Synergistic adsorption of ciprofloxacin on an amine-functionalized Zn-MOF/chitosan-polyethylenimine composite sponge:...

The ongoing discharge of ciprofloxacin (CIP) into aquatic environments presents significant ecological and public health challenges due to its environmental persistence and role in facilitating the proliferation of antibiotic resistance, underscoring the pressing necessity for effective removal technologies. This investigation introduces a novel composite sponge, composed of a amine-functionalized zinc metal-organic framework (NH₂-Zn-MOF) and chitosan-polyethylenimine (CS/PEI), referred to as FZCP, which was successfully synthesized and assessed for its capacity to adsorb CIP from aqueous environments. The synthesis of the FZCP composite sponge yields an adsorbent that is mechanically robust, highly porous, and capable of being reused. Extensive characterization utilizing methods such as XRD, BET surface area, FT-IR and two-dimensional FT-IR correlation spectroscopy, SEM-EDX, and zero point of charge (pH_zpc) analyses affirm the successful functionalization, uniform dispersion of the MOF, and the presence of a significant number of active sites. Batch adsorption experiments revealed a remarkably high adsorption capability, reaching values of up to 487 mg g^-1. The efficiency of the adsorption was found to be significantly affected by several variables, including the solution pH, duration of contact, and the quantity of adsorbent used. Through the application of response surface methodology (RSM) utilizing the Box-Behnken design (BBD) for process optimization, it emerged that the interaction time was the most serious issue influencing adsorption competence. With an overall desirability value of 0.991, the ideal parameters were found to be a solution pH of 7, a duration of contact of 100 min, and an adsorbent dosage of 0.02 g. A pseudo-second-order model adequately explained the adsorption kinetics, and isotherm and thermodynamic investigations indicated that the adsorption process was favorable, spontaneous, and mostly controlled by chemisorption. Ciprofloxacin is adsorbed through a combination of electrostatic forces, π-π stacking, hydrogen bonding, coordination with Zn(ii) sites, and pore filling, according to mechanistic studies. All of these results point to the potential of the FZCP composite sponge as a very successful adsorbent for eliminating ciprofloxacin from wastewater.