Preparation of cationic poly(ionic liquids) functionalization of silica nanoparticles via multicomponent condensation reaction with significant enhancement of adsorption capacity

Abstract

In this work, we present for the first time for surface functionalization of SiO2 nanoparticles with cationic poly(ionic liquids) through the Debus–Radziszewski condensation reaction. The resultant SiO2@PIL composites were further utilized for removal of Congo red (CR). Characterization results demonstrated that the cationic poly(ionic liquids) were successfully introduced on SiO2 nanoparticles. So as to assess the maximum adsorption capacity (Qmax) of SiO2@PIL for dyes, a batch of experiments were performed under different adsorption parameters. The SiO2@PIL adsorbents exhibited an excellent adsorptive capacity for CR, with the Qmax of 205.3 mg g−1, which is obvious greater than that of unmodified SiO2 nanoparticles (22.4 mg g−1). Experimental data described well with the pseudo-second order model. The adsorption isotherms indicate that the equilibrium data of adsorption process were better fitted by Freundlich model. The thermodynamics further indicated that the process for CR into SiO2@PIL composites was endothermic. The adsorption mechanism was proposed that include hydrogen bonding, electrostatic interactions between the positive charged imidazole ring of SiO2@PIL and anionic dyes. This method could be an interest and useful tool for fabrication of functional materials for various applications.