Preparation of starch fumaropimarate and its efficient removal of ciprofloxacin hydrochloride from water.

Ciprofloxacin (CIP), a widely used fluoroquinolone antibiotic, is difficult to degrade in the environment. Residual CIP in water poses risks to ecosystems and human health, as it readily induces antibiotic resistance genes. Therefore, efficient and renewable adsorbents are urgently needed to mitigate CIP pollution. In this study, we report the synthesis and characterization of fumaropimarate starch (FPS), an adsorbent derived from starch and fumaropimaric acid, and evaluate its performance in removing CIP from water. The effects of adsorbent dosage, solution pH, temperature, initial concentration, and contact time on CIP adsorption were systematically investigated. Under optimal conditions (20 mg·L-1 CIP, pH 7.0, 1 g·L-1 FPS dosage, 0.5 h contact time), FPS achieved a removal efficiency of 99.9%. The adsorption process followed pseudo-second-order and Elovich kinetic model, while the isotherm data fitted Temkin model well rather than the Langmuir model. Thermodynamic analysis indicated a spontaneous, endothermic process with low adsorption enthalpy, enabling easy desorption and regeneration of FPS. Consistently, FPS showed negligible loss of performance after six adsorption-desorption cycles. Characterization by FTIR and XPS, together with the pH-dependent adsorption behavior and theoretical calculations, revealed that hydrogen bonding between the hydroxyl groups of FPS and CIP was the dominant interaction, providing mechanistic insight into the adsorption process.