Evaluation of soil washing process with carboxymethyl-β-cyclodextrin and carboxymethyl chitosan for recovery of PAHs/heavy metals/fluorine from metallurgic plant site

Mao Ye , Mingming Sun , Fredrick Orori Kengara , Jingting Wang , Ni Ni , Li Wang , Yang Song , Xinglun Yang , Huixin Li , Feng Hu , Xin Jiang


Received September 09, 2013,Revised November 22, 2013, Accepted , Available online August 28, 2014

Volume 26,2014,Pages 1661-1672

Polycyclic aromatic hydrocarbons (PAHs)/heavy metals/fluorine (F) mixed-contaminated sites caused by abandonedmetallurgic plants are receiving wide attention. To address the associated environmental problems, this study was initiated to investigate the feasibility of using carboxymethyl-β-cyclodextrin (CMCD) and carboxymethyl chitosan (CMC) solution to enhance ex situ soil washing for extracting mixed contaminants. Further, Tenax extraction method was combined with a first-three-compartment model to evaluate the environmental risk of residual PAHs in washed soil. In addition, the redistribution of heavymetals/F after decontamination was also estimated using a sequential extraction procedure. Three successive washing cycles using 50 g/L CMCD and 5 g/L CMC solution were effective to remove 94.3% of total PAHs, 93.2% of Pb, 85.8% of Cd, 93.4% of Cr, 83.2% of Ni and 97.3% of F simultaneously. After the 3rd washing, the residual PAHs mainly existed as very slowly desorbing fractions, which were in the form of well-aged, well-sequestered compounds;while the remaining Pb, Cd, Cr, Ni and Fmainly existed as Fe-Mn oxide and residual fractions, which were always present in stable mineral forms or bound to non-labile soil fractions. Therefore, this combined cleanup strategy proved to be effective and environmentally friendly.

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