291
particle size, porosity, and surface area makes it a potential adsorbent for dye
removal (Ahmaruzzaman 2011; Yagub et al. 2014). Red mud is obtained in the alumina production process during the bauxite processing (Yagub et al. 2014).
Namasivayam and Sumithra (2005) applied Fe(III)/Cr(III) hydroxide (particle
size 250–500 μm) for direct red 12B and methylene blue removal at different phases
contact time, adsorbent dose, dye concentration before sorption, and pH. Equilibrium
and kinetic sorption of dyes followed the Langmuir and Freundlich models and
pseudo second-order model, respectively. The maximum sorption capacity for
direct red 12B was equal to 5.0 mg/g and for methylene blue 22.8 mg/g, and the
acidic pH was chosen as favorable for direct red 12B, whereas the alkaline one for
methylene blue. The authors pointed out that chemisorption could play a main role
in the adsorption process (percentage desorption of dyes was below 10.0
(pH = 3.0–10.0, the dye concentrations 10 and 20 mg/L)).
Metal hydroxide sludge sorptive properties and mechanism of sorption for the
azo-reactive dyes such as reactive red 2, reactive red 120, and reactive red 141 containing sulfonic groups from aqueous solution were examined by Netpradit et al.
(2003). As it was proved the solution pH influences the sorption process of the
abovementioned dyes, and the pH = 8–9 was selected as optimal (at pH = 2 precipitation of dye–metal complexes occurred). The sorption capacity of the metal
hydroxide sludge for the azo dyes was in the range from 48 to 62 mg/g and the sorption process proceeded according to the ion-exchange mechanism. Moreover, sorption of reactive red 120, reactive red 141, and reactive red 2 is temperature dependent;
the sorption capacities decreased with the increasing temperature (reactive red 2) or
increase with the increasing temperature (reactive red 120, reactive red 141)
(Netpradit et al. 2004). The adsorption of reactive red 2 was mainly physical,
whereas it was chemical for more charged dyes (reactive red 120 and reactive red
141). Adsorption efficiency decreased with electrolyte concentration or valence
increase.
The calcium-rich fly ash was utilized for the Congo red sorption. It was observed
that with the concentration and temperature increase, the amount of dye adsorbed
also increases or negligibly decreases with the increasing pH. The sorption efficiency was from 93% to 98%, whereas the percentage desorption was equal to
29.18% using 0.1 mol/L HCl and 47.21% using 50% v/v CH 3 COOH. The pseudo
second-order model and Freundlich and Dubinin–Radushkevich ones show the best
experimental results fitting (Acemiǒglu 2004).
The bagasse fly ash was applied for Congo red removal from aqueous solutions.
The optimal pH 0 was 7.0, the dosage was 1 g/L, and the system reached equilibrium
after 4 h. The pseudo second-order and the Redlich–Peterson isotherm models well
describe the sorption data (Mall et al. 2005).
Ahmaruzzaman (2010) presented the review paper concerning the utilization of
fly ash in which many examples of various fly ash types applied for such dyes such
as methylene blue, crystal violet, rhodamine B, acid blue 9, acid blue 29, acid blue
91, etc. removal could be found.
Wang et al. (2005) used the fly ash as well as the red mud for methylene blue
removal and shows that the fly ash usually possesses bigger sorption capacity for
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes
particle size, porosity, and surface area makes it a potential adsorbent for dye
removal (Ahmaruzzaman 2011; Yagub et al. 2014). Red mud is obtained in the alumina production process during the bauxite processing (Yagub et al. 2014).
Namasivayam and Sumithra (2005) applied Fe(III)/Cr(III) hydroxide (particle
size 250–500 μm) for direct red 12B and methylene blue removal at different phases
contact time, adsorbent dose, dye concentration before sorption, and pH. Equilibrium
and kinetic sorption of dyes followed the Langmuir and Freundlich models and
pseudo second-order model, respectively. The maximum sorption capacity for
direct red 12B was equal to 5.0 mg/g and for methylene blue 22.8 mg/g, and the
acidic pH was chosen as favorable for direct red 12B, whereas the alkaline one for
methylene blue. The authors pointed out that chemisorption could play a main role
in the adsorption process (percentage desorption of dyes was below 10.0
(pH = 3.0–10.0, the dye concentrations 10 and 20 mg/L)).
Metal hydroxide sludge sorptive properties and mechanism of sorption for the
azo-reactive dyes such as reactive red 2, reactive red 120, and reactive red 141 containing sulfonic groups from aqueous solution were examined by Netpradit et al.
(2003). As it was proved the solution pH influences the sorption process of the
abovementioned dyes, and the pH = 8–9 was selected as optimal (at pH = 2 precipitation of dye–metal complexes occurred). The sorption capacity of the metal
hydroxide sludge for the azo dyes was in the range from 48 to 62 mg/g and the sorption process proceeded according to the ion-exchange mechanism. Moreover, sorption of reactive red 120, reactive red 141, and reactive red 2 is temperature dependent;
the sorption capacities decreased with the increasing temperature (reactive red 2) or
increase with the increasing temperature (reactive red 120, reactive red 141)
(Netpradit et al. 2004). The adsorption of reactive red 2 was mainly physical,
whereas it was chemical for more charged dyes (reactive red 120 and reactive red
141). Adsorption efficiency decreased with electrolyte concentration or valence
increase.
The calcium-rich fly ash was utilized for the Congo red sorption. It was observed
that with the concentration and temperature increase, the amount of dye adsorbed
also increases or negligibly decreases with the increasing pH. The sorption efficiency was from 93% to 98%, whereas the percentage desorption was equal to
29.18% using 0.1 mol/L HCl and 47.21% using 50% v/v CH 3 COOH. The pseudo
second-order model and Freundlich and Dubinin–Radushkevich ones show the best
experimental results fitting (Acemiǒglu 2004).
The bagasse fly ash was applied for Congo red removal from aqueous solutions.
The optimal pH 0 was 7.0, the dosage was 1 g/L, and the system reached equilibrium
after 4 h. The pseudo second-order and the Redlich–Peterson isotherm models well
describe the sorption data (Mall et al. 2005).
Ahmaruzzaman (2010) presented the review paper concerning the utilization of
fly ash in which many examples of various fly ash types applied for such dyes such
as methylene blue, crystal violet, rhodamine B, acid blue 9, acid blue 29, acid blue
91, etc. removal could be found.
Wang et al. (2005) used the fly ash as well as the red mud for methylene blue
removal and shows that the fly ash usually possesses bigger sorption capacity for
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes