Used with one of two surfactants (SDS, an anionic surfactant, and Triton X-100, a nonionic surfactant), the ligand, I− was evaluated as a washing agent for the desorption of Cd from naturally and artificially contaminated soils.
Increasing amounts of the ligand, I−, with a surfactant, specifically removes higher levels of Cd but not Cu, Zn and Pb. After seven washings, the ligand, I− with the nonionic surfactant, Triton X-100, removed 65 and 90% of the Cd from soils I and II, containing respectively, to 15 and 1275 mg of Cd/kg. The ligand, I−, and the anionic surfactant, SDS, removed 35 and 70% of the Cd from soils I and II, respectively. Before washing, the carbonate fraction of soil I contained the most Cd (48%) while the exchangeable and carbonate fractions of soil II contained 29 and 33% of the total Cd, respectively. For soil I, SDS with/ without the ligand desorbed Cd mainly from the carbonate and oxide fractions, while only Triton X-100 with ligand I− could remove Cd from the exchangeable fraction. For soil II, Cd was desorbed from the exchangeable fraction only when either surfactant was used in combination with the ligand. Thus, a surfactant with ligand can extract specific heavy metals from soils and selective sequential extraction is useful in identifying which fraction can be targeted by the surfactant – ligand agent.