Remediation of lead-contaminated soil by washing with choline chloride-based deep eutectic solvents

Abstract

A promising technology has been proposed for the remediation of lead-contaminated soil by using diluted deep eutectic solvents (DESs) in this research. The DESs were synthesized by mixing choline chloride with ethylene glycol, urea, propylene glycol, glycerin and malonic acid. The experiment influences factors on the lead-contaminated soil remediation were investigated, and a response surface analysis was conducted. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) were applied to detect the mineral phase of contaminated soil before and after remediation. The changes of DESs dissolving lead nitrate (Pb(NO3)2) were analyzed by high resolution mass spectrometry (HRMS) and Fourier transform infrared spectroscopy (FT-IR). The results showed that up to 92.12% of lead could be removed from soil after washing 40 ℃ for 0.5 h. In the diluted choline chloride-malonate acid (Ch-M) solution, the carboxyl group and the hydrogen bond complex lead ions into complexes such as C3H2O3Pb, [Pb‧Chcl‧COOH] and [Ch‧Pb]. Taking the remediation of one ton of lead-contaminated soil (14074.38 mg/Kg), it only costs $41.23 when the Pb removal rate reaches 92.12% using Ch-M as washing agent. This research provided an environmentally friendly and cost-effective remediation method for the lead-contaminated soil.