Optimized photodegradation of palm oil agroindustry waste effluent using multivalent manganese–modified black titanium dioxide

This article presents a methodological approach to use manganese (Mn³⁺Mn⁷⁺)-modified black titanium dioxide (Mn/BTiO₂) as a photocatalyst to optimize and improve visible-light-driven photodegradation of treated agro-industrial effluent (TPOME). A modified wet chemical process was used to prepare BTiO₂. The BTiO₂ was then wet impregnated with Mn and calcined at 300 °C for 1 h to produce Mn/BTiO₂. The activity of Mn/BTiO₂ was investigated in terms of photo-assisted elimination of chemical oxygen demand (COD), phenolic compounds (PCs), color, and total organic carbon (TOC). Using the design of experiments (DOE), the conditions of the photocatalytic process, including photocatalyst loading, Mn concentration, hydrogen peroxide (H₂O₂) dose, and irradiation time, were optimized. Under the optimum conditions (0.85 g/L photocatalyst loading, 0.048 mol/L H₂O₂ dose, 0.301 wt.% Mn concentration, and 204 min irradiation time) COD, PCs, color, and TOC removal efficiencies of 88.87%, 86.04%, 62.8%, and 84.66%, respectively, were obtained. Statistical analysis showed that the response variable’s removal from TPOME estimation had high R ² and low RMSE, MSE, MAD, MAE, and MAPE values, indicating high reliability. This study demonstrated the significant potential of the developed photocatalytic system for the treatment of waste effluent generated by the palm oil industry and other agro-industries, with the ability to simultaneously reduce a number of organic pollution indicators (OPIs).