Another study opened the horizons of wastewater decolorization containing dyes
using MgCl 2 /red mud as an adsorbent with an efficiency of 98% against reactive
blue, acid red, and direct dye. Adsorption data was best correlated to both the
Langmuir adsorption isotherm and Freundlich adsorption isotherm models. Langmuir adsorption capacities of reactive blue, acid red, and direct dye were around
28, 9, and 23 mg g
À1 , respectively (Wang et al. 2009). Reactive Red 198 (23) was
adsorbed onto active red mud, providing 90% efficiency of dye removal at pH 2–3.
The increasing adsorbent dose and contact time lead to more removal efficiency.
Adsorption data suited well to Freundlich adsorption isotherm and Temkin isotherms (Zazouli et al. 2013b). Another study revealed significant removal efficiency
of phenol, enhanced by an increase in pH. The results showed coherence to
Freundlich adsorption isotherm model and pseudo-second-order kinetics (ShirzadSiboni et al. 2013).
Iron-zeolitic tuff and carbonaceous substances were employed to remove indigo
carmine from water, and the latter was more efficient regarding adsorption and
pH-independent nature. Adsorption data fitted to the Langmuir-Freundlich adsorption isotherm model, and kinetics was reported to be pseudo-second-order (Gutiérrez-Segura et al. 2009). The granular activated carbon based on sewage sludge was
employed to remove 1 following Langmuir adsorption isotherm model with maximum 1 adsorption amount of 132.0 mg g
À1 and the overall adsorption process as
heterogeneous, spontaneous, and endothermic with pseudo-second-order kinetics
(Liu et al. 2013b). Another study disclosed that activated carbon prepared from
sewage sludge could be efficiently applied for the removal of 4-chlorophenol, as
inexpensive, environmentally benign, and cheap adsorbent (Monsalvo et al. 2011;
Monsalvo et al. 2012).
Biochar prepared from sewage sludge was opted to remove 1 and 2, and results
conformed with Langmuir adsorption isotherm model and pseudo-second-order
kinetics with spontaneous and endothermic nature (Leng et al. 2015). Activated
carbon-based sludge derived from paper mill waste had been optimized to remove
1 from the aqueous solution (Li et al. 2011b). In another study, activated carbonbased sludge from paper mill waste was applied for adsorptive removal of 1 and 11.
Experimental data provided the q max values of 263 and 34 mg g
À1 for 1 and 11,
respectively, following Langmuir adsorption isotherm model (Li et al. 2011a, c). The
removal of 1 from palm oil effluent remediation plant by waste-activated sludge was
studied considering the reaction parameters. The adsorption data was best fit to both
the Langmuir adsorption isotherm and the Freundlich adsorption isotherm models,
and kinetics confirmed with pseudo-second-order reaction (Gobi et al. 2011; Zaini
et al. 2014).
Natural Adsorbents
Owing to high adsorption capacity, excellent selectivity, greater surface area, and
negative charge density, mesoporous silica materials have gained considerable
attention as adsorbents to remove basic dyes from wastewater (Anbia et al. 2010).
610
R. S. Ashraf et al.
using MgCl 2 /red mud as an adsorbent with an efficiency of 98% against reactive
blue, acid red, and direct dye. Adsorption data was best correlated to both the
Langmuir adsorption isotherm and Freundlich adsorption isotherm models. Langmuir adsorption capacities of reactive blue, acid red, and direct dye were around
28, 9, and 23 mg g
À1 , respectively (Wang et al. 2009). Reactive Red 198 (23) was
adsorbed onto active red mud, providing 90% efficiency of dye removal at pH 2–3.
The increasing adsorbent dose and contact time lead to more removal efficiency.
Adsorption data suited well to Freundlich adsorption isotherm and Temkin isotherms (Zazouli et al. 2013b). Another study revealed significant removal efficiency
of phenol, enhanced by an increase in pH. The results showed coherence to
Freundlich adsorption isotherm model and pseudo-second-order kinetics (ShirzadSiboni et al. 2013).
Iron-zeolitic tuff and carbonaceous substances were employed to remove indigo
carmine from water, and the latter was more efficient regarding adsorption and
pH-independent nature. Adsorption data fitted to the Langmuir-Freundlich adsorption isotherm model, and kinetics was reported to be pseudo-second-order (Gutiérrez-Segura et al. 2009). The granular activated carbon based on sewage sludge was
employed to remove 1 following Langmuir adsorption isotherm model with maximum 1 adsorption amount of 132.0 mg g
À1 and the overall adsorption process as
heterogeneous, spontaneous, and endothermic with pseudo-second-order kinetics
(Liu et al. 2013b). Another study disclosed that activated carbon prepared from
sewage sludge could be efficiently applied for the removal of 4-chlorophenol, as
inexpensive, environmentally benign, and cheap adsorbent (Monsalvo et al. 2011;
Monsalvo et al. 2012).
Biochar prepared from sewage sludge was opted to remove 1 and 2, and results
conformed with Langmuir adsorption isotherm model and pseudo-second-order
kinetics with spontaneous and endothermic nature (Leng et al. 2015). Activated
carbon-based sludge derived from paper mill waste had been optimized to remove
1 from the aqueous solution (Li et al. 2011b). In another study, activated carbonbased sludge from paper mill waste was applied for adsorptive removal of 1 and 11.
Experimental data provided the q max values of 263 and 34 mg g
À1 for 1 and 11,
respectively, following Langmuir adsorption isotherm model (Li et al. 2011a, c). The
removal of 1 from palm oil effluent remediation plant by waste-activated sludge was
studied considering the reaction parameters. The adsorption data was best fit to both
the Langmuir adsorption isotherm and the Freundlich adsorption isotherm models,
and kinetics confirmed with pseudo-second-order reaction (Gobi et al. 2011; Zaini
et al. 2014).
Natural Adsorbents
Owing to high adsorption capacity, excellent selectivity, greater surface area, and
negative charge density, mesoporous silica materials have gained considerable
attention as adsorbents to remove basic dyes from wastewater (Anbia et al. 2010).
610
R. S. Ashraf et al.