297
acids. This material is polar due to the presence of alcohols, carboxylic acids, aldehydes, ketones, phenolic hydroxides, and ether functional groups capable for chemical binding; therefore they are useful for dyes and heavy metal ions removal (Crini
2006; Crini and Badot 2011). The removal efficiency of dyes is similar for acid and
basic dyes whereas higher for dispersive ones, e.g., basic blue 9, acid blue 29, acid
red 91, and disperse red 1 sorption onto peat (Konduru and Viraraghavan 1996).
Similar observation was made by Ramakrishna and Viraraghavan (1997). Raw peat
possesses low mechanical strength, poor chemical stability, high affinity for water,
tendency to shrink, and/or swell; therefore its applicability may be limited; therefore they required the modification or activation step (Crini and Badot 2011).
Results presented by Ho and McKay (1998b), Poots et al. (1976), and Sun and Yang
(2003) show that peat modification gives better removal efficiency of dyes compared with raw peat. Ho and McKay (1998b) use peat for basic blue 69 and acid
blue 25 retention. The maximum capacity was 195 mg/g for basic blue 69 and only
12.7 mg/g for acid blue 25 and was much lower than that obtained for modified peat.
Sun and Yang (2003) applied functionalized peat (using sulfuric acid, polyvinylalcohol, formaldehyde) for basic violet 14 and basic green 4 removal and obtained
sorption capacities equal to 400 and 350 mg/g, respectively.
In recent years, there has been an intensive research concerning application of
biomass, fungi, algae, yeast, etc. for decolorization of dyes wastewaters. The use of
dead biomass seems to be more reasonable than living biomass because dead biomass not only is insensitive to toxic dyes but also does not require maintaining
sterile conditions and providing nutrients during the research (Kabbout and Taha
2014). The removal of dyes from aqueous solutions can be based on several mechanisms. Among them, chemisorption of dyes with functional groups of the cell wall
can be distinguished, which may occur as a result of ion exchange, complexation,
and chelation reactions. Moreover, physical adsorption is also possible (binding of
dyes to the biosorbent occurs due to electrostatic interactions and van der Waals
forces), oxidation, and reduction or micro-extraction reactions. The biosorption
process may also take place according to the mixed mechanism. The type and
charge of the adsorbate, composition of the external solution, as well as kind and
origin of biomass affect the binding mechanism (Crini 2006; Fu and
Viraraghavan 2001).
Many examples of above mentioned biosorbents application can be found in literature (Aksu 2005; Fu and Viraraghavan 2001; McMullan et al. 2001; Robinson
et al. 2001; Stolz 2001). Aksu (2005) presented review papers examines fungi and
living or dead cell applicability for dyes decolorization and discusses binding mechanisms and the effect of various parameters on this process. Moreover the elution
and regeneration methods for fungal biomass were summarized. Other authors presented current treatment technologies for dye decolorization, microbial degradation
of textile, and azo dyes (Aksu 2005; McMullan et al. 2001; Robinson et al. 2001;
Stolz 2001). Crini (2006) collected and compare the sorption capacities of different
biosorbents among other activated sludge biomass, yeasts, Chlorella vulgaris,
Rhizopus arrhizus, Spirodela polyrhiza biomass, dead fungus Aspergillus niger,
modified fungal biomass, and living biomass which was compered in Fig. 11.8.
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes
acids. This material is polar due to the presence of alcohols, carboxylic acids, aldehydes, ketones, phenolic hydroxides, and ether functional groups capable for chemical binding; therefore they are useful for dyes and heavy metal ions removal (Crini
2006; Crini and Badot 2011). The removal efficiency of dyes is similar for acid and
basic dyes whereas higher for dispersive ones, e.g., basic blue 9, acid blue 29, acid
red 91, and disperse red 1 sorption onto peat (Konduru and Viraraghavan 1996).
Similar observation was made by Ramakrishna and Viraraghavan (1997). Raw peat
possesses low mechanical strength, poor chemical stability, high affinity for water,
tendency to shrink, and/or swell; therefore its applicability may be limited; therefore they required the modification or activation step (Crini and Badot 2011).
Results presented by Ho and McKay (1998b), Poots et al. (1976), and Sun and Yang
(2003) show that peat modification gives better removal efficiency of dyes compared with raw peat. Ho and McKay (1998b) use peat for basic blue 69 and acid
blue 25 retention. The maximum capacity was 195 mg/g for basic blue 69 and only
12.7 mg/g for acid blue 25 and was much lower than that obtained for modified peat.
Sun and Yang (2003) applied functionalized peat (using sulfuric acid, polyvinylalcohol, formaldehyde) for basic violet 14 and basic green 4 removal and obtained
sorption capacities equal to 400 and 350 mg/g, respectively.
In recent years, there has been an intensive research concerning application of
biomass, fungi, algae, yeast, etc. for decolorization of dyes wastewaters. The use of
dead biomass seems to be more reasonable than living biomass because dead biomass not only is insensitive to toxic dyes but also does not require maintaining
sterile conditions and providing nutrients during the research (Kabbout and Taha
2014). The removal of dyes from aqueous solutions can be based on several mechanisms. Among them, chemisorption of dyes with functional groups of the cell wall
can be distinguished, which may occur as a result of ion exchange, complexation,
and chelation reactions. Moreover, physical adsorption is also possible (binding of
dyes to the biosorbent occurs due to electrostatic interactions and van der Waals
forces), oxidation, and reduction or micro-extraction reactions. The biosorption
process may also take place according to the mixed mechanism. The type and
charge of the adsorbate, composition of the external solution, as well as kind and
origin of biomass affect the binding mechanism (Crini 2006; Fu and
Viraraghavan 2001).
Many examples of above mentioned biosorbents application can be found in literature (Aksu 2005; Fu and Viraraghavan 2001; McMullan et al. 2001; Robinson
et al. 2001; Stolz 2001). Aksu (2005) presented review papers examines fungi and
living or dead cell applicability for dyes decolorization and discusses binding mechanisms and the effect of various parameters on this process. Moreover the elution
and regeneration methods for fungal biomass were summarized. Other authors presented current treatment technologies for dye decolorization, microbial degradation
of textile, and azo dyes (Aksu 2005; McMullan et al. 2001; Robinson et al. 2001;
Stolz 2001). Crini (2006) collected and compare the sorption capacities of different
biosorbents among other activated sludge biomass, yeasts, Chlorella vulgaris,
Rhizopus arrhizus, Spirodela polyrhiza biomass, dead fungus Aspergillus niger,
modified fungal biomass, and living biomass which was compered in Fig. 11.8.
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes