Adsorção de arsênio: seleção de classes de solos mineiros indicadas para utilização como barreira geoquímica na imobilização deste elemento

• Autor(a) principal: Almeida, Cecília Calhau
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5457
• topic: Metais pesados; Mineralogia; Adsorção; Heavy metal; Mineralogy; Adsorption; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA::CIENCIA DO SOLO

Water is considered a natural resource of strategic importance for the man in the future. It is recognized that maintaining the quality of natural resources and water supply, safely, for the development of human activities is the great challenge facing humanity in the coming years. One of the problems that add to water scarcity in some areas is the contamination of water bodies, which have jeopardized the supply of water in several locations around the world. Among the possible contaminants, arsenic (As) is one of the most problematic, being considered by the World Health Organization (WHO), the second most important public health overall, behind only of microbiological contamination of water. The toxicological potential of As has been known for hundreds of years, but only in recent decades, after the improvement in the analytical detection, was that the relationship between very low concentrations of As and some types of cancer might be best evidenced. It is known that at concentrations of the order of a few mg/L affects health when combined with prolonged periods of exposure. The occurrence of As in surface water and groundwater depends on the source this element, the quantity available and the local. The mobility depends largely of characteristics of geochemical environment, especially under conditions of pH and Eh, and the equilibrium adsorption and desorption, these controlled by matrix mineral and organic of soils. In Minas Gerais State, Oxisols and Ultisols have a predominantly mineral composition kaolinite, iron oxides and Al oxides. We collected samples of the A and B horizons, representative of dominant soil classes from Minas Gerais State, and characterized physically, chemically and mineralogically in order to correlate these properties with arsenic adsorption. The adsorption experiment was conducted using solutions of NaNO3 0.001 mol/L containing Na2HAsO4.7H2O doses: 0; 0.08; 0.16; 0.24; xi 0.40,0.56; 0.72; 0.88; 1.12; 1.36 and 1.60 mmol/L As (V), with pH adjusted to 5.5 and adjusting the data to Langmuir and Freundlich, with the highest correlations were obtained in the first model. In the arsenic adsorption, one of the features that most interfere with the ability of soil to act as an absorbent surface for this element is the texture, due specific surface. The Ultisols, in general, had coarse mineralogy and more kaolinite and/or mica than Oxisols. The lower clay content and higher content of organic matter confer lower arsenic adsorption capacity (CMAAs) compared to the subsurface horizon. The Oxisols had the highest CMAAs, followed by Ultisols, Inceptisols, and sandy soils. Most CMAAs was the Bw horizon (3.6 mg/g of As). High clay content interfered markedly in CMAAs, and the mineralogy of samples, in general, evidenced the presence of peaks indicative of goethite and hematite in the XRD patterns representative of the clay soil that had higher CMAAs and high levels of gibbsite obtained by Thermogravimetric Analysis. We can say, that mineralogical A and Bw horizons do not differ, factors such: lower organic matter content, depth and structure will make subsurface horizon acts more satisfactorily as a barrier geochemical in the As immobilization. Thus, monitoring and new studies are required involving the arsenic behavior in soil.