Destruction of gasoline compounds and fractions – benzene, toluene, ethylbenzene, xylenes (BTEX), trimethylbenzenes (TMBs) and naphthalene, gasoline fractions (F1 and F2) and total petroleum hydrocarbons (TPH) – by activated and unactivated persulfate was studied at the bench-scale.

Unactivated batch reactor systems employed persulfate at 1 or 20 g/L and activated systems employed persulfate at 20 g/L and H₂O₂ as activator at two experimental conditions - 0.1 or 1.0 mol H₂O₂/mol S₂O₈^2-. All treatments and controls contained API standard gasoline at ~25 mg/L and were run in triplicate. Sampling was conducted over a ~28 day period.

Controls showed insignificant degradation for all gasoline compounds and fractions examined while unactivated persulfate at 1 g/L showed small (<10%) decrease in concentration of gasoline compounds over the reaction period. Unactivated persulfate at 20 g/L demonstrated a large decrease in concentration of BTEX (>99%), TMBs (>94%) and naphthalene (>71%). Oxidation of F1 (>94%) seemed to be more impacted than F2 (>80%) while >93% TPH was oxidized. Use of peroxide as activator at 0.1 mol H₂O₂/mol S₂O₈^2- improved the conversion of TMBs (>99%) and naphthalene (>85%). Increase in activator strength to 1.0 mol H₂O₂/mol S₂O₈^2- decreased the conversion for xylenes (>86%) and TMBs (>81%) implying that an optimal H₂O₂ molar ratio with persulfate may be required to maximize treatment of gasoline compounds. With H₂O₂ alone at the two conditions, the treatment of compounds was higher for molar ratio 1.0 (<27%) than for molar ratio 0.1 (<11%). Overall, while persulfate at 20 g/L alone removed >92% TPH, H₂O₂ alone at the same molar ratio oxidized only ~17% TPH.

Use of persulfate at ~20 g/L by itself or in combination with optimal doses of peroxide seems to be a viable option for remediation of gasoline compounds examined in this study.