Adsorption Mechanism of Methylene Blue by Graphene Oxide-Shielded Mg–Al-Layered Double Hydroxide From Synthetic Wastewater

Abstract

Pollution of water resources by various pollutants is a global environmental issue, particularly, dye pollution has a major contribution to it. From various studies, it is confirmed that adsorption is an excellent remediation technique compared to others. Mg−Allayered double hydroxides (LDHs) intercalated with NO 3 − ions act as an effective adsorbent-removing ionic species like heavy metal and dyes. Another popular nanomaterial is graphene oxide (GO), which is successfully used as an adsorbent for different pollutants like dye and heavy metal ions. It is prepared based on the modified Hummers method. In this study, GO was introduced on the surface of LDH to improve its adsorption capacity. The adsorption process is well described by the Freundlich model. The maximum adsorption capacity was obtained at around 0.5 and 0.85 mmol of methylene blue (MB) per gram of Mg−Al LDH and modified Mg−Al LDH with GO, respectively. The reaction kinetics of MB with both adsorbents is determined to be the pseudo-second-order. To get more insights of the mechanism, molecular dynamics (MD) simulation was conducted among the modified Mg−Al LDH with GO and MB molecules at both low-and high-concentration environments, which demonstrated that the developed composite adsorbs MB molecules predominantly onto its GO surface and then the MB molecules are adsorbed by the LDH surface. C−H•••O (2.49−3.04 Å) and pi-donor•••H−O (2.45−3.05 Å) are the major driving forces behind the strong adsorbability. Besides, S•••H−O, S•••O,N•••O−H, pi•••lone pair, pi•••sigma, pi•••cation, and alkyl•••hydrophobic interactions play important roles in stabilizing the MB molecules onto the surface of the composite.

Removal of anionic and cationic dyes using porous copolymer networks made from a Sonogashira cross‐coupling reaction of diethynyl iron (II) clathrochelate with various arylamines

“…Therefore, the Langmuir isotherm is apparently a more favorable model to describe the equilibrium data, thus, suggesting a homogenous adsorption and formation of MEB and CR monolayers on the adsorbate CLA4 . Furthermore, the maximum adsorption capacity (q m ) derived from the Langmuir model for MEB and CR was found to be 146.63 and 787.40 mg g −1 , respectively, and to the best of our knowledge, these results are either superior or equivalent to adsorption capacity values for several materials reported in the literature 2,3,52–55 …”

“…On the other hand, the linear equation below was employed for Freundlich isotherm model: where q e (mg g −1 ) denotes the equilibrium adsorption capacity, C e (mg L −1 ) represents the equilibrium dye concentration, and q m (mg g −1 ) indicates the maximum adsorption capacity. K L is the Langmuir constant whereas K F and n are Freundlich constants correlated to the sorption capacity and sorption intensity, respectively 52 …”

“…K L is the Langmuir constant whereas K F and n are Freundlich constants correlated to the sorption capacity and sorption intensity, respectively. 52 Figure 8 below discloses the Langmuir parameters which were obtained by plotting 1/q e versus 1/C e and those for Freundlich which were derived from the plot of log q e versus log C e . Both models were used to fit the equilibrium data obtained for MEB and CR adsorption (Table 2).…”

High Uptake of the Carcinogenic Pararosaniline Hydrochloride Dye from Water Using Carbazole-Containing Conjugated Copolymers Synthesized from a One-Pot Cyclopentannulation Reaction

“…Similarly, the equation below expresses the pseudo -second order model: italict / italicq normalt = italict / italicq normale + 1 / italick 2 italicq normale 2 Where q e (mg g –1 ) is the adsorption capacity at equilibrium, whereas q t (mg g –1 ) is the adsorption capacity at time t (min). k 1 and k 2 represent the rate constants of the pseudo first- and pseudo second- order models, repectively …”

Recent advances on the removal of dyes from wastewater using various adsorbents: a critical review

“…10. FE-SEM image of GO-NiFe LDH [Reprinted with permission from reference ; Copyright 2019 Elseveir].Further, GO-based nanocomposites are reported for dye removal like porous core-shell graphene/SiO 2 nanocomposites for the removal of cationic neutral red dye , whereas GOshielded Mg-Al-LDH185 , Au nanorod-doped Cu 2 O core-shell nanocube-embedded rGO composite186 , and GO fabricated Fe-Al bimetal oxide composite187 , for MB removal. Several other GO-based nanocomposites have also been reported to adsorb various classes of dyes, for example, removal of MB using impregnated graphene into porous wood filters188 , Fe 3 O 4 /GO composite 189 , Fe 3 O 4 nanoparticles functionalized GO/g-C 3 N 4 nanocomposite 190 , and metal ferrite-enabled GO 191 , and PANI-GO-Fe 3 O 4 hybrid nanocomposite 192 for the removal of CR and MO.…”