CHROMIUM (VI) REMOVAL FROM AQUEOUS SOLUTIONS BY PUROLITE BASE ANION-EXCHANGE RESINS WITH GEL STRUCTURE

The removal of Cr (VI) from aqueous solution using two strong base anionic resins with gel structure, purolite A-400 (styrene-divinylbenzene matrix) and purolite A-850 (acrylic matrix) was investigated using a batch technique. The sorption efficiency was determined as a function of phases contact time, solution pH, resin dose, temperature and initial Cr (VI) concentration. The percentage of Cr (VI) removed reached maximum values (up to 99%) in the pH range 4.0-5.3 at a resin dose of 6 g/L and Cr (VI) concentration up to 100 mg/L. An increase in temperature had a positive effect on the Cr (VI) sorption process. The equilibrium sorption data were fitted with the Freundlich, Langmuir and Dubinin-Radushkevich isotherm models, using both linear and nonlinear regression methods. The Langmuir model verified the experimental data very well and gave a maximum sorption capacity of 120.55 and 95.82 mg Cr (VI)/g for the A-400 and A-850 resins, respectively. The thermodynamic study and mean free energy of sorption values calculated using Dubinin-Radushkevich equation indicated the sorption is a chemical endothermic process. The kinetic data were well described by the pseudo-second order kinetic equation and the sorption process is controlled by external (film) diffusion and intraparticle diffusion.