Efficiency of industrial minerals on the removal of mercury species from liquid effluents

Increasing attention has been given, by the industrial sector, to the removal of heavy metals from liquid effluents to satisfy environmental regulations. For this purpose, the most common methods utilized include: chemical precipitation, cementation, ion exchange, adsorption and solvent extraction. All these methods have limitations such as slow kinetics, low adsorption capacity and they are usually very expensive. Thus, new technologies for heavy metal removal are of great interest. This study consisted on a screening of industrial minerals to check their efficiencies to remove mercury from liquid effluents. The methodology employed a batch adsorption technique. The tested minerals included: atapulgites, zeolites, magnetites, kaolin, vermiculite and bentonite. Results show relatively high efficiencies of magnetite and zeolite on mercury removal. These minerals were capable to remove mercury species from effluents with concentrations reaching 1000 ppm, corresponding to a sorption capacity of 10,000 mg Hg/kg. The sorption maximum was not reached in these tests. In addition, it became evident the importance of mercury speciation at the solid : liquid interface, with relevant consequences on the application of this technology to effluent treatment.