Remoção de cádmio e chumbo por adsorção em minerais micáceos.

Abstract

This study was done in laboratory scale and has the objective of removing Pb2+ and Cd2+, from liquid effluents. The sorvers used were: vermiculite, biotite and moscovite in the grain size (-0,5+0,3)mm. The material used consisted of about 400 kg of ore and concentrate. It was collected in the mineral processing plant of União Brasileira de Mineração (UBM) that is located in Santa Luzia County, Paraíba. The adsorption tests were done using a becker with a synthetic solution of the metal. The solution was re-circulated in continuous flow regime through a percolation column. In the interior of the column the sorver was added as the samples of the effluent were taken at pre defined intervals of time. The control of pH and temperature were made in the becker containing the solution. The residual concentrations were analyzed using atomic absorption spectrophotometry. The sorption results were defined using the following parameters: (a) efficiency of metal removal, in percents and (b) loading capacity, in mg per gram of substratum. The ionic interaction favored higher efficiencies for removing both metals, depending on the type of cation or cations in the electrolyte used; on the time of percolation of the effluent; on the pH; and on the metal concentration in the solution, among other factors. Higher efficiencies were observed when the vermiculite was modified using NaCl, that when using NaNO3 or NaOH. However, in all cases the results were superior, as compared with the vermiculite in the natural state. Regarding the sorption results, it has been observed that vermiculite showed higher capacity of loading for Pb2+ than for Cd2+. In comparison with others minerals, vermiculite showed a loading capacity largely superior to biotite and moscovite. The mechanism acting in the sorption of both metals on vermiculite has been identified as ionic change.