Design a WO 3 /Zn heterojunction for boosting the photodegradation of Favipiravir in aqueous solutions

This study was aimed at designing a new type of heterojunction catalyst for the degradation of Favipiravir using visible light. Several WO3–ZnO nanocomposites with different Zn contents varying from 1 to 20 wt% were successfully developed via a simple one-step microwave irradiation procedure. Various analytical methods, including XRD, TEM, FESEM, EDAX, FTIR, and BET, BJH characterised the WO3-Zn catalysts. XRD pattern revealed that the small size of Zn ions is caused by the easy penetration of Zn ions into the WO3 crystalline with a monoclinic phase, which will lead to an increase in the surface area and a decrease in the size of the particles. According to FESEM and TEM images, nanocomposite particles had a non-uniform, irregular shape and a smaller particle size (20 to 40 nm). EDAX analysis related to WO3-Zn synthesised showed the O, W and Zn elements are 10%, 67%, and 23%, respectively. Response surface methodology using R software was used as a tool to optimise the amount of catalyst and Favipiravir concentration, time and pH. Effective parameters in the process, including the amount of catalyst in the range (0.5 to 2.5 g L−1), Favipiravir concentration in the range (1–10 mg L−1), time in the range (10–90 min) and pH in the range (4 to 9) were entered into the software and analysed. Under the optimised conditions of the parameters (pH, 4.96; amount of catalyst, 2 g L−1; amount of Favipiravir concentration, 10 mg L−1; and time, 60 min), the maximum removal efficiency (99.99%) was obtained. Also, 85.8% of the mineralisation of Favipiravir was found under the determined optimum conditions. Quenching experiments were conducted to investigate the reaction mechanism, the results showed that superoxide and hydroxyl oxidising radicals play an essential role in Favipiravir degradation..