4 dye.

Improved Surface Functional and Photocatalytic Properties of Hybrid ZnO-MoS2-Deposited Membrane for Photocatalysis-Assisted Dye Filtration

“…to be ~1.55 eV; this value is in conjunction with the Raman data implying the exfoliation with most MoS2 sheets is achieved when lying between two and six layers. As is obtained from the energy band gap analysis shown in Figure 5b, it is confirmed that the wide band gap of ZnO ~3.2 eV [39] has been shortened to ~2.77 eV upon doping E-MoS2, which typically holds a narrow direct band gap energy of 1.9 eV [40,41]. The addition of the narrow indirect gap p-type E-MoS2 to ZnO has decreased its band gap through the creation of a p-n heterojunction [42].…”

Kinetic study and Box–Behnken design approach to optimize the sorption process of toxic azo dye onto organo-modified bentonite

“…9 To remove dye contaminants that damage the ecosystem and water supply (used for drinking water supply, water industry needs, agriculture, etc. ), numerous processes are implemented, including adsorption, 10 ozonation, 11 coagulation/flocculation, 12 membrane separation, 13 advanced oxidation processes, 14,15 and biological treatment. 16,17 Adsorption has been recognized as the most popular treatment process for dye removal in aqueous solution and has the advantages of high efficiency, simple operation, and easy recovery and reuse of adsorbent.…”