Cleaning up tar-contaminated sediments using renewable and recycled materials

Many gas plant sites that distilled coal to produce fuel for light and heat in the 1800s and early 1900s remain heavily contaminated with coal tar. Current remediation strategies involve excavating contaminated sediment and hauling it away to dump it, incinerate it, or treat it to desorb contaminants. But mixing contaminated sediments with polystyrene pellets and biosurfactant compounds extracted from corn gluten meal and hemp may provide a way to clean up sediments on-site at lower cost, reports a team led by Albert Robbat Jr. of Tufts University (Soil Sediment Contam. 2016, DOI: 10.1080/15320383.2016.1190955). The researchers mixed contaminated sediments from the Grand Calumet River in Indiana with the biosurfactant and pellets from ground-up polystyrene home insulation panels. The biosurfactant mobilizes the tar, the chemical components of which then stick to the pellets by forming π-π interactions with the polystyrene. The pellets rise to the surface of the mixture while the sediments sink, allowing for easy separation. Using conditions that would remove 80% of the polycyclic aromatic hydrocarbons from the sediments, the team estimates that the approach would reduce treatment costs by 28%.