The intermediate products in the degradation of 4-chlorophenol by pulsed high voltage discharge in water

• Published in: Journal of hazardous materials Vol. 192; no. 3; pp. 1330 - 1339
• Main Authors: Bian, Wenjuan, Song, Xuehong, Liu, Deqi, Zhang, Jiao, Chen, Xihua
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15.09.2011; Elsevier
• Subjects: 2,4-dichlorophenol; 4-Chlorophenol; acetic acid; Acetic Acid - chemistry; Applied sciences; aqueous solutions; Carbon; Chemical engineering; Chlorides - chemistry; Chlorophenols - chemistry; Chromatography, Ion Exchange - methods; Degradation; Discharge; Discharge in water; Electrochemistry - methods; Exact sciences and technology; Freshwater; Gas Chromatography-Mass Spectrometry - methods; High voltages; Hydroquinone; Hydroxylation; Intermediates; Ions; Malic acid; Molecular Weight; Organic acids; Oxalates; Oxalates - chemistry; oxalic acid; Pollution; Reactors; Time Factors; Water Pollutants, Chemical - analysis; Water Purification - methods; Degradation; Discharge in water; 4-Chlorophenol; Intermediates; Intermediate product; Hydroxylation; Chemical reaction; Chlorides; Cleavage; Aromatic compound; Aqueous solution; Chemical reactivity
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2011.06.045

► Intermediates are identified to illustrate 4-chlorophenol degradation by discharge. ► Aromatic compounds are quantified and the important ring-opened steps are focused on. ► The carbon balance during 4-chlorophenol degradation is conducted. ► All 4-chlorophenol and its aromatic intermediates are removed completely in 60 min. ► After that the organic carbons are mainly presented as acetic and oxalate acid. Degradation of 4-chlorophenol by pulsed high voltage discharge is an intricate process involving a series of complex chemical reactions. Hydroxylation of 4-chlorophenol to form hydroquinone, 4-chlororesorcinol and 4-chlorocatechol is the first step, though a very small amount of direct cleavage products of the C 1–C 2 or C 5–C 6 bond are observed. The yield of 4-chlorocatechol is about twice as much as that of hydroquinone. Less 4-chloresorcinol is produced. The free chloride ions dropped from the 4-chlorophenol degradation can obtain reactivity again from the discharge, and react with undegraded 4-chlorophenol to form 2,4-dichlorophenol. Some ring-opened products have also been identified and their possible reaction routes are proposed. Several compounds are verified by use of authentic samples. The more stable ring-opened products are low molecular weight (LMW) acids such as formic, acetic, oxalic, malonate, maleic and malic acid. By discharging 4-chlorophenol aqueous solution for 36 min, the amount of carbons obtained from organic acids is more than 50% while that of carbons from aromatic products less than 20% in the carbons of degraded 4-chlorophenol, which is about 94% of initial carbons. After 60 min of discharge, all the 4-chlorophenol and its aromatic intermediates have been removed completely and the organic carbons are mainly presented as organic acid such as acetic and oxalate acid. At the end of the 120 min discharge, the amount of the remaining organic carbons is not more than 14% of the initial carbons.