Photoperoxi-coagulation using activated carbon fiber cathode as an efficient method for benzotriazole removal from aqueous solutions: Modeling, optimization and mechanism

• The benzotriazole was effectively removed by photoperoxi-coagulation (PPC).
• The high R-squared was obtained by box-behnken design for benzotriazole removal.
• The contribution of each mechanism was determined for PPC.
• Optimization of PPC were determined based on efficiency and economic criteria.
• Mineralization was considered by TOC, COD, AOS and COS parameters.

In this research, benzotriazole (BTA) was removed from aqueous solution using photoperoxi-coagulation (PPC) in which activated carbon fiber (ACF) was used as a cathode. Box-Behnken design was used to optimize and analyze four parameters i.e. time, applied current, initial BTA concentration and UV light power. According to the results, the R-squared and adjusted R-squared were 0.982 and 0.964, respectively, implying that the model was statistically suitable. It was shown that under the optimal condition for BTA removal i.e. 60 mg/L initial BTA concentration, 50 min time, 200 mA applied current and UV light power of 12W, the efficiency of the PPC process was maximum (97.8%). The removal mechanisms were determined and their results showed that the oxidation mechanism of photoperoxi-coagulation process had a more contribution in BTA removal in comparison with coagulation mechanism. The results of scavenging experiments also confirmed the determined removal mechanisms. Synergistic effect was observed in PPC while first order rate constant of PPC was 2.7 fold more than that of sum of each mechanism. The removals of TOC and COD were 64.5% and 76.3% respectively. Average oxidation state and carbon oxidation state of BTA solution were increased after PPC process indicating biodegradability improvement indirectly.

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