Oxidation of 4-Chloro-3-methylphenol in Pressurized Hot Water/Supercritical Water with Potassium Persulfate as Oxidant

Abstract

4-Chloro-3-methylphenol (c = 2.0 mM), representing a model pollutant, was oxidized in pressurized hot water and in supercritical water in a continuous flow system. Potassium persulfate was used as oxidant in concentrations of 8.0 and 40.0 mM. Contact times (reaction times) were 3-59 s, temperatures 110-390 degrees C, and pressures 235-310 bar. A wide temperature range was tested to determine the range over which potassium persulfate can be used effectively. Good oxidation efficiencies for 4-chloro-3-methylphenol were obtained at both oxidant concentrations and with short contact times at temperatures clearly underthe critical temperature of water; total organic carbon content of the effluent was low under optimized conditions. Corrosion, measured as nickel and chromium concentrations of the effluent, was more severe at oxidant concentration of 40.0 mM. Sulfate was present in the effluent in high concentrations. Sulfate is the limiting factor in the use of potassium persulfate in wastewater treatment and requires further water treatment.

Insights into Heterogeneous Catalysis of Persulfate Activation on Dimensional-Structured Nanocarbons

“…5 Physical activation such as UV irradiation or heating is able to effectively stimulate PS to produce sulfate radicals for oxidation of pollutants. [8][9][10] Chemical activation such as bases, phenols, and quinones were reported to be effective for activating PS for in situ chemical oxidation (ISCO). [11][12][13] Recent studies also applied electrochemical methods or electron donors (zero-valent iron or ferrous ion (II)) for PS activation.…”

Metal-free catalysis of persulfate activation and organic-pollutant degradation by nitrogen-doped graphene and aminated graphene

“…After activation, PS then becomes a strong oxidant (up to E ¼ 2.05 V), and therefore, interest is significant for activating PS in water treatment to degrade emerging contaminants under a broad spectrum of environmental conditions. Both physical activation like UV irradiation and heating (Kronholm et al, 2001;Yang et al, 2014) and chemical activation such as bases, phenols, and quinones have been reported to be effective for PS activation (Furman et al, 2010;Ahmad et al, 2013;Fang et al, 2013). The PS activation may occur either through generation of free radicals or by nonracial processes (Zhang et al, 2013).…”

Degradations of 2,4-dichlorophenol and polychlorinated biphenyls with zero valent iron under subcritical conditions. Importance of subcritical water oxidation

“…They also observed that chlorinated aliphatic compounds including lindane, dieldrin, tetrachloroethene and trichloroethene could be completely dechlorinated with subcritical water in 1 h at 150-300 °C [13]. In addition, the combination of subcritical water with oxidizing agents such as permanganate, O 2 and air, via so-called subcritical water oxidation (SCWO) can effectively oxidize organic compounds that are normally very difficult to oxidize [14,15]. Dadkhah and Akgerman [14] showed that more than 99.99% of PAHs could be removed from soil with the combination of extraction and oxidation with air and O 2 at 250 °C.…”

“…Dadkhah and Akgerman [14] showed that more than 99.99% of PAHs could be removed from soil with the combination of extraction and oxidation with air and O 2 at 250 °C. Kronholm et al [15] reported that more than 99.9% of 4-chloro-3-methylphenol was oxidized by potassium persulfate within 1 min at 250-300 °C under 23.5-31.0 MPa. Under subcritical and supercritical conditions, PCBs were rapidly degraded with oxidants within minutes [16,17].…”