| Halobenzoquinone is a potential carcinogen for bladder cancer.A determination method of 2,6-dichloro-1,4-benzoquinone?DCBQ?and 2,6-dibromo-1,4-benzoquinone?DBBQ?was developed upon using liquid-liquid extraction and a gas chromatography with an electronic capture detector?LLE-GC-ECD?.The limits of quantitation?LOQ?of the LLE-GC-ECD method were 2.4 ng/L and 2.7 ng/L in 1 L water for DCBQ and DBBQ.Therefor this method can be used to determine the levels of DCBQ and DBBQ in the actual water samples.With the aid of the LLE-GC-ECD method,the degradation of DCBQ and DBBQ and the consequent formation of low-molecular-weight disinfection byproducts?DBPs,including volatile disinfection byproduce?VDBPs?and halocaetic acid?HAAs??with or without the presence of chlorine were investigated.Without the presence chlorine,the degradation rates of DCBQ and DBBQ both increased with the increase of pH.The first-order reaction rate constants of DCBQ and DBBQ were 6.4×10-4 h-10.38 h-1 and7.6×10-4 h-10.45 h-1 at pH 6.58.5,respectively.When pH was elevated from 6.5 to8.5,the half-lives of DCBQ and DBBQ shortened from 108.3 h and 91.2 h to 1.8 h and1.5 h,respectively.The degradation rates of DCBQ and DBBQ increased with temperature.When the temperature was 20°C35°C,the first-order reaction rate constants of DCBQ and DBBQ were 2.1×10-2 h-10.17 h-1 and 2.8×10-2 h-10.20 h-1,respectively.The formation of low-molecular-weight DBPs was not detected during the degradation DCBQ and DBBQ without the presence chlorine.With the presence of chlorine,the degradation rates of DCBQ and DBBQ increased with the chlorine concentration.When the concentration of chlorine increased from 0.02 mg/L to 0.05 mg/L,the first-order reaction rate constants of DCBQ and DBBQ increased from 2.06 h-11 and 2.54 h-1 to 4.78 h-1 and 8.09 h-1,and correspondingly.The species and amount of low-molecular-weight DBPs increased with the chlorine concentration.DCBQ produced more VDBPs than HAAs,whereas DBBQ produced more HAAs at high chlorine concentrations.The first-order reaction rate constants of DCBQ and DBBQ increased with pH.When the pH was 6.08.0,the first-order reaction rates of DCBQ and DBBQ were 0.22 h-11.74 h-1?half-lives were 3.15 h0.40 h?and0.27 h-16.17 h-1?2.56 h0.11 h?.The presence of bromide in water slowed the degradation of DCBQ.When the bromide concentration was 00.10 mg/L,the first-order reaction rate constants was 1.32 h-10.68 h-1.Bromide promoted the conversion of DCBQ to VDBPs and HAAs,and brominated VDBPs and HAAs were generated.When the bromide concentration was 0.02 mg/L0.10 mg/L,5.15%28.49%of bromide was converted to organic bromine. |
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