Degradations of acetaminophen via a K2S2O8-doped TiO2 photocatalyst under visible light irradiation

• Doping TiO2 with K2S2O8 extends visible-light activity and facilitates to degrade ACT.
• Four parameters utilizing as-doped photocatalyst were systematically examined.
• Optimal conditions can achieve 100% ACT degradation efficiently.
• Three types of degradation kinetic models were computed and studied.

Acetaminophen (ACT) is a mild analgesic commonly used for relief of fever, headache and some minor pains. It had been detected in both fixed factory-discharged wastewaters, and diverse sources, e.g. surface waters during festival events. Degradation of such trace emergent pollutants by titanium dioxide (TiO2) photocatalysts is a common approach; however, the band gap that can be utilized in the UV range is limited. In order to extend downward the energy required to excite the photocatalytic material, doping with potassium peroxodisulfate (K2S2O8) by a sol-gel method was done in this work. The visible-light active photocatalyst was tested on the degradation of ACT under four parameters including: initial ACT concentration, catalyst dose, initial pH, and system temperature. Optimal conditions, which achieved 100% ACT degradation, were obtained by using 0.1 mM ACT initial concentration, catalyst dose of 1 g L−1, initial pH of 9.0 and system temperature of 22 °C at the end of 9-h irradiation. Meanwhile, three types of degradation kinetic models (i.e. zero, pseudo first and second order) were tested. The feasible model followed a pseudo-first order model with the computed constant (kapp) of 7.29 × 10−3 min−1. The present study provides a better photocatalytic degradation route by K2S2O8-modified TiO2 in comparison with pristine TiO2, in wastewater treatment dealing with ACT and other persistent organic pollutants.

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