Oxidation of 1,1,1-Trichloroethane Stimulated by Thermally Activated Persulfate

Abstract

In this study, thermally activated persulfate (PS) to stimulate the oxidation of 1,1,1-trichloroethane (TCA) in groundwater remediation was investigated. The effects of various factors including temperature; initial TCA concentration; PS/ TCA molar ratio; solution pH; and common constituents in groundwater such as Cl À , HCO 3 À , SO 4 2À , and NO 3 À anions and humic acid (HA) were evaluated. The experimental results showed that TCA can be completely oxidized in 2 h at 50 °C with a PS/ TCA molar ratio of 100/1, indicating the effectiveness of thermally activated PS oxidation for TCA removal. TCA oxidation was fitted with a pseudo-first-order kinetic model, and the rate constant was found to increase with increasing temperature and PS/TCA molar ratio, but to decrease with increasing initial TCA concentration. In addition, acidic conditions were favorable to TCA removal and elevating, the initial solution pH value (from pH 3 to 11) decreased the TCA degradation rate. Anions Cl À and HCO 3 À had negative effects on TCA removal, whereas the effects of both SO 4 2À and NO 3 À were negligible. With 5À10 mg L À1 concentrations of HA in solution, an inhibitive effect was observed, indicating that dissolved organic matter consumed some of the oxidant. However, the anticipated effective thermally activated PS oxidation of TCA in groundwater from a real contaminated site was not achieved because of the complex solution matrix. On the other hand, the TCA degradation mechanism derived from GC/MS analytical results confirmed formic acid, dichloromethane, and trichloromethane as the primary intermediates, and therefore, two TCA decomposition pathways were proposed. In conclusion, thermally activated PS oxidation is a highly promising technique for TCA-contaminated groundwater remediation, but more complex constituents in in situ groundwater should be carefully considered for its practical application.

Thermally activated persulfate (TAP) oxidation of antiepileptic drug carbamazepine in water

“…As the persulfate dosage increases from 0.2 to 4 mM, the degradation rate constant of CBZ enhances from 0.0034 to 0.0744 min À1 . This phenomenon was also observed by other researchers when treating 1,1,1-trichloroethane (TCA) and methyl tert-butyl ether (MTBE) contaminants at various persulfate dosage in TAP system [19,23]. Furthermore, as shown in the insert image of Fig.…”

Kinetic and mechanistic investigations of the degradation of sulfamethazine in heat-activated persulfate oxidation process

“…•− [18][19][20][21][22][23]. In this study, k obs of SMZ degradation increased noticeably with an increase in PS concentration ( Fig.…”

“…In heat activation, PS is usually utilized as a precursor of SO 4 •− , and symmetrical cleavage of the peroxide bond results in the formation of SO 4 •− , which further oxidizes the pollutants [15]. Several recent studies documented the effectiveness of heat-activated PS oxidation of herbicides [18,19], industrial chemicals [20,21], and pharmaceuticals [22,23]. Heat-activation possesses several advantages compared with other activation approaches.…”

“…pH plays a complex role in heat-activated PS oxidation of contaminants [15,[18][19][20][21][22][23]. At low pH, PS can undergo acid-catalyzed decomposition which depletes PS through non-radical pathways without producing SO 4 •− [26].…”

Degradation of trichloroethylene in aqueous solution by persulfate activated with citric acid chelated ferrous ion

“…However, Khan and Adewuyi [46] reported that the absorption and oxidation of nitric oxide (NO) significantly improved with the addition of NaCl in sodium persulfate solutions. In addition, in our previous study of 1,1,1-trichloroethane oxidation stimulated by thermally activated persulfate [47], we found anions Cl À and HCO 3 À had negative effects on TCA removal over the range of 1 to 100 mM.…”