Remediating diesel-contaminated soil with a biodegradble surfactant as Triton alternative: Nonylcyclohexanol ethoxylate

Abstract

The newly forbidden surfactant nonylphenol polyethoxylates (NPEOn, similar as Triton) was considered as a promising eluent for remediating diesel-contaminated soil but remaining a secondary pollution due to their aquatic toxicity. Herein, a comprehensive study is conducted about the performance of a group of new surfactants nonylcyclohexanol ethoxylates (NPEOn</sub) on remediating diesel-contaminated soil, with comparison of NPEO10, along with the nonionic-anionic combination of NCEO9-sodium dodecylbenzene sulfonate (NCEO9-SDBS). With 1 wt% of NPEOn</sub solution, the elution efficiency on diesel in soil reached up to 86.8% at 25°C in 24 h, which was comparable to that of NPEO10. The mechanism of reducing polyethoxylate surfactant adsorption on soil surface by anionic surfactant was profiled with energy dispersive X-ray spectroscopy, thermogravimetric analysis and zeta-potential analysis. The kinetics of diesel desorption from contaminated soil enhanced with surfactants is found to follow the Elovich equation. Moreover, the bean germination and growth experiment further prove that the NCEO9 washing improved the cultivability of diesel-contaminated soils, especially inspiring the red bean growth that did not germinate in the contaminated soil at all. The findings will be benefit for developing environmentally friendly surfactant systems to clean-up diesel-contaminated soils, and for replacing NPEO10 with NCEO9 in soil remediation applications.