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Complex Formation between Iron(III) and Highly Charged Ligands: Equilibria and Reactions Mechanisms
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Mechanism of Complex Formation: Kinetics and Equilibria of the Nickel(II)-Salicylate Ion System
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Adsorption of heavy metals on Na-montmorillonite. Effect of pH and organic substances
No full textClays (especially montmorillonite and bentonite) are widely used as barriers in landfills to prevent contamination of subsoil and groundwater by leachates containing heavy metals. For this reason it is important to study the adsorption of metals by these clays. The sorption of seven metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) on Na-montmorillonite was studied as a function of pH and in the presence of ligands, forming complexes of different stabilities with the metals of interest. The continuous column method was used as it better simulates natural conditions. The total capacity of Na-montmorillonite towards these metals was determined. The pH variations influence to a higher extent the concentrations of Cu, Pb and Cd in the effluent. Moreover the results suggest that complex formation hinders the sorption of the metals on the clay, with an increasing influence in the order: Mn less than or equal to Pb less than or equal to Cd less than or equal to Zn < Ni < Cu < Cr. The evaluation of the total capacity of Na-montmorillonite shows that this clay is a good sorbent towards all examined metals
AN NMR-STUDY OF THE INTERACTION BETWEEN MELANIN FREE ACID AND MN2+ IONS AS A MODEL TO MIMIC THE ENHANCED PROTON RELAXATION RATES IN MELANOTIC MELANOMA
No full textThe use of mosses as environmental metal pollution indicators
No full textNaturally growing mosses have been extensively employed for surveying trace metal deposition from the atmosphere. Mosses represent suitable monitors for assessing the long-term accumulation of deposited airborne metals by virtue of their physicochemical properties. Indeed, they occur in almost all terrestrial ecosystems because, for their ability to tolerate long periods of drought, they may even colonize areas with extreme environmental conditions; they obtain most of their elemental supply from the atmosphere and efficiently retain many elements received from precipitation because they have a high surface:volume ratio, a simple anatomy and no cuticle. The monitoring technique using mosses has, therefore, led to reliable estimates of large-scale geographic patterns of trace metal deposition, in spite of possible flaws due to variabilities in local elemental concentrations and interferences with soil dust contamination.
While in northern Europe from the late 1960s mosses have been used as passive or active bioindicators, the countries in southern Europe have initiated to participate to the European programme on heavy metal atmospheric deposition in Europe measured from mosses only since 1995. The objectives of the present chapter are therefore: i) to show the last developments of the biomonitoring technique by mosses in Europe; ii) to compare the surveys made in European southern countries, namely France, Spain and Italy; iii) to indicate the changes made to the recommendations of European protocol defined by Rühling in 1994 because of different environmental conditions in these geographic areas; iv) to provide information that can be useful for the next large-scale surveys. Finally, as moss biomonitoring example, a more detailed study is reported regarding the use of mosses as environmental bioindicators in order to evaluate the metal atmospheric deposition in different areas in Piedmont (Italy)
The retention of metal species by different solid sorbents. Mechanisms for heavy metal speciation by sequential three column uptake
No full textAn apparatus consisting of three columns packed with different substrates, namely an anion exchange resin, a reversed phase sorbent and a chelating ion exchange resin, was developed. The retention of cadmium, copper and lead onto the substrates at different pH conditions was investigated, first by considering each column separately, then by connecting them in series. The aim of the study is to distinguish among species with different charge or chemical behaviour. Experiments were performed with the free metal ions, their anionic complexes with EDTA and 8-hydroxyquinoline-5-sulphonic acid, and their neutral complexes with 8-hydroxyquinoline. The results obtained were compared with those computed according to the theoretical species distribution of all species as a function of pH. The applicability of the technique to seawater was demonstrated
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