Adsorption Mechanism Of Methylene Blue Research Articles

High-efficient removal of methylene blue by zirconium-based organic frameworks modified with 1,3,5-benzenetricarboxylic acid: Characterization, performances, and mechanisms

The vast discharge of methylene blue (MB) dye in industrial effluent, risks the ecological environment, thus making its removal unavoidable. Recently, metal organic frameworks (MOFs) due to their larger pore volume, surface area and easy synthesis have proved to be exceptionally promising materials for contaminant treatment. Based on 1,3,5-benzenetricarboxylic acid (BTC) as a modifier, a new composite material consisting of BTC and Zr-based MOF (UIO-66-BTC) was fabricated for the effective removal of MB from the effluent. Its synthesis and efficient application has been confirmed by characterization analysis. The influencing factors, adsorption isotherms, and adsorption kinetics of MB adsorption by adsorbent were studied. It was demonstrated that the removal rate of MB adsorption by UIO-66-BTC reached 98.45% and the adsorption amount reached 393.80 mg g−1 at temperature (298 K), pH 7, adsorbent dosage (0.5 g L−1), MB initial concentration (200 mg L−1), and contact time of 720 min, respectively. The maximum adsorption of MB by UIO-66-BTC was 20.827 times higher than that of UIO-66 (18.908 mg g−1). The experimental data fits with the pseudo-second-order kinetic model and Langmuir isotherm, implying that the adsorption process is a monolayer chemisorption process. The thermodynamic and regeneration experiments showed that the spontaneous process enhanced the adsorption of MB at lower temperatures and the adsorption efficiency of MB remained above 68% after five successive cycles. The mechanism of MB adsorption on adsorbents is mainly based on electrostatic interactions, pore filling, hydrogen bonding and π-π interactions. It is concluded that this new adsorbent can be effectively used to treat MB in effluents.

Thermodynamic study and the development of a support vector machine model for predicting adsorption behavior of orange peel-derived beads in wastewater treatment

This study investigates the use of orange peels as a precursor for synthesizing sodium alginate-encapsulated beads for methylene blue (MB) removal. The prepared beads (BOP1 and BOP2) underwent characterization through FTIR, XRF, SEM and TGA. Subsequently, the impacts of various factors, including temperature, the initial pH, initial concentration, salt and humic acid, are studied. The adsorption isotherms show high adsorbed quantities of 764.92 and 659.78 mg/g for BOP1 and BOP2 respectively, while the obtained data are best described by the monolayer with two energies (MMTE) model, which is then used to perform a thermodynamic study of the MB adsorption mechanism. Additionally, the adsorption kinetics data are modeled using three models, with the PFO model identified as the most appropriate. The regenerated beads demonstrate the ability to be reused up to 7 cycles, The effects of NaCl and humic acid on MB adsorption reveal that NaCl inhibits adsorption due to competition with Na+, while humic acid has no effect. Finally, a support vector machine (SVM) model optimized by the Levy Flight Distribution Optimization (LFD) algorithm is developed and found to be capable of accurately predicting the adsorption behavior of the prepared beads. This model is then used in optimizing the process conditions for maximal MB removal. Overall, this study demonstrates that the prepared beads could be potential low-cost and environmentally friendly adsorbents for wastewater treatment applications.

Efficient dye adsorption of mesoporous activated carbon from bamboo parenchyma cells by phosphoric acid activation.

In order to solve the environmental damage caused by the discharge of dyes as industrial wastewater, the development of efficient and sustainable adsorbents is the key, while most of the previous studies on bamboo parenchyma cells have focused on their microstructural, functional and mechanical properties, and few of the properties in adsorption have been investigated. To evaluate the role of the unique microstructure of bamboo parenchyma cells on adsorption after carbonization and activation, PC-based activated carbon (PPAC) was fabricated by the phosphoric acid activation method and tested for adsorption using methylene blue (MB). The effect of mesoporous structure on MB adsorption was investigated in detail using PPAC-30C impregnated with phosphoric acid at a concentration of 30%. The results showed that the adsorption performance was influenced by single-factor experiments (e.g., pH, activated carbon dosing). The adsorption isotherms and kinetics could conform to the Langmuir model (R2 = 0.983-0.994) and pseudo-second-order kinetic model (R2 = 0.822-0.991) respectively, and the maximum MB adsorption capacity of adsorbent was 576 mg g-1. The adsorption mechanism of MB on PPAC-30C includes physical adsorption, electrostatic attraction, hydrogen bonding, and the π-π conjugation effect, which was dominated by physical adsorption. The results of this study show that PPAC has good application prospects for cationic dye removal.

Rapid preparation of porous carbon by Flash Joule heating from bituminous coal and its adsorption mechanism of methylene blue

Porous carbon is an extensively used adsorbent for the removal of dye. However, the conventional high-temperature carbonization and activation method with prolonged heating and annealing process was complicated, energy-consuming and polluting, which greatly limit the large-scale production. In this study, rapid and efficient preparation of porous carbon by the Flash Joule heating (FJH) method was realized for the first time using three bituminous coal samples with different degrees of metamorphism. The preparation process was completed in less than 1 s without chemical treatment, the process was more environmentally friendly. The physical and chemical properties of porous carbon were analyzed and the adsorption mechanism of porous carbon on methylene blue (MB) was investigated. The results showed that the specific surface area of porous carbon prepared by Shuozhou (PC-SZ), Gujiao (PC-GJ) and Changzhi (PC-CZ) could reach 601.95, 361.91 and 256.33 m2·g−1, respectively. The diversity in chemical properties of coal with different metamorphic degrees leads to the different properties of porous carbon. PC-SZ had a higher content of oxygen-containing functional groups and defects. The adsorption experiments indicate that PC-SZ had the best adsorption capacity on MB. The adsorption process was fitted by pseudo-second-order model commendably. It was found that more lattice defects and larger interlayer spacing made PC-SZ to become an excellent adsorbent of methylene blue (MB). Therefore, FJH can be an innovative approach for preparing porous carbon with excellent adsorption properties and is expected to achieve large-scale production.

Kinetics and Mechanism of Methylene Blue Adsorption by a TiO2/Diatomite Nanocomposite and Its Components

Kinetics and Mechanism of Methylene Blue Adsorption by a TiO2/Diatomite Nanocomposite and Its Components

Preparation of novel polyurethane/activated carbon/cellulose nano-whisker nanocomposite film as an efficient adsorbent for the removal of methylene blue and basic violet 16 dyes from wastewater

The purpose of this research was to evaluate the effectiveness of a porous and flexible polyurethane (PU)-based nanocomposite consists activated carbon (AC) and cellulose nano-whisker (CNW) on adsorption of methylene blue (MB) and basic violet16 (BV16) as two industrial dyes. The morphology, hydrophilicity, chemical structure, and mechanical properties of the fabricated nanocomposite films were investigated using FE-SEM, water contact angle, ATR-FTIR and tensile tests respectively. The water contact angle tests exhibited that the addition of 1.0 wt% CNW resulted in the highest hydrophilicity in the nanocomposite film. The results of the adsorption tests showed that the nanocomposites containing 1.0 wt% AC have the best performance in the adsorption of dyes. In addition, the effect of parameters such as contact time, pH, adsorbent dosage, and temperature on the removal efficiency of dyes was investigated. It was found that the adsorption mechanism of MB and BV16 dyes by the PU nanocomposite can occur as a combination of chemical and physical adsorption. Kinetic and isotherm studies of the adsorption also showed that the adsorption of MB and BV16 dyes on the PU/AC/CNW nanocomposite follows the pseudo-second-order kinetic model and the Freundlich isotherm. The maximum adsorption capacity (qm) of 71.4 mgg-1 for BV16 dye and 67.1 mgg-1 for MB dye showed that the PU/AC/CNW nanocomposite can be used as an efficient adsorbent for adsorption of BV16 and MB dyes.

Application of Fe3O4/thiamine Magnetic Particles in the Removal of Methylene Blue

Fe3O4/thiamine particles were prepared in this work via precipitation method. The synthesis method is based on the principle of precipitation of Fe3O4 particles in the presence of thiamine coating agent. Also, the potential application of Fe3O4/ thiamine in the removal of methylene blue (MB) was investigated. Several factors that affect the synthesis of Fe3O4/thiamine such as base concentration, mass ratio of FeCl2 to thiamine, reaction temperature, and reaction time were determined. Optimal conditions for preparing Fe3O4/thiamine are NH4OH concentration = 10%, mass ratio of FeCl2:thiamine = 5:1 (g g-1), reaction temperature = 30 °C, reaction time = 120 min. The average particle size of Fe3O4/thiamine is 293.7 nm while the specific surface area, pore diameter, and magnetization of the obtained Fe3O4/ thiamine particles are 57 m2 g-1, 192.67 Å, and 2.4 emu g-1, respectively. The interesting point of this work is to obtain the Fe3O4/thiamine at low temperature with less amount of NH4OH used. Furthermore, 79.08% of MB could be removed using Fe3O4/thiamine as an adsorbent, with a maximum adsorption capacity of 31.63 mg g-1 at pH of 10, a MB concentration of 50 mg L-1, and an adsorption time of 15 min. Adsorption kinetics studies showed that the pseudo-second-order model fitted the experimental data better than the pseudo-first-order and the adsorption process is physical adsorption following the Freundlich adsorption isotherm model. An adsorption mechanism of MB onto Fe3O4/thiamine was also suggested. The synthesized Fe3O4/ thiamine particles could be a potential material for treating wastewater.

Surface modification of chitin nanofibers with dopamine as efficient nanosorbents for enhanced removal of dye pollution and metal ions

The development of environmentally friendly and low-cost adsorbents with high adsorption capacity remains a challenge. Herein, chitin nanofiber-polydopamine composite materials (CNDA) have been obtained by surface modification of chitin nanofiber using dopamine. According to the results of transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), and X-ray photoelectron spectrometer (XPS), polydopamine have been successfully coated on the surface of chitin nanofiber (ChNF). The ability to remove methylene blue (MB) has been analyzed via standard adsorption experiments, indicating that the maximum adsorption capacity (qmax) can reach 196.6 mg/g at MB initial concentration of 50 mg/L. Most importantly, the adsorption kinetics, isotherm, and thermodynamics were used to investigate the MB adsorption mechanism on composites. This indicated that the polydopamine on the surface of chitin nanofiber (ChNF) plays an important role in the MB dye adsorption. Moreover, the removal ability of CNDA to metal ions has also been investigated, indicating high capacities for Fe3+, Mn2+, Cu2+, and Ni2+. Based on their biodegradability and good adsorption capacity, the CNDA composite material can be considered a promising adsorbent for wastewater treatment.

Green preparation of magnetic ferroferric oxide-polyvinyl alcohol-alginate coated UiO-67 nanospheres: Characterization, adsorption properties and adsorption mechanism of methylene blue

In this paper, a kind of magnetic ferric oxide/polyvinyl alcohol/calcium alginate/UiO-67 (Fe3O4/PVA/CA/UiO-67) nanospheres with homogeneous surface interconnecting structures was prepared by using macromolecular polymer polyvinyl alcohol and sodium alginate as carriers and zirconium organic skeleton as nanocrystals. The properties of magnetic nanospheres were studied by SEM, FT-IR, TGA, XRD, BET, VSM and Zeta potential. The impression of diverse temperatures, MB concentrations, interaction time, pH, and magnetic aerogel sphere dose on MB removal was studied. The optimum adsorption temperature and pH of magnetic nanospheres for MB were 298 K, and 10, respectively. Langmuir simulated that the maximum removal of MB by magnetic nanospheres at room temperature (298 K) was 1371.8 mg/g. The removal of MB by magnetic nanospheres complied with the pseudo-first-order kinetic model. The isotherm simulation can infer that the Langmuir model was more comply with MB adsorption on magnetic aerogel spheres. Thermodynamic studies have confirmed that the removal of MB by magnetic nanospheres was exothermic and spontaneous. The interaction mechanism of MB on magnetic nanospheres can be deduced by FT-IR and BET, including hydrogen bond, π-π bond, electrostatic interaction, and mesoporous pore flow. The removal rate of nanospheres for MB still reached 70.06 % after six cycles.

Preparation of low-cost activated carbon from Doum fiber (Chamaerops humilis) for the removal of methylene blue: Optimization process by DOE/FFD design, characterization, and mechanism

Within the context of a circular economy, this work aims to valorize local lignocellulosic biomass of Doum fiber (Chamaerops humilis), as a highly promising adsorbent material for the removal efficiency of methylene blue (MB) dye via the adsorption process. Thus, this study investigates the potential of both raw (RDF) and activated carbon from Doum fiber (ACDF) as adsorbents. The first task was to enhance the adsorption efficiency of MB onto activated carbon by systematically optimizing its synthesis conditions. To achieve this, a full factorial design (FFD) approach of four factors (activation time, activation temperature, contact time, and concentration of H3PO4) at two levels was employed, using H3PO4 as the activating agent. A series of batch experiments were performed to characterize the adsorption properties of MB onto RDF and ACDF by describing the adsorption conditions, determining the kinetic and isotherm models, and evaluating the thermodynamic parameters. The results obtained revealed that ACDF had significantly higher surface affinity for MB than RDF, with an adsorption capacity of 83.82 mg. g−1. The adsorption process was found to be spontaneous and endothermic for ACDF, while for RDF, it was exothermic. The adsorption data for both ACDF and RDF exhibited a good fit to the Langmuir isotherm model, indicating monolayer adsorption. Furthermore, the kinetic data demonstrated excellent agreement with the pseudo-second-order model, suggesting a three-step rate-controlling mechanism. According to the results of density functional theory (DFT) calculations, the adsorption mechanism of MB mainly involves electrostatic interactions, hydrogen bonds, and n-π, π-π interactions with the two adsorbents.

Simple Alkali-Modified Persimmon Peel–Montmorillonite Composite Hydrochar for Rapid and Efficient Removal of Methylene Blue

Modified persimmon peel–montmorillonite composites (PMHC-KOH/NaHCO3) for efficient and rapid removal of methylene blue (MB) were synthesized using hydrothermal carbonization and simple alkali impregnation. The surface properties and material compositions of the hydrochars were determined with SEM, zeta potential, and XRD, and the adsorption mechanism of MB on two modified hydrochars was analyzed with FTIR, XPS, and DFT calculation. The results showed that modified hydrochars with a rough surface structure and rich oxygen-containing groups exhibited a strong affinity for MB, and the adsorption capacity of PMHC-NaHCO3 and PMHC-KOH for MB reached 121.28 mg/g and 278.41 mg/g, respectively, with PMHC-KOH achieving more rapid adsorption of MB, at a rate of 0.043 g/mg/min. After five adsorption/desorption cycles, the two modified hydrochars still maintained a high adsorption rate of MB (92.32%/98.43%). The excellent adsorption performance of the modified hydrochars was attributed to hydrogen bonding, π-π interaction, electrostatic attraction, and ion exchange. DFT calculations revealed that oxygen-containing groups of the modified hydrochars played an important role in the adsorption of MB and confirmed that electrostatic attraction, hydrogen bonding, and π-π interactions were the key forces for rapid and efficient adsorption of MB. The prepared adsorbents gave full play to the regenerative applicability of agricultural waste, the simple alkali impregnation method eliminated the need for the additional cost of pyrolysis and activation, and their application in MB adsorption realized the treatment of waste with waste.

Adsorption mechanism of methylene blue by magnesium salt-modified lignite-based adsorbents

The rich pore structure and carbon structure of lignite make it a suitable adsorbent for effectively removing methylene blue (MB) from wastewater. This article reports the preparation of lignite-based adsorbents modified by magnesium salts, and the key factors and adsorption mechanism are analyzed to effectively improve the adsorption performance for MB. The results showed that the lignite was modified by magnesium salts, and the Mg2+ in the magnesium salts had a good binding effect on the oxygen-containing functional groups in the lignite. This improved the adsorption performance of the lignite-based adsorbents for MB. The Mg(NO3)2-modified lignite-based adsorbent showed the best adsorption performance and removal rate of MB (99.33%) when prepared with 8 wt % Mg(NO3)2. Characterization analysis showed that a “-COOMg” structure was formed between Mg2+ in the magnesium salts and the carboxylic acid functional group in the lignite, which was postulated to be the absorption site that promoted the adsorption performance for MB. It is speculated that the MB adsorption mechanism of this lignite-based adsorbent is ion exchange.

Engineered biochar derived from lemon peel waste for highly efficient removal of organic pollutants from water

The urgent need for efficient decontamination of organic dyes from polluted waters necessitates the search for a low-cost and suitable adsorbent. The large amount of lemon peel residue in actual production can be an ideal raw material for the preparation of adsorbents. Herein, a novel magnetic nanocomposite derived from lemon (Citrus limon L.) peel residue (Fe3O4/Lp-biochar) was successfully synthesized by one-step hydrothermal method and used for the adsorptive capture of methylene blue (MB) in aqueous solution. The prepared Fe3O4/Lp-biochar are spherical with a particle size of 8.3 nm and have a saturation magnetization intensity of 52.9 emu/g and a specific surface area of 64.30 m2/g. It was found that the maximum MB adsorption capacity of 26.36 mg/g by the Fe3O4/Lp-biochar can be achieved when the amount of nanocomposite was 0.10 mg/mL, the system's pH value was 10, the reaction temperature was 25 °C, and the adsorption time was 60 min. Adsorption kinetics of MB on the Fe3O4/Lp-biochar followed the pseudo-second-order kinetic model whilst the Freundlich isotherm model could well simulate the adsorption behavior of MB on magnetic biochar. The adsorption mechanism of MB by the Fe3O4/Lp-biochar predominantly include electrostatic attraction and mesoporous interaction. Furthermore, the Fe3O4/Lp-biochar exhibited a remarkable retention of 94.7% of the initial adsorption efficiency even after the 10th cycle of repeated use. It was concluded that the lemon peel-derived magnetic biochar can be a promising alternative to conventional adsorbents for wastewater treatment.

Methylene blue adsorption mechanism onto palm kernel shell-derived activated carbon: From particle diffusion to site adsorption

The mechanism of methylene blue adsorption was investigated for palm kernel shell-derived activated carbon from the bulk solution to active sites. For different initial dye concentrations, 100 ppm methylene blue led to approximately 10 mg/g adsorption capacity while experiencing a decreasing trend at lower initial dye concentrations as follows: 50 ppm (approximately 5 mg/g) > 20 ppm (approximately 2 mg/g) > 5 ppm (approximately 0.5 mg/g). Based on the Boyd external diffusion model, the mechanism of methylene blue adsorption started with its diffusion from the bulk solution via the bounding film encapsulating the activated carbon. The adsorbed species occupied more than one class of active site with an adsorption rate of 0.54 mg/g.min, while the adsorption capacity accounted for 14.7 mg/g. The information about methylene blue offers useful insights into describing the steps of dye adsorption onto palm kernel shell-activated carbon.

Preparation and evaluation of poplar waste derived adsorbent for dye removal

Poplar waste is employed to prepare the high quality adsorbent (PWA) using one-pot method for methylene blue (MB) removal from wastewater. The H2 rich fuel gas is recycled during preparation process. The adsorption isotherms and adsorption kinetics are used to describe the MB adsorption process. The MB adsorption capacity of the PWA is 254.21 mg/g based on the Langmuir model calculation. Pseudo-second-order model describe well with the adsorption kinetic process. The MB column adsorption process of the PWA is analyzed by the Thomas and Yoon-Nelson, which indicates that the adsorption capacity is 54 mg/g and saturation time is 540 min. PWA has excellent reusability, which still maintains 75.59% MB adsorption amount after five cycles. The MB adsorption mechanism of PWA includes chemical functional groups, electrostatic interaction and pore filling. Density functional theory calculation indicates that hydroxyl groups play an important role in MB adsorption process. MB adsorption performance of PWA is investigated in the actual water with excellent MB removal. This result demonstrates that PWA could be acted as the recoverability and efficient adsorbent for MB removal from wastewater.

Green composites based on volcanic red algae Cyanidiales, cellulose, and coffee waste biomass modified with magnetic nanoparticles for the removal of methylene blue

In this paper, green nanocomposites based on biomass and superparamagnetic nanoparticles were synthesized and used as adsorbents to remove methylene blue (MB) from water with magnetic separation. The adsorbents were synthesized through the wet co-precipitation technique, in which iron-oxide nanoparticles coated the cores based on coffee, cellulose, and red volcanic algae waste. The procedure resulted in materials that could be easily separated from aqueous solutions with magnets. The morphology and chemical composition of the nanocomposites were characterized by SEM, FT-IR, and XPS methods. The adsorption studies of MB removal with UV-vis spectrometry showed that the adsorption performance of the prepared materials strongly depended on their morphology and the type of the organic adsorbent. The adsorption studies presented the highest effectiveness in neutral pH with only a slight effect on ionic strength. The MB removal undergoes pseudo-second kinetics for all adsorbents. The maximal adsorption capacity for the coffee@Fe3O4–2, cellulose@Fe3O4–1, and algae@Fe3O4–1 is 38.23 mg g−1, 41.61 mg g−1, and 48.41 mg g−1, respectively. The mechanism of MB adsorption follows the Langmuir model using coffee@Fe3O4 and cellulose@Fe3O4, while for algae@Fe3O4 the process fits to the Redlich-Peterson model. The removal efficiency analysis based on UV-vis adsorption spectra revealed that the adsorption effectiveness of the nanocomposites increased as follows: coffee@Fe3O4–2 > cellulose@Fe3O4–1 > algae@Fe3O4–1, demonstrating an MB removal efficiency of up to 90%.

Interlayer adsorption of cationic dye on cationic surfactant-modified and unmodified montmorillonite.

Water pollution by toxic organic dyes is one of the most critical health and environmental problems worldwide. By means of molecular dynamics method, the present work aims to evaluate the applicability of montmorillonite (Mt) modified by hexadecyltrimethylammonium cations (HDTMA+) compared to unmodified Na-Mt for the adsorption of cationic methylene blue (MB) dye. The results showed that the adsorption energy of MB on both HDTMA-Mt and Na-Mt absorbent ranged from -100 to -250kJ/mol, indicating the effectiveness of two types of adsorbents in dye water treatment. The highest adsorption energy was found at w =50% in each adsorbent system. Adsorption mechanisms of MB depend on molecular orientations, which is influenced by the surfactant and water content. The adsorption mechanism of MB is chemisorption dominated by strong electrostatic interaction between CH3 groups of MB and oxygen atoms of Mt surfaces. Besides, physisorption also plays a minor role in MB orientations. It is found that the existence of cationic surfactants can slightly improve the adsorption capacity of MB only at higher water content through enlarging the interlayer space of Mt and reducing mobility of MB. However, there will be a negative impact on the reduction of adsorption sites for dyes especially at low water content. Our results provide a possible application for swelling clay minerals being a promising adsorbent for dyes-surfactants co-existing wastewater treatment.

Adsorption of methylene blue and Congo red from aqueous solution on 3D MXene/carbon foam hybrid aerogels: A study by experimental and statistical physics modeling

In this paper, a new type of adsorbent MXene/carbon foam hybrid aerogel (MCF) was synthesized from Ti3C2TX-MXene and melamine foam (MF), and its removal properties of both cationic and anionic dyes were studied. The physicochemical properties of MCF were analyzed by a variety of characterization techniques, while its dye adsorption mechanism was further elucidated by the statistical physics models. The results show that MCF exhibited excellent adsorptive efficiency towards the two hazardous dyes methylene blue (MB) and Congo red (CR), and their adsorption capacity were 356.97 mg/g and 647.75 mg/g, respectively, which were fitted better for the Langmuir equation and quasi-second-order kinetic model. Moreover, the mechanism of MCF-MB and MCF-CR adsorption systems was discussed through the saturated multilayer model at the molecular level. The numerical simulation results show that the MB molecules were adsorbed by MCF in the form of dimer, which was a process of multi-anchoring (303 K and 318 K), single connection (333 K) and mixed adsorption orientation. On the contrary, CR molecules were adsorbed as monomers, which was a process of multi-anchored and pure non-parallel adsorption directions (303 K and 318 K) and mixed adsorption orientation (333 K). From the statistical physical and thermodynamic analysis, the adsorption mechanism of MB and CR onto MCF was mainly determined by the receptor density (Dm), which was a reversible endothermic adsorption process driven by the physical interaction, and high temperature was beneficial to the occurrence of high adsorption capacity.

Sustainable phosphorylated microcrystalline cellulose toward enhanced removal performance of methylene blue

In this study, microcrystalline cellulose (MCC) was phosphorylated using phosphoric acid in the presence of urea and used as an adsorbent for methylene blue (MB) dye removal from an aqueous solution. The obtained products were characterized by different techniques. Batch adsorption experiments were conducted under varying conditions of incubation time, initial MB concentration, pH, and phosphorylation degree. All the samples exhibited similar and fast adsorption kinetics, described by pseudo-second-order model for MB adsorption, whereas the retention capacity depended significantly on the phosphate content and the surface charge of the adsorbents. The experimental adsorption data in the examined MB initial concentrations (0–2000 mg/L) were best suited by the Langmuir isotherm model. The study revealed that the presence of phosphates groups in the cellulose structure significantly enhanced the adsorption of the MB pollutant. The maximum dye removal capacity at pH of 7 was obtained for the phosphorylated microcrystalline cellulose (284.03 mg/g) with a high phosphorylation degree (1.92 % of P), which is 20 times higher than unmodified MCC (15.29 mg/g). This property increased from 284.03 to 328.32 mg/g when increasing the pH from 7 to 11. The MB adsorption mechanism involves hydrogen bonding, electrostatic and ion-dipole interactions. These findings are relevant to a better understanding of the role of cellulose phosphorylation in the recovery of organic dyes from the waste liquid of many industries.

Fe3O4 Nanoparticles Loaded Bentonite/Sawdust Interface for the Removal of Methylene Blue: Insights into Adsorption Performance and Mechanism via Experiments and Theoretical Calculations

Herein, magnetite nanoparticles (MNPs) synthesized from altered basalt were used to develop a composite with H2O2–activated bentonite (BE) and fibrous sawdust (SD). The as-prepared BE/SD–MNPs were characterized by FTIR, FESEM, TEM, TGA, DSC, and Zeta potential techniques and utilized as an effective multifunctional composite for removing methylene blue (MB). The adsorption isotherms of MB at 25–55 °C were analyzed via kinetics, classical, and advanced statistical physics models. Theoretically, the pseudo-second-order of kinetics and the Freundlich isotherms model fit the experimental data well without microscopically clarifying the adsorption mechanism. Studying a multilayer model’s steric and energetic parameters was a reliable approach to understanding the MB uptake mechanism at the molecular scale. Sterically, the removed MB molecules offered a combination of horizontal and vertical geometry (i.e., mixed orientation). The MB adsorption capacity at saturation (Qsat) increased from 829 to 849 mg/g with temperature, suggesting endothermic interactions. Energetically, the MB uptake by BE/SD–MNPs was controlled by physical interactions (i.e., adsorption energy < 20 kJ/mol). The BE/SD–MNPs retained more than 85% of the MB uptake after five adsorption-desorption rounds. Overall, this study aimed to understand the MB adsorption mechanism using a magnetic clays/lignocellulosic interface such as the utilized BE/SD–MNPs composite as a promising strategy in wastewater remediation.