Rapid and efficient mineralization of methylene blue dye (above 95 % in 20 min) catalyzed by ZnO nanoparticles under sunlight

This novel communication reports rapid mineralization of methylene blue dye, reaching above 95% in 20 min under cloudy sunlight catalyzed by ZnO nanoparticles, which were synthesized from N-Dipentene as a reducing agent, at different zinc acetate concentrations from 0.1 M to 0.4 M. The synthesized ZnO nanoparticles structural, morphological, compositional, and optical characterizations were done using X-ray diffraction (XRD), high resolution scanning microscopy (HRSEM), energy dispersive spectroscopy (EDS) and photoluminescence (PL) respectively. From these characterizations ZnO wurtzite crystalline structure, average crystallite size (18-25 nm) with heterogeneous elongated nanoparticles mixed to triangle like particles and low content of byproducts as well as the presence of oxygen Vacancies transitions at the red-orange bands, which contributes to the PL main emission related to the visible region at the electromagnetic spectrum were obtained, these results were correlated to the photocatalytic activity. Meanwhile direct sunlight photocatalyst using 17 mg of ZnO for 10 ppm of methylene blue dye (MB) degradation was performed, the efficiency was analyzed by Fourier transform infrared spectroscopy (FT-IR) and UV-Vis spectroscopy, obtaining the kinetic adsorption ratio fitted to the pseudo second order (PSO) and the pseudo first order (PFO) to determine the mechanism that governs this process. All those analyses were correlated to the material characteristics and synthesis concentration. A 95.38 % efficiency was reached at 20 min for the champion sample D3R followed by D4R, D2R and D1R reaching an 89.19, 80.40 and 66.86 % for the same time. The maximum mineralization efficiency for D3RA was 98.08 % at 30 min, albeit it was observed that the adsorption kinetics obeys the Pseudo second order (PSO) for D3R, D4R and D2R meanwhile for D1R is governed by the Pseudo First Order mechanism (PFO), mainly by the diffusive chemical mechanism.