Treatment of PAH-contaminated soil using cement-activated persulfate

In this study, a novel method for the treatment of polycyclic aromatic hydrocarbon -contaminated soil using cement-activated persulfate was developed. The removal of PAHs in soil rose with increasing initial persulfate concentration, initial Portland cement (PC) concentration, and oxidation reaction time. At an initial persulfate and PC concentration of 19.20 mmol/kg and 10% of soil weight and a reaction time of 2 h, the removal rate of PAHs reached 57.3%. Residual PAHs were mainly adsorbed within the soil granules and thus became less available. The mechanism of PC facilitating the oxidation reaction was that PC addition can increase the pH and temperature of the system. When the soil was stabilized/solidified by 10% of PC, the leaching concentration of PAHs and TOC was significantly higher than that leached from untreated soil. Persulfate oxidation decreased the leaching concentration of PAHs but increased the leaching concentration of TOC in solidification/stabilization products. The addition of activated carbon can decrease the leaching concentrations of both PAHs and TOC. Freeze-thaw durability tests revealed that the leachability of PAHs was not affected by freeze-thaw cycles. The unconfined compressive strength (UCS) of treated soil samples after 12 freeze-thaw cycles was only 49.0% of that curing for 52 days, but the UCS was still > 1 MPa. The treated soil samples can resist disintegration during the process of freeze-thaw cycles.