Application of Photo-oxidative Processes for the Remediation of Bleached Kraft Pulp Effluent

Abstract

Photo-Fenton, H2O2/UV, and H2O2/TiO2/UV processes were tested and optimized to remediate organic material from bleached pulp mill effluent. Those processes were considered as part of a tertiary treatment protocol in which the optimal pH conditions for successful installation of the processes were analyzed. In the photo-Fenton and H2O2/TiO2/UV processes, a response curve was constructed to obtain the best relative proportions for the concentrations of the reagents inside and outside the experimental space. All experimental conclusions were drawn by the analysis of the relevant COD, color, and TOC data. One of the chief findings in this work is that among the photo-oxidative paths employed, the photo-Fenton treatment furnished the highest reduction in COD (78%) and TOC (91%) via the application of a concentration ratio of H2O2 to Fe2+ of 700:3.8 (mg L−1). The H2O2/UV process demonstrated a high removal of COD (61%), color (100%), and TOC (86%) when the H2O2 concentrations were 500 mg L−1. The application of a photo-Fenton process, a heterogeneous photocatalysis coupled with hydrogen peroxide (H2O2/Fe2+/UV), can be considered as more meritorious in a materials sense relative to the H2O2/UV process because lower H2O2 amounts are used. In a broad tertiary remediation perspective, all photo-oxidative processes using high H2O2 concentrations achieved COD reductions in the range of 60−70% removal, 100% color removal, and a 70−90% reduction range for TOC.