Application of plasma-sprayed TiO2 coatings for industrial (tannery) wastewater treatment

Fine-structured photocatalytic TiO2 coatings were deposited by atmospheric plasma spraying (APS) on austenitic stainless steel coupons. One commercial spray-dried nanostructured TiO2 powder and five spray-dried powders obtained from suspensions containing mixtures of submicrometric and nanometric TiO2 particles were used as feedstock materials. Coating microstructure and phase composition were characterised using FEG-SEM and XRD techniques. The photocatalytic activity of the coatings was determined by measuring the degradation of methylene blue dye in aqueous solution. The experimental data were observed to follow a pseudo-first-order kinetic. The kinetic constants displayed a clear relationship with coating anatase content. The photocatalytic decontamination capability of one of these APS coatings was subsequently investigated by treating an industrial tannery wastewater. The photocatalytic experiments with these TiO2 coated coupons were carried out in a self-designed reactor. Partial degradation of the pollutants was observed, owing to a decrease in Total Organic Carbon (TOC), in addition to a significant decolouration effect, mainly relating to the removal of aromatic organic compounds typically present in tannery wastewater. The results demonstrate the potential use of plasma-sprayed photocatalytic TiO2 coatings in tannery wastewater treatment.