Solochrome Dark Blue Azo Dye Removal by Sonophotocatalysis Using Mn2+ Doped ZnS Quantum Dots

Abstract

This work investigates the degradation of the azo dye solochrome dark blue (SDB) by measurement of the photocatalytic, sonocatalytic and sonophotocatalytic activities, under low ultrasonic frequency (40 kHz) and UV-C (254 nm) light, using Mn-doped ZnS semiconductor quantum dots (Mn2+:ZnS Qds) as catalysts, prepared by a simple chemical precipitation procedure. In order to study the different morphological and optical crystal properties, various characterization techniques were used, such as high resolution transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, N2 adsorption-desorption at −196 °C and ultraviolet-visible spectroscopy. The average particle size of the semiconductor Qds was in the range of 3–4 nm. The optimal parameters affecting dye degradation, such as the catalyst loading, solution pH, time of irradiation, initial concentration of dye, dopant concentration, ultrasonic power and frequency effect were evaluated. The synthesized catalytic material exhibited a high activity for sonophotocatalytic degradation of SDB (89%), larger than that observed for sonocatalysis (69.7%) or photocatalysis (55.2%) alone, which was due to the improved electron-holes separation, formation of more reactive radicals and enhancement of the active surface area. Qds showed good stability and reusability after five repeated cycles. Finally, the degradation products were identified by liquid chromatography-mass spectrometry (LC-MS).

Recent Advances in Advanced Oxidation Processes for Degrading Pharmaceuticals in Wastewater—A Review

“…A coupled Fenton reaction with high-frequency sonolysis (862 kHz) has been demonstrated to degrade ibuprofen from both distilled water and wastewater [125]. Another important combination is photocatalysis and sonication [126,127], where applying ultrasonic waves (20-1000 kHz) in photocatalysis could induce cavitation bubbles, enhancing the generation of • OH radicals and the degradation of organic pollutants. It is worth noting that, in these combinations of AOPs, the mechanisms of respective sonolysis, ozonation, and photocatalytic degradation of the organic pollutants are unchanged.…”

Active removal of anionic azo dyes (MO,CR,EBT) from aqueous solution by potential adsorptive capacity of zinc oxide quantum dots

“…3 A large number of these dyes are azo compounds ( N N ) linked by an azo bridge that is non-degradable, and a wide range of industries rely on these specific dye groups. 4 Among these industries, textile mills use them predominantly as a coloring agent. 5 These color dyes contain azo linkages ( N N ), sulfonic groups and aromatic rings, all of which are poisonous, carcinogenic and mutagenic.…”

“…[13][14][15] These adsorbents, however, have some drawbacks, such as low efficiency, high cost, recycling and low adsorption rates. 4 As a result, more efficient and cost-effective adsorbents for the removal of dyes from wastewater on an industrial scale are urgently needed. 16 In this regard, metal and metal oxide nanoparticles have gained considerable attention because of their small size, large surface area and high adsorption efficiency.…”

“…According to an estimate, approximately 10 000 distinct dyes and pigments are generated each year 3 . A large number of these dyes are azo compounds (NN) linked by an azo bridge that is non‐degradable, and a wide range of industries rely on these specific dye groups 4 . Among these industries, textile mills use them predominantly as a coloring agent 5 .…”

“…For the adsorptive removal of dyes various types of adsorbents are used, such as activated carbon, zeolites, polymers, alumina, titanium dioxide, peat, chitin, composite polymers, fungi, graphene oxide and tea bark 13‐15 . These adsorbents, however, have some drawbacks, such as low efficiency, high cost, recycling and low adsorption rates 4 . As a result, more efficient and cost‐effective adsorbents for the removal of dyes from wastewater on an industrial scale are urgently needed 16 .…”