293
modification or activation, e.g., bentonite (Alexander et al. 2019; Crini and Badot
2011; Shichi and Katsuhiko 2000).
Many researchers, e.g., Alexander et al. (2019), Crini (2006), Raval et al. (2016),
and Yagub et al. (2014), show comparison of various clays ability for reactive, acid,
basic dyes removal. Hu et al. (2017) reported basic red 2 removal using bentonite.
The authors pointed out that the main dye sorption mechanism is cation exchange.
The sorption kinetics was very fast, after 2–3 min of phase contact time the adsorption yield was about 80–90%, and the adsorption capacity depends on pH of solutions (increases with pH of solutions increase). Alshammari (2014) applied Saudi
bentonite clay for acid dye 25 removal from aqueous phase. The adsorption capacity
was 12.7 mg/g and diffusion was a major rate controlling step. Congo red removal
on unmodified bentonite as well as surfactant modified bentonite was presented by
Aki et al. (2013). Better sorption efficiency was obtained for modified bentonite
(adsorption capacity 210 mg/g) than for unmodified (sorption capacity 37 mg/g).
The adsorption efficiency increases with the initial dye concentration, bentonite
mass, temperature, and pH of solutions (pH from 5 to 9). The system reached equilibrium after 120 min, and the adsorption of dye onto modified bentonite is endothermic and spontaneous in nature. Al-Asheh et al. (2003) reported the results of
methylene blue adsorption on unmodified and modified bentonite (modification
using anionic surfactant – sodium dodecyl sulfate or thermal treatment at 850 °C
bentonite). The methylene blue removal selectivity series was as follows: thermaltreated bentonite > modified bentonite using sodium dodecyl sulfate > natural bentonite. The adsorption capacity increases with temperature. High efficiency of
reactive red 223 adsorption using acid modified bentonite (95.15%) and desorption
efficiency 78% by alkaline solution was obtained by Tahir et al. (2013). The hexadecyltrimethylammonium bromide-modified bentonite was applied by FossoKankeu et al. (2015) for tartrazine and brilliant blue sorption. Impregnation of
bentonite ensures removal of anionic dyes (sorption capacity 24 mg/g) compare to
unmodified bentonite (incapable for anionic dyes removal). Kyzioł-Komosińska et
al. (2014) applied thermal treated and chemically modified smectite clays for the
adsorption of reactive blue 81 and direct blue 74 dyes. At pH above point of zero
charge-modified smectite surface is negatively charged; therefore the electrostatic
interaction between the molecules of anionic dye and the surface of clay is inherit,
and the dye sorption is possible due to the hydrogen bonds formation. Montmorillonite
was applied for the removal of methyl red from aqueous solution. The sorption
capacity was equal to 30.84 mg/g after 30 min. The sorption of methyl red on montmorillonite can be depicted by the pseudo second-order and Freundlich models
(Mohammadi et al. 2017).
Siliceous materials (available, abundant, and low-cost inorganic materials)
include silica beads, perlite, glasses, alunite, dolomite, etc., and among these group
silica beads deserve particular attention due to its chemical reactivity, hydrophilic
surface, and presence of among others silanol groups. Moreover its porous structure, mechanical stability, and high surface area make them very good materials for
dyes wastewaters treatment. Other advantages of siliceous materials are availability
in many countries, e.g., perlite (amorphous siliceous mineral), not necessary of
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes
modification or activation, e.g., bentonite (Alexander et al. 2019; Crini and Badot
2011; Shichi and Katsuhiko 2000).
Many researchers, e.g., Alexander et al. (2019), Crini (2006), Raval et al. (2016),
and Yagub et al. (2014), show comparison of various clays ability for reactive, acid,
basic dyes removal. Hu et al. (2017) reported basic red 2 removal using bentonite.
The authors pointed out that the main dye sorption mechanism is cation exchange.
The sorption kinetics was very fast, after 2–3 min of phase contact time the adsorption yield was about 80–90%, and the adsorption capacity depends on pH of solutions (increases with pH of solutions increase). Alshammari (2014) applied Saudi
bentonite clay for acid dye 25 removal from aqueous phase. The adsorption capacity
was 12.7 mg/g and diffusion was a major rate controlling step. Congo red removal
on unmodified bentonite as well as surfactant modified bentonite was presented by
Aki et al. (2013). Better sorption efficiency was obtained for modified bentonite
(adsorption capacity 210 mg/g) than for unmodified (sorption capacity 37 mg/g).
The adsorption efficiency increases with the initial dye concentration, bentonite
mass, temperature, and pH of solutions (pH from 5 to 9). The system reached equilibrium after 120 min, and the adsorption of dye onto modified bentonite is endothermic and spontaneous in nature. Al-Asheh et al. (2003) reported the results of
methylene blue adsorption on unmodified and modified bentonite (modification
using anionic surfactant – sodium dodecyl sulfate or thermal treatment at 850 °C
bentonite). The methylene blue removal selectivity series was as follows: thermaltreated bentonite > modified bentonite using sodium dodecyl sulfate > natural bentonite. The adsorption capacity increases with temperature. High efficiency of
reactive red 223 adsorption using acid modified bentonite (95.15%) and desorption
efficiency 78% by alkaline solution was obtained by Tahir et al. (2013). The hexadecyltrimethylammonium bromide-modified bentonite was applied by FossoKankeu et al. (2015) for tartrazine and brilliant blue sorption. Impregnation of
bentonite ensures removal of anionic dyes (sorption capacity 24 mg/g) compare to
unmodified bentonite (incapable for anionic dyes removal). Kyzioł-Komosińska et
al. (2014) applied thermal treated and chemically modified smectite clays for the
adsorption of reactive blue 81 and direct blue 74 dyes. At pH above point of zero
charge-modified smectite surface is negatively charged; therefore the electrostatic
interaction between the molecules of anionic dye and the surface of clay is inherit,
and the dye sorption is possible due to the hydrogen bonds formation. Montmorillonite
was applied for the removal of methyl red from aqueous solution. The sorption
capacity was equal to 30.84 mg/g after 30 min. The sorption of methyl red on montmorillonite can be depicted by the pseudo second-order and Freundlich models
(Mohammadi et al. 2017).
Siliceous materials (available, abundant, and low-cost inorganic materials)
include silica beads, perlite, glasses, alunite, dolomite, etc., and among these group
silica beads deserve particular attention due to its chemical reactivity, hydrophilic
surface, and presence of among others silanol groups. Moreover its porous structure, mechanical stability, and high surface area make them very good materials for
dyes wastewaters treatment. Other advantages of siliceous materials are availability
in many countries, e.g., perlite (amorphous siliceous mineral), not necessary of
11 Characteristics and Adsorptive Treatment of Wastewaters Containing Dyes