Rapid synthesis of Ag/AgCl@ZIF-8 as a highly efficient photocatalyst for degradation of acetaminophen under visible light

The presence of acetaminophen (ACT) used for painkillers has attracted great attention in the world, which have potentially adverse effects on aquatic lives and human beings. Advanced oxidation technology applied to water repair has received increasing concerns in recent years. In this study, photodegradation ACT in aqueous solution over Ag/AgCl@ZIF-8 synthesised by a simple stirring method was investigated under visible light irradiation. The prepared photocatalyst was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and UV-visible diffuse reflectance spectra (UV-vis). The degradation rates of ACT under different parameters were studied to get the optimal operating conditions in water. Results showed that the photodegradation process fitted pseudo-first order model well. 99% ACT degradation achieved when Ag/AgCl@ZIF-8 was delivered to the solution compared with ZIF-8 and Ag/AgCl with the maximum value of constant (kapp). The degradation rate obviously slowed down when the initial concentration of ACT increased to 2 mg/L while it increased with the increasing of dosage of photocatalyst. In contrast, pH has little effect on the degradation of ACT over Ag/AgCl@ZIF-8. The Ag/AgCl@ZIF-8 showed high efficiency for degradation after three repeated cycles which demonstrated the prepared photocatalyst has high stability. The O2− turned out to be the main active group during the photodegradation process responsible for the disappearance of ACT. Intermediate products analysis results by LC-MS showed that photolysis was the first step of photocatalytic degradation for ACT followed by a ring cleavage.