Removal efficiency of Pb(II) from aqueous solution by 1-alkyl-3-methylimidazolium bromide ionic liquid mediated mesoporous silica

In this research, mesoporous silica was synthesized via modified sol-gel technique using a series of 1-alky-3-methylimidazolium bromide [(CnMIM) Br (n = 4, 10, 16)], one kind of amphiphilic room temperature ionic liquids (RTILs), as a template. Subsequently, the material was characterized and identified by various techniques such as N-2 adsorption-desorption isotherm, SEM, TGA and FT-IR analysis. To obtain the optimum condition, different variables such as adsorbent dose, contact time, initial concentration, temperature and pH were studied, and the optimum conditions were found to be 0.7 g/100 mL, 30 min, 10 mg L-1, 40 degrees C and pH of 6.0, respectively, for the adsorption of lead ions from aqueous solution. The results showed that the RTIL bearing longer alkyl chain 1-hexadecyl-3-methylimidazolium bromide [(C16MIM)Br] was a suitable adsorbent for Pb(II) removal among all the adsorbents. The adsorption of lead ions follows pseudo-second-order rate equation, and the equilibrium data fitted well with the Freundlich model with maximum adsorption capacity 5.18 mg g(-1). Various thermodynamic parameters were calculated, and the results showed that the adsorption of lead ions on the material was feasible and endothermic in nature. The results from the adsorption-desorption cycles showed that the material held good desorption and reusability. It is concluded from the results that the material can be used to remove the Pb(II) from contaminated water to permissible limit. (C) 2014 Elsevier Ltd. All rights reserved.