Removal of polycyclic aromatic hydrocarbons from sediments using sodium persulfate activated by temperature and...

The oxidation of 16 polycyclic aromatic hydrocarbons (PAHs) compounds in sediments by sodium persulfate (Na2S2O8) simultaneously activated by temperature and nano zero-valent iron (nZVI) as the source of catalytic ferrous iron was investigated. The effect of various controlling factors, including S2O8(2-) (0.017-170 g/L), nZVI (0.01-1 g/L), and temperature (50-70 °C) were performed. The efficiency to remove PAHs was 10.7-39.1% for unactivated persulfate. The treated sample had over 50% of the persulfate still remaining from an initial persulfate dose of 170 g/L, whereas less than 1% of the persulfate remained from an initial persulfate dose of 0.017, 0.17, and 1.7 g/L. Adequate persulfate (170 g/L) must be present because it is the source of the sulfate radicals responsible for the degradation of PAHs. Results indicated that increasing temperature and the addition of nZVI into a persulfate-slurry system could enhance the persulfate oxidation process. The best removal efficiency (90%) was achieved after 24 hr while adding nZVI (0.01 g/L) to persulfate (170 g/L) at temperature of 70 °C. The results suggested that nZVI assisted persulfate oxidation without elevating temperature may be a suitable and economic alternative for the ex situ treatment of PAH-contaminated sediments.

Nano zero-valent iron (nZVI) has been successfully applied to transform/degrade contaminants in soils and water. Additionally, nZVI has been used as a catalyst to activate persulfate for the treatment of various contaminants. In this study, with the support of temperature, nZVI-persulfate oxidation system for treatment of PAH-contaminated sediments was improved significantly and the treated sediment could meet remediation goals.