Subcritical water extraction for the remediation of phthalate ester-contaminated soil

Subcritical water has been used as an environment-friendly extraction fluid for many classes of organic compounds. It was used for the removal of phthalate esters (PEs), such as di-methyl phthalate, DMP; di-ethyl phthalate, DEP; di-iso-propyl phthalate, DIPP; di-n-butyl phthalate, DBP; benzyl butyl phthalate, BBP; di-n-pentyl phthalate, DpentP; di-n-hexyl phthalate, DHXP; di-heptyl phthalate, DheptP; di-2-ethylhexyl phthalate, DEHP; di-n-nonyl phthalate, DNP; di-n-octyl phthalate, DOP; di-n-decyl phthalate, DDP, in soil samples under the optimum condition of 250°C and 10. MPa in our study. The soil samples cleaned with subcritical water were extracted by homemade accelerated solvent extraction system (ASE) and analyzed by HPLC-UV to check for soil remediation efficiency. Three types of soil collected at different sites in Taiwan have been tested. Although at higher PEs concentration levels, the modification of treatments may be necessary for satisfactory removal of the contaminants, soil samples of different PEs levels treated with subcritical water extraction (SCWE) were analyzed and the results indicated removal efficiency ranges of 80-90% for PEs spiked in soil samples. Soil samples contaminated with native DEHP were treated and gave comparable recovery efficiencies. Our results indicate that the applications of subcritical water as soil remediation for removal of PEs contaminant are feasible.