Microwave assisted synthesis of poly (N-vinylimidazole) grafted chitosan as an effective adsorbent for mercury (II) removal from aqueous solution: Equilibrium, kinetic, thermodynamics and regeneration studies

Abstract

In the present study, chitosan-N-vinyl imidazole was first synthesized and characterized and then its capacity for removal of mercury (II) ions from water was assessed. The graft copolymerization of N-vinyl imidazole onto chitosan chains has been developed in aqueous medium using microwave irradiation. The obtained copolymer was characterized by Fourier Transform Infrared (ATR-FTIR), solid-state ¹³C Nuclear Magnetic Resonance (NMR), Differential Scanning Calorimetric (DSC) and Thermogravimetric Analysis (TGA). Mercury (II) ions removal capacity by the chitosan-N-vinyl imidazole were investigated in aqueous solutions using different amounts of these ions at pH = 6.0. The effect of the contact time, kinetics and thermodynamic studies on the adsorption of mercury ions was also reported. The maximum adsorption capacity was found to be 112.35 mg g⁻¹ from the Langmuir isotherm model at 25 °C. The obtained negative value of $\Delta \mathrm{H}°$ (kJ mol⁻¹) and${\mathrm{ }\Delta \mathrm{G}}^{°}$ (kJ mol⁻¹) indicated the spontaneous and endothermic nature of the reactions. The regeneration of CS-N-vinyl imidazole was investigated using PEG-400 in water as desorbing agent. This data make chitosan-N-vinyl imidazole a potential material adsorbent for mercury (II) removal.

Highlights

• Synthesize of CS-N-vinyl imidazole is done under microwave irradiation.

• Removal of mercury in aqueous solution was performed in batch studies.

• Mercury adsorption has been simulated using Langmuir and Freundlich models.

• Thermodynamic properties of the adsorption process have been determined.

• Regeneration has been studied using PEG-400 as desorbing agent.

Graphical Abstract

Keywords:

• Chitosan
• N-vinyl imidazole
• microwave irradiation
• adsorption capacity
• mercury (II)

Additional information

Funding

Ministry of Higher Education and Scientific Research of Tunisia; Department of Education of Basque Government.