title: Application of UV-irradiated Fe(III)-nitrilotriacetic acid (UV-Fe(III)NTA) and UV-NTA-Fenton systems to degrade model and natural occurring naphthenic acids.
abstract: Naphthenic acids (NAs) are a highly complex mixture of organic compounds naturally present in bitumen and identified as the primary toxic constituent of oil sands process-affected water (OSPW). This work investigated the degradation of cyclohexanoic acid (CHA), a model NA compound, and natural occurring NAs during the UV photolysis of Fe(III)-nitrilotriacetic acid (UV-Fe(III)NTA) and UV-NTA-Fenton processes. The results indicated that in the UV-Fe(III)NTA process at pH 8, the CHA removal increased with increasing NTA dose (0.18, 0.36 and 0.72 mM), while it was independent of the Fe(III) dose (0.09, 0.18 and 0.36 mM). Moreover, the three Fe concentrations had no influence on the photolysis of the Fe(III)NTA complex. The main responsible species for the CHA degradation was hydroxyl radical (OH), and the role of dissolved O2in the OH generation was found to be negligible. Real OSPW was treated with the UV-Fe(III)NTA and UV-NTA-Fenton advanced oxidation processes (AOPs). The removals of classical NAs (O2-NAs), oxidized NAs with one additional oxygen atom (O3-NAs) and with two additional oxygen atoms (O4-NAs) were 44.5%, 21.3%, and 25.2% in the UV-Fe(III)NTA process, respectively, and 98.4%, 86.0%, and 81.0% in the UV-NTA-Fenton process, respectively. There was no influence of O2on the NA removal in these two processes. The results also confirmed the high reactivity of the O2-NA species with more carbons and increasing number of rings or double bond equivalents. This work opens a new window for the possible treatment of OSPW at natural pH using these AOPs.
authors.affiliation: Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
authors.forename: Pamela
authors.initials: P
authors.lastname: Chelme-Ayala
authors.affiliation: Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Klamerth
authors.affiliation: Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada. Electronic address: mgamalel-din@ualberta.ca.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Gamal El-Din
mesh_terms: D002208:Caproates / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry* / Q000528:radiation effects; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D009571:Nitrilotriacetic Acid / Q000737:chemistry*; D061329:Oil and Gas Fields / Q000737:chemistry; D010084:Oxidation-Reduction; D010782:Photolysis; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects
chemical_list: D002208:Caproates; D002264:Carboxylic Acids; C045076:Fenton's reagent; D005290:Ferric Compounds; D014874:Water Pollutants, Chemical; C037652:hexanoic acid; D006861:Hydrogen Peroxide; D007501:Iron; D009571:Nitrilotriacetic Acid; C046170:naphthenic acid
keywords: Cyclohexanoic acid; Fe(III)-nitrilotriacetic acid; Naphthenic acids; Oil sands process-affected water; Photolysis