Biochar and humus sediment mixture attenuates crude oil-derived PAHs in a simulated tropical ultisol

Abstract

The potential of sewage sludge-derived biochar and humus mixtures for attenuation of polycyclic aromatic hydrocarbons (PAHs) in crude oil contaminated soil was evaluated. Laboratory-scale experiments involving ultisol samples spiked with crude oil, sewage sludge-derived biochar, and mixed biochar with humus sediment were monitored for removal of PAHs at the intervals of 1, 6, and 12 months. The results revealed that out of the three biochar products obtained at different pyrolysis temperatures: 500, 700, and 900 °C (designated BC500, BC700, and BC900, respectively), BC700 recorded desirable properties and acceptable levels of PAHs suitable for soil amendment. Characterisation of the mixture for functional groups using Fourier transform infrared spectroscopy (FTIR) and surface morphology using scanning electron microscopy (SEM) revealed the presence of oxygenated and nitrogenated species that could support mineralisation of PAHs, increased surface area as well as pores to aid pollutant adsorption. The study revealed that the derived mixture demonstrated the potential to reduce the level of PAHs in contaminated soil. About 70% maximum reduction in the levels of total PAHs was recorded within 1 month for soil treated with the derived mixture in comparison to the control experiment.