title: The effect of Ni(2+) and Cu(2+) on the photocatalytic degradation of dyes by the chitosan-TiO(2) complex.
abstract: The present research combines biosorption and photocatalysis in a functional TiO(2)-immobilized chitosan adsorbent (CTA). CTA can degrade organic pollutants and adsorb metal ions simultaneously. Target pollutants were dyes of cationic (rhodamine B, Rh.B) and anionic (methyl orange, MO) nature, with Ni(2+) and Cu(2+) selected as heavy metals. The presence of Ni(2+) or Cu(2+) improved the degradation ability of CTA for MO, but inhibited the degradation of Rh.B, with Cu(2+) exhibiting stronger effects than Ni(2+). There was no significant difference in CTA activity when the metal ions were pre-adsorbed or when they coexisted in the solution with the organic dyes. Protons in the reaction system affected the degradation performance in a similar way for Ni(2+) and Cu(2+) leading to a different effect on the degradation for MO and Rh.B. An X-ray photoelectron spectroscopy analysis of the binding energies of the metal ions on the surface in the presence of the cationic or anionic dyes explained the different behaviors. Since anionic and cationic dyes possess chromogenic groups of different charges, they adversely affect the production of OH• radicals when coexisting with Cu(2+) or Ni(2+).
authors: State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
authors: Xiaolei
authors: X
authors: Zhao
authors: Gang
authors: G
authors: Xiao
authors: Xin
authors: X
authors: Zhang
authors: Haijia
authors: H
authors: Su
authors: Tianwei
authors: T
authors: Tan
mesh_terms: D000327:Adsorption; D001391:Azo Compounds / Q000737:chemistry; D002384:Catalysis; D048271:Chitosan / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009532:Nickel / Q000737:chemistry*; D056951:Photoelectron Spectroscopy; D010782:Photolysis; D012235:Rhodamines / Q000737:chemistry; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D012235:Rhodamines; C009495:titanium dioxide; C100258:methyl orange; D003300:Copper; D009532:Nickel; D048271:Chitosan; D014025:Titanium; C029773:rhodamine B