Exfoliated Clay Decorated with Magnetic Iron Nanoparticles for Crystal Violet Adsorption: Modeling and Physicochemical Interpretation

Abstract

Surfactant–modified exfoliated Fayum clay (CTAB–EC) obtained after chemical treatment with a CTAB/H2O2 solution was further decorated with magnetic Fe3O4 nanoparticles (MNP). The final nanocomposite (MNP/CTAB–EC) was characterized by XRD, SEM, FTIR, TEM and its adsorptive capability against a model cationic dye, crystal violet (CV), was evaluated. A comparison of the adsorption performance of the raw clay and its modified counterparts using H2O2, CTAB, CTAB/H2O2 or MNP indicated that the adsorption capacity of MNP/CTAB–EC was the highest for CV removal at pH 8.0. The pseudo‒second order for the kinetics and Freundlich model for adsorption equilibrium fitted well the CV removal experimental data at all tested temperatures (25, 40 and 55 °C). The enhancement of the Langmuir adsorption capacity from 447.1 to 499.4 mg g−1 with increasing the temperature from 25 to 55 °C revealed an endothermic nature of the removal process. The interactions between CV and MNP/CTAB–EC were interpreted using advanced statistical physics models (ASPM) in order to elucidate the adsorption mechanism. Multilayer model fitted the adsorption process and therefore, the steric and energetic factors that impacted the CV adsorption were also interpreted using this model. The aggregated number of CV molecules per MNP/CTAB–EC active site ( n ) was more than unity at all temperatures, representing thus a vertical adsorption orientation and a multi‒interactions mechanism. It was determined that the increase of CV uptake with temperature was mainly controlled by the increase of the number of active sites (NM). Calculated adsorption energies (ΔE) revealed that CV removal was an endothermic and a physisorption process (ΔE < 40 kJ mol −1). MNP/CTAB–EC was magnetically separated, regenerated by NaOH, and reused without significant decrease in its adsorption efficiency, supporting a prosperity of its utilization as an effective adsorbent against hazardous dyes from wastewaters.

Tartaric Acid-Modified Holarrhena antidysenterica and Citrullus colocynthis Biowaste for Efficient Eradication of Crystal Violet Dye from Water

“…Band at 1029 cm −1 contributes to C-N groups of aliphatic amines. Acid-modified CC adsorbent when reacts with CV dye (Figure 2(d)) displays reduced consecutive peaks from 3902 cm −1 to 3447 cm −1 , showing the presence of freed OH groups which is due to the reaction between dye and adsorbent [19]. Peak at 2132 cm −1 contributes towards unsaturated -C�C bonds of alkyne moieties.…”

“…Dual nature was observed for the plots for diffusion mechanism with the (a) first to be a curved line contributing towards boundary layer (surface diffusion) (b) and the straight line in the later stages inferring towards intraparticle diffusion (Figures 5(d) and 5(e)). is leads towards complex mechanism of the CV dye adsorption [19], as clear from Table 2. Not even one of the graphical plots passed through the origin; hence, it is concluded intraparticle diffusion model was not the complete mechanism involved [89].…”

“…Analysis. HA (Figure 3(a)) displayed voids [19] in between compact, agglomerated, spherical structures [10].…”

“…In extreme cases, absorption through skin results in skin and digestive tract irritation causing permanent blindness, respiratory, and kidney failure [18]. It has been removed from wastewaters using membrane separation techniques, electrocoagulation, ozonization, photocatalysis, and adsorption [19][20][21][22] among which the most promising is adsorption [13]. Various adsorbents such as NaOH-modified rice husk, bottom ash, coir pith, sawdust, sugarcane fiber, zeolites, stalks, clays, stems, wheat straws, and pyrophyllites have been utilized for CV dye removal [6,[23][24][25][26][27][28][29][30][31][32][33][34].…”

Adsorptive Separation of Brilliant Green Dye from Water by Tartaric Acid-Treated Holarrhena antidysenterica and Citrullus colocynthis Biowaste

“…Journal of Chemistry adsorbents. From the images, it can be seen that hollow spaces [61] are present among the rigid, spherical edifices [5] of Ha, which facilitated the adsorption of BG dye through physisorption. Acidic treatment resulted in the svelte, etched structures consisting of multifold channels providing more potential sites for BG adsorption [27].…”