Screening of bio-derived surfactants for soil washing of PAHs: effects of substrate sources and trace metals distribution

Abstract

In this study, we screened the performance of aqueous extracts of Talinum triangulare (AET) and soap solution prepared from Hura crepitans seed oil saponified by aqueous solution of ashed plantain peels (HCS) for removal of naphthalene and phenanthrene from soil. The distribution of trace metals in the soil before and after soil washing was also investigated. The results revealed maximum removal efficiencies after 25 min washing time of 96.25, 96.14, and 25.70% naphthalene, for Tween 80, AET and HCS, respectively. While for phenanthrene, the recorded maximum removal efficiencies after 25 min washing time were: 91.80, 26.00, and 94.0 for Tween 80, AET and HCS, respectively. Based on results from other experiments, AET generally showed slightly lower removal efficiencies compared to the commercial Tween 80 surfactant. Also, the results revealed that the three remediants affected the distribution of trace metals (Cd, Pb, and Zn) in the soil after surfactant washing. Based on the amount of trace metals extracted, the performance of the three remediants are as follows: AET > Tween 80 > HCS. The performance of AET has been attributed to the presence of multiple heteroatomic moieties for trace metals adsorption and moderation of the acidic conditions of the soil.