Sol-gel preparation of TiO₂/AC photocatalysts and ultrasound reduction of chromium(Ⅵ) and copper(Ⅱ) wastewater

TiO₂/AC composites were prepared via the sol-gel method from a carrier of activated carbon (AC) and Ti(OBu)₄. Photocatalysts were characterized by TGA-DSC, SEM, XRD, diffuse reflectance spectroscopy (DRS) and FTIR. The ultrasound-TiO₂ photocatalytic reduction removal rate by determination concentration of chrome(Ⅵ) and copper (Ⅱ) was also studied by atomic absorption spectrophotometer (AAS). The results show that TiO₂/AC prepared by sol-gel method transforms from rutile into anatase at the temperature of 290℃ and shows the highest catalytic activity at 500℃. TiO₂/AC composites which formed C—O—Ti between the AC bulk and TiO₂ has good dispersion, low agglomeration and high surface area. The mechanism of photocatalytic reduction and adsorption follows the first order kinetics equation ln(c₀/c)=kt and Langmuir-Hinshelwood adsorption. Compared with the no-ultrasound, the reductive removal rate of Cr(Ⅵ) and Cu(Ⅱ) can be improved by 39.32% and 52.95% using ultrasound-photocatalytic technology. Cr(Ⅵ) and Cu(Ⅱ) removal rate is 70.61% and 75.30% even when the catalysts are recycled three times.