Eco-engineered bio-based palladium MOF–chitosan–carboxymethyl cellulose composite sponge: mechanistic insights, Box–Behnken optimization, and high-performance reusability for advanced ciprofloxacin removal from wastewater

Abstract

In this work,a new bio-based palladium metal–organic framework (Pd-MOF)/chitosan (CS)–carboxymethyl cellulose (CMC) composite (PMCC) sponge created by inserting a Pd-MOF into a medium comprising CS and CMC. The PMCC sponge was produced via a straightforward, environmentally friendly technique and was verified as an effective adsorbent for removing ciprofloxacin (CIP), a commonly used fluoroquinolone antibiotic, from water. A thorough classification of the sponge was conducted using methods such as FTIR spectroscopy, XPS, XRD, BET analysis, and SEM-EDX mapping. These methods confirmed the successful integration and porous nature of the composite material. Moreover, batch adsorption experiments were performed to evaluate how factors such as pH, contact time, adsorbent quantity, and temperature affected the uptake of CIP. The adsorption process adhered to the Langmuir isotherm model, with an adsorption energy of 33.6 kJ mol⁻¹, suggesting that the mechanism is chemisorption. The kinetic behavior was predominantly characterized by the pseudo-second-order model. A thermodynamic evaluation specified that the adsorption was both spontaneous and endothermic, with an enthalpy (ΔH°) of 91.2 kJ mol⁻¹ and entropy (ΔS°) of 315.2 J mol⁻¹ K⁻¹. The proposed adsorption mechanism involves interactions such as hydrogen bonding, π–π interactions, and electrostatic forces. Furthermore, the PMCC demonstrated excellent reusability, retaining substantial adsorption capacity after five regeneration cycles. An optimization process utilizing the Box–Behnken design established the adsorbent's competency under ideal conditions. Overall, these results position the PMCC sponge as a practical, reusable, and eco-friendly solution for the elimination of antibiotics from polluted water sources.