Influence of ZnO content on activated carbon/ZnO for enhanced acetaminophen removal under very low light intensity: Kinetics, operational variables, and radical trapping response

Abstract

The activated carbon-supported ZnO (AC/ZnO) photocatalyst was prepared using a simple mixing approach with varying ZnO mass ratio. The photoactivity was tested against acetaminophen (ACE) in an aqueous solution, assisted by low UVC light intensity (7 W). Characterization analyses revealed that the AC/ZnO particles mainly exhibited irregular shapes with uniform distributions and high crystallinity, and the primary oxidation state in the structure is Zn²⁺ with standard chemical state difference of 23 eV. The band gap of the AC/ZnO composite photocatalysts decreased when AC was integrated with ZnO. Among the composite photocatalysts, higher separation efficiency was observed comparatively with a low ZnO content. Interestingly, the fabrication of AC onto ZnO appeared to contribute to a significant enhancement in photoactivity of pristine ZnO. The photodegradation of ACE by AC/ZnO (0.05:1.5) followed pseudo-first order kinetics and almost complete removal of ACE was achieved under normal conditions. The photo-induced charge carrier's excellent separation efficiency, as demonstrated by the band gap and photoluminescence spectra, was associated with the optimized activities beneath UVC irradiation. The best photocatalyst can be recycled up to five times towards ACE degradation without any regeneration step or severe deactivation.