removal efficiency of the proposed process was over 70% which was far better than
efficiencies of H 2 O 2 (10%), granular activated carbon (44%), granular activated
carbon/H 2 O 2 (43%) under acidic conditions, and 7.4 mM concentration of H 2 O 2
(Chen et al. 2011).
In a combined chemical-biological process designed for biodegradability
enhancement and operating cost reduction, Fenton’s reaction was used to assist
biological oxidation in a sequential batch reactor to remove color and organic matter
from synthetic textile effluents. The combined approach successfully removed over
99% of color and 88–98% of organic matter. Additional benefits included meeting
the wastewaters discharge limits and reduction of the individual operating costs of
individual processes (Rodrigues et al. 2014).
Electrochemical Oxidation
Electrochemical oxidation or electro-oxidation is an effective technique to remove
contaminants from effluents that are rich in anionic content (Abdessamad et al. 2013;
Guzmán-Duque et al. 2014). The mechanism of electrochemical oxidation involves
a redox reaction initiated by electric current leading to the transformation of organic
components into CO 2 and H 2 O. The electrochemical treatment of dyeing wastewater
comprises of direct and indirect oxidation processes. The direct oxidation process
starts with adsorption of pollutants on the surface of anode followed by degradation
through electron transferring reaction. On the other hand, the indirect oxidation
process electrochemically generates strong oxidizing agents to breakdown contaminants with oxidation reactions (Zhan et al. 2001).
An important factor that defines the efficiency of electrochemical oxidation is the
type and properties of the electrode. Boron-doped diamond is known to be the most
efficient electrode materials for the electro-oxidation of wastewaters. The success of
boron-doped diamond electrode is attributed to the physicochemical stability, reliable oxidative strength, controllable adsorption, and the convenient water discharge
(Peralta-Hernández et al. 2012; Shen et al. 2006). Doped boron-doped diamond
films with boron grown on titanium plates by hot filament chemical vapor technique
were used to remove 10 from dyeing wastewater. Complete decolorization of 10 was
achieved with boron-doped diamond/Ti electrode at 100 mA cm
À2 current density.
Electrodes also showed the capacity to transform aromatic hydrocarbons into aliphatic species, which may further degrade into CO 2 (Vasconcelos et al. 2015).
Boron-doped diamond anodes were employed for galvanostatic electrolysis by
anodic oxidation of mixtures contaminated with containing Alphazurine
A. Electrolysis caused 100% color and chemical oxygen demand removal at varying
reaction parameters (Bensalah et al. 2009).
Large-scale application of the electrochemical method is hampered by the single
great disadvantage of high operational cost. Some researchers have suggested an
indirect electrochemical process using Cl
À and UV irradiation-assisted electrochemical process. Synthetic textile wastewater polluted with reactive dyes subjected to
low current density electrochemical oxidation followed by UV irradiation with Ti/Pt
17 Methods for the Treatment of Wastewaters Containing Dyes and Pigments
631
efficiencies of H 2 O 2 (10%), granular activated carbon (44%), granular activated
carbon/H 2 O 2 (43%) under acidic conditions, and 7.4 mM concentration of H 2 O 2
(Chen et al. 2011).
In a combined chemical-biological process designed for biodegradability
enhancement and operating cost reduction, Fenton’s reaction was used to assist
biological oxidation in a sequential batch reactor to remove color and organic matter
from synthetic textile effluents. The combined approach successfully removed over
99% of color and 88–98% of organic matter. Additional benefits included meeting
the wastewaters discharge limits and reduction of the individual operating costs of
individual processes (Rodrigues et al. 2014).
Electrochemical Oxidation
Electrochemical oxidation or electro-oxidation is an effective technique to remove
contaminants from effluents that are rich in anionic content (Abdessamad et al. 2013;
Guzmán-Duque et al. 2014). The mechanism of electrochemical oxidation involves
a redox reaction initiated by electric current leading to the transformation of organic
components into CO 2 and H 2 O. The electrochemical treatment of dyeing wastewater
comprises of direct and indirect oxidation processes. The direct oxidation process
starts with adsorption of pollutants on the surface of anode followed by degradation
through electron transferring reaction. On the other hand, the indirect oxidation
process electrochemically generates strong oxidizing agents to breakdown contaminants with oxidation reactions (Zhan et al. 2001).
An important factor that defines the efficiency of electrochemical oxidation is the
type and properties of the electrode. Boron-doped diamond is known to be the most
efficient electrode materials for the electro-oxidation of wastewaters. The success of
boron-doped diamond electrode is attributed to the physicochemical stability, reliable oxidative strength, controllable adsorption, and the convenient water discharge
(Peralta-Hernández et al. 2012; Shen et al. 2006). Doped boron-doped diamond
films with boron grown on titanium plates by hot filament chemical vapor technique
were used to remove 10 from dyeing wastewater. Complete decolorization of 10 was
achieved with boron-doped diamond/Ti electrode at 100 mA cm
À2 current density.
Electrodes also showed the capacity to transform aromatic hydrocarbons into aliphatic species, which may further degrade into CO 2 (Vasconcelos et al. 2015).
Boron-doped diamond anodes were employed for galvanostatic electrolysis by
anodic oxidation of mixtures contaminated with containing Alphazurine
A. Electrolysis caused 100% color and chemical oxygen demand removal at varying
reaction parameters (Bensalah et al. 2009).
Large-scale application of the electrochemical method is hampered by the single
great disadvantage of high operational cost. Some researchers have suggested an
indirect electrochemical process using Cl
À and UV irradiation-assisted electrochemical process. Synthetic textile wastewater polluted with reactive dyes subjected to
low current density electrochemical oxidation followed by UV irradiation with Ti/Pt
17 Methods for the Treatment of Wastewaters Containing Dyes and Pigments
631