title: Heterogeneous photocatalytic degradation of methyl orange in schwertmannite/oxalate suspension under UV irradiation.
abstract: BACKGROUND
  Schwertmannite was synthesized through an oxidation of FeSO(4) by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH 2.5 and 28°C for 3 days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The schwertmannite photocatalytic degradation of methyl orange (MO) by oxalate was investigated at different initial pH values, concentrations of schwertmannite, oxalate, and MO.
  
  
  RESULTS
  The results demonstrated that photodegradation of MO in the presence of schwertmannite or oxalate alone was very weak. However, the removal of MO was significantly enhanced when schwertmannite and oxalate coexisted in the reaction system. Low pH (4 or less) was beneficial to the degradation of MO. The optimal doses of schwertmannite and oxalate were 0.2 g L(-1) and 2 mM, respectively. Hydroxyl radicals (·OH) and Fe(II), the intermediate products, were also examined during the reaction to explore their correlation with the degradation of MO.
  
  
  CONCLUSIONS
  A possible mechanism for the photocatalytic decomposition of MO in the study was proposed. The formation of Fe(III)-oxalate complexes on the surface of schwertmannite was a precursor of H(2)O(2) and Fe(II) production, further leading to the yield of ·OH responsible for the decomposition of MO.
authors.affiliation: College of Sciences, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wu
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.forename: Danjun
authors.initials: D
authors.lastname: Jiang
authors.forename: Pei
authors.initials: P
authors.lastname: Zhou
authors.forename: Yeqing
authors.initials: Y
authors.lastname: Lan
authors.forename: Lixiang
authors.initials: L
authors.lastname: Zhou
mesh_terms: D001391:Azo Compounds / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004785:Environmental Pollutants / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry; D010070:Oxalates / Q000032:analysis / Q000737:chemistry; D010782:Photolysis / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; D004785:Environmental Pollutants; D058085:Iron Compounds; D010070:Oxalates; C511969:schwertmannite; D017665:Hydroxyl Radical; C100258:methyl orange