We reviewed a large number of research articles to provide a connoisseur
scientific insight based on the existing methodologies and recent advancements in
the treatment of dye-contaminated wastewaters. All physical, chemical, and biological methods show the capability to remove selective dyes; however, the mechanisms, conditions, and limitations of each procedure are different. The use of
adsorbents, nanofiltration, coagulation-flocculation, and ion-exchange methods
have gained popularity because of feasible operational measures, flexibility, low
cost, and harmless end products. Chemical, photocatalytic, and electrochemical
processes are considered equally useful but involve sludge production, causing a
secondary pollution problem. Biological methods, on the other hand, utilize microorganisms or biocatalysts for dye remediation and provide cost-competitive and
eco-friendly alternatives to other methods. Current research is focused on improving
the specificity, robustness, and scalability of individual practices as well as designing
the novel approaches based on integrated and emerging techniques.
Keywords Wastewater treatment · Pollution control · Dyes and pigments ·
Remediation · Dye degradation · Dye decolorization · Adsorption · Chemical
oxidation · Biosorption · Environment
17.1 Introduction
The intensive industrialization and rampant modern textile production facilities
coupled with inadequate wastewater treatment have enhanced the discharge of
poisonous, baleful, and carcinogenic pollutants, which include dyes and pigments
into the environment. Pigments are generally insoluble substances with no chemical
affinity to the substrate to be colored; however, dyes being soluble or partially
soluble compounds interact with the leather or fiber to impart color. The classification of various dyes is given in Fig. 17.1.
Recently, the risks of dye pollution have reached an all-time high in a multitude of
industries, especially in the textile industry. With the annual production of over
700,000 tons, industrial consumption of 10,000 types of dyes and pigments, approximately, releases about 20% as effluent at some point in textile dyeing processes
(Almeida and Corso 2019; Ogugbue and Sawidis 2011). Figure 17.2 shows structures of some prominent dyes.
Adulterated water affects human health and aquatic life severely on direct contact
with the water bodies or hydrosphere through different mutagenic and carcinogenic
effects. Toxic chemicals present in dyes and pigments show lethal effects by
damaging the reproductive system, liver, brain, and renal failure (Baskaralingam
et al. 2006).
The development of novel treatments for dyes and pigments before discharging to
safeguard our ecosystem and natural resources is crucial. Biological degradation,
598
R. S. Ashraf et al.
scientific insight based on the existing methodologies and recent advancements in
the treatment of dye-contaminated wastewaters. All physical, chemical, and biological methods show the capability to remove selective dyes; however, the mechanisms, conditions, and limitations of each procedure are different. The use of
adsorbents, nanofiltration, coagulation-flocculation, and ion-exchange methods
have gained popularity because of feasible operational measures, flexibility, low
cost, and harmless end products. Chemical, photocatalytic, and electrochemical
processes are considered equally useful but involve sludge production, causing a
secondary pollution problem. Biological methods, on the other hand, utilize microorganisms or biocatalysts for dye remediation and provide cost-competitive and
eco-friendly alternatives to other methods. Current research is focused on improving
the specificity, robustness, and scalability of individual practices as well as designing
the novel approaches based on integrated and emerging techniques.
Keywords Wastewater treatment · Pollution control · Dyes and pigments ·
Remediation · Dye degradation · Dye decolorization · Adsorption · Chemical
oxidation · Biosorption · Environment
17.1 Introduction
The intensive industrialization and rampant modern textile production facilities
coupled with inadequate wastewater treatment have enhanced the discharge of
poisonous, baleful, and carcinogenic pollutants, which include dyes and pigments
into the environment. Pigments are generally insoluble substances with no chemical
affinity to the substrate to be colored; however, dyes being soluble or partially
soluble compounds interact with the leather or fiber to impart color. The classification of various dyes is given in Fig. 17.1.
Recently, the risks of dye pollution have reached an all-time high in a multitude of
industries, especially in the textile industry. With the annual production of over
700,000 tons, industrial consumption of 10,000 types of dyes and pigments, approximately, releases about 20% as effluent at some point in textile dyeing processes
(Almeida and Corso 2019; Ogugbue and Sawidis 2011). Figure 17.2 shows structures of some prominent dyes.
Adulterated water affects human health and aquatic life severely on direct contact
with the water bodies or hydrosphere through different mutagenic and carcinogenic
effects. Toxic chemicals present in dyes and pigments show lethal effects by
damaging the reproductive system, liver, brain, and renal failure (Baskaralingam
et al. 2006).
The development of novel treatments for dyes and pigments before discharging to
safeguard our ecosystem and natural resources is crucial. Biological degradation,
598
R. S. Ashraf et al.