Macroporous polymeric ion exchangers as adsorbents for the removal of cationic dye basic blue 9 from aqueous solutions

摘要

Two macroporous cation-exchange resins, Purolite C145, a strongly acidic cation macroporous resin, and Purolite C107E, a weakly acidic cation-exchange resin, were used to remove the dye Basic Blue 9 (BB9) from an aqueous medium. Batch adsorption experiments were carried out to analyze the effect of various parameters, such as the phase contact time, initial dye concentration, initial solution pH, resin dose, and temperature. The experimental equilibrium data were evaluated by the Langmuir, Freundlich, and Dubinin-Radushkevich (DR) adsorption models. The Freundlich model better described the adsorption processes of the BB9 dye onto both cation exchangers, and the monolayer adsorption capacities were established as 31.9846 mg/g (C145) and 27.77 mg/g (C107E) at 20°C. The values of the mean free adsorption energy (E) obtained from the DR model suggested a porous structure of the adsorbents and proposed ion exchange at the main mechanism of the adsorption process. The values of the thermodynamic parameters showed that the retention of the cationic dye was a spontaneous and endothermic process. Environmental scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize the sorbent and also to validate the adsorption mechanism as ion-exchange ones. The desorption experiments by a batch method were performed with different solutions: 0.1 and 1 mol/L HCl, 2.5 mol/L H_2SO_4, CH_3OH, and a mixture between 1 mol/L HCl and CH_3OH. Desorption performed with sulfuric acid was shown to be most effective because more than 85 of the adsorbed dye was removed.