Sustainable iron-based nanomaterials for efficient removal of non-steroidal anti-inflammatory drugs: Adsorption performance and ANN prediction

Diclofenac, one of the most widely prescribed non-steroidal anti-inflammatory drugs (NSAIDs), is frequently detected in aquatic environments due to its extensive use and limited removal by conventional wastewater treatment. This study evaluated environmentally friendly multi-walled carbon nanotubes (m-MWCNTs) functionalized with iron nanoparticles via eucalyptus leaf extract-mediated green synthesis as adsorbents for diclofenac removal from aqueous solutions. Batch experiments investigated adsorption kinetics, equilibrium, thermodynamics, reusability, phytotoxicity reduction, and post-adsorption material characterization. Results confirmed successful green functionalization, with iron nanoparticles playing a key role in enhancing adsorption performance. The process exhibited very fast kinetics, reaching equilibrium within ~5 min and achieving capacities up to 0.212 mmol/g, best described by the pseudo-first-order model. Equilibrium data showed minimal temperature dependence and fitted well to Langmuir and Sips isotherms, with a maximum Langmuir capacity of 0.752 mmol/g at 25 °C. Thermodynamic analysis indicated a spontaneous, favorable, and exothermic process. Multiple mechanisms – including electrostatic interactions, hydrogen bonding, and π–π interactions – contributed to diclofenac adsorption. The adsorbent maintained high efficiency across five regeneration cycles, and phytotoxicity assays showed substantial reduction in toxicity post-treatment. Artificial neural networks (ANN), trained using data from similar adsorbent–adsorbate systems, proved effective in predicting both kinetic and equilibrium adsorption behavior of diclofenac removal by m-MWCNT. These findings demonstrate that green-functionalized m-MWCNTs represent a promising, sustainable solution for removing pharmaceutical contaminants from water.