Adsorption chelates oxide minerals

A number of attempts have been made to understand the mechanism of the adsorption of chelates on oxide minerals. For instance, IR spectroscopic studies10 have indicated the presence of a basic monosalicylaldoximate copper complex as well as the bis-salicylaldoximate complex on the surface of malachite (basic copper carbonate) treated with salicylaldoxime. However, other workers4 have shown that the copper chelate is partitioned between the surface and dispersed within the solution, and that a dissolution-precipitation process is responsible for the formation of the chelate. Research into the chemistry of the interaction of chelating collectors with mineral surfaces is still in its infancy, and it can be expected that future developments will depend on a better understanding of the surface coordination chemistry involved. 

The advantage of the selective adsorption of a particular element oxidation state has been exploited for on-line element preconcentration and speciation analysis of Cr by FAAS. Cespon Romero et al. [21] described an FIA system employing a minicolumn made of a chelating resin containing poly(aminopho-sphonic) acid groups, able to selectively retain Cr(III) ions. An FIA manifold was employed for efficient preconcentration and subsequent elution of Cr(III) with a small volume of 0.5 M HC1. The original sample was also treated with ascorbic acid to reduce Cr(VI) to Cr(III) and total Cr is determined as Cr(III) after appropriate retention and elution. Eluates are introduced into an N20-acetylene flame connected to the column outlet. The concentration of Cr (VI) is obtained by difference. Employing a sample volume of 6.6 mL, LoD for total Cr is 0.2 pg l-1. A study of FI operational variables, interferences, and precision is reported for the analysis of tap, mineral, and river waters. 

The produced sulphuric acid facilitates the solution of Cu in waters and its migration in the form of sulphates or other compounds like organic and inorganic complexes, especially chelates. The migration of Cu in aquatic systems is hindered by the presence of CaC03, by adsorption on hydrous Fe-Mn-oxides, clay minerals and organic substances. In addition to this, the presence of H2S in extreme situations may reduce completely the aureole of waters enriched in Cu around the deposit. 

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