Choline-based deep eutectic solvent combined with EDTA-2Na as novel soil washing agent for lead removal in contaminated soil

• Published in: Chemosphere (Oxford) 2021-09, Vol.279, p.130568-130568, Article 130568
• Main Authors: Huang, Kaiyou, Shen, Yingjie, Wang, Xiaoyan, Song, Xiaolong, Yuan, Wenyi, Xie, Junying, Wang, Shenyang, Bai, Jianfeng, Wang, Jingwei
• Format: Article
• Language: English
• Subjects: Choline chloride; Ethylene glycol; Ethylene-diamine-teraacetic acid disodium salt; Lead-contaminated soil; Washing agent
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.130568

Lead-contaminated soil was cleaned through ethylene-diamine-teraacetic acid disodium salt (EDTA-2Na) combined with diluted deep eutectic solvent (DES) which was prepared by mixing choline chloride with ethylene glycol. The influences of leaching temperature, leaching time, liquid-solid (L/S) ratio, concentration of EDTA-2Na, water-DES ratio, and the molar ratio of choline chloride-ethylene glycol (Ch-E) on the leaching rate of lead were investigated. The mineral phases of the soil and DES before and after washing were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The changes to the DESs before and after dissolving lead nitrate (Pb(NO3)2) were analyzed by high resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR). Hydrogen bonds and EDTA-2Na in the Ch-M system resulted in the conversion of Pb(NO3)2 to other complex ions such as [Pb·Ch-E]− and [Pb·EDTA-2Na]− and other complex ions due to the dissolution of the washing agent. The results showed that the soil mineral phase did not change significantly and up to 95.79% of Pb could be washed under temperature, time, L/S ratio, EDTA-2Na concentration, DES/water ratio, Ch-E molar ratio, and stirring speed conditions of 40 °C, 2 h, 6, 0.02 M, 2, 0.75 and 300 rpm, respectively. The hydrogen bonds and EDTA-2Na may play a key role in the remediation of lead-contaminated soil by a washing agent. This research describes a rapid, efficient, and environmentally friendly method for remediation of lead-contaminated soil. [Display omitted] •Diluted DES combined with EDTA-2Na was used as a washing agent to remediate lead-contaminated soil.•Up to 95.79% of lead could be washed under mild leaching condition.•Pb2+ was transferred as Pb·Ch-E and EDTA·Pb in dissolution regent.•Hydrogen bonds and EDTA-2Na play a key role in lead-contaminated soil remediation.