Process efficiency and life cycle assessment of novel waste-derived Chl/TiO2 photocatalyst for rhodamine B removal

Visible-light photocatalysis is a promising approach toward cleaner production and environmental impact reduction. Dye sensitization of TiO2 nanoparticles with chlorophyll (Chl) pigments is a potential alternative for the improvement of photocatalysis efficiency but must be modified for higher activity in visible light. Herein, a novel and green Chl/TiO2 photocatalyst was constructed for rhodamine B removal using the TiO2 waste of the gas refinery Clause process, sensitized with extracted chlorophyll from orange tree leaf pigments. The effects of pH, pigment ratios, photocatalyst dosage, and temperature on the Chl/TiO2 photocatalyst performance accompanied by its environmental impacts were investigated. The results indicated that the pristine TiO2 before sensitization could degrade ~30 % of rhodamine B while the photocatalytic activity was enhanced to ~98 % after modification by 0.6 wt% chlorophyll pigments. The optimum conditions were achieved at 25 mg/l Chl/TiO2, pH = 4, and 50 mg/l rhodamine B after 2 h irradiation of visible light (LED lamp 50 W). Recycling studies showed a rhodamine B decolorization of 90 % after 5 cycles and demonstrated that Chl/TiO2 is a promising heterogeneous photocatalyst for the long-term removal of dyes from wastewater. The Chl/TiO2 followed the pseudo-first-order kinetic model and illustrated negative impacts on global warming (6.3 kg CO2) and terrestrial ecotoxicity (10.7 kg 1.4-DCB) from a life cycle assessment (LCA) perspective, originating from electricity consumption and acetone. Summing up, the present study offers a new and eco-efficient photocatalyst to facilitate wastewater treatment in real-world applications and gives perspectives to manage its long-term concern.