Cellulose–chitosan composites for ciprofloxacin removal from pharmaceutical wastewater: experimental and DFT insights

This study extracted cellulose from wastepaper and utilized it to make composites, specifically cellulose/chitosan and cellulose/iron oxide, to assess their efficacy in removing aspirin, paracetamol and ciprofloxacin from aqueous solutions. A screening experiment was performed and ciprofloxacin showed maximum adsorption capacity against cellulose/chitosan composite. The functional groups in the selected composite were identified through characterization using FTIR analysis. In order to optimize the batch adsorption process, factors like starting adsorbate concentration, contact time, pH and temperature were carefully considered. Interestingly, the cellulose/chitosan composite showed a promising adsorption capacity of 16.05 mg/g (at an initial concentration of 100 mg/L) for ciprofloxacin at pH 7. The cellulose/chitosan composite's point of zero charge (PZC) was noted at 6.5 pH. Freundlich and Halsey isotherms (R 2 = 0.96), as well as the pseudo-second-order model (R 2 = 0.99), provided the best match to the kinetic and equilibrium data. According to thermodynamic data, the adsorption process was exothermic (-ΔH o ) and spontaneous (−ΔG o ). Theoretical study via Density Functional Theory (DFT) also revealed that the ciprofloxacin drug is more stable after adsorption with the cellulose/chitosan composite due to greater negative total energy and adsorption energy (−3704.4571HF and −17.62 Kcal). Comprehensive adsorption studies strongly suggest that cellulose/chitosan composite holds significant potential for ciprofloxacin removal from pharmaceutical wastewater. This eco-friendly approach not only addresses the issue of water contamination, but also showcases the potential of sustainable materials derived from waste sources in addressing contemporary environmental challenges.