Efficacy of carbon-based materials for remediating polychlorinated biphenyls (PCBs) in sediment

Polychlorinated biphenyls (PCBs) are persistent hydrophobic compounds that are present widely in the environment. Due to poorly maintained hazardous waste sites, electrical equipment leakage, and illegal disposal, PCBs were deposited in sediments present in bays and estuaries. PCBs continuously partition into the overlying water posing a long-term exposure risk to the environment and human health. This study demonstrates the efficacy of carbon-based materials in reducing the partitioning of PCBs from sediment to the water column. Both existing carbon-based materials [activated carbon (AC), black carbon (BC)] and emerging nanomaterials [graphene (GE), graphene oxide (GO), carbon nanotube (CNT)] were tested to determine their efficacy to bind PCBs in sediment. The comparison between the sorbents was accomplished by examining their distribution coefficient (K_s). The magnitude of K_s provides an idea about the bioavailable fraction of PCBs in the system; the higher the K_s, the greater the strength of sorption by the sorbent and therefore, the lower the PCB bioavailability. Results from the sorption experiment indicated that CNT performed the best overall followed by AC, BC, GO and GE. Results indicated that the K_s value for CNT was 1.16, 1.15, 1.13 and 1.04 log units greater than GE, GO, BC, and AC.