Removal of Cr(VI) from aqueous solution by macroporous resin adsorption

The removal of Cr(VI) by macroporous anion exchange resin adsorption was investigated. Batch adsorption studies demonstrate that the resin has a significant capacity for adsorption of Cr(VI) from aqueous solution. The parameters investigated in this study included pH, contact time, initial chromium concentration, resin dosage and temperature. The adsorption process of Cr(VI) can be described by Langmuir isotherm and Freundlich isotherm model. Application of the Langmuir isotherm to the systems yielded maximum adsorption capacity of 53.03 mg/g resin. The specific surface areas of the macroporous resin was calculated to be 47.35 m(2)/g. The kinetics and thermodynamic parameters were also evaluated. It was found that the separation process is partly diffusion controlled. The mass transfer coefficient was calculated to be 8.62x10(-5) cm/s. The activation energy and change of enthalpy were evaluated and found to be 4.81 kcal/mol and 8.79 kcal/mol at the temperature of 25 degrees C, respectively. The free energy of the process was small but positive, and it decreases with an increase of temperature. The change of entropy was found to be small and remains almost unchanged over the 20 to 35 degrees C temperature range. The desorption studies are also performed and the results show that the Cr(VI) adsorbed by macroporous resin can be eluted by 4 M NaOH. This suggested that the resin saturated with chromium can be regenerated by NaOH solution.