Sodium nonylcyclohexanol ethoxylate sulfate-based strategy for remediating dye-contaminated soil with low surfactant adsorption

Abstract

Surfactant-assisted soil cleaning has been considered as a promising technology for remediating of dye-contaminated soil, but is significantly impeded by limitations such as the adsorption or precipitation of surfactants in soil. To take the advantage of effective remediation of anionic surfactant and lower adsorption of nonionic surfactant, a remediation system has been developed in this study for soil contaminated with model dyes methyl orange and alizarin red, employing a designed anionic-nonionic surfactant known as sodium nonylcyclohexanol ethoxylates sulfate (NCEO₅S) and a commercial surfactant—sodium alkyl alcohol ethoxylate sulfate (AES). Using simple wash, the elution efficiency on highly-contaminated soil (methyl orange and alizarin red) reached up to 94.34% and 97.66%, respectively, at 25°C in 24 h with 1 wt% of surfactant solution. Electrostatic repulsion noticeably mitigates surfactant adsorption on the soil surface. The low adsorption of surfactants on the eluted soil surface was characterized with SEM-EDS and thermogravimetric analysis. The kinetics of surfactant-enhanced dyes desorption from contaminated soil follow the Elovich equation. The findings will be benefit for developing eco-friendly surfactant systems to clean-up dyes-contaminated soils while minimizing surfactant adsorption.