Magnetic hybrid spheres of glauconite/calcium alginate interface for methylene blue adsorption: Synthesis, characterization, and novel physicochemical insights through theoretical treatment.

Fe3O4 nanoparticles were embedded within a glauconite­calcium alginate (G/CA) matrix to create magnetic hybrid spheres (MNPs-G/CA), with the aim of purifying water from methylene blue (MB) at temperatures of 25, 40, and 50 °C. MNPs-G/CA adsorbent was characterized using numerous techniques, including elemental mapping, zeta potential, FTIR, FESEM, XRD, EDX, and TEM. The greatest amount of the removed MB was achieved under definite conditions of solution pH 8.0, MNPs-G/CA mass (25 mg), interaction time (2 h), and 200 mg/L of MB concentration. The MB uptake process kinetic followed a pseudo-second-order equation (R2 > 0.99) at all tested temperatures. The equilibrium data were fitted to a statistical physics multilayer model in conjunction with the Langmuir and Freundlich equations. The steric n parameter reveals that MNPs-G/CA adsorbent possesses a mixed adsorption orientation (i.e., ranging from 0.69 to 0.93) across various temperatures. The amount of MNPs-G/CA active positions (the NM parameter) was progressively increased from 245 mg/g to 419 mg/g. The measured adsorption capacities (Qsat) ranged from 466.49 to 664.37 mg/g, and the removal of MB molecules was consistent with an endothermic interaction. The interface between the MNPs-G/CA-MB was principally dictated by electrostatic attractions, as evidenced by the values of adsorption energies (∆E), which varied from 16.75 to 21.52 kJ/mol. The regenerated MNPs-G/CA offered over 80 % of its adsorption strength after the fourth adsorption-desorption cycle. This study contributes to our understanding of the physicochemical parameters controlling the MB adsorption mechanism on multifunctional hybrid adsorbents, like the interface between glauconite, alginate, and MNPs.

Facile synthesis and characterization of a magnetic biosorbent derived from sodium alginate and activated graphite schist: Experimental and statistical physics analysis for Mn(VII) remediation.

H2O2-modified graphite schist (GS) and sodium alginate (SA) interface was loaded by Fe3O4 nanoparticles (MNPs) to prepare a magnetic biosorbent that was employed in removing Mn(VII) from solutions. The prepared GS/SA/MNPs adsorbent was investigated using a variety of techniques, including elemental mapping, TEM, XPS, FTIR, FESEM, EDX, XRD, XPS, and zeta potential. An experimental study supported by statistical physics calculations was carried out to obtain a new outline of the Mn(VII) uptake mechanism. The classical Freundlich and the statistical physical double-layer models adequately described the Mn(VII) uptake process at pH 3.0 and a temperature of 25-55 °C. The removed number of Mn ions (such as Mn+7 and Mn+2) per GS/SA/MNPs active site ranged from 0.70 to 0.84, indicating a mixed adsorption orientation driven by surface complexation and attraction forces mechanisms. The adsorption energies (∆E) calculated by the double-layer model ranged from 18.79 to 24.94 kJ/mol, suggesting that the interaction between Mn(VII) and GS/SA/MNPs was controlled by physical forces. Increasing the adsorption capacity at saturation (Qsat) from 333.14 to 369.52 mg/g with temperature proposed an endothermic capture process. Thermodynamic functions clarified the viability and spontaneity of Mn(VII) uptake on the GS/SA/MNPs adsorbent.

Sodium alginate-modified alkali-activated eggshell/Fe3O4 nanoparticles: A magnetic bio-based spherical adsorbent for cationic dyes adsorption.

Herein, a mixture of eggshell (ES) and magnetite nanoparticles (MNPs) was alkali-activated using NaOH/Na2SiO3 solution and then, impregnated with sodium alginate (SA) to prepare a magnetic bio-based adsorbent (namely SAAES/SA/MNPs) for the decontamination of water containing basic dyes, in particular, methylene blue (MB) and crystal violet (CV). The physicochemical properties of magnetic spheres of SAAES/SA/MNPs were characterized using XRD, FTIR, FESEM, EDX, elemental mapping, TEM, and zeta potential techniques. Dye adsorption equilibrium was studied experimentally at pH 8.0 and 25-55 °C, and a statistical physics multilayer model was applied to understand the removal mechanism of these dyes including the adsorption orientations on the adsorbent surface. The number of adsorbed dye molecules per functional group (n) of this bio-based adsorbent ranged from 0.70 to 0.91, indicating the presence of vertical and horizontal adsorption orientations for these organic molecules at all tested solution temperatures. The calculated saturation adsorption capacities (Qsat) were 332.57-256.62 mg/g for CV and 304.47-240.62 mg/g for MB, and an exothermic adsorption was observed for both adsorbates. The estimated adsorption energies (∆E) were < 25 kJ/mol, confirming that the SAAES/SA/MNPs-dye interactions were governed by physical forces as electrostatic interactions. This bio-based adsorbent was effectively regenerated using ethanol and it can be reused showing a removal of 71 and 74 % of MB and CV, respectively, after fourth adsorption-desorption cycles. Overall, the results of this article suggest the attractive performance of SAAES/SA/MNPs for removing basic dyes from aqueous solutions, thus highlighting the promising potential of this magnetic bio-based adsorbent for sustainable wastewater treatment at an industrial level.

Dual-functional marine algal carbon-based materials with highly efficient dye removal and disinfection control.

The design and simple, green preparation of dual-functional materials for the decontamination of both hazardous dyes and pathogenic microorganisms from wastewater remain challenging currently. Herein, a promising marine algal carbon-based material (named C-SA/SP) with both highly efficient dye adsorptive and antibacterial properties was fabricated based on the incorporation of sodium alginate and a low dose of silver phosphate via a facile and eco-friendly approach. The structure, removal of malachite green (MG) and congo red (CR), and their antibacterial performance were studied, and the adsorption mechanism was further interpreted by the statistical physics models, besides the classic models. The results show that the maximum simulated adsorption capacity for MG reached 2798.27 mg/g, and its minimal inhibit concentration for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was 0.4 mg/mL and 0.2 mg/mL, respectively. The mechanistic study suggests that silver phosphate exerted the effects of catalytic carbon formation and pore formation, while reducing the electronegativity of the material as well, thus improving its dye adsorptive performance. Moreover, the MG adsorption onto C-SA/SP showed vertical orientation and a multi-molecular way, and its adsorption sites were involved in the adsorption process with the increase of temperature. Overall, the study indicates that the as-made dual-functional materials have good applied prospects for water remediation.

Effectiveness of a novel polyaniline@Fe-ZSM-5 hybrid composite for Orange G dye removal from aqueous media: Experimental study and advanced statistical physics insights.

A polyaniline@Fe-ZSM-5 composite was synthesized via an in situ interfacial polymerization procedure. The morphology, crystallinity, and structural features of the as-developed PANI@Fe-ZSM-5 composite were assessed using scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The composite was efficiently employed for the first time as an adsorbent Orange G (OG) dyestuff from water. The OG dye adsorption performance was investigated as a function of several operating conditions. The kinetic study demonstrated that a pseudo-second-order model was appropriate to anticipate the OG adsorption process. The maximum adsorption capacity was found to be 217 mg/g. The adsorption equilibrium data at different temperatures were calculated via advanced statistical physics formalism. The entropy function indicated that the disorder of OG molecules improved at low concentrations and lessened at high concentrations. The free enthalpy and internal energy functions suggested that the OG adsorption was a spontaneous process and physisorption in nature. Regeneration investigation showed that the PANI@Fe-ZSM-5 could be effectively reused up to five cycles. The main results of this work provided a deep insight on the experimental study supported by advanced statistical physics prediction for the adsorption of Orange G dye onto the novel polyaniline@Fe-ZSM-5 hybrid composite. Additionally, the experimental and advanced statistical physics findings stated in this study may arouse research interest in the field of wastewater treatment.

Efficient detoxification of Cr(VI)-containing effluents by sequential adsorption and reduction using a novel cysteine-doped PANi@faujasite composite: Experimental study supported by advanced statistical physics prediction.

Nowadays, the global spreading of hazardous heavy metals becomes a top-priority environmental challenge, owing to its serious detrimental health outcomes. Herein, a novel cysteine-doped polyaniline@faujasite hybrid composite (Cys-PANi@FAU-50) was synthesized via a facile in-situ polymerization route for the effective detoxification of Cr(VI)-bearing wastewaters. The Cys-PANi@FAU-50 composite displayed an open mesoporous structure richly decorated with nitrogen/oxygen-containing functional groups, which consequently boosted the diffusion, adsorption and reduction of Cr(VI) oxyanions. The Cr(VI) adsorption behavior was satisfactorily tailored via pseudo-second-order law and Langmuir model with a maximum uptake capacity of 384.6 mg/g. Based on the advanced statistical physics theory, the monolayer model with two distinct receptor sites provided a reliable microscopic and macroscopic prediction of the Cr(VI) adsorption process. Stereographically, the Cr(VI) ions were adsorbed through horizontal multi-anchorage and vertical multi-molecular mechanisms on the amine and hydroxyl groups of Cys-PANi@FAU-50, respectively. The thermodynamic functions evidenced that the Cr(VI) adsorption was an endothermic spontaneous process. XPS analysis proved that Cr(VI) ions were electrostatically adsorbed, and subsequently reduced to Cr(III), which were in turn immobilized by chelation with imine/sulfonate groups and electrostatic interactions with carboxylate groups. The Cys-PANi@FAU-50 featured an effortless regenerability and good reusability. Overall, the Cys-PANi@FAU-50 composite owns outstanding potentiality for detoxifying Cr(VI)-laden effluents.

Chitosan/activated coal composite as an effective adsorbent for Mn(VII): Modeling and interpretation of physicochemical parameters.

Chitosan was impregnated into porous activated coal to produce a multifunctional chitosan/activated coal (Cs/Ac) composite. The resulted Cs/Ac was characterized and utilized as a cost-effective adsorbent for Mn(VII) at altered temperatures (i.e., 25, 35, and 45 °C). The adsorption results were fitted to classical as well as advanced statistical physics models. The Freundlich equation described well the achieved experimental data at all temperatures. Enhancing the Langmuir adsorption capacity from 203.26 to 224.03 mg/g with temperature indicated that Mn(VII) adsorption was an endothermic process. Steric, energetic and thermodynamics data of the double layer model with two energy sites (i.e., the best fit statistical model) were completely interpreted. The number of Mn(VII) per adsorption site (n) was between 0.76 and 0.92 suggested the presence of multi-docking and multi-interactions mechanisms. The active sites density (NM) of the Cs/Ac decreased with improving temperature. Energetically, Mn(VII) uptake by Cs/Ac was governed by physical interactions (i.e., adsorption energy <40 kJ/mol). Macroscopically, the interaction between Mn(VII) and Cs/Ac was spontaneous. Overall, modification of the Ac by the used marine biomass (Cs) produced a promising Mn(VII) adsorbent and also, the application of physical analysis offered a deep interpretation for the adsorption mechanism.

Insights Into the Mn(VII) and Cr(VI) Adsorption Mechanisms on Purified Diatomite/MCM-41 Composite: Experimental Study and Statistical Physics Analysis.

In this study, a purified diatomite (PD) with a concentration of diatom frustules more than 92% SiO2 was utilized to synthesize a composite of MCM-41 silica under hydrothermal conditions. The as-synthesized PD/MCM-41 composite was characterized and tested as an adsorbent for the removal of Cr(VI) and Mn(VII) ions from aqueous solution. Results of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) revealed that the diatom frustules of the PD were coated with MCM-41 mesoporous silica. Experimental isotherms of Cr(VI) and Mn(VII) adsorption were fitted to classical and advanced statistical physics models at 25°C-55°C and pH 3. The Langmuir model estimated monolayer adsorption capacities ranging from 144.1 to 162.2 mg/g for Cr(VI) and 166.2 to 177.0 mg/g for Mn(VII), which improved with increasing the solution temperature. Steric and energetic parameters obtained from a monolayer adsorption model with one adsorption site was utilized to explain the adsorption mechanism at a microscopic level. The number of Cr(VI) and Mn(VII) ions adsorbed on PD/MCM-41 active site (n) were 1.25-1.27 for Cr(VI) and 1.27-1.32 for Mn(VII), thus suggesting multi-interaction mechanisms. The density of PD/MCM-41 active sites (D M) was a key parameter to explain the adsorption of these heavy metals. The adsorbed quantities were maximum at 55°C, thus obtaining 102.8 and 110.7 mg/g for Cr(VI) and Mn(VII), respectively. Cr(VI) and Mn(VII) adsorption energies ranged from 18.48 to 26.70 kJ/mol and corresponded to an endothermic adsorption with physical forces. Entropy, free enthalpy, and internal energy associated to the adsorption of Cr(VI) and Mn(VII) ions were calculated, thus indicating that the removal of these pollutants was spontaneous. Overall, this article offers new interpretations for the Cr(VI) and Mn(VII) adsorption mechanisms on PD/MCM-41 composite, which are relevant to contribute to the development of effective water treatment processes.

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

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.

Experimental and Theoretical Studies of Methyl Orange Uptake by Mn-Rich Synthetic Mica: Insights into Manganese Role in Adsorption and Selectivity.

Manganese-containing mica (Mn-mica) was synthesized at 200 °C/96 h using Mn-carbonate, Al-nitrate, silicic acid, and high KOH concentration under hydrothermal conditions. Mn-mica was characterized and tested as a new adsorbent for the removal of methyl orange (MO) dye from aqueous solutions. Compared to naturally occurring mica, the Mn-mica with manganese in the octahedral sheet resulted in enhanced MO uptake by four times at pH 3.0 and 25 °C. The pseudo-second order equation for kinetics and Freundlich equation for adsorption isotherm fitted well to the experimental data at all adsorption temperatures (i.e., 25, 40 and 55 °C). The decrease of Langmuir uptake capacity from 107.3 to 92.76 mg·g-1 within the temperature range of 25-55 °C suggested that MO adsorption is an exothermic process. The role of manganese in MO selectivity and the adsorption mechanism was analyzed via the physicochemical parameters of a multilayer adsorption model. The aggregated number of MO ions per Mn-mica active site ( n ) was superior to unity at all temperatures signifying a vertical geometry and a mechanism of multi-interactions. The active sites number (DM) of Mn-mica and the total removed MO layers (Nt) slightly changed with temperature. The decrease in the MO adsorption capacities (Qsat = n·DM·Nt) from 190.44 to 140.33 mg·g-1 in the temperature range of 25-55 °C was mainly controlled by the n parameter. The results of adsorption energies revealed that MO uptake was an exothermic (i.e., negative ΔE values) and a physisorption process (ΔE < 40 kJ mol -1). Accordingly, the adsorption of MO onto Mn-mica was governed by the number of active sites and the adsorption energy. This study offers insights into the manganese control of the interactions between MO ions and Mn-mica active sites.

Enhancing adsorption capacity of Egyptian diatomaceous earth by thermo-chemical purification: Methylene blue uptake.

In the current study, calcination and thermo-chemical methods were applied in treatment of the processed diatomite fraction (<45 µm), which containing nearly 82.6 wt.% of the raw Egyptian diatomaceous earth. The untreated and modified diatomite fractions were characterized by optical microscopy (OM), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Thermo-chemical purification produced the highest concentration of diatom frustules (>92% SiO2) without blocking impurities and created SiOSi active sites. These fractions were tested for Methylene blue (MB) adsorption at different pH solutions (2.0-10.0). The purified diatomite via thermo-chemical treatment (PD) gave the greatest adsorption capacity for MB compared to the untreated (UD) and calcinated (CUD) diatomite fractions. Effects of experimental parameters such as MB concentration (60-200 mg L-1), contact time (5-480 min), adsorbent mass (50-250 mg) and temperature (30-55 °C) on MB uptake were investigated. Linear and non-linear forms of Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models indicated that Langmuir model with a maximum adsorption capacity (qmax=105.03mgg-1) fitted well the adsorption data. The chemical nature of MB uptake was revealed by the values of mean free energy E=8.655kJ/moland correlation coefficient of the pseudo-second-order model (R2=0.9997). The calculated thermodynamic parameters (ΔH0, ΔG0 and ΔS0) indicated that the removal of MB is spontaneous and endothermic.