Abstract Owing to the stability and resistance to biodegradation of synthetic dyes,
their elimination from industrial wastewater is a very difficult task. This problem has
triggered environmental engineers and scientists to search for innovative solutions.
Over the last two decades, considerable attention has been paid to the use of
ultrasound as an alternative advanced oxidation process for the degradation of textile
dyes in wastewater. This process offers effective destruction of contaminants via
reaction with
●
OH radical or pyrolysis in different reaction zones.
In this chapter, we reviewed the major progresses in the application of ultrasound,
i.e., sonochemical process, for the destruction of textile dyes in aqueous solutions:
(i) principles of the sonochemical process and sonoreactors were given, (ii) the most
interesting works conducted in the field were summarized together with their
significant findings, (iii) the influence of sonochemical and environmental parameters on the process performance was discussed in depth, (iv) the impact of the water
matrix on the sonochemical treatment of dyes was elucidated, and (v) the most recent
intensification techniques of the sonochemical process were emphasized. Finally,
some interesting trends and perspectives were reported together with some highlighting needs to innovation.
Keywords Industrial wastewater · Synthetic dyes · Advanced oxidation processes ·
Ultrasound · Sonoreactors · Hydroxyl radical · Process intensification
5.1 Introduction
Among different industrial sectors, the textile industry is one of the largest water
consumers and produces about 50–100 L wastewater per kg of finished product
(Arslan-Alaton et al. 2008). Estimates indicate that approximately 280,000 tons of
the textile dyes are released in water basins through textile effluents (Asghar et al.
2015). These compounds are chemically stable and non-biodegradable and exist as
substances that may provoke toxic and carcinogenic effects (Brown and De Vito
1993; Konstantinou and Albanis 2004). Additionally, dye effluent damages the
aesthetics of receiving waters and hinders the penetration of oxygen provoking an
effective perturbation of the aquatic life (Eren 2012). Therefore, the treatment of
textile dyes in wastewater has received great care from the researchers.
Conventional treatment processes for textile wastewater usually involve physical
and biological methods. Physical methods, i.e., precipitation, adsorption on activated
carbon, coagulation–flocculation, and reverse osmosis, are mostly nondestructive
and only transfer pollutants into other phases that require secondary treatment.
Biological processes are in general slow, generate large amounts of sludge, and do
not degrade the organic load to a suitable level (Konstantinou and Albanis 2004).
Facing this situation, advanced oxidation processes have been proposed to
suppress the drawbacks of the conventional treatment techniques. These innovative
148
S. Merouani and O. Hamdaoui
their elimination from industrial wastewater is a very difficult task. This problem has
triggered environmental engineers and scientists to search for innovative solutions.
Over the last two decades, considerable attention has been paid to the use of
ultrasound as an alternative advanced oxidation process for the degradation of textile
dyes in wastewater. This process offers effective destruction of contaminants via
reaction with
●
OH radical or pyrolysis in different reaction zones.
In this chapter, we reviewed the major progresses in the application of ultrasound,
i.e., sonochemical process, for the destruction of textile dyes in aqueous solutions:
(i) principles of the sonochemical process and sonoreactors were given, (ii) the most
interesting works conducted in the field were summarized together with their
significant findings, (iii) the influence of sonochemical and environmental parameters on the process performance was discussed in depth, (iv) the impact of the water
matrix on the sonochemical treatment of dyes was elucidated, and (v) the most recent
intensification techniques of the sonochemical process were emphasized. Finally,
some interesting trends and perspectives were reported together with some highlighting needs to innovation.
Keywords Industrial wastewater · Synthetic dyes · Advanced oxidation processes ·
Ultrasound · Sonoreactors · Hydroxyl radical · Process intensification
5.1 Introduction
Among different industrial sectors, the textile industry is one of the largest water
consumers and produces about 50–100 L wastewater per kg of finished product
(Arslan-Alaton et al. 2008). Estimates indicate that approximately 280,000 tons of
the textile dyes are released in water basins through textile effluents (Asghar et al.
2015). These compounds are chemically stable and non-biodegradable and exist as
substances that may provoke toxic and carcinogenic effects (Brown and De Vito
1993; Konstantinou and Albanis 2004). Additionally, dye effluent damages the
aesthetics of receiving waters and hinders the penetration of oxygen provoking an
effective perturbation of the aquatic life (Eren 2012). Therefore, the treatment of
textile dyes in wastewater has received great care from the researchers.
Conventional treatment processes for textile wastewater usually involve physical
and biological methods. Physical methods, i.e., precipitation, adsorption on activated
carbon, coagulation–flocculation, and reverse osmosis, are mostly nondestructive
and only transfer pollutants into other phases that require secondary treatment.
Biological processes are in general slow, generate large amounts of sludge, and do
not degrade the organic load to a suitable level (Konstantinou and Albanis 2004).
Facing this situation, advanced oxidation processes have been proposed to
suppress the drawbacks of the conventional treatment techniques. These innovative
148
S. Merouani and O. Hamdaoui