Elimination of antibiotic contaminants from wastewater using polycarbazole nanocomposites as microwave-activated catalysts

Ciprofloxacin (CIP) is a widely used antibiotic, and its presence in water bodies poses a risk due to its resistance to conventional wastewater treatment processes. The accumulation of such pharmaceuticals can disrupt aquatic ecosystems, harm aquatic life, and contribute to ecological imbalances. Therefore, the degradation of CIP is of immense environmental significance. This study presents the microwave-assisted catalytic degradation of the antibiotic drug CIP using nanocomposites of carbazole copolymerized with pyrrole (PCz-co-PPy) and with thiophene (PCz-co-PTh). The PCz-co-PPy and PCz-co-PTh nanocomposites were synthesized through an ultrasound-assisted method. The resulting nanocomposites were characterized using spectral and morphological analyses. FT-IR and UV-Vis spectroscopy confirmed successful intercalation and copolymerization, while FESEM images revealed a chain-like morphology. These copolymer nanocomposites were employed as microwave-active catalysts for CIP degradation, achieving an optimal degradation efficiency of 95% within 21 min using PCz-co-PPy-50/50 and PCz-co-PTh-50/50 at 600 W microwave power. The degradation followed pseudo-first-order kinetics, with rate constants calculated as 0.031 min⁻¹, 0.020 min⁻¹, 0.030 min⁻¹, 0.056 min⁻¹, and 0.071 min⁻¹ for PCz, PPy, PTh, PCz-co-PPy-50/50, and PCz-co-PTh-50/50 nanocomposites, respectively, for a 50 mg l⁻¹ CIP solution. The catalytic efficiency is attributed to the formation of microwave-induced active species, including hot spots, electrons (e⁻), holes (h⁺), superoxide radicals (•O₂⁻), and hydroxyl radicals (•OH). Scavenger analysis verified that •OH and •O₂⁻ radicals play a crucial role in CIP degradation. A possible degradation mechanism and pathway for the nanocomposite system is proposed.