Novel Carbon-Based Nanoadsorbents for Removal of Synthetic Textile Dyes from Wastewaters - Green Chemistry for Dyes Removal from Wastewater - page 59

adsorption capacity of 66.09 mg g -1 at 297 K. The results from thermody-
namic studies indicated that the adsorption was feasible, spontaneous and
exothermic in nature.
Yu and Fugetsu [113] developed a novel nanoadsorbent by insert-
ing MWCNTs into the cavities of dolomite for scavenging of Ethidium
Bromide, Acridine Orange, Methylene Blue, Eosin B, and Eosin Y dyes
from wastewater. Polyurethane polymer was used as binder to produce the
foam line MWCNTs/dolomite adsorbent. The adsorption process reached
equilibrium within 30 min for the cationic dyes Acridine Orange, Ethidium
Bromide, and Methylene Blue, while it was about 60 min for the anionic
dyes, Eosin B and Eosin Y. The Langmuir adsorption isotherm model best
fitted to the experimental equilibrium data. To evaluate the possibility of
regeneration of the dye-saturated adsorbent, desorption experiments were
carried out using used ethanol/water (50/50) solution in an ultrasonic gen-
erator. After three adsorption/regeneration cycles, the dye uptake capacity
of the ternary composite remained unchanged.
Recently, Konikci et al. [110] used magnetic MWCNT-Fe 3 C nano-
composite (MMWCNTs-Fe 3 C) as an adsorbent for the removal of Direct
Red 23 from aqueous solution. The effects of various parameters such as
initial dye concentration (9-54 mg L -1 ), solution pH (3.7-11.1) and tem-
perature (293-333 K) were investigated through batch adsorption studies.
The adsorption kinetics followed the pseudo-second-order model, while
a thermodynamic assessment indicated the endothermic and sponta-
neous nature of adsorption of Direct Red 23 on MMWCNTs-Fe 3 C. he
Freundlich isotherm model showed a good fit to the experimental equilib-
rium data, implying that adsorption of Direct Red 23 on MMWCNTs-Fe 3 C
was multilayer and applicable to heterogeneous surfaces. More recently,
Konikci et al. [111] studied the adsorption of Acid Red 88 by MMWCNTs-
Fe 3 C composites. Although quite similar results were obtained, the adsorp-
tion of Acid Red 88 onto MMWCNTs was found to be spontaneous and
exothermic in nature.

2.3.2 Adsorption by Graphene and Its Related Materials

In recent years, graphene and its related materials, including GO and RGO,
as well as their nanocomposites, have all been widely examined as a prom-
ising class of adsorbents for removal of synthetic dyes from aqueous envi-
ronments (Table 2.3). Without going into too much detail, some of the
latest important results on the dye adsorption characteristics of graphene
materials are discussed in the following sections.