A novel method for the remediation of wastewater containing acid red 131 dye using acoustic cavitation combined with sulphur-doped TiO2 and oxidants

Abstract

The present study investigated the degradation of Acid Red 131 (AR131) dye using a combination of ultrasound-induced cavitation, ultraviolet (UV) irradiation, chemical oxidants, and photocatalyst, focusing on the effect of operating parameters. It was established that acidic pH, higher input power, and lower initial concentration resulted in higher degradation. Sulphur-doped titanium dioxide (S-TiO₂) synthesized using a novel ultrasound-assisted method showed an optimum dosage of 300 ppm for the AR131 degradation with sulphur to titanium ratio of 2:1. In the combination approach, the optimum dosage of hydrogen peroxide (H₂O₂) and potassium persulfate (KPS) was established as 100 ppm and 400 ppm respectively. The maximum degradation of 90.3% was obtained using a combined approach of US + KPS + UV/S-TiO₂ whereas, a maximum synergetic coefficient of 1.57 was obtained for the approach of US + UV/S-TiO₂ with degradation of 86.96%. It was also elucidated that for combination approaches of US + H₂O₂, US + H₂O₂ + KPS, and US + H₂O₂ + KPS + UV/S-TiO₂, the synergetic coefficients were lower than one due to undesirable side reactions and radical scavenging. Scale-up studies performed at 15 times of the laboratory scale volume, elucidated that the maximum degradation was obtained as 58.01% for the approach of US + KPS + UV/S-TiO₂. Therefore, the approach of US + KPS + UV/S-TiO₂ was elucidated as the most efficient in degrading the AR131 dye at both small and large scale of operation. In terms of synergy, the approach of US + UV/S-TiO₂ was more efficient. Overall, an optimized combination approach was successfully demonstrated for the effective degradation of AR131 dye with synergism and better results at a large scale.

Keywords: Advanced oxidation processes; Photocatalyst synthesis; Sonochemistry; Sulphur doped titanium dioxide; Ultrasonic reactor.