A Hybrid Approach for PAHs and Metals Removal from Field-Contaminated Sediment Using Activated Persulfate Oxidation Coupled with Chemical-Enhanced Washing

Abstract

The aim of this study was to investigate the removal of both polycyclic aromatic hydrocarbons (PAHs) and heavy metals from field-contaminated sediments by activated persulfate oxidation. Various chemicals, including hydroxypropyl-β-cyclodextrin (HPCD), S,S-ethylenediaminedisuccinic acid (EDDS), tetrasodium pyrophosphate (Na4P2O7), and hydrochloric acid (HCl), were applied individually before or after activated persulfate oxidation to enhance the co-removal of both types of pollutants. It was found that the organic removal efficiency was not significantly enhanced by increasing the concentration of HPCD from 2.5 to 5.0 mM. The removal efficiency of heavy metals was not improved even at an excess amount of EDDS after activated persulfate oxidation. However, the addition of EDDS acted as the Fe2+ carrier for activated persulfate oxidation. In addition, no significant enhancement of heavy metal removal was observed by increasing the concentrations of Na4P2O7 and HCl from 0.01 to 0.1 M after activated persulfate oxidation. However, comparing 0.1 M HCl with 0.1 M Na4P2O7, HCl was shown to be more effective in promoting the removal of organic pollutants. With further adjustments on the experimental conditions, the highest removal amount of metals and PAHs was achieved by adding 2 M of HCl with 3 days mixing, followed by Fe2+-activated persulfate oxidation (PS/Fe2+ molar ratio at 4:1) for further 6 h mixing. The removal efficiency of low and high molecular weight PAHs was about 70 and 20 %, respectively, while the removal efficiency of metals was 70, 100, 40, 65, 65, 80, and 100 % for Cr, Cu, Hg, Mn, Ni, Pb, and Zn, respectively.