The suitability of brown coal as a sorbent for heavy metals in polluted soils

The aim of the study was to evaluate the suitability of brown coal from the strip surface mine “Sieniawa” for the reclamation of soils polluted with Pb and Cu and still exposed to metal emissions. A column experiment was carried out in order to estimate the sorption capacity of brown coal with respect to Pb and Cu as well as to examine its protective effects if mixed with limestone and used on the surface of polluted sandy soil. Columns filled with soil and covered with a layer of coal + limestone were percolated with solutions of Pb and Cu nitrates. The metal load added to the soil considerably exceeded the soil and coal CEC. Finally, some of the columns were percolated with NH4OAc in order to release the adsorbed metals. It was shown that brown coal mixed with ground limestone was efficient in immobilizing Pb and Cu. Not only adsorption but also complexation and precipitation were involved in the immobilization process. A homogeneous layer of brown coal and limestone covering the soil surface gave better protective results than if mixed with the soil.