title: Enhanced photocatalytic activity of V₂O₅-ZnO composites for the mineralization of nitrophenols.
abstract: In an effort to enhance the photocatalytic activity of ZnO in natural sunlight, V2O5-ZnO nanocomposites were synthesized by co-precipitation technique. The characterization of the synthesized powders by FESEM, XRD and UV-visible diffuse reflectance spectroscopy (DRS) revealed that the both V2O5 and ZnO retain their individual identity in the composites but the increasing concentration of V2O5 affect the particle size of ZnO. As estimated by photoluminescence spectroscopy, in comparison to pure ZnO, the presence of V2O5 significantly suppressed the charge carrier's recombination process. The photocatalytic activity of the synthesized powders was evaluated for the degradation/mineralization of three potential nitrophenol pollutants (2-nitrophenol, 4-nitrophenol, and 2,4-dinitrophenol). The synthesized composites showed significantly higher activity for both degradation and mineralization of nitrophenols compared to pure ZnO. The progress of the degradation process was evaluated by HPLC while mineralization was monitored by TOC analysis. The degradation/mineralization route was estimated by identifying the intermediates using GC-MS. The correlation of the experimental data revealed that the position of NO2 group in 2- and 4-nitrophenol significantly affect the rate of degradation. The identification of hydroxyl group containing intermediates in the degradation of 4-NP confirmed the formation and vital role of hydroxyl radicals in degradation process. The rapid mineralization of nitrophenol substrates pointed out superoxide anions as major contributors in degradation and mineralization process. The assessment of the release of relevant ions (NO2(-), NO3(-), ONOO(-) and NH4(+)) during the degradation process assisted in identifying the plausible interaction sites.
authors.affiliation: Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: M
authors.initials: M
authors.lastname: Aslam
authors.affiliation: Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589, Saudi Arabia; Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Iqbal M I
authors.initials: IM
authors.lastname: Ismail
authors.affiliation: Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589, Saudi Arabia; Department of Environmental Sciences, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: T
authors.initials: T
authors.lastname: Almeelbi
authors.affiliation: Center of Nanotechnology, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: Numan
authors.initials: N
authors.lastname: Salah
authors.affiliation: Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors.forename: S
authors.initials: S
authors.lastname: Chandrasekaran
authors.affiliation: Centre of Excellence in Environmental Studies (CEES), King Abdulaziz University, Jeddah 21589, Saudi Arabia; National Centre for Physics, Quaid-e-Azam University, Islamabad 44000, Pakistan. Electronic address: afmuhammad@kau.edu.sa.
authors.forename: A
authors.initials: A
authors.lastname: Hameed
mesh_terms: D019297:2,4-Dinitrophenol / Q000737:chemistry; D011232:Chemical Precipitation; D052918:Environmental Restoration and Remediation; D009596:Nitrophenols / Q000737:chemistry*; D010782:Photolysis; D017968:Vanadium Compounds / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014877:Water Pollution, Chemical / Q000517:prevention & control; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D009596:Nitrophenols; D017968:Vanadium Compounds; D014874:Water Pollutants, Chemical; C045573:2-nitrophenol; C066075:vanadium pentoxide; D019297:2,4-Dinitrophenol; D015034:Zinc Oxide; C024836:4-nitrophenol
keywords: Composite photocatalyst; Nitrophenol degradation; Sunlight photocatalysis; V(2)O(5); ZnO