application of more than a single advanced technique has been presented. For
effective and efficient treatment of wastewater, different hybrid techniques have
been employed, and the degree of mineralization was estimated. Under the sonohybrid technique, more than 90% of degradation was obtained within 30 min of
treatment in most of the homogeneous hybrid techniques. However, the maximum
total organic carbon removal of 68.4% was achieved with the sono-persulfate
oxidation process.
Keywords Wastewater treatment · Degradation · Advanced oxidation processes ·
Fenton · Photolysis · Photocatalysis · Ferrioxalate · Sonolysis · Ultrasound ·
Cavitation
6.1 Introduction
The growing industrialization and urbanization is increasing the environmental
sustainability issues, especially water contamination and scarcity. Water is one of
the most substantial components of our daily life. But the percentage of potable
water is very less though the world is covered with 70% of water. On the other hand,
water discharged from various process industries such as pharmaceutical industries,
chemical industries, and textile industries contain numerous toxic and hazardous
recalcitrant organic molecules. These molecules are difficult to degrade using biological techniques or conventional methods such as adsorption, membrane separation, etc. which are being used in most of the wastewater treatment plants (Poyatos
et al. 2010). In order to address these issues, many advanced techniques have been
developed. However, advanced oxidation processes have been found to be promising techniques for effective degradation or mineralization of the toxic or hazardous
molecules present in the wastewater (Andreozzi et al. 1999; Chakma and Moholkar
2015a; Bagal and Gogate 2014a). The working principle of all the advanced
oxidation processes is to produce the energetic
• OH radicals which have 2.8 eV
oxidation potential. These
•
OH radicals react with the recalcitrant pollutant molecules present in the wastewater and produce complete mineralization of the recalcitrant pollutants through converting them into CO 2 , H 2 O, or other inorganic
compounds. Sometimes the organic molecules are difficult to degrade due to formation of chelate (Giri and Golder 2014). In that case, advanced oxidation processes
at least transform them into innocuous products. On the basis of phases in the
reaction system, advanced oxidation processes can be categorized into two,
(i) homogeneous and (ii) heterogeneous, as shown in Fig. 6.1 (Poyatos et al.
2010). The widely used homogeneous advanced oxidation processes for wastewater
treatment are Fenton reaction, photolysis, photo-ferrioxalate, ozonation, and
persulfate oxidation process. The conventional heterogeneous advanced oxidation
processes for wastewater treatment include photocatalysis, catalytic ozonation, and
190
S. Chakma et al.
effective and efficient treatment of wastewater, different hybrid techniques have
been employed, and the degree of mineralization was estimated. Under the sonohybrid technique, more than 90% of degradation was obtained within 30 min of
treatment in most of the homogeneous hybrid techniques. However, the maximum
total organic carbon removal of 68.4% was achieved with the sono-persulfate
oxidation process.
Keywords Wastewater treatment · Degradation · Advanced oxidation processes ·
Fenton · Photolysis · Photocatalysis · Ferrioxalate · Sonolysis · Ultrasound ·
Cavitation
6.1 Introduction
The growing industrialization and urbanization is increasing the environmental
sustainability issues, especially water contamination and scarcity. Water is one of
the most substantial components of our daily life. But the percentage of potable
water is very less though the world is covered with 70% of water. On the other hand,
water discharged from various process industries such as pharmaceutical industries,
chemical industries, and textile industries contain numerous toxic and hazardous
recalcitrant organic molecules. These molecules are difficult to degrade using biological techniques or conventional methods such as adsorption, membrane separation, etc. which are being used in most of the wastewater treatment plants (Poyatos
et al. 2010). In order to address these issues, many advanced techniques have been
developed. However, advanced oxidation processes have been found to be promising techniques for effective degradation or mineralization of the toxic or hazardous
molecules present in the wastewater (Andreozzi et al. 1999; Chakma and Moholkar
2015a; Bagal and Gogate 2014a). The working principle of all the advanced
oxidation processes is to produce the energetic
• OH radicals which have 2.8 eV
oxidation potential. These
•
OH radicals react with the recalcitrant pollutant molecules present in the wastewater and produce complete mineralization of the recalcitrant pollutants through converting them into CO 2 , H 2 O, or other inorganic
compounds. Sometimes the organic molecules are difficult to degrade due to formation of chelate (Giri and Golder 2014). In that case, advanced oxidation processes
at least transform them into innocuous products. On the basis of phases in the
reaction system, advanced oxidation processes can be categorized into two,
(i) homogeneous and (ii) heterogeneous, as shown in Fig. 6.1 (Poyatos et al.
2010). The widely used homogeneous advanced oxidation processes for wastewater
treatment are Fenton reaction, photolysis, photo-ferrioxalate, ozonation, and
persulfate oxidation process. The conventional heterogeneous advanced oxidation
processes for wastewater treatment include photocatalysis, catalytic ozonation, and
190
S. Chakma et al.