Synthesis of ZnO@VC for enhancement of synergic photocatalytic degradation of SMX: Toxicity assessment, kinetics and transformation pathway determination

Nanocomposite-based photocatalytic degradation of sulfamethoxazole (SMX) is frequently used for wastewater treatment. However, applying various nanoparticles led to different removal efficiencies and levels of environmental toxicity. Herein, we synthesized and characterized ZnO@VC to enhance the photocatalytic degradation of SMX. Effects of SMX concentration, catalyst dosage, pH, water matrix and role of reactive oxygen specious (ROS) were evaluated. Results confirmed 97.69±0.95% (5 mg L −1 SMX/0.05 g L −1 catalyst) removal efficiency followed pseudo-first-order kinetic. Higher SMX concentration and higher catalyst dosage reduced degradation efficiency because of the prevention of catalyst active-sites and limiting light availability. SMX removal efficiency was slightly reduced in synthetic wastewater (SWW) and tap water (TW) by anions scavenging ROS. Due to pH reliance of SMX anionic-density, the degradation efficiency was positively and negatively impacted by acidic and basic environment, and pH values below and over the catalyst point of zero charge (PZC), respectively. Quenching test revealed that some specious of ROS play more important role in photocatalytic degradation of SMX. Two degradation pathways of SMX photocatalytic decomposition were described. The synthesized catalyst showed good stability in terms of reusability. The results revealed that ZnO@VC with high detoxification ability (97%) could be a promising photocatalyst for treatment of antibiotics from water and wastewater.