Adsorption of Methylene Blue on Montmorillonite

Nanostructured Cellulose-Based Aerogels: Influence of Chemical/Mechanical Cascade Processes on Quality Index for Benchmarking Dye Pollutant Adsorbents in Wastewater Treatment

(1) Background: Nanostructured cellulose has emerged as an efficient bio-adsorbent aerogel material, offering biocompatibility and renewable sourcing advantages. This study focuses on isolating (ligno)cellulose nanofibers ((L)CNFs) from barley straw and producing aerogels to develop sustainable and highly efficient decontamination systems. (2) Methods: (Ligno)cellulose pulp has been isolated from barley straw through a pulping process, and was subsequently deconstructed into nanofibers employing various pre-treatment methods (TEMPO-mediated oxidation process or PFI beater mechanical treatment) followed by the high-pressure homogenization (HPH) process. (3) Results: The aerogels made by (L)CNFs, with a higher crystallinity degree, larger aspect ratio, lower shrinkage rate, and higher Young's modulus than cellulose aerogels, successfully adsorb and remove organic dye pollutants from wastewater. (L)CNF-based aerogels, with a quality index (determined using four characterization parameters) above 70%, exhibited outstanding contaminant removal capacity over 80%. The high specific surface area of nanocellulose isolated using the TEMPO oxidation process significantly enhanced the affinity and interactions between hydroxyl and carboxyl groups of nanofibers and cationic groups of contaminants. The efficacy in adsorbing cationic dyes in wastewater onto the aerogels was verified by the Langmuir adsorption isotherm model. (4) Conclusions: This study offers insights into designing and applying advanced (L)CNF-based aerogels as efficient wastewater decontamination and environmental remediation platforms.

Thermal activation, characterization and performance evaluation of Ethiopian bentonite for sodium removal

Bentonite is one of the clay materials that have important characteristics and is applicable to construction and for different industrial uses. Treatment of this material to enhance some of its physicochemical properties to suit the desired applicability has been a focus research area. In this work, natural bentonite from Warseisso, Afar region, Ethiopia was activated with thermal treatment. The raw and treated bentonites were then characterized using SEM, FTIR, XRD, BET, and cation exchange capacity. The effects of activation parameters (time and temperature) on its physiochemical properties and its performance for the removal of sodium ions from water were investigated. Bentonite activated for 6 h at 300 °C showed a maximum specific surface area of 81.74 m²/g while the raw one showed 57.6 m²/g. However, the cation exchange capacity value of the raw bentonite was found to be 82.1 meq/100 g while the value was reduced to 67.2 meq/100 g for treated bentonite with high specific surface area. To check the performance of the activated bentonite for desalination application, batch adsorption of sodium from synthetically produced sodium chloride solution was made. A sodium removal performance of 10% was achieved with treated bentonite at the maximum specific surface area.

Drug Molecular Immobilization and Photofunctionalization of Calcium Phosphates for Exploring Theranostic Functions

Theranostics (bifunction of therapeutics and diagnostics) has attracted increasing attention due to its efficiency that can reduce the physical and financial burden on patients. One of the promising materials for theranostics is calcium phosphate (CP) and it is biocompatible and can be functionalized not only with drug molecules but also with rare earth ions to show photoluminescence that is necessary for the diagnostic purpose. Such the CP-based hybrids are formed in vivo by interacting between functional groups of organic molecules and inorganic ions. It is of great importance to elucidate the interaction of CP with the photofunctional species and the drug molecules to clarify the relationship between the existing state and function. Well-designed photofunctional CPs will contribute to biomedical fields as highly-functional ormultifunctional theranostic materials at the nanoscales. In this review, we describe the hybridization between CPs and heterogeneous species, mainly focusing on europium(III) ion and methylene blue molecule as the representative photofunctional species for theranostics applications.

A Study of Methylene Blue Dye Interaction and Adsorption by Monolayer Graphene Oxide

The graphene oxide (GO) interaction with methylene blue (MB) cationic dye was studied in an aqueous solution at different pH during MB adsorption. The mutual interaction of MB with GO surface was studied and evaluated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The π-π and electrostatic interaction of MB with GO surface are the main types of interactions, and the XRD data show the monomeric arrangement of MB cation with GO. The GO surface functional groups and point of zero charge (PZC) were determined by acid-base titration. Suitability of zeta-potential measurement and acid-base titration method was briefly discussed. The quality of prepared GO was evaluated by Raman spectroscopy, XRD, and atomic force microscope (AFM). The experimental adsorption equilibrium data were analyzed using Langmuir, Langmuir-Freundlich, Freundlich, and Temkin isotherms. The GO maximum adsorption capacity increases with higher pH, that is ascribed to the facile interaction of negatively charged GO with positively charged MB structure.

Synthesis and Characterization of Hydroxyapatite- (HAP-) Clay Composites and Adsorption Studies on Methylene Blue for Water Treatment

Dyes used by the textile, tannery, and food industries tend to pollute water bodies and must be removed to get clean water. Hydroxyapatite (HAP) was synthesized from eggshells using the wet precipitation process. The as-synthesized HAP was characterized using Fourier Transform Infrared (FTIR) and X-ray powder diffraction (XRD). The synthesized HAP was mixed with three different clays: halloysite (HNT), kaolinite (KAO), and bentonite (BENT). The removal efficiency values of methylene blue (MB) from the data showed that HAP-BENT adsorbents had higher values, followed by HAP-HNT and then HAP-KAO adsorbents. The combined masses of 24 mg, 34.5 mg, and 33 mg (representing 20%, 15%, and 10% of HAP-BENT mass) had average adsorption capacity values of 20.7 mg/g, 17.2 mg/g, and 17.9 mg/g, respectively. For each mass percentage, the adsorption capacity values were found to decrease with adsorbent dosage. The HAP-BENT composites had removal efficiency values of 98.4, 91.9%, and 91.9%, respectively. Adsorption data for the HAP-BENT adsorbents were found to be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The effect of temperature on adsorption capacity was evaluated and thermodynamical modeling was undertaken. The thermodynamical modeling predicts that based on the value of the change in enthalpy and Gibbs free energy the process was exothermic and spontaneous. This work confirms the potential of HAP-clay composites in removing MB from water.

Characterization and adsorption applications of composite biochars of clay minerals and biomass

Composite mineral-biochars of a homogeneous biomass (cellulose) and heterogeneous biomass (oak leaves) were fabricated with either 5 wt% or 10 wt% minerals (montmorillonite (MMT), kaolinite, and sand) and then pyrolyzed at 600 °C for 60 min. Characterizations including proximate analysis, ultimate analysis, surface area and porosity, morphology, and surface chemistry confirmed that minerals were present on the surface of biochar, and MMT/kaolinite-biochar composites showed a strengthening in the chars' aromatic structures, as well as increases in oxygen-containing surface functional groups. Methylene blue adsorption isotherms indicated that the MMT/kaolinite-biochars had higher adsorption capacities than pure biomass or biomass-sand biochars (110 mg_MB/g_char and 24 mg_MB/g_char for MMT-cellulose char and cellulose char, respectively). A multilinear model relating adsorption capacity and adsorbent properties was developed to measure the relative contribution of biochar properties to adsorption behavior. The model indicates that pore volume and hydrogen bonding were the dominant properties in controlling the adsorption of methylene blue onto the biochars. Findings from this work indicate that composite biochars prepared from biomass and inexpensive clay minerals are a promising adsorbent for remediating organic contaminants from water.

Liquid-Phase Removal of Methylene Blue as Organic Pollutant by Mesoporous Activated Carbon Prepared from Water Caltrop Husk Using Carbon Dioxide Activation

In this work, a mesoporous activated carbon (AC) was prepared from a unique lignocellulosic biomass (water caltrop husk) in triplicate using a single-step physical activation process at lower temperature (i.e., 750 °C) and longer holding time (i.e., 90 min). Based on the pore properties and adsorption properties for removal of methylene blue (MB) as organic pollutant, the results proved that the resulting AC possesses a mesoporous feature with the Brunauer–Emmett–Teller (BET) surface area of 810.5 m2/g and mesopore volume of about 0.13 cm3/g. Due to its fast adsorption rate and maximal adsorption capacity fitted (126.6 mg/g), the mesoporous carbon material could be used as an excellent adsorbent for liquid-phase removal of MB. In addition, the pseudo-second-order model is well suited for describing the adsorption system between the cationic adsorbate and the resulting AC with oxygen surface groups.

Valorization of Oued Sebou Natural Sediments (Fez-Morocco Area) as Adsorbent of Methylene Blue Dye: Kinetic and Thermodynamic Study

The objective of this study is to evaluate the efficiency of methylene blue removal using Oued Sebou sediments as an adsorbent. The presence of carboxyl functional group demonstrated by infrared (IR) analysis of the sediment favorized the methylene blue (MB) adsorption. Sediment collected from Oued Sebou could remove the most MB molecules at pH 8. The Freundlich model described suitably the adsorption process. The experimental measured enthalpy (ΔH) and entropy (ΔS°) are 118.1 kJ mol−1 and 395.2 J mol−1 K−1, respectively, indicating that the reaction was endothermic with an increase of randomness at the solid/liquid interface during the adsorption. The kinetics of MB adsorption by sediment were adequately fitted to the pseudo-second-order model. Experimental results showed that the adsorption capacity of the methylene blue dye depends on the solution pH, the initial dye concentration, the adsorbent mass, the sediment particle diameter, and the temperature of the reaction medium. The removal efficiency of the MB molecules reaches 100% after 60 minutes under the optimum conditions.

Valorization of Oued Sebou Natural Sediments (Fez-Morocco Area) as Adsorbent of Methylene Blue Dye: Kinetic and Thermodynamic Study

The objective of this study is to evaluate the efficiency of methylene blue removal using Oued Sebou sediments as an adsorbent. The presence of carboxyl functional group demonstrated by infrared (IR) analysis of the sediment favorized the methylene blue (MB) adsorption. Sediment collected from Oued Sebou could remove the most MB molecules at pH 8. The Freundlich model described suitably the adsorption process. The experimental measured enthalpy (ΔH) and entropy (ΔS°) are 118.1 kJ mol−1 and 395.2 J mol−1 K−1, respectively, indicating that the reaction was endothermic with an increase of randomness at the solid/liquid interface during the adsorption. The kinetics of MB adsorption by sediment were adequately fitted to the pseudo-second-order model. Experimental results showed that the adsorption capacity of the methylene blue dye depends on the solution pH, the initial dye concentration, the adsorbent mass, the sediment particle diameter, and the temperature of the reaction medium. The removal efficiency of the MB molecules reaches 100% after 60 minutes under the optimum conditions.

Removal of Methylene Blue Using Used Paper Powder

Methylene blue removal by adsorption method had been done in batch method using adsorbent of used paper powder. Adsorption parameters covering adsorbent doses, contact times, pH, adsorbate concentrations and adsorption isotherm as well as desorption study of the absorbed methylene blue were evaluated. The results showed the highest adsorption of methylene blue was obtained at an optimum adsorbent dose, for 30 min at pH > 9. The maximum adsorption capacity of 30.77 mg/g was obtained with Langmuir isotherm model. While the effective methylene blue desorption on the used paper powder adsorbent was obtained c.a. 0.27 mg/g at pH 1.

Order of magnitude increase in photocatalytic rate for hierarchically porous anatase thin films synthesized from zinc titanate coatings

Zinc titanate films are converted into porous anatase showing a 12-fold increase in rate compared to non-porous titania films.

The influence of acid treatments over vermiculite based material as adsorbent for cationic textile dyestuffs

The influence of different acid treatments over vermiculite was evaluated. Equilibrium, kinetic and column studies have been conducted. The results showed that vermiculite first treated with nitric acid and then with citric acid has higher adsorption capacity, presenting maximum adsorption capacities in column experiments: for Astrazon Red (AR), 100.8 ± 0.8 mg g(-1) and 54 ± 1 mg g(-1) for modified and raw material, respectively; for Methylene Blue (MB) 150 ± 4 mg g(-1) and 55 ± 2 mg g(-1) for modified and raw material, respectively. Materials characterization by X-ray diffraction, UV-vis-diffuse reflectance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, X-ray fluorescence, N2 adsorption and CEC determination, has been performed. The results suggest the existence of exchange of interlayer cations, leaching of metals from vermiculite's sheets and formation of an amorphous phase in the material. Adsorption follows pseudo 2(nd) order model kinetics for both dyestuffs and equilibrium occurs accordingly to Langmuir's model for AR and Freundlich's model for MB. In column systems Yan's model is the best fit. The enhanced properties of acid treated vermiculite offer new perspectives for the use of this adsorbent in wastewater treatment.

Acid-modified clays as green catalysts for the hydrolysis of hemicellulosic oligosaccharides

Hemicellulosic oligosaccharide hydrolysis over acid clay catalysts.

Methylene blue and iodine adsorption onto an activated desert plant

Although frequently less toxic than many colorless effluents, colored effluents are generally considered by the public as an indicator of pollution. The present investigation aimed at identifying the effectiveness of a local desert plant characteristic of Southwest Algeria and known as Salsolavermiculata, which was pyrolyzed and treated chemically with a 50% zinc chloride solution, to remove methylene blue and iodine. The natural plant adsorption capacities were respectively 23mg/g and 272mg/g for methylene blue and iodine. Corresponding results for the pyrolyzed plant uptakes were 53mg/g and 951mg/g, while those for the pyrolyzed plant, chemically treated and activated at 650 degrees C, were 130mg/g and 1178mg/g, respectively. In comparison, the standard Merck activated carbon capacities were 200mg/g for methylene blue and 950mg/g for iodine. Consequently, this low-cost local plant may also prove useful for the removal of large organic molecules as well as potential inorganic contaminants.

The influence of modification on structural, textural and adsorption properties of bentonite

Natural bentonite clay from the Bogovina locality in Serbia was Na-exchanged and modified using hexadecyll-trimethylammonium bromide as surfactant and organobentonite was obtained. The influence of modifications on the structural, textural and sorption properties of bentonite was investigated. It was estimated that modifications solely replace exchangeable cations in smectite layers, whereas other admixture minerals (quartz, calcite, feldspar) in bentonite remain unaffected. According to X-ray results the modification lead to changes in the smectite structure by either decreasing, for Na-bentonite, or increasing, for organobentonite, the interplanar spacing, JQOI- The appearance of three new bands in IR spectra of HDTMA-bentonite comparing to those of raw and Na-bentonite assigned to the methylene vibrations confirmed the embedding of aliphatic cations into smectite structure. In organobentonite a significant change in textural properties was observed. In particular, specific surface area dramatically decreased while originally meso and microporous material became almost completely non-porous. Despite almost insignificant specific surface area the synthesized organobentonite due to gained organophyllity of its surface exhibits exquisite adsorption properties toward investigated textile dyes having adsorption capacity approx. 2 times higher than activated carbon.

Composition, structure, and luminescence of montmorillonites saturated with different aggregates of methylene blue

The distribution of various aggregates (dimers, trimers, and tetramers) of methylene blue (MB) formed in aqueous solution at various concentrations of dye has been calculated using the equilibrium aggregation constants betaq. Two montmorillonite samples with different cation exchange capacities, surface areas, and interlayer distances d001, Na-SWy, and Ca-Cheto, were saturated with methylene blue (MB) solutions with various ratios between monomers and higher aggregates of dye. The total amount of MB in the intercalated montmorillonite samples (MB-SWy and MB-Cheto) increases with increasing concentration of dye in water solutions, i.e., with increasing aggregates/monomers ratio of MB in water solution. In all intercalated montmorillonite samples with methylene blue except guest qth aggregate cations [MBqq+] low contents of Na+ (in MB-SWy) and Ca2+ (in MB-Cheto) cations were also determined. A very good positive correlation between the basal spacing d001 and the MB/montmorillonite molar ratio was revealed for saturated MB-montmorillonite samples. Structural analysis using a combination of diffraction data with molecular modeling revealed the differences in the interlayer arrangement of MB guests in MB-SWy and MB-Cheto intercalates. Also, fluorescence measurements showed the strong effect of the silicate layer charge on the spectroscopic behavior of MB guests intercalated in montmorillonite. Methylene blue exhibits a certain luminescence in MB-SWy samples with cation exchange capacity 0.80 meq g-1 and almost no luminescence in MB-Cheto samples with higher cation exchange capacity 1.50 meq g-1.

Investigations into the mechanism of adsorption of carbon nanotubes onto aminopropylsiloxane functionalized surfaces

The factors that control carbon nanotube (CNT) adsorption onto aminopropyl siloxane (APS)-derivatized surfaces were investigated using two distinct types of well-characterized films with significant differences in their detailed structures. Both types of APS films showed a marked increase in CNT adsorption relative to untreated SiO2 surfaces but differed in the amount of CNTs adsorbed. To gain insight into the factors governing adsorption, the surface coverage of the CNTs was monitored as a function of the pH during the deposition, the surfactant used to suspend the CNTs, and the type and amount of salt added to the deposition solution. The adsorption is shown to be governed by electrostatic and VDW forces. In the case of complimentarily charged surfaces, the adsorption is proposed to occur through an ion exchange mechanism.

Thermodynamic and functional properties of legumin (11S globulin from Vicia faba) in the presence of small-molecule surfactants: effect of temperature and pH

We report on the effect of a set of water-dispersible small-molecule surfactants (the main and the longest-hydrocarbon components of which are a citric acid ester of monostearate, a sodium salt of stearol-lactoyl lactic acid, and a polyglycerol ester of stearic acid) on molecular, thermodynamic, and functional properties of the major storage protein of broad beans (Vicia faba) legumin in different molecular states (native, heated, and acid-denatured). The interaction between legumin and the surfactants has been characterized by a combination of thermodynamic methods, namely, mixing calorimetry and multiangle laser static and dynamic light scattering. It was found that hydrogen bonds, electrostatic interactions, and hydrophobic contacts provided a basis for the interactions between the surfactants and both the native and the denatured protein in aqueous medium. Intensive association of the protein molecules in a bulk aqueous medium in the presence of the surfactants was revealed by static and dynamic laser light scattering. In consequence of this, both the surface activity and the gel-forming ability of legumin increased markedly, which has been shown by tensiometry, estimation of protein foaming capacity, and steady-state viscometry. A likely molecular mechanism underlying the effects of small-molecule surfactants on legumin structure-forming properties at the interface and in a bulk aqueous medium is discussed.