Optimization of hydrogen peroxide-to-hemoglobin ratio for biocatalytic mineralization of polycyclic aromatic hydrocarbons (PAHs)-contaminated soils.

This study investigates the efficiency of hemoglobin (Hb)-catalyzed biocatalytic reactions for removal of polycyclic aromatic hydrocarbons (PAHs) in a historically PAHs-contaminated soil and of benzo(a)pyrene (BaP) in an artificially BaP-contaminated soil. PAHs removal tests at various HO-to-Hb mass ratios (0-3.7) showed that the PAHs removal was greater at HO-to-Hb mass ratio of ≥3. This was attributed to the greater removal of high molecular weight PAHs at higher HO-to-Hb mass ratios. The BaP removal increased from 36% to 85% with increasing HO-to-Hb mass ratio from 1 to 3, and further increase in HO-to-Hb mass ratio decreased the BaP removal. Thus, the optimal HO-to-Hb mass ratio for BaP removal was determined to be 3 in the artificially BaP-contaminated soil. The BaP removal in the presence of only Hb can be attributed to the capture of BaP by Hb. The increased BaP removal in the presence of HO is likely due to BaP mineralization as the BaP removal and the CO generated showed a strong positive correlation (R = 0.999). Overall, this study shows that the Hb-catalyzed biocatalytic reactions can effectively remove PAHs in soil.