Modelling of Cr(VI) removal from polluted groundwaters by ion exchange

This work reports the viability and modelling of the removal of Cr(VI) from polluted groundwaters by means of ion exchange using the resin Lewatit MP-64. Feed groundwaters that contained Cr(VI) at an average concentration of 2431 mg dm(-3) and 1187 mg dm(-3) of chloride and 1735 mg dm(-3) of sulfate as main anions were acidified to a pH of 2.0 prior to the removal process. Dynamic experiments were carried out in a fixed bed column with feed waters at flow rates in the range of 2.78 x 10(-7) m(3) s(-1) to 5.55 x 10(-7) m(3) s(-1). Regeneration was achieved with NaOH (2 mol dm(-3)). From the experimental results, the equilibrium of the ion exchange reaction was successfully modelled, obtaining an equilibrium constant (K'(AB)) = 44.90. Finally, a mass balance that included mass transfer resistances in the liquid and solid phases was developed and from the comparison between simulated and experimental data the value of the effective intraparticle diffusivity (D-s) was determined as 1.43 x 10(-12) m(2) s(-1). (C) 2004 Society of Chemical Industry.