Carbon nanotubes as novel redox mediators for dyed wastewaters biodegradation

• Author(s): Pereira, Luciana ; Pereira, Raquel ; Pereira, Fernando ; Alves, M. M.
• Date: 2013
• Persistent ID: http://hdl.handle.net/1822/26331
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Activated carbon; Nanotubes; Carbon xerogels; Azo dyes; Anaerobic biodegradation
• Document Type: Conference Object
• Language: English

Description

Due to their large-scale production and extensive application, dyes have turned serious pollutants as when improperly handled and disposed, they may create serious public health and environmental problems. One of the problems that textile industry is facing is related with the incomplete exhaustion of dyes onto textile fibre from an aqueous dyeing process and the need to implement innovative and sustainable effluent treatment methods to remove colour. Biological treatment systems were shown to be promising technologies. The main limiting factor of the reductive transformations by anaerobic sludge is the electron transfer, a slow process. This limitation can be overcome by making use of redox mediators, compounds that accelerate the electron transfer from a primary electron donor to a terminal electron acceptor, to speed up the process. Activated carbon (AC) has been shown as a feasible redox mediator. Samples of microporous thermal treated AC (ACH2) and mesoporous carbons: Xerogels (XA, XB) and Carbon nanotubes (CNT) were tested on azo dye and textile wastewater biodegradation. ~80 % Mordant Yellow 10 (MY10) and 70 % of Reactive Red 120 (RR120) colour removal was obtained with all the carbon materials. Acid Orange 10 (AO10) is not biodegraded in the absence of Carbon Materials, but with XB a 98 % of colour removal at 4.48 ± 0.74 d-1 of reduction rate was achieved. For MY10 and RR120, rates increased in the order: control < ACH2 < XA < XB < CNT. HPLC analysis confirmed the reduction of dyes with the corresponding aromatic amines formation. Biological treatments of real wastewater lead to 65 % of colour removal with rate improvement in the presence of CNT.