Adsorção competitiva de ferro, cobre, zinco e manganês, em pó de coco, vermiculita e latossolo

• Autor(a) principal: Menezes, Antonio José Duarte de
• Data de Publicação: 2007
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/21606
• topic: Adsorção competitiva; Micronutrientes; Substratos

The adsorption phenomenon is one of the major physical-chemical reactions in soil which directly influence nutrient availability for plants. The chemical behavior of iron, copper, zinc and manganese in soil can be studied by applying adsorption empirical models where adsorbed quantities of these elements on the soil solid phase are in equilibrium with concentrations of the same elements standing free in the soil solution. The Langmuir, Freundlich and Temkin equations (isotherm lines) have been widely used to describe the micronutrient adsorption phenomenon in Brazilian soils. The present study had the objective to evaluate the competitive adsorption of Fe, Cu, Zn and Mn on the following substrates: dry powder coconut, vermiculite and Red-Yellow Oxisol soil by using the Langmuir, Freundlich and Temkin equations (isotherms). The experiment was conducted in plastic containers with 0.25g material samples (dry powder coconut, vermiculite and soil) and for each container it was added 50 mL CaCl2 0.01M solution containing the following Fe, Cu, Zn and Mn concentrations: 0.0, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 7.0, 10.0, 20.0, 30.0, 40.0, and 50.0 ppm; all the above concentrations were added simultaneously (competitive system) to the containers. The solutions were shaken for 4 hours, afterwards filtered. The cation concentrations in the equilibrium solutions were determined by atomic absorption spectrometry. The amount of adsorbed micronutrient was estimated by subtracting the concentration in equilibrium from the initial concentration. The Red-Yellow Oxisol presented the highest exchange site adsorption energy and also the maximum adsorption capacity for Cu as compared to Fe, Zn and Mn. The adsorption maximum values (b), adsorptive capacity (KF), adsorption energy (k) and energy distribution sites (n) for Fe, Cu, Zn and Mn were higher in the dry powder coconut material, being followed by the Red-Yellow Oxisol and vermiculite. Considering all simultaneous micronutrient adsorptions, the Langmuir equation fitted adequately only for Cu, while that for Fe, Zn and Mn the adsorption isotherms presented a linear shape, which indicated that the adsorptions of these micronutrients are under the adsorbat solution concentration control.