PAHs removal by soil washing with thiacalix[4]arene tetrasulfonate

Abstract

Remediating soil contaminated with polycyclic aromatic hydrocarbons (PAHs) presents a significant environmental challenge due to their toxic and carcinogenic properties. Traditional PAHs remediation methods—chemical, thermal, and bioremediation—along with conventional soil-washing agents like surfactants and cyclodextrins face challenges of cost, ecological harm, and inefficiency. Here we show an effective and environmentally friendly calixarene derivative for PAHs removal through soil washing. Thiacalix[4]arene tetrasulfonate (TCAS) has a unique molecular structure of a sulfonate group and a sulfur atom, which enhances its solubility and facilitates selective binding with PAHs. It forms host-guest complexes with PAHs through π-π stacking, OH-π interactions, hydrogen bonding, van der Waals forces, and electrostatic interactions. These interactions enable partial encapsulation of PAH molecules, aiding their desorption from the soil matrix. Our results show that a 0.7% solution of TCAS can extract approximately 50% of PAHs from contaminated soil while preserving soil nutrients and minimizing adverse environmental effects. This research unveils the pioneering application of TCAS in removing PAHs from contaminated soil, marking a transformative advancement in resource-efficient and sustainable soil remediation strategies.