Sustainable treatment of wastewaters resulted in the textile dyeing industry

Adsorption on fly-ash-based substrates is discussed as a possible alternative to the industrial processes used for the treatment of wastewaters resulted in the dyeing industry. Three samples, containing four dyes and one conditioner, were collected from the dyeing and rinsing baths in a textile company. Adsorption on fly ash was comparatively discussed with adsorption and photocatalysis, both on fly ash and a mixed suspension with TiO₂. The fly-ash crystalline substrates are characterized by X-ray diffraction (XRD) and morphology studies were done using atomic force microscopy. The wastewater, before and after treatment is characterized by quality indicators (pH, TDS, BOD₅, COD, TOC, color, and total chromium content). The studies allow to calculate the efficiency of the dyes removal process and the kinetic parameters, for the pseudo-second order mechanism. The results show that, in designing an industrial wastewater treatment process, the results obtained in the investigations on single-dye solutions must be completed with data specifically obtained on industrial wastewaters. The data also support the assumption of competitive adsorption, between the initial components and between these and the possible by-products resulted after photocatalysis.