engleski

Adsorption / desorption of lead and copper traces from electrolyte to solid surface

The adsorption and desorption of disolved trace metals onto the solid surface, as well as on particulate matter have been studied by several authors. However, according to most papers, the experiments were performed in model solutions at significantly higher metal concentrations (10-7-10-5 M) than in natural seawater samples. Various electroanalytical techniques, mainly differential pulse anodic stripping voltammetry (DPASV), were used for the determination of trace metals at ppb levels in water samples. However, difficulties arise at very low - natural concentration levels of dissolved metals. Namely, adsorption and desorption of trace metals from and onto sampling, storing and measuring vessel surfaces yield irreproducible analytical data and biased results of metal complexing capacity. The adsorption rates of dissolved lead(II) and copper(II) (at the level from 2 to 8´10-8 M) from seawater as well as adsorption/desorption rates from a 0.55 M NaCl on the electrochemical glass, quartz cells and assembly at pH values of 2.0, 4.0, 6.0 and 8.1 were measured by a DPASV. The results obtained for the contamination of water samples from a pH electrode at various pH values will also be discussed. The aim of this research is oriented towards natural seawater conditions (pH and ionic strength) as well as the study of the adsorption and desorption of dissolved Pb(II) and Cu(II) ions at low concentration levels in a glass cell and assembly. It is very important to establish experimental conditions (sampling, pH, electrode assembly composition) under which the sample can be unaffected by a release and/or adsorption of trace metals.

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