Copper adsorption by tropical soils with different soil mineralogies

Abstract

This paper had the objective to evaluate the adsorption of copper in three different classes of soils of a toposequence present in the metropolitan region of the city of Maringá. The influence of pH and the mineralogic composition on the process of the metal adsorption were evaluated. Samples of soil, previously dried to air, were sieved in a 0,074 mm-mesh sieve. Fractions of 1,000g soil were weighted in test tubes and added to 7 mL of CaCl₂.2H₂O 0,002 M solution containing 0, 5, 10, 20, 40, 60, 80, e 100mg . kg^-1 copper in the CuCl₂.2H₂O form. The process of adsorption was evaluated on the natural pH of the solutions (5,8) and pH 4,0. The samples were shaken, centrifuged, and the excess copper was read in an atomic absorption spectrometer. The Langmuir isotherm linear relation was used to obtain values referring to copper maximum adsorption capacity (CuMAC). The data revealed that CuMAC was higher for the V soil due to the significative presence of 2:1 phyllosilicates, but the amount of Cu adsorbed by m² of the total surface area was greater in LR soil, confirming the high metal adsorption capacity of tropical soils.