Decolorization and mineralization of Allura Red AC aqueous solutions by electrochemical advanced oxidation processes.
The decolorization and mineralization of solutions containing 230 mg L(-1) of the food azo dye Allura Red AC at pH 3.0 have been studied upon treatment by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF). Experiments were performed with a stirred tank reactor containing a boron-doped diamond (BDD) or Pt anode and an air-diffusion cathode to generate H2O2. The main oxidants were hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between H2O2 and added Fe(2+). The oxidation ability increased in the sequence EO-H2O2 < EF < PEF and faster degradation was always obtained using BDD. PEF process with BDD yielded almost total mineralization following similar trends in SO4(2-), ClO4(-) and NO3(-) media, whereas in Cl(-) medium, mineralization was inhibited by the formation of recalcitrant chloroderivatives. GC-MS analysis confirmed the cleavage of the −N=N− bond with formation of two main aromatics in SO4(2-) medium and three chloroaromatics in Cl(-) solutions. The effective oxidation of final oxalic and oxamic acids by BDD along with the photolysis of Fe(III)-oxalate species by UVA light accounted for the superiority of PEF with BDD. NH4(+), NO3(-) and SO4(2-) ions were released during the mineralization.
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Abdoulaye
A
Thiam
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Ignasi
I
Sirés
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
José A
JA
Garrido
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain.
Rosa M
RM
Rodríguez
Laboratori d'Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain. Electronic address: brillas@ub.edu.
Enric
E
Brillas
D001391:Azo Compounds / Q000737:chemistry*; D003116:Color; D004563:Electrochemistry; D005505:Food Coloring Agents / Q000737:chemistry*; D006861:Hydrogen Peroxide; D007501:Iron / Q000737:chemistry; D010084:Oxidation-Reduction; D012996:Solutions; D014867:Water; D014874:Water Pollutants, Chemical / Q000737:chemistry
D001391:Azo Compounds; C045076:Fenton's reagent; D005505:Food Coloring Agents; D012996:Solutions; D014874:Water Pollutants, Chemical; D014867:Water; C005915:Allura Red AC Dye; D006861:Hydrogen Peroxide; D007501:Iron
Allura Red AC; Electro-Fenton; Electrochemical oxidation; Oxidation products; Photoelectro-Fenton