Characterization of Green ZnO Supported Curcumin Intercalated Bentonite (ZnO@CU/BEN) as Environmental Catalysts for Effective Oxidation of 5-Fluorouracil Residuals: Pathway and Toxicity

Ecofriendly organically modified bentonite based on curcumin-extracted compounds was applied as a catalytic carrier for green ZnO particulates (Zn@CU/BEN). The composite developed was evaluated as a cost-effective, highly efficient, and versatile photocatalyst for improving the oxidation of 5-fluorouracil (5-FU) residues in water resources. The ZnO@CU/BEN blend, with a dose of 0.5 g/L, exhibits notable catalytic characteristics, leading to the full oxidation of 5-FU at a concentration of 25 mg/L within 80 min. The kinetic assessment reflects the high fitness of the Firs order model with best rate constant value of 0.0156 and quantum yield (phi) value of 2.9 x 10(-7). Nevertheless, the total reduction in organic carbon (TOC) was identified only after 160 min, indicating the existence of considerable byproducts of intermediates. The secondary compounds that were detected, alongside the establishment of hydroxyl radicals as the crucial oxidizing agent, revealed a degradation path consisting of two steps: hydroxylation and defluorination reactions. The toxicity characteristics of untreated pollutants and their resulting oxidized products were evaluated by measuring the inhibitory effects of the solutions on Vibrio fischeri at various time intervals. The sample that underwent partial oxidation during the first period exhibited a greater degree of toxicity compared to the unprocessed 5-FU. Nevertheless, the sample that underwent treatment for 200 min exhibited noteworthy characteristics of biosafety and non-toxicity. The synergistic effect of bentonite and organo-modified bentonite with curcumin extracts improves both the retention and oxidation activities of green ZnO.