title: Use of titanium dioxide photocatalysis on the remediation of model textile wastewaters containing azo dyes.
abstract: The photocatalytic degradation of two commercial textile azo dyes, namely C.I Reactive Black 5 and C.I Reactive Red 239, has been studied. TiO(2) P25 Degussa was used as catalyst and photodegradation was carried out in aqueous solution under artificial irradiation with a 125 W mercury vapor lamp. The effects of the amount of TiO(2) used, UV-light irradiation time, pH of the solution under treatment, initial concentration of the azo dye and addition of different concentrations of hydrogen peroxide were investigated. The effect of the simultaneous photodegradation of the two azo dyes was also investigated and we observed that the degradation rates achieved in mono and bi-component systems were identical. The repeatability of photocatalytic activity of the photocatalyst was also tested. After five cycles of TiO(2) reuse the rate of colour lost was still 77% of the initial rate. The degradation was followed monitoring the change of azo dye concentration by UV-Vis spectroscopy. Results show that the use of an efficient photocatalyst and the adequate selection of optimal operational parameters may easily lead to a complete decolorization of the aqueous solutions of both azo dyes.
authors.affiliation: Centro de Estudos da Saúde do Trabalhador e Ecologia Humana Escola Nacional de Saúde Pública - Fundação Oswaldo Cruz, Av. Leopoldo Bulhões, 1480, Rio de Janeiro 21041-210 RJ, Brazil. saggi_br@hotmail.com
authors.forename: Enrico Mendes
authors.initials: EM
authors.lastname: Saggioro
authors.forename: Anabela Sousa
authors.initials: AS
authors.lastname: Oliveira
authors.forename: Thelma
authors.initials: T
authors.lastname: Pavesi
authors.forename: Cátia Gil
authors.initials: CG
authors.lastname: Maia
authors.forename: Luis Filipe Vieira
authors.initials: LF
authors.lastname: Ferreira
authors.forename: Josino Costa
authors.initials: JC
authors.lastname: Moreira
mesh_terms: D001391:Azo Compounds / Q000737:chemistry / Q000302:isolation & purification*; D002384:Catalysis / Q000528:radiation effects; D004396:Coloring Agents / Q000737:chemistry / Q000302:isolation & purification*; D052918:Environmental Restoration and Remediation; D006861:Hydrogen Peroxide / Q000737:chemistry; D006863:Hydrogen-Ion Concentration / Q000528:radiation effects; D007220:Industrial Waste / Q000032:analysis; D009282:Naphthalenesulfonates / Q000737:chemistry / Q000302:isolation & purification; D010782:Photolysis / Q000528:radiation effects; D059027:Recycling; D013784:Textiles; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid; D018508:Water Purification
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D007220:Industrial Waste; D009282:Naphthalenesulfonates; C009495:titanium dioxide; D006861:Hydrogen Peroxide; D014025:Titanium; C063421:Remazol black B