Degradation of metformin in water by TiO2–ZrO2 photocatalysis

The increasing use of pharmaceutical products also increases their release in aquatic environment. These contaminants are considered emerging pollutants, and induce adverse ecological and human health effects. The antidiabetic metformin is one example that has been detected in the aquatic environment at unusual concentrations. This fact indicates that conventional wastewater treatment is inefficient on eliminating this compound. Here we show that metformin can be effectively removed from water by photocatalysis. We found the optimised conditions for pH and concentration of catalyst on the photocatalytic process. TiO2 and TiO2–ZrO2 were successful in oxidising metformin under UV radiation following a pseudo-first order kinetics. Intermediates of metformin photodegradation appeared after photocatalytic treatment. Toxicity analysis showed that the degradation products are non-toxic to Lactuca sativa seeds. •Metformin is treated by photocatalysis with TiO2–ZrO2.•Metformin and the intermediates were identified through UV/Vis spectrophotometry analysis.•TiO2–ZrO2 is more efficient than P25 on the degradation of metformin.•TiO2–ZrO2 degraded almost 50% of metformin after 30 min of UV irradiation.•The treated wastewater was analysed through phyto-toxicity tests.