Sorption of Congo Red onto p-tert-Butylcalix[4]arene Based Silica Resin

M.A. Kamboh, I.B. Solangi, S.T.H. Sherazi and S. Memon*

National Center of Excellence in Analytical Chemistry, University of Sindh,Jamshoro-76080, Pakistan

The present study deals with the application of p-tert-butylcalix[4]arene based silica resin (4) for the removal of Congo Red (CR) from aqueous solution through batch-wise sorption. Different parameters such as pH, temperature, sorbent dosage and contact time were optimized to achieve better sorption results. It has been found that the sorption of CR dye on resin 4 was highly pH dependent and significant percent sorption (80%) was achieved at its original pH (i.e. 5.8 pH). The equation isotherms and the thermodynamic parameters such as Gibbs free energy ΔG, enthalpy ΔH and entropy ΔS were also applied to evaluate experimental data. The positive and negative value of ΔH and ΔG demonstrates that sorption process is endothermic and spontaneous in nature. It has also been noticed that the Freundlich isotherm model could provide the best fit to describe the sorption equilibrium.

Keywords: Calixarene, Silica, Congo Red, pH, Thermodynamics, Sorption isotherms