Choline-based deep eutectic solvents (DESs) have many outstanding features as they are easy to prepare, inexpensive, low-toxic, low volatile, and biodegradable, which make them increasingly attractive in industrial chemistry and green chemistry. In this paper, the abilities of three different kinds of DESs for crude oil removal from contaminated soils were compared and it was found the DES formed by phenylpropionic acid and choline chloride (mole ratio = 2:1) had the best performance. The effects of extraction time, temperature and the solvent-soil ratio on phenylpropionic acid/choline chloride DES performance were evaluated. The rational extraction conditions were recommended as follows: mass ratio of DES to soil was 10:1 and 60 min extraction time at 80°C. The extraction (desorption) process could be described by Freundlich desorption isotherm mode. In addition, the phenylpropionic acid/choline chloride DES could be recycled and the oil removal efficiency was about 90% after 10 cycles. This finding suggested that choline-based DES extraction was a promising technology for crude oil removal from contaminated soil.
Keywords: Crude oil-contaminated soil; deep eutectic solvent; environmental; extraction; recycle.