Mercury Adsorption in Tropical Soils and Zeolite: Characterization by Fourier-transform Infrared Spectroscopy

The aim of this study was to evaluate the capacity for Hg adsorption, understand the mechanisms of Hg sorption in tropical soils, and study the potential for Hg sorption by a natural zeolite for possible application in remediation of soils contaminated with Hg. The soil samples used in this study were collected from the 0 to 20 cm layer in areas of native vegetation in the state of Minas Gerais, Brazil. The experiment was conducted in a completely randomized design in a 5 x 8 factorial arrangement, with five soils of contrasting characteristics and eight Hg concentrations (0, 0.05, 0.1, 0.2, 0.4, 0.8, 1.2, and 2.4 mg L-1). A zeolite material was also added in the sorption study for purposes of comparison. Samples of the five soils under study and the zeolite before and after Hg adsorption were characterized by Fourier-transform infrared spectroscopy (FTIR). The species HgOH2, HgClOH, and HgCl2 predominates in the contaminating solutions. Analysis through FTIR showed that the oxygenated functional groups (Al-O, Si-O, Fe-O) of the clay minerals and oxides present in the soil are responsible for the high Hg adsorption capacity. The zeolite clinoptilolite has the potential for remediation of soils contaminated with Hg.