Abstract
The present study investigates degradation of caffeine using biogenic Ag@ZnO as a heterogeneous photocatalyst. Zinc nitrate (Zn (NO3)2) and silver nitrate (AgNO3) were utilized as the precursor and dopant in the biogenic synthesis of silver doped zinc oxide (Ag@ZnO) nanoparticles (NPs). The reduction in the bandgap energy of ZnO from 3.33 eV to 2.29 eV after Ag doping indicates the synthesis of Ag@ZnO NPs. The effects of catalyst loading (5, 10, 15, 20mg), initial pollutant concentration (20, 40, 60, 80, 100, 120, 140ppm), hydrogen peroxide (H2O2) concentration (1, 3, 5, 7mM), and radiation exposure duration (20, 40, 60, 80, 100, 120, 140, 160, 200min) were optimized to improve caffeine degradation efficiency. The highest degradation efficiency was observed at 15 mg/100 ml of catalyst loading at pH 8 with 5 mM H2O2 as an electron acceptor and it follows the pseudo-first-order kinetic process. Chemical oxygen demand and total organic carbon analysis were conducted to investigate and describe the level of caffeine mineralization.