A system consisting of hydrogen peroxide/persulfate (H2O2/S2O82-) catalyzed by siderite was attempted to oxidize nine representative petroleum hydrocarbon compounds [benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene, 1,2,4-trimethylbenzene, methyl-tert-butyl ether, and naphthalene] that tend to persist in the environment. Oxidation under different siderite dosages, H2O2:S2O82- ratios, and pH conditions were investigated. Results indicated that oxidation rates increased from 1.21-4.62 to 1.77-8.94 d-1 as siderite increased from 0.16 to 0.48 g/40 mL (H2O2:Na2S2O8 = 5:1, initial pH = 3.0), except for naphthalene (decreased from 0.58 to 0.45 d-1 with increased siderite dosage). When the H2O2:S2O82- ratio was increased from 1:1 to 5:1 (siderite = 0.16 g, initial pH = 3.0), the oxidation rates increased from 0.02-0.73 to 0.33-2.19 d-1. However, as pH increased to > 5.5 (siderite = 0.16 g, H2O2:Na2S2O8 = 2.5:1), the oxidation rates of petroleum hydrocarbons decreased to 0.003-0.09 d-1, which was approximately 90% less than that at pH = 3.0. The partial correlations and principal component analysis of the experimental data were conducted. Overall, both siderite dosage and H2O2:S2O82- ratio correlated positively with oxidation efficiency. The oxidation potential by H2O2/S2O82- mixtures towards the target petroleum hydrocarbon compounds seemed to be more sensitive to pH conditions than to siderite dosages or H2O2:S2O82- ratios.
Keywords: Advanced oxidation; Combined oxidants; Monoaromatic compounds; Naphthalene; Persulfate oxidation.