Laboratory tests of in situ methods of PCB extraction from contaminated building materials

Three different methods for in situ extraction of PCBs from concrete were tested. The methods were: Non-activated Metal Treatment System (NMTS), clay plaster with ethanol and an activated carbon gel with propylene glycol and ethanol. The methods were tested on concrete blocks from a contaminated building, which were treated, cut up and analysed in small fractions to yield information on the penetration profile. The results showed an exponential decrease in the control sample, while a steeper decline was observed for clay and carbon treatments, and for NMTS a very flat curve was observed. The congener profile changed through the blocks (generally being enriched in lighter congeners further into the concrete), except after NMTS treatment, where a uniform congener distribution was observed. This indicated that NMTS not only removed PCBs from the block, it also redistributed and transported them further into the concrete. Finally, the observed extraction efficiency of the tested methods was 15%, 7% and 10% for NMTS, clay plaster and activated carbon gel, respectively. Thus, all methods showed potential for in situ PCB extraction, though common for all was that several consecutive treatments would be required in order to obtain a substantial reduction of PCBs in the treated concrete.