A critical review on ultrasonic-assisted dye adsorption: Mass transfer, half-life and half-capacity concentration approach with future industrial perspectives

Dyes are developing as a dangerous category of toxins to the ecosystem. The discharge of dyes in aquatic system has horrible health and esthetic impacts, needs to be expelled from nature. In this review article, authors displayed up-to-date advancement on use of ultrasonic-assisted adsorption in elimination of textile dyes from wastewater. This starts with a discussion about dyes, toxicity and its classification. It delivers broad literature evidence on acoustic cavitation and physical effects of ultrasound followed by an overview of the key information available on this technique in dye adsorption. The parameters that influence the efficacy of ultrasonic-assisted dye adsorption incorporates the temperature, pH, initial dye concentration, adsorbent dosage, sonication time, frequency, power and ionic strength. Unlike initial pH, dispersion, formation of cavitational bubbles and sponge effect influenced the process significantly. Improved mass transfer by eliminating internal resistance enhanced the adsorption. The values of half-life period and half-capacity concentration indicates less number of stages and adsorbent in ultrasonic-assisted dye adsorption. The application of this hybrid technique at larger level is highly feasible by considering low use of material, water, energy and time. This survey is proposed to be a source box for the use of ultrasonication on dye adsorption.