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TRANSPORT OF HEAVY METALS THROUGH SILICA SPONGOLITE AND ACTIVATED CARBON TREATMENT ZONES

Dr. Eng. Joanna Fronczyk, Dr. Eng. Katarzyna Pawluk

Abstract

This paper presents the results of column tests conducted to investigate the potential use of silica spongolite as a reactive material for the treatment of groundwater impacted by stormwater containing toxic heavy metals (Cd, Cu, Ni, Pb and Zn). Such research material was selected due to its widespread use as an aggregate in road construction. Furthermore, silica spongolite was compared with activated carbon, which is commonly used in permeable reactive barrier (PRB) technology. The column experiments were carried out in vertical columns with a diameter of 0.1 m and a height of 1.0 m using a multichannel peristaltic pump (ZALIMP) to transport the multi-component solution (20 mg/L of each heavy metal) at a constant flow rate of 4.16пїЅ10-8 m3/s (from the bottom to the top). Liquid samples for chemical analysis (pH, EC and heavy metals) were taken from the column effluent in appropriate intervals. Column test results were interpreted using the CXTFIT software package, which solves a one-dimensional advection-dispersion equation. The results have shown that the value of retardation factors (R) for activated carbon was in the order: Cu (no breakthrough) > Pb (R=66) > Cd (R=33) > Ni (R=30) > Zn (R=27). During the experiment, the concentration of Cd, Cu, Pb and Zn in the effluent solution from a column filled with silica spongolite was close to zero. The retardation factor was calculated only for nickel (R=20). Moreover, the PпїЅclet number values (5.45 for silica spongolite and 1.20 for activated carbon) indicated the dominance of advection over dispersion.

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