Novel Carbon-Based Nanoadsorbents for Removal of Synthetic Textile Dyes from Wastewaters - Green Chemistry for Dyes Removal from Wastewater - page 73

been studied by Fan et al. [142]. In this case, as much as 84.32 mg g -1 of
Methylene Blue could be adsorbed as determined by the Langmuir model.
The possibility of using GO/calcium alginate (GO/CA) composite as an
adsorbent for the removal of Methylene Blue from its aqueous solution has
recently been explored by Li et al. [143]. The optimum pH for dye removal
was found to be in the range of 4.5 to 10.2. The adsorption capacity decreased
from 163.93 to 140.85 mg g -1 with an increase in temperature from 298 to
328 K, indicating the exothermic nature of the adsorption process. A maxi-
mum adsorption capacity of 181.81 mg g -1 for an adsorbent dose of 0.05 g
per 100 mL dye solution was recorded. The adsorption kinetic data could be
best described by the pseudo-second-order rate equation.
RGO-based nanocomposites have also been developed and investigated
for their dye removal potential. Sun et al. [144] prepared magnetite/RGO
(MRGO) nanocomposites for the removal of Rhodamine B and Malachite
Green dyes from aqueous solutions. The MRGO nanocomposite exhibited
excellent dye removal efficiency, with over 91% of Rhodamine B and over
94% of Malachite Green being removed within 2 h of dye-MRGO contact
at room temperature. Desorption studies showed that by using an inexpen-
sive eluent such as ethylene glycol, MRGO could be subjected to multiple
rounds of recycle and reuse without any significant change in its adsorp-
tion efficiency. In order to further evaluate the practical applicability of
the prepared adsorbent material, real water samples, including local indus-
trial wastewater and lake water collected from Lake Tai in China, were first
contaminated with dyes and then treated using the as-prepared MRGO.
It was found that real water samples had little interference with the decol-
orization efficiency of MRGO. In addition, MRGO also showed excellent
removal efficiency for other dye pollutants including Crystal Violet and
Methylene Blue from industrial wastewater. Nguyen-Phan et al. [146] fab-
ricated RGO-titanate (RGO-Ti) hybrids by incorporating spherical TiO 2
nanoparticles within GO layers in the presence of NaOH, followed by
solvothermal treatment. The adsorption characteristic of Methylene Blue
onto the RGO-Ti hybrids was then investigated. The equilibrium adsorp-
tion capacity was reported as 83.26 mg g -1 and the kinetics of adsorption
indicated the process to be chemisorption.

2.4 Mechanism of Dye Adsorption onto

Carbon-Based Nanoadsorbents

Based on experimental evidence, several factors have been identified to
affect the overall efficiency of CBNAs. These include the size of adsor-
bent and adsorbate, charge of the adsorbate and adsorbent surface,