Fixation of Cu (II) on the Digested Sludge and Determination of Kex Using Chronopotentiometric Method with Cathodic Dissolution

The investigation was carried out on the sediments obtained after biological treatment from digesters in wastewater treatment plant of Montpellier city in France.Theses digested sludge are mainly organic material that are in the form of humic acid. Ion exchange properties of humic acid is due to the presence of carboxylic and phenolic functional groups in its structure. In this work fixation of cations on humic acid have been investigated using ion exchange mechanisim.Kinetic studies indicate that this reaction is slow and takes two days for complition and is pH dependent. The results obtained indicate that the distriution cofficient (P) has the value of 105lit/kg and the amount of adsorbed Cu+2 is 3.0398 eq/kg of dry material at pH=7.As the pH of medium increases the ion gets activated and thus the electrostatic attraction between Cu+2 and functional groups on humic acid as well as retention time increases. At this state, the distribution coefficients get their limits and the slope of the curve Log P=f(pH). On ploting the line Log P=f(pH) for an initial concentration of Cu+2 (C0=0.125*10-3 eq/kg) the cationic exchange constant (kex) is 0.71 and for every metallic ion a hydrogen ion exchanges. Relative error and CV were found –0.77% and 2.27% respectively.