Application of Photocatalysis and Sonocatalysis for Treatment of Organic Dye Wastewater and the Synergistic Effect of Ultrasound and Light

Abstract

Organic dyes play vital roles in the textile industry, while the discharge of organic dye wastewater in the production and utilization of dyes has caused significant damage to the aquatic ecosystem. This review aims to summarize the mechanisms of photocatalysis, sonocatalysis, and sonophotocatalysis in the treatment of organic dye wastewater and the recent advances in catalyst development, with a focus on the synergistic effect of ultrasound and light in the catalytic degradation of organic dyes. The performance of TiO2-based catalysts for organic dye degradation in photocatalytic, sonocatalytic, and sonophotocatalytic systems is compared. With significant synergistic effect of ultrasound and light, sonophotocatalysis generally performs much better than sonocatalysis or photocatalysis alone in pollutant degradation, yet it has a much higher energy requirement. Future research directions are proposed to expand the fundamental knowledge on the sonophotocatalysis process and to enhance its practical application in degrading organic dyes in wastewater.

Semiconductor Catalyst: Investigation for the Degradation of BB9 Azo Dye by Sonophotocatalytic Process

“…Photocatalytic degradation allows photons to be absorbed by the catalyst producing electronhole pairs. [45] The electrons are excited from the valence band (VB) to the conduction band (CB), creating holes in the VB and e À in the CB when the photocatalyst is exposed to visible light. [46] These excitons can interact with hydroxyl groups at the surface and generate highly oxidative species such as superoxide and hydroxyl radicals leading to dye degradation.…”

“…[43] At the same time, hot spots form as a result of cavitation, and these hot spots promote pyrolysis of water molecules in contact with the surface of the sonocatalyst, and hydroxyl radicals (OH * ) and hydrogen radicals (H•) are produced (Reaction 1-6). [2,45]…”

“…However, in the presence of a semiconductor catalyst, a synergistic effect occurs with the combination of US and UV processes, and more successful results can be obtained in the removal of pollutants. [45] The primary impact of ultrasound is the generation of reactive radical species, such as OH, under the extreme pressure and temperature conditions created by the implosion of cavitation bubbles during sonolysis. [43] At the same time, hot spots form as a result of cavitation, and these hot spots promote pyrolysis of water molecules in contact with the surface of the sonocatalyst, and hydroxyl radicals (OH * ) and hydrogen radicals (H•) are produced (Reaction 1-6).…”

Stirling Engine-Inspired Parallel Triboelectric Nanogenerator Drives the Electro-Fenton Process

“…The textile sector has long been associated with the most serious pollution source , because of the effluent from printing and dyeing . Worse still, dye molecules have a stable aromatic structure that can stay in the water for a long time, resulting in toxicity on aquatic and agricultural lands and severely damaging the ecosystem. , As a result, the degradation of organic dyes in wastewater has emerged as a critical issue in the treatment of water pollution. , …”

Applications of Catalytic Nanomaterials in Energy and Environment

“…In recent years, great progress has been made in thermal catalysis, photocatalysis, and electrocatalysis for energy and environmental applications. In particular, pollutant degradation [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ], green hydrogen production [ 8 ], indoor formaldehyde purification [ 9 ], oxygen reduction [ 10 ], and other fields [ 11 , 12 , 13 ] have ushered in major developmental opportunities and important original breakthroughs.…”