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

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(NO 3 ) 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 C 3 H 2 O 3 Pb, [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. • Choline chloride/malonic acid used as a washing agent to remediate lead-contaminated soil. • Up to 92.12% of lead could be washed under mild leaching condition. • Pb2 + was transferred in form of [Pb‧Chcl‧COOH] and [Ch‧Pb]. • Carboxyl and hydrogen bonds play a key role in lead-contaminated soil remediation.