title: Enhanced microbial decolorization of methyl red with oxidized carbon fiber as redox mediator.
abstract: The anaerobic degradation of azo dyes under anaerobic conditions is possible but at a slow rate. Redox mediators (quinones, activated carbon) are used to improve the reduction rate. The aim of this work was to use activated carbon fiber (ACF) as a redox mediator for the anaerobic reduction of the azo dye methyl red. ACF was chemically modified with 8M HNO₃ to increase its redox-mediating capacity and used in chemical and anaerobic biological batch assays for the reduction of methyl red. ACF increased its redox-mediating capacity up to 3-fold in chemical assays; in biological assays ACF increased the reduction rate up to 8-fold compared to controls without ACF. However, since the ACF served as support for biomass, a biofilm formed on the fiber significantly reduced its redox-mediating capacity; substrate consumption suggested that the electron transport from ACF to methyl red was the rate-limiting step in the process. These results are the first evidence of the role of ACF as a redox mediator in the reductive decolorization of methyl red, in addition to the effect of biofilm attached to ACF on methyl red reduction. Due to the versatile characteristics of ACF and its redox-mediating capacity, carbon fibers could be used in biological wastewater treatment systems to accelerate the reductive transformation of pollutants commonly found in industrial effluents.
authors.affiliation: División de Ciencias Ambientales, Instituto Potosino de Investigación Científica y Tecnológica, Camino a Presa San José 2055, Col. Lomas 4ª Sección, San Luis Potosí, SLP 78216, Mexico.
authors.forename: E
authors.initials: E
authors.lastname: Emilia Rios-Del Toro
authors.forename: Lourdes B
authors.initials: LB
authors.lastname: Celis
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Cervantes
authors.forename: J Rene
authors.initials: JR
authors.lastname: Rangel-Mendez
mesh_terms: D001391:Azo Compounds / Q000032:analysis* / Q000378:metabolism; D001673:Biodegradation, Environmental; D018441:Biofilms; D018533:Biomass; D019149:Bioreactors; D002244:Carbon / Q000737:chemistry*; D000077482:Carbon Fiber; D002384:Catalysis; D004396:Coloring Agents / Q000032:analysis* / Q000737:chemistry; D004583:Electrons; D005947:Glucose / Q000737:chemistry; D007220:Industrial Waste; D059013:Microbial Consortia; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D013783:Textile Industry; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D001391:Azo Compounds; D000077482:Carbon Fiber; D004396:Coloring Agents; D007220:Industrial Waste; C008492:methyl red; D002244:Carbon; D005947:Glucose; D010100:Oxygen
keywords: Activated carbon fibers; Anaerobic; Biofilm; Decolorization; Methyl red; Redox mediator