Investigation on the Mechanism of O3/GAC System on Ortho-dichlorobenzene
LEI Caihong
SUN Ying
YANG Ying
ZHAO Suping
Abstract：Ortho-dichlorobenzene (o-DCB) is characterized by low biodegradability and bioaccumulation in water. It is considered to be one of the most dangerous environmental pollutants. In order to investigate the effect of O3/GAC system on oDCB, activated carbon dosage, ozone gas flow rate and p H value used as the important variable factors, the trend and variation of o-DCB concentration were analyzed. The results showed that the addition of GAC was more favorable for the removal of o-DCB, and the high removal rate of O3/GAC system was mainly due to the adsorption and catalytic O3 decomposition of GAC. p H has a significant impact on removal efficiency of o-DCB. At p H 4.0, the degradation rate of o-DCB was the slowest, and that of o-DCB was similar at p H 8.0 and 10.0. Ozone and activated carbon has a good synergistic effect. The effect of p H on the O3/GAC system was more significant at p H 8 and 10, and the reaction rate of o-DCB was significantly increased in the O3/GAC system. Especially, at p H 10.0, the o-DCB reaction was 0.15 min, and the synergistic factor reached 2.17.Humic acid, metal ions (Fe3+, Al3+) and free radical trapping agents have some influence on the removal of o-DCB in O3/GAC system. The effect of O3/GAC system was better than that of O3 on humic acid and o-DCB. When the dosage of Fe3+was 1～5 mg/L, the removal of o-DCB was increased. The concentration of o-DCB was greatly reduced by the addition of tert-butanol, which proved that the formation of ·OH was in the process of O3/GAC/Fe3+. The intermediate products of o-DCB degradation in O3/GAC system are o-chlorophenol, phenol, hydroquinone, catechol, o-benzoquinone, acetic acid, formic acid and so on. Cl is a para-to-position group, ·OH is liable to attack the carbon atoms in its ortho position to rapidly produce 2, 3-dichlorophenol and 3, 4-dichlorophenol, and then the chlorine atoms on the benzene ring are successively substituted with OHnucleophilic substitution/elimination to produce 3-chloro catechol and other substances. o-DCB on a chlorine atom is easily OH-nucleophilic substitution/elimination after the formation of o-chlorophenol, o-chlorophenol has two conversion pathway.
Keywords：ozoneactivated carbonortho-dichlorobenzenepHdegradation pathway
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：8( 17-24 )