Application of photocatalytic and Fenton processes for the degradation of toxic pollutants from pulp and paper industry effluents

Abstract

Pulp and paper mill effluents contain a range of toxic organic and inorganic pollutants, with the potential for adverse environmental effects even at low concentrations. Currently, the paper production process requires approximately 200 tons of water per ton of paper, and the effluents generated at various stages of manufacturing contain around 250 different chemicals. The pulp and paper (PP) industry is frequently associated with pollution issues, characterized by elevated levels of chemical oxygen demand (COD), total organic carbon (TOC), total suspended solids (TSS), biochemical oxygen demand (BOD), adsorbable organic halides (AOX), toxic dyes, dark liquor, lignin, and chlorinated compounds. Several treatment methods have been proposed to address these pollutants and mitigate the environmental impact of the PP industry. This study aims to evaluate the efficacy of both heterogeneous and homogeneous photocatalytic treatments for PP industry-derived effluents, targeting reductions in major pollutant concentrations (i.e., COD, BOD, lignin, and color) to levels below environmental standards. A review of the literature on the efficiency of pollutant removal from PP effluents using photocatalytic treatment, particularly employing UV/TiO2 and UV/ZnO photocatalysts, revealed substantial removal rates. Specifically, removal rates of 97%, 90%, 96%, and 86% were observed for BOD, COD, color, and lignin, respectively. The use of doped photocatalysts demonstrated enhanced performance, achieving removal percentages of 98% for BOD and COD, and 99% for color and lignin. Furthermore, the application of Fenton and photo-Fenton treatment techniques yielded maximum removal percentages of 87%, 90%, 96%, and 99% for BOD, COD, color, and lignin, respectively.