Natural zeolites for PAH removal from liquid effluents.

The properties of the natural zeolites as cation exchangers are very well established and they are widely used either for heavy metal removal1 and ammonia-nitrogen removal2 from contaminated liquid effluents. Some tuffs from the Roman province does contain a high amount of natural zeolites, mainly philipsite and chabazite. The aim of the present work was to demonstrate the possible use of these rocks as removing agent for organic micropollutants, after their milling due to the quarrying operations as building materials. In particular, it was assessed their capacity to remove PAHs from a simulated polluted liquid stream, by the means of some batch leaching experiments. Contact time was extended up to more than 144 h. At the end of each experiment a solid-liquid separation was performed and the pollutants were recovered by liquid-liquid extraction from the water. After concentration the samples were cleaned-up by a Gel Permeation Chromatography (GPC) and analysed by HRGC/LRMS. The results showed that zeolited tuffs extracted nearly completely the PAHs from water already after 24 h. Subsequently, to investigate if the “capture” is irreversible, the zeolites were extracted by Soxhlet with toluene and than processed as above: the amount re-extracted was very low for some PAHs but not at all negligible for some others. Anyway the zeolited tuffs showed to have high potential capability to “sequestrate” the PAH and not to release them in the environment. A treatment with finely milled zeolitized tuffs could therefore enable to make “inert” the waste water of municipal dumps, relating to organic micropollutants charge such as PAHs and dioxins.