A kinetic and mechanistic study of adsorptive removal of metal ions by imidazole-functionalized polymer graft banana fiber

Highlights: • Banana trunk fibers, an agricultural waste was used as trunk polymer. • Pre-irradiation grafting technique with the aid of electron beam accelerator was utilized. • The adsorption studies of Cu²⁺, Pb²⁺ and Zn²⁺ in aqueous solution were extensively conducted. • Effectiveness of prepared adsorbent were tested on actual domestic sewage effluent. - Abstract: Chemically modified fibrous bio-adsorbent extracted from banana trunk was synthesized for potential application in adsorption of heavy metal from wastewater. Glycidyl methacrylate (GMA) polymer graft was first introduced onto the fiber through electron beam irradiation technique. GMA-grafted fiber was subsequently functionalized with imidazole (IMI) group through epoxide ring-opening reaction where amine density of 2.00 mmol/g was achieved. The adsorbent was characterized with Scanning Electron Microscopy (SEM), Fourier Transformed Infrared Spectroscopy (ATR-FTIR), and Thermogravimetric Analyzer (TGA). An extensive kinetic and mechanistic study on the adsorptive removal of metal ions (Cu²⁺, Pb²⁺ and Zn²⁺) by IMI-functionalized GMA-grafted banana fiber is presented. The effects of pH and initial concentration on adsorption capacity were investigated. The adsorption data were correlated with pseudo-first and second order model and the isotherms were analyzed with Langmuir and Freundlich model in order to explain the kinetics and adsorption mechanisms of different metal ions. The thermodynamic studies revealed that the adsorption process for metal ions was exothermic. We also demonstrated that the IMI-GMA-grafted fiber can be regenerated using dilute HNO₃ solution, and can be recycled up to 10 times while maintaining satisfactory adsorption performance. Lastly, the chemically modified bio-sorbent was used to treat a local domestic sewage water.