title: Quantitative assessment on the contribution of direct photolysis and radical oxidation in photochemical degradation of 4-chlorophenol and oxytetracycline.
abstract: In UV-254 nm/H2O2 advanced oxidation process (AOP), the potential degradation pathways for organic pollutants include (1) hydrolysis, (2) direct H2O2 oxidation, (3) UV direct photolysis, and (4) hydroxyl radical (HO(•)) reaction. In this study, the contribution of these pathways was quantitatively assessed in the photochemical destruction of 4-chlorophenol (4-CP), demonstrating pathways (3) and (4) to be predominantly responsible for the removal of 4-CP by UV/H2O2 in 50 mM phosphate buffer solution. Increasing reaction pH could significantly enhance the contribution of direct photolysis in UV/H2O2 process. The contribution of HO(•) oxidation was improved with increasing initial H2O2 concentration probably due to the increased formation of HO(•). Presence of sodium carbonate (Na2CO3) as in UV/H2O2/Na2CO3 system promoted the degradation of 4-CP, with carbonate radical (CO3 (•-)) reaction and direct photolysis identified to be the main contributing pathways. The trends in the contribution of each factor were further evaluated and validated on the degradation of the antibiotic compound oxytetracycline (OTC). This study provides valuable information on the relative importance of different reaction pathways on the photochemical degradation of organic contaminants such as 4-CP and OTC in the presence and absence of a CO3 (•-) precursor.
authors.affiliation: Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China.|Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH, 45221-0012, USA.
authors.forename: Yiqing
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH, 45221-0012, USA.
authors.forename: Xuexiang
authors.initials: X
authors.lastname: He
authors.affiliation: Faculty of Geosciences and Environmental Engineering, Southwest Jiaotong University, Chengdu, 611756, China. fuyosh@163.com.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Fu
authors.affiliation: Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH, 45221-0012, USA. dionysios.d.dionysiou@uc.edu.
authors.forename: Dionysios D
authors.initials: DD
authors.lastname: Dionysiou
mesh_terms: D002733:Chlorophenols / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010118:Oxytetracycline / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D010782:Photolysis; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D018508:Water Purification / Q000379:methods*
chemical_list: D002733:Chlorophenols; D014874:Water Pollutants, Chemical; C029107:4-chlorophenol; D006861:Hydrogen Peroxide; D010118:Oxytetracycline
keywords: 4-Chlorophenol; Carbonate radical; Hydroxyl radical; Oxytetracycline; UV-254 nm direct photolysis