Simultaneous and Repetitious Removal of 2,4-Dichlorophenol and Copper from Soils Using an Aqueous Solution of Ethyl-Lactate-Amended EDDS

Abstract

Heavy metals and the transformation products of herbicides, such as 2,4-dichlorophenol (2,4-DCP), are toxic soil pollutants. We assessed the ability of an aqueous solution of the “green solvent” ethyl lactate alone and combined with [S,S]-ethylenediaminedisuccinic acid (EDDS) to remove 2,4-DCP and copper simultaneously from soils. Ethyl lactate extracted 2,4-DCP from contaminated soil comparable to Triton X-100. Ethyl lactate/EDDS extracted more 2,4-DCP and Cu from contaminated soils than ethyl lactate alone. The enhanced extraction of Cu increased slightly with an increase in the EDDS/Cu molar ratio; the maximum Cu extraction efficiency was about 32.3% at an EDDS/Cu ratio of 5. An increase in the ionic strength (NaCl) of the ethyl lactate/EDDS solution decreased the amount of 2,4-DCP extracted by maximally 12% but increased the amount of Cu extracted by >500%. We tested the recycling of the ethyl lactate/EDDS solution with the cation-exchange resin 001×7 and the hyper-cross-linked polymer resin NDA-150. Fresh ethyl lactate/EDDS solution and two sequentially recycled solutions removed 31.4, 28.3, and 26.7% of the Cu in Cu-contaminated soil and 77.7, 62.9, and 56.8% of the 2,4-DCP in 2,4-DCP-contaminated soils, respectively. The ethyl lactate/EDDS solution removed 31.8% of the Cu and 73.0% of the 2,4-DCP in Cu- and 2,4-DCP-contaminated soils, and the solution remained effective even after two recyclings. The aqueous solution of ethyl lactate/EDDS can be used to effectively remove Cu and 2,4-DCP from complex contaminated soils and can be reactivated.