Preparation and characterization of activated carbon-supported zinc oxide/graphitic carbon nitride for degradation of acetaminophen

Pharmaceutical waste in wastewater has been causing great environmental concerns as it cannot be degraded with traditional wastewater treatment plants. To address this issue, a cost-effective UV-active photocatalyst, activated carbon-supported ZnO/g-C₃N₄ (AZG), was synthesized using a facile mixing method with different g-C₃N₄ ratios (0.01. 0.03, 0.05, 0.07 and 0.09 g). The photocatalytic performance of the composites was tested for the degradation of acetaminophen (ACE) under low-intensity UV light (7 W). The influence of parameters such as photocatalyst dosage, initial pH, ACE concentration, radical scavengers, and recyclability was also investigated. X-ray diffraction (XRD) confirmed that all AZG samples retained the characteristic ZnO diffraction peaks, indicating that the addition of activated carbon and g-C₃N₄ did not alter ZnO’s crystal structure. Scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) analysis showed irregular cubic ZnO particles distributed across the sheet-like g-C₃N₄ surface, while EDX verified the presence of Zn, C, O, and N elements. The reduced photoluminescence (PL) intensity suggested improved charge separation and lower electron–hole recombination. Among all samples, the AZG2 composite (AC:ZnO:g-C₃N₄ = 1.5:1:0.005) achieved the highest photocatalytic activity, removing 96.17% of ACE within 240 minutes with a rate constant of 1.357 × 10⁻² min⁻¹, following pseudo-first-order kinetics under the optimal conditions of photocatalyst loading of 0.1 g, initial concentration of ACE of 10 mg/L and initial pH of 5.8. Overall, the results demonstrate that the AC-supported ZnO/g-C₃N₄ photocatalyst is an efficient and low-cost material for removing pharmaceutical contaminants from water.