Treatment of real wastewater with TiO₂-films sensitized by a natural-dye obtained from Picramnia sellowii

A natural dye extracted from Picramnia sellowii (Chokanari) was used to prepare sensitized TiO₂ films. Dyes and heterotrophic microorganisms present in wastewater were treated by photocatalysis using visible light. A factorial design 2³ was employed to select the operational conditions to sensitize TiO₂ films. The combined treatment using a concentration of 0.03% w/v of sensitizer (natural dye), 700 rpm (spin-coating) and 300 color units of wastewater showed interesting results, removing close to 60% of the color and 60% of Chemical Oxygen Demand. Kinetic experiments using the best coated films showed that Total Organic Carbon abatement was higher using sensitized films, conversely, no statistical differences were found in color removal when comparing sensitized and non-sensitized films. Heterotrophic microorganisms were completely inactivated following 12 h of treatment with sensitized films. Films can be used up to 5 operational cycles with loss of catalytic activity close to 10%.