Evaluation of UV/TiO(2) and UV/ZnO photocatalytic systems coupled to a biological process for the treatment of bleaching pulp mill effluent

This paper presents an exploratory study of pulp mill bleaching effluent treatment by a biological-photocatalytic coupled system. A fungus, Trametes pubescens, immobilized on polyurethane foam was used to inoculate the biological pre-treatment system. The pretreated effluent was then exposed to a photocatalytic treatment in which two catalysts (TiO₂ and ZnO) and two supports (aluminum foil and Luffa cylindrica) were tested. Catalyst characterization was carried out by means of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Information about crystalline structure, chemical composition, morphology, homogeneity and distribution on the support surface area was obtained. The overall biological-photocatalytic coupled system achieved degradation of 96% of initial total organic carbon (TOC), 97% of 2-chlorophenol (2-CP), 90% of 2,4-dichlorophenol (2,4-CP) and 99% of 2,4,6-trichlorophenol (2,4,6-TCP). This approach of synergistic coupling of T. pubescens and a semiconductor photocatalyst appears to be a viable alternative for the treatment of these non-biodegradable effluents.