Kinetics, Isotherm, Thermodynamics, and Recyclability of Exfoliated Graphene-Decorated MnFe₂O₄ Nanocomposite Towards Congo Red Dye

Abstract

Herein, we described the use of exfoliated graphene- (EG-) decorated magnetic MnFe2O4 nanocomposite (EG@MnFe2O4) for the removal and adsorption of Congo red (CR) dye from wastewater. Firstly, the precursors (EG, MnFe2O4) and EG@MnFe2O4 were fabricated, characterized using several physical analytical techniques such as X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), and N2adsorption/desorption isotherm measurement. For the adsorption experiments, the effect of contact time (0–240 min), concentration (10–60 mg/L), solution pH (2–10), adsorbent dosage (0.03–0.07 g), and temperature (283–313 K) was rigorously studied. To elucidate the adsorption mechanism and behaviour of CR over EG@MnFe2O4 and MnFe2O4 adsorbents, the kinetic models (pseudo-first-order, pseudo-second-order, Elovich, and Bangham) and isotherm models (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) have been adopted. The kinetic results indicated that models adhered to the pseudo-second-order equation, exhibiting the chemisorption mechanism in heterogeneous phrase. Meanwhile, the isotherm results revealed the adsorption of CR over EG@MnFe2O4 obeyed the monolayer behaviour (Langmuir model) rather than multilayer behaviour (Freundlich equation) over MnFe2O4. The thermodynamic study also suggested that such adsorption was an endothermic and spontaneous process. With high maximum adsorption capacity (71.79 mg/g) and good recyclability (at least 4 times), EG@MnFe2O4 can be a potential alternative for the adsorptive removal of CR dye from water.

Synthesis of polyamino styrene from post-consumption expanded polystyrene and analysis of its CO2 scavenger capacity

“…The data obtained presented a relative uncertainty of 0.05%. The plot shows a linear behavior against the change of pressure, suggesting a weak interaction between adsorbent-adsorbate system (Pham et al 2019). For the experimental adsorption plot, Langmuir and Freundlich data (obtained by linear models) (Table 1) were evidenced that Langmuir model describes the formation of a monolayer in the system between 0 and 152 mmHg.…”

“…On the other hand, describes the formation of multilayer between PSNH 2 and CO in the adsorption phenomenon after 152 mmHg. For that reason, the adsorbent-adsorbate tested system works trough of a multilayer behavior or type II isotherm (Pham et al 2019;Rouquerol et al 1999). Finally, Eq.…”

“…( 6), ( 7)], in their linear expressions [Eq. ( 8), ( 9)] (Pham et al 2019). Here, q t and q e are the adsorption capacities in any time and equilibrium, respectively, K 1 is the pseudo-first-order constant (h −1 ), K 2 is the pseudo-second-order constant (cm 3 g −1 h −1 ) and t is the contact time between PSNH 2 and gas (h) for the pseudo-second-order linear model (Nasri et al 2014).…”

“…In the same way, Elovich's mathematical model and its linear expression (Eq. 10 and 11) were used, where α is the rate of the initial adsorption (cm 3 g −1 h −1 ) while β is the superficial extension that is covered and the activation energy of the process (Pham et al 2019).…”

Process Optimization Studies of Congo Red Dye Adsorption onto Magnesium Aluminium Layered Double Hydroxide Using Response Surface Methodology

“…It is acknowledged that textile and dyeing industry has a large production network, many categories, goods and fast growth [24][25][26]. However, a large amount of industrial dyes and untreated wastewater has been discharging into the environment, directly causing serious pollution issues towards human, anima, and plant health.…”