Cr(VI)-containing wastewater treatment by means of ion exchange on weak- and strong-base anion exchangers

摘要

The aim of this research work was a thermodynamic and kinetic study of the retention of Cr(VI) ions from a K2CrO4 solution on macroporous weak- and strong-base anion exchangers, Lewatit M 64 A and Lowatit MP 500 A, respectively. Also, the correlations among the ion-exchange rate, the retention capacity of Cr(VI), and some process parameters were established. The parameters studied mainly were the concentration of Cr(VI) ions and the type of the counterions coupled with active groups from the anion exchangers. The results led to the conclusion that, for the Lewatit M 64 A resin, there is the following order of the Cr(VI) retention capacity: RC1 > R2SO4 > ROH, while for the strong-base anion exchanger, the retention capacity for the Cr(VI) ions is different: ROH > RC1 > R2SO4. In the Cl- form, both anion exchangers have the same retention-capacity values. On the other side, the weak-base anion exchanger in SO42- and OH- forms presents the lowest retention-capacity, values. The process kinetics also presents some differences: for the Lewatit M 64 A resin, the ion-exchange rate has lower values, especially in the OH- form. This result is attributed to the increase of the OH- ion concentration in the solution and its presence hinders the dissociation of the active groups of a weak-base anion exchanger. (C) 2002 Wiley Periodicals, Inc. [References: 17]