Experimental design approach for the removal of the antidiabetic drug, metformin at a high concentration by photocatalytic processes

The metformin, is an emerging contaminant and one of the most consumed drugs in the world that has a high power of endocrine disruption across species in the ecosystem. The focus of this study was to determine the best photocatalytic processes through the study of TiO 2 ‐based photocatalytic, photo–Fenton and photo–ferrioxalate reactions for the metformin removal. The experimental results demonstrated that a high removal of metformin is obtained using TiO 2 ‐based photocatalytic (97 %), followed by photo–Fenton (66%) and photo–ferrioxalate (41%). The zero‐order rate constant (k) for TiO 2 ‐based photocatalytic, photo–Fenton and photo–ferrioxalate reaction was 2.36, 1.95 and 1.92 mg/L.min, respectively. The metformin was transformed into NH 4 + ‐N, NO 2 − ‐N and NO 3 − ‐N. According to results obtained, the proposed Box–Behnken experimental design can be used in photocatalytic processes to obtain the optimum conditions of the significant variables (H 2 O 2 concentration, catalytic concentration, pH and reaction time) for removal of metformin in a few runs.