Photocatalytic degradation of imidacloprid using semiconductor hybrid nano-catalyst: kinetics, surface reactions and degradation pathways

The presence of imidacloprid in surface waters has raised major environmental concern worldwide. Herein, for degradation and mineralization of imidacloprid, hybrid nano-catalysts g-C3N4/ZnO (< 20 nm) with different compositions were synthesized and characterized. Under UV-C light intensity of 15 W/m(2)and at pH 7, degradation was observed to be highest (95.6%) for g-C3N4/ZnO (20:80) in comparison to bare ZnO (80.6%) and g-C3N4(84.1%) nano-catalysts in just 35 min. The remarkable increase in photocatalytic activity was due to improved surface area (42.87 m(2)g(-1)), lower bandgap (2.76 eV) and lower photoluminescence intensity which resulted in lowering the recombination rate of electron-hole charge carriers. Further, higher zeta potential (+28 mV) at pH 7 might have increased intimacy in positively charged catalyst and high electron rich aromatic ring of imidacloprid which enhanced the degradation. The study was extended to analyze the reaction intermediates using LC-MS. The degradation mechanism revealed the formation of by-products such as ethylenediamine, nitroamine, acrolein, CO(2)and H2O. Overall, g-C3N4/ZnO (20:80) was found to be a promising catalyst for the degradation of imidacloprid at neutral pH.

Automated summary

The study focused on the degradation and mineralization of imidacloprid in surface waters using hybrid nano-catalysts g-C3N4/ZnO with different compositions. The g-C3N4/ZnO (20:80) catalyst showed the highest degradation efficiency (95.6%) under UV-C light intensity of 15 W/m(2) and pH 7, attributed to its improved surface area, lower bandgap, and lower photoluminescence intensity. Analysis using LC-MS revealed the formation of various by-products during the degradation process.