Organic matter deactivation can increase the amount of hydroxyl radical transfer leading to the oriented oxidation of long-chains alkanes

Abstract

In order to investigate the effect of deactivated organic matter in soils on the removal of long-chain alkanes (C20-C30), eight sets of deactivation experiments were carried out on two soil samples (S1 and S2) with the four deactivation conditions (soil: NaOH = 50:1, 100:1, 150:1, 200:1). Subsequently, a series of crude oil oxidation experiments were conducted on the oil-spiked S1 and S2 using the modified Fenton process (Fe2+ = 5.8 mM and H2O2 = 100 mM). The results showed that the amount of oriented oxidation of long chains (C20-C30) was 3201–4712 mg/kg in the completely deactivated group with deactivated degree K ＞ 47.5%, which was 3.5–7.5 times than that of the incompletely deactivated group (K ＜ 47.5%). In addition, the oriented oxidation of long-chains (C20-C30) increased from 3201 to 4712 mg/kg with the increase of •OH transfer from 0.20 to 0.85 a.u. For the completely deactivated group, the deactivation of the C-O and COO- on the organic matter led to the deactivation of the protein-like substances. The deactivation of the protein-like substances resulted in a K value greater than 47.5%, which ultimately increased the amount of •OH transfer. The results showed that the maximum amounts of oriented oxidation in both S1 (4712 mg/kg) and S2 (3201 mg/kg) were achieved when the ratio of soil to NaOH was 100:1.