The removal of toxic metals from liquid effluents by ion exchange resins. Part XV: Iron(II)/H+/Lewatit TP208

Iron(II) was removed from aqueous solutions by the use of the cationic ion exchange resin Lewatit TP208 (Na+ form). The influence of different experimental variables was investigated on the ion exchange process: stirring speed, temperature, pH of the solution and resin dosage. At stirring speeds included in the 300-1200 min-1, iron(II) uptake onto the resin fitted well to the film-diffusion model, whereas the increase of the temperature, from 20 to 60 C, was accompanied by an increase in the metal loaded onto the resin, thus, resulting in an endothermic ion exchange process. This ion exchange process was influenced by the variation of the pH of the solution: There was a decrease in metal uptake when the pH of the solution was shifted towards more acidic values. Also the ion exchange process was sensitive towards the variation of Lewatit TP208 resin dosage, being the process associated to the Freundlich isotherm model. This variation in the resin dosage had also an influence in the fitting of the experimental data, at various resin dosages, with the kinetics model associated to them. At the highest resin dosage (1 gL-1) the exchange process fitted well (r2= 0.999) to the pseudo-second order model, however, at the lowest resin dosage (0.13 gL-1), the process fitted (r2= 0.997) the first-order model. Metal uptake was compared with that yielded with other cation-exchange resins and also against the use of multiwalled carbon nanotubes. Iron(II) loaded onto the resin was eluted using acidic solutions.CSI