Title
Removal of phenolic compounds from pulp and paper industrial effluent using the S₂O₈²/UV photocatalytic process: optimization by multivariate analysis
Authors
MARÍA C. YEBER and JENNIFER ZAMBRANO

Received August 10, 2024
Published Volume 58 Issue 9-10 September-December
Keywords advanced oxidation process, phenolic compounds, sulphate radical, pulp and paper industry, wastewater treatment, multivariate analysis

Abstract
Advanced oxidation processes (AOPs) are presented as a viable alternative for treating wastewater generated by the cellulose production industry, as these waters contain high concentrations of phenolic compounds and elevated levels of color, which are difficult to remove by conventional methods. AOPs require short treatment times and can lead to the mineralization of organic matter present in the wastewater. The oxidation process used in this study employs persulfate as the oxidant, which, when activated by UV radiation, generates sulphate radicals over a broad pH range (1 ≤ pH ≤ 10.5). The sulphate radical is a highly reactive species due to its high oxidation potential (E0 2.6-3.1 eV). For process optimization, two experimental variables were studied: pH, ranging from 2.0 to 11.0, and persulfate concentration, ranging from 0.1 to 1.0 gL-1. An experimental design was constructed using a full factorial design with three levels, resulting in 15 experiments. The experimental design revealed an optimal response at pH 6.0 and 0.55 gL-1 of oxidant, determining that within 1 hour of treatment, it is possible to achieve a reduction of 87.8% in phenolic compounds, with a constant rate of 0.022 min-1 (R2=0.83) and EEO = 20 Kwh-1. At the same time, the COD was reduced by 90.5%, the TOC by 79%, and the color was 100% eliminated, while increasing the effluent’s bioavailability from 0.35 to 1.4 (p ≤ 0.001, 95% confidence). The high bioavailability of the organic matter obtained after the treatment is an excellent outcome for the subsequent management of the usage of the treated water, whether it is for reuse in the industrial process itself, for irrigation purposes, or for return to the aquifer without causing environmental harm.