2,4-DICHLOROPHENOL

Cl CASRN: 120-83-2; DOT: 2020; molecular formula: C6H4Cl2O; FW: 163.00; RTECS: SK8575000; Merck Index: 12, 3122 Physical state, color, and odor: Colorless to yellow crystals with a sweet, musty, or medicinal odor. At 40 °C, the average odor threshold concentration and the lowest concentration at which an odor was detected were 29 and 5.4 µg/L, respectively. Similarly, at 25 °C, the average taste threshold concentration and the lowest concentration at which a taste was detected were 2.5 and 0.98 µg/L, respectively (Young et al., 1996). Melting point (°C): 45.0 (Stull, 1947) 43.0 (Renner, 1990) Boiling point (°C): 210 (Weast, 1986) 216 (Weiss, 1986) Density (g/cm3): 1.40 at 15 °C (Weiss, 1986) Dissociation constant, pKa: 7.70 (Xie, 1983) 7.80 (Blackman et al., 1980) 7.85 (Leuenberger et al., 1985) Flash point (°C): 113.9, 93.3 (open cup, Weiss, 1986) Entropy of fusion (cal/mol⋅K): 15.10 (Poeti et al., 1982) Henry’s law constant (x 10-6 atm⋅m3/mol): 2.88 at 20 °C (Sheikheldin et al., 2001) 3.23 at 25 °C (estimated, Leuenberger et al., 1985a) Bioconcentration factor, log BCF: 2.53 (activated sludge), 2.41 (algae), 2.00 (golden ide) (Freitag et al., 1985) 1.53 (goldfish, Kobayashi, 1979) 1.0 (brown trout, Hattula et al., 1981)

oc 3.60 (fine sediments), 3.50 (coarse sediments) (Isaacson and Frink, 1984) 2.10 (Brookstone clay loam, Boyd, 1982) 2.81 (river sediment, Eder and Weber, 1980) 2.17 (loamy sand, Kjeldsen et al., 1990) 2.37 (sandy soil), 2.93 (sand), 2.77 (peaty sand) (Van Gestel and Ma, 1993) 2.22, 2.26, and 2.32 in aerobic, anaerobic, and autoclaved Brookstone clay loam soil, respectively

(Boyd and King, 1984) 3.19, 3.22 (glaciofluvial, sandy aquifer, Nielsen et al., 1996) 2.55, 2.84 (forest soil), >2.68 (agricultural soil) (Seip et al., 1986) 2.64 (German sand), 2.26 (48% sand, 43% silt, 9% clay), 2.68 (78% sand, 12% silt, 10%), 2.27

(22% sand, 55% silt, 23% clay) (Haberhauer et al., 2000) 2.609, 2.654, 2.460, 2.346, 2.540 (various European soils, Gawlik et al., 2000) 2.69 at pH 3, 2.47 at pH 5.5, 2.10 at pH 7 (aquatic humic sorbent, Peuravuori et al., 2002) Octanol/water partition coefficient, log Kow: 3.15 (Roberts, 1981) 3.06 (Banerjee et al., 1984; Hansch and Leo, 1979) 3.08 (quoted, Leo et al., 1971) 3.23 (Schellenberg et al., 1984; Leuenberger et al., 1985) 3.20 (shake flask-HPLC, Kishi and Kobayashi, 1994) Solubility in organics: Soluble in ethanol, benzene, ether, chloroform (U.S. EPA, 1985), and carbon tetrachloride (ITII, 1986) Solubility in water: 4.50 g/L at 20 °C (quoted, Krijgsheld and van der Gen, 1986a) 5.00 g/L at 25 °C (Roberts et al., 1977) 6.194 g/L at 25 °C and pH 5.1 (Blackman, 1955) 15.00 g/L at 25 °C (Caturla, 1988) In g/L: 3.896, 5.517, 6.075, and 6.501 at 15.3, 25.2, 29.8, and 35.1 °C, respectively (shake flask-

conductimetry, Achard et al., 1996) In g/L at 25 °C: 4.66 (pH 4.80), 4.96 (pH 4.98), 7.35 (pH 7.40), 8.18 (pH 7.72), 16.2 (pH 8.20),

55.8 (pH 8.93), 57.4 (pH 9.00), 67.7 (pH 9.09), 110 (pH 9.30) (Huang et al., 2000) In mmol/kg solution: 26.5 at 18.2 °C, 29.7 at 21.4 °C, 29.8 at 21.5 °C, 30.3 at 22.0 °C, 36.1 at 26.3

°C, 36.6 at 27.6 °C, 37.1 at 28.8 °C, 37.6 at 29.9 °C, 37.8 at 30.5 °C, 39.0 at 33.4 °C, 39.2 at 33.9 °C, 39.9 at 35.6 °C, 41.0 at 38.3 °C, 41.1 at 38.6 °C, 41.4 at 39.2 °C, 42.5 at 41.9 °C, 43.5 at 44.3 °C, 43.8 at 44.9 °C, 45.0 at 47.8 °C, 45.6 at 49.2 °C, 45.9 at 50.0 °C, 46.9 at 52.3 °C, 51.9 at 63.5 °C, and 52.3 at 64.5 °C (light transmission technique, Jaoui et al., 2002)

Vapor pressure (x 10-2 mmHg): 1.5 at 8 °C, 8.9 at 25 °C (quoted, Leuenberger et al., 1985a) Environmental fate: Biological. In activated sludge, 2.8% mineralized to carbon dioxide after 5 d (Freitag et al., 1985). In freshwater lake sediments, anaerobic reductive dechlorination produced 4-chlorophenol (Kohring et al., 1989). Chloroperoxidase, a fungal enzyme isolated from Caldariomyces fumago, converted 9 to 12% of 2,4-dichlorophenol to 2,4,6-trichlorophenol (Wannstedt et al., 1990). When 2,4-dichlorophenol was statically incubated in the dark at 25 °C with yeast extract and settled domestic wastewater inoculum, significant biodegradation with rapid adaptation was observed. At

d (Tabak et al., 1981). In activated sludge inoculum, 98.0% COD removal was achieved. The average rate of biodegradation was 10.5 mg COD/g⋅h (Pitter, 1976). Surface Water. Hoigné and Bader (1983) reported 2,4-dichlorophenol reacts with ozone at a rate constant of <1,500/M⋅sec at the pH range of 1.5 to 3.0. Groundwater. Nielsen et al. (1996) studied the degradation of 2,4-dichlorophenol in a shallow, glaciofluvial, unconfined sandy aquifer in Jutland, Denmark. As part of the in situ microcosm study, a cylinder that was open at the bottom and screened at the top was installed through a cased borehole approximately 5 m below grade. Five liters of water was aerated with atmospheric air to ensure aerobic conditions were maintained. Groundwater was analyzed weekly for approximately 3 months to determine 2,4-dichlorophenol concentrations with time. The experimentally determined first-order biodegradation rate constant and corresponding half-life were 0.20/d and 3.47 d, respectively. Photolytic. In distilled water, photolysis occurs at a slower rate than in estuarine waters containing humic substances. Photolysis products identified in distilled water were the three isomers of chlorocyclopentadienic acid. The following half-lives were reported for 2,4dichlorophenol in estuarine water exposed to sunlight and microbes: 0.6 and 2.0 h during summer (24 °C) and winter (10 °C), respectively; in distilled water: 0.8 and 3.0 h during summer and winter, respectively; in poisoned estuarine water: 0.7 and 2.0 h during summer and winter, respectively (Hwang et al., 1986). When titanium dioxide suspended in an aqueous solution was irradiated with UV light (λ = 365 nm), 2,4-dichlorophenol was converted to carbon dioxide at a significant rate (Matthews, 1986). An aqueous solution containing hydrogen peroxide and irradiated by UV light (λ = 296 nm) converted 2,4-dichlorophenol to chlorohydroquinone and 1,4dihydroquinone (Moza et al., 1988). A carbon dioxide yield of 50.4% was achieved when 2,4dichlorophenol adsorbed on silica gel was irradiated with UV light (λ >290 nm) for 17 h (Freitag et al., 1985). 2,4-Dichlorophenol in aqueous solution was illuminated with filtered xenon light (λ >295 nm) at various time intervals. The first-order conversion rate constant was 5.73 x 10-5/sec. The loss of chlorine atoms seemed to be the major early process during the reaction (Svenson and Kaj, 1989). Larson et al. (1992) studied the photosensitizing ability of 2′,3′,4′,5′-tetraacetylriboflavin to various organic compounds. An aqueous solution containing 2,4-dichlorophenol was subjected to a medium-pressure mercury arc lamp (λ >290 nm). The investigators reported that 2′,3′,4′,5′-tetraacetylriboflavin was superior to another photosensitizer, namely riboflavin, in the degradation of 2,4-dichlorophenol and other compounds. Direct photolysis of 2,4-dichlorophenol without any photosensitizer present resulted in a half-life of 21 min. In the presence of ribloflavin and 2′,3′,4′,5′-tetraacetylriboflavin, the half-lives were 6.3 and 4.1 min, respectively. Chemical/Physical. 2,4-Dichlorophenol will not hydrolyze to any reasonable extent (Kollig, 1993). Reported second-order rate constants for the reaction of 2,4-dichlorophenol and singlet oxygen in water at 292 K: 7 x 106/M⋅sec at pH 5.5, 2 x 106/M⋅sec at pH 6, 1.0 x 105/M⋅sec at pH 6.65, 1.5 x 106/M⋅sec at pH 7.0, 7.6 x 105/M⋅sec at pH 7.9, 1.20 x 104/M⋅sec at pH 9.0 to 9.6. At pH 8, the half-life of 2,4-dichlorophenol is 62 h (Scully and Hoigné, 1987). In an aqueous phosphate buffer at 27 °C, 2,4-dichlorophenol reacted with singlet oxygen at a rate of 5.1 x 106/M⋅sec (Tratnyek and Hoigné, 1991). At neutral pH, 2,4-dichlorophenol was completely oxidized by potassium permanganate (2.0 mg/L) after 15 min (quoted, Verschueren, 1983). At influent concentrations (pH 3.0) of 1.0, 0.1, 0.01, and 0.001 mg/L, the GAC adsorption capacities were 147, 65, 29, and 13 mg/g, respectively. At pH 5.3 and pH 9.0 at influent concentrations of 1.0, 0.1, 0.01, and 0.001 mg/L, the GAC adsorption capacities were 157, 112, 80, and 57 mg/g and 141, 72, 37, and 19 mg/g, respectively (Dobbs and Cohen, 1980). Toxicity: EC50 (24-h) for Daphnia pulex 6,600 µg/L (Shigeoka et al., 1988).