Feasibility and Statistical Analysis of Sulfanilic Acid Degradation in a Batch Photo-Fenton Process

Sulfanilic acid (SA) is a representative sulfonated aromatic amine commonly found in industrial effluents, posing significant risks to both human health and the ecosystem. Efficient and cost-effective treatment of SA-containing wastewater is crucial for sustainable environmental management. This study investigates the performance of the photo-Fenton process in degrading SA-containing wastewater. Three process variables are selected to study their effects on percent total organic carbon (%TOC) removal and final pH (pHFinal): initial total organic carbon concentration (TOC0) (150–250 mg/L), Fe2+ concentration (15–85 mg/L), and H2O2 concentration (1000–1500 mg/L). A combination of response surface methodology (RSM) and Box-Behnken design (BBD) is applied to examine both the individual and interactive effects of these variables. A total of 15 experimental trials are conducted, with the center point repeated three times. The results indicate significant interaction effects between Fe2+ and H2O2 concentrations on %TOC removal, while the interaction between TOC0 and H2O2 concentration notably influences pHFinal. The optimal operating parameters to maximize %TOC removal within 45 min of operation are determined as a TOC0 of 54.2 mg/L, an Fe2+ catalyst concentration of 33.7 mg/L, and an H2O2 concentration of 1403 mg/L. Under these conditions, the predicted %TOC removal and pHFinal were 89.2% and 2.93, respectively, which confirmed through validation experiments. Additionally, a correlation between pHFinal, TOC0, and final TOC concentration (TOCFinal) is observed, leading to the development of a linear model capable of predicting TOCFinal based on TOC0 and pHFinal within the experimental space. The latter finding facilitates online monitoring of the process progress.