Autor(es):
Pereira, Luciana 
; Pereira, Ricardo ; Pereira, M. F. R. ; Van der Zee, F. P. ; Cervantes, F. J. ; Alves, M. M.
Data: 2010
Identificador Persistente: http://hdl.handle.net/1822/11361
Origem: RepositóriUM - Universidade do Minho
Assunto(s): Activated carbon; Redox mediator; Azo dye; Reduction; Decolourisation
Descrição
The surface chemistry of a commercial AC (AC0) was selectively modified, without changing significantly
its textural properties, by chemical oxidation with HNO3 (ACHNO3 ) and O2 (ACO2 ), and thermal
treatments under H2 (ACH2) or N2 (ACN2 ) flow. The effect of modified AC on anaerobic chemical dye
reduction was assayed with sulphide at different pH values 5, 7 and 9. Four dyes were tested: Acid
Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71. Batch experiments with low amounts
of AC (0.1 g L−1) demonstrated an increase of the first-order reduction rate constants, up to 9-fold, as
compared with assays without AC. Optimum rates were obtained at pH 5 except for MY10, higher at pH
7. In general, rates increased with increasing the pH of point zero charge (pHpzc), following the trend
ACHNO3 < ACO2 < AC0 < ACN2 < ACH2 . The highest reduction rate was obtained for MY10 with ACH2 at
pH 7, which corresponded to the double, as compared with non-modified AC. In a biological system using
granular biomass, ACH2 also duplicated and increase 4.5-fold the decolourisation rates of MY10 and RR2,
respectively. In this last experiment, reaction rate was independent of AC concentration in the tested
range 0.1–0.6 g L−1.
