[en] The adsorption of lead(II) and copper(II) on an activated carbon (Filtrasorb 300, Chemviron) was characterized assuming that it takes place by formation of complexes with functional groups, present in the activated carbon. Their concentration and conditional adsorption coefficients were determined for each metal by titration of the carbon in suspension in aqueous phase, at constant acidity, with the metal itself. For each titration point, the concentration of the metal in the solution phase after equilibration was determined, and the data were processed by the Ruzic linearization method, to obtain the concentration of the active sites involved in the sorption, and the conditional constant. The effect of the pH was also examined, in the range 4-6, obtaining that the adsorption increases at increasing pH. The protonation and adsorption constants were determined from the conditional adsorption coefficients obtained at the different acidities. The concentration of the active sites is 0.023 and 0.042 mmol g^-1, and the protonation constants are 1.0x10⁶ and 4.6x10⁴ M^-1 for Pb(II) and Cu(II). The corresponding adsorption constants are respectively 1.4x10⁵ and 6.3x10³ M^-1. All the parameters are affected by a large uncertainty, probably due to the heterogeneity of the active groups in the activated carbon. Even if so, these parameters make it possible a good prediction of the adsorption in a wide range of conditions. Other sorption mechanism can be set up at different conditions, in particular at different pH, as it has been demonstrated in the case of copper(II)

[en] A method for determining iodate and iodine (+1) in aqueous solutions is proposed. The assay is similar to a previously described method for the determination of iodide and iodine (O), which were titrated with standard iodate in hydrochloric acid solution. A sample solution made 0.5-1.5 M in hydrochloric acid is titrated with a standard iodide solution and monitored spectrophotometrically at 230 nm. The species involved have strong absorbances that are well differentiated at this wavelength. By combining the two titrations it is possible to resolve any mixture of species of iodine in different oxidation states. The precision of the method (standard deviation) is the same both when determining a single species (IO₃-,I+,1₂ or I-) and a mixture, and is equal to 2 x 10^-7 M. Chloride and bromide, even at very high concentrations, do not interfere. (author)

[en] The sorption of uranium(VI) on two cationic resins containing different complexing groups, the iminodiacetic resin Chelex 100 and the weak carboxylic resin Amberlite CG-50, was investigated. The Gibbs-Donnan model was used to describe and to predict the sorption through the determination of the intrinsic complexation constants. These quantities, even though non-thermodynamic, characterize the sorption as being independent of experimental conditions. The sorption mechanism of the metal on the complexing resins was also studied by adding a competitive soluble ligand that shifts the sorption curves to higher pH values. The ligand competes with the resin for the complexation with the metal ion. Uranium is also strongly sorbed on Chelex 100 at very acid pH, through formation of two complexes in the resin phase: ML with logβ_110i=-1.16, in more acidic solution, and ML₂with log β_120i=-5.72. Only the presence of the competitive ligand in solution makes the determination of the second complex possible. Also on Amberlite CG-50 the sorption is strong and involves the formation of the complex ML ₂, in more acidic solution, with log β_120i=-3.16. In the presence of the ligand EDTA, the complex ML ₂(OH) ₂was characterized with log β_12-2i=-5.15. In all the experiments the hydrolysis reaction in the aqueous phase was quantitatively considered. (orig.)