title: Photocatalytic degradation of commercially sourced naphthenic acids by TiO2-graphene composite nanomaterial.
abstract: Naphthenic acids (NAs) are a major contributor to the toxicity in oil sands process-affected water (OSPW), which is produced by hot water extraction of bitumen. NAs are extremely difficult to be degraded due to its complex ring and side chain structure. Photocatalysis is recognized as a promising technology in the removal of refractory organic pollutants. In this work, TiO2-graphene (P25-GR) composites were synthesized by means of solvothermal method. The results showed that P25-GR composite exhibited better photocatalytic activity than pure P25. The removal efficiency of naphthenic acids in acid solution was higher than that in neutral and alkaline solutions. It was the first report ever known on the photodegradation of NAs based on graphene, and this process achieved a higher removal rate than other photocatalysis degradation of NAs in a shorter reaction time. LC/MS analysis showed that macromolecular NAs (carbon number 17-22, z value -2) were easy to be degraded than the micromolecular ones (carbon number 11-16, z value -2). Furthermore, the reactive oxygen species that play the main role in the photocatalysis system were studied. It was found that holes and ·OH were the main reactive species in the UV/P25-GR photocatalysis system. Given the high removal efficiency of refractory organic pollutants and the short degradation time, photodegradation based on composite catalysts has a broad and practical prospect. The study on the photodegradation of commercially sourced NAs may provide a guidance for the degradation of OSPW NAs by this method.
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Juncheng
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China; Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education), Tianjin 300071, China; Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, Tianjin 300071, China. Electronic address: tangjch@nankai.edu.cn.
authors.forename: Jingchun
authors.initials: J
authors.lastname: Tang
authors.affiliation: Tianjin Academy of Environmental Sciences, Tianjin 300191, China.
authors.forename: Jianli
authors.initials: J
authors.lastname: Ma
mesh_terms: D002264:Carboxylic Acids / Q000032:analysis / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry*; D006838:Hydrocarbons; D008956:Models, Chemical; D049329:Nanostructures; D061329:Oil and Gas Fields; D010782:Photolysis; D014025:Titanium / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D006838:Hydrocarbons; D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D006108:Graphite; C006647:asphalt; D014025:Titanium; C046170:naphthenic acid
keywords: Holes; Hydroxyl radicals; Naphthenic acids; Photocatalytic degradation; TiO(2) graphene composite