A feasibility study on Pd/Mg application in historically contaminated sediments and PCB spiked substrates

A vast majority of literature on bimetals deals with aqueous contaminants, very little being on organics strongly adsorbed on sediments and hence very challenging to remediate. Having previously reported materials, mechanistic and parametric aspects of PCB dechlorination with Pd/Mg bimetals, here we evaluate their ability to dechlorinate (i) PCBs spiked in clean clays and sediments and (ii) historically contaminated aged sediments (Waukegan Harbor, WHS). It was determined that while water, as a medium, dechlorinated low surface area clays it was ineffective with high surface area clays and sediments. Dechlorination was governed by desorption of PCBs, hence addition of 10-25% ethanol improved dechlorination performance. Triton X-100, a surfactant, effectively desorbed PCBs from WHS but their dechlorination was not observed. Investigating possible causes, we found that while (i) Pd/Mg completely dechlorinated multi-component commercial PCB mixtures (i.e. complex PCB distribution in WHS did not limit Pd/Mg effectiveness) and (ii) active components in extraction media did not inhibit dechlorination, sulfide in WHS was poisoning Pd, compromising its activity.