Mechanistic Insights into Ciprofloxacin Adsorption on Natural and Fe-NP-Modified Zeolite: A Comprehensive Kinetic, Isotherm, and Statistical Analysis

This study evaluates the green synthesis of iron nanoparticles (Fe-NPs) using agricultural waste extracts and their application for modifying natural zeolite from Chihuahua (Mexico) to remove ciprofloxacin (CPX) from aqueous media. The approach provides an environmentally friendly alternative to conventional nanoparticle synthesis by employing biomass-derived reducing agents. The natural and Fe-NP-modified zeolites were characterized by FTIR, EDX, and XRD. CPX adsorption was evaluated through kinetic and equilibrium isotherm experiments, supported by comprehensive statistical analyses, including correlation coefficients (R), ANOVA and statistical evaluation of model parameters. Langmuir modeling yielded maximum adsorption capacities (qmax) of 19.11 mg g−1 for natural zeolite and 22.99 mg g−1 for Fe-NP-modified zeolite, representing an approximately 20.3% higher model-estimated capacity after Fe modification. However, the overlapping confidence intervals indicate that this increase should be interpreted cautiously. Isotherm analysis showed that both the Langmuir and Freundlich models adequately described CPX adsorption, while statistical criteria indicated a better fit of the Freundlich model for the Fe-modified zeolite, consistent with a more heterogeneous adsorption surface. Overall, Fe-NP modification appears to alter the adsorption capacity and energetic characteristics of zeolite rather than simply producing a large increase in experimentally observed uptake. These findings highlight the potential of green Fe-NP-modified zeolites as tunable, low-cost materials for antibiotic removal from water.