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

- PAHs removal in a contaminated soil was greater at H2O2-to-Hb mass ratio ≥3.
- Greater high molecular weight PAHs were removed at higher H2O2-to-Hb mass ratios.
- The optimal H2O2-to-Hb mass ratio for BaP removal in soil was determined to be 3.
- BaP removal in the presence of only Hb can be attributed to the BaP capture by Hb.
- BaP removal and CO2 generation was positively correlated supporting mineralization.

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 H2O2-to-Hb mass ratios (0-3.7) showed that the PAHs removal was greater at H2O2-to-Hb mass ratio of ≥3. This was attributed to the greater removal of high molecular weight PAHs at higher H2O2-to-Hb mass ratios. The BaP removal increased from 36% to 85% with increasing H2O2-to-Hb mass ratio from 1 to 3, and further increase in H2O2-to-Hb mass ratio decreased the BaP removal. Thus, the optimal H2O2-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 H2O2 is likely due to BaP mineralization as the BaP removal and the CO2 generated showed a strong positive correlation (R2 = 0.999). Overall, this study shows that the Hb-catalyzed biocatalytic reactions can effectively remove PAHs in soil.