Effect of coagulant addition on the sedimentation of a surfactant-containing washing solution used for phenanthrene-contaminated soil

The coagulation of soil particles from a soil-washing solution containing the nonionic surfactant Triton X-100 (TX100) was investigated using various coagulants, such as chitosan (CS), polyacrylamide (PAA), and polyaluminum chloride (PAC). Soil contaminated with phenanthrene (PHE) was washed with aqueous TX100 solutions at concentrations ranging from 0.1 to 20 g/L. The effectiveness of CS (5 mg/L) as a coagulant in the system was compared with PAA (50mg/L) and PAC (50 mg/L), and the results indicated that the system with CS exhibited a more effective separation of soil than those with PAA and PAC. The removal efficiency of PHE (Rj=81.7%) and the selective separation factor (SSF=14.2) at 10 g/L TX100 were the highest for the system with CS (5 mg/L), indicating that the selection of CS as a coagulant in surfactant-mediated soil washing markedly improved both PHE removal and soil separation.