Functionalization of porous silica with graphene oxide and polyethyleneimine, containing zinc copper ferrite nanoparticles for water treatment and antibacterial application

The article discusses the removal of methylene blue (MB) dye, a common cationic dye used in the textile industry, from aqueous solutions through an adsorption process. The use of porous components as adsorbents are shown to facilitate complete separation after the process is completed. The substrate was synthesized by connecting zinc copper ferrite (ZnCuFe2O4), polyethyleneimine (PEI), and Graphene Oxide (GO) sheets to MCM-48, which is a mesoporous material. The surface of MCM-48 was modified using CPTMS, which created an O-Si-Cl bridge, thereby improving the adsorption rate. The substrate was shown to have suitable sites for electrostatic interactions and creating hydrogen bonds with MB. The adsorption process from the Freundlich isotherm (R2 = 0.9224) and the pseudo-second-order diagram (R2 = 0.9927) demonstrates the adsorption of several layers of dye on the heterogeneous surface of the substrate. The synthesized substrate was also shown to have good bactericidal activity against E. coli and S. aureus bacterial strain. Furthermore, the substrate maintained its initial ability to adsorb MB dye for four consecutive cycles. The research resulted that ZnCuFe2O4@MCM-48/PEI-GO substrate has the potential for efficient and economical removal of MB dye from aqueous solutions (R = 88.82%) (qmax = 294.1176 mg. g-1), making it a promising solution for the disposal of harmful industrial waste.

The Antimicrobial Potency of Mesoporous Silica Nanoparticles Loaded with Melissa officinalis Extract

Melissa officinalis is an important medicinal plant that is used and studied intensively due to its numerous pharmacological effects. This plant has numerous active compounds with biomedical potential; some are volatile, while others are sensitive to heat or oxygen. Therefore, to increase stability and prolong biological activities, the natural extract can be loaded into various nanostructured systems. In this study, different loading systems were obtained from mesoporous silica, like Mobile Composition of Matter family (MCM) with a hexagonal (MCM-41) or cubic (MCM-48) pore structure, simple or functionalized with amino groups (using 3-aminopropyl) such as triethoxysilane (APTES). Thus, the four materials were characterized from morphological and structural points of view by scanning electron microscopy, a BET analysis with adsorption-desorption isotherms, Fourier-transform infrared spectroscopy (FTIR) and a thermogravimetric analysis coupled with differential scanning calorimetry. Natural extract from Melissa officinalis was concentrated and analyzed by High-Performance Liquid Chromatography to identify the polyphenolic compounds. The obtained materials were tested against Gram-negative bacteria and yeasts and against both reference strains and clinical strains belonging to Gram-positive bacteria that were previously isolated from intra-hospital infections. The highest antimicrobial efficiency was found against Gram-positive and fungal strains. Good activity was also recorded against methicillin-resistant S. aureus, the Melissa officinalis extract inhibiting the production of various virulence factors.

Hard tissue formation in pulpotomized primary teeth in dogs with nanomaterials MCM-48 and MCM-48/hydroxyapatite: an in vivo animal study

BACKGROUND

This animal study sought to evaluate two novel nanomaterials for pulpotomy of primary teeth and assess the short-term pulpal response and hard tissue formation in dogs. The results were compared with mineral trioxide aggregate (MTA).

METHODS

This in vivo animal study on dogs evaluated 48 primary premolar teeth of 4 mongrel female dogs the age of 6-8 weeks, randomly divided into four groups (n = 12). The teeth underwent complete pulpotomy under general anesthesia. The pulp tissue was capped with MCM-48, MCM-48/Hydroxyapatite (HA), MTA (positive control), and gutta-percha (negative control), and the teeth were restored with intermediate restorative material (IRM) paste and amalgam. After 4-6 weeks, the teeth were extracted and histologically analyzed to assess the pulpal response to the pulpotomy agent.

RESULTS

The data were analyzed using the Kruskal‒Wallis, Fisher's exact, Spearman's, and Mann‒Whitney tests. The four groups were not significantly different regarding the severity of inflammation (P = 0.53), extent of inflammation (P = 0.72), necrosis (P = 0.361), severity of edema (P = 0.52), extent of edema (P = 0.06), or connective tissue formation (P = 0.064). A significant correlation was noted between the severity and extent of inflammation (r = 0.954, P < 0.001). The four groups were significantly different regarding the frequency of bone formation (P = 0.012), extent of connective tissue formation (P = 0.047), severity of congestion (P = 0.02), and extent of congestion (P = 0.01). No bone formation was noted in the gutta-percha group. The type of newly formed bone was not significantly different among the three experimental groups (P = 0.320).

CONCLUSION

MCM-48 and MCM-48/HA are bioactive nanomaterials that may serve as alternatives for pulpotomy of primary teeth due to their ability to induce hard tissue formation. The MCM-48 and MCM-48/HA mesoporous silica nanomaterials have the potential to induce osteogenesis and tertiary (reparative) dentin formation.

Adsorption of high-temperature CO2 by Ca2+/Na+-doped lithium orthosilicate: characterization, kinetics, and recycle

High-temperature solid adsorbent Li4SiO4 has received broad attention due to its high theoretical adsorption capacity, high regeneration capacity, and wide range of raw materials for preparation. In this paper, a Li4SiO4 adsorbent was prepared by MCM-48 as the silica precursor and modified by doping with metal ions (Ca2+ and Na+) for high-temperature capture of low-concentration CO2. The results showed that the surface of the Ca-doped (or Na-doped) Li4SiO4 adsorbent developed some particles that are primarily composed by Li2CaSiO4 (or Li3NaSiO4). Furthermore, the grains of the adsorbents became finer, effectively increasing the specific surface area and enhancing adsorption performance. Under 15 vol% CO2, the maximum CO2 adsorption was 25.63 wt% and 32.86 wt% when the Ca2+ doping amount was 0.06 and the Na+ doping amount was 0.12, respectively. These values were both higher than the adsorption capacity before the metal ion doping. After 10 adsorption/desorption cycles, the adsorption capacity of Na-doped Li4SiO4 increased by 9.68 wt%, while that of Ca-doped Li4SiO4 decreased by 7.98 wt%. This difference could be attributed to the easy sintering of the Ca-containing adsorbent. Furthermore, a biexponential model was used to fit the CO2 adsorption curve of the adsorbent in order to study the adsorption kinetics. Compared to the conventional Li4SiO4, the Ca/Na-doped adsorbent offers several advantages, such as a high CO2 adsorption capacity and stable cycling ability.

Extraction of heavy metals from wastewater using amine-modified mesoporous silica

Presence of heavy metals in wastewater is a critical environmental issue, and efficient extraction of the metals remains a challenging task. In this study, the adsorption behavior of Ce(III), Hg(II), and Cu(II) metal ions using MCM-48 material modified with acid and base functional groups was examined. The modified materials were characterized using various techniques, including XRD, BET, FT-IR, NMR, and SEM, which revealed that the materials' properties remained unchanged after modification. The adsorption capacity of the modified materials for metal ions was then evaluated and was found that the amine-modified MCM-48 material exhibited the highest adsorption efficiency. Precisely, the amine-modified material achieved an adsorption capacity of 97% for Ce(III), 98% for Hg(II), and 90% for Cu(II) after 180 min of adsorption. These results highlight the effectiveness of amine functionalization in enhancing the adsorption capacity of silica material for heavy metals.

Low temperature synthesis of MCM-48 and its adsorbent capacity for the removal of basic red 29 dye from model solutions

The low temperature synthesis of MCM-48 was performed and its adsorptive properties were investigated for the first time in literature by studying Basic Red 29 (BR29) dye adsorption from model solutions. The modification of the surface properties and pore structure of silica-based material MCM-48 induced by BR29 adsorption were characterized using XRD, nitrogen physisorption, and SEM methods before and after dye adsorption. The effects of contact time, solution pH, dye concentration, and temperature on the adsorption capacity of MCM-48 were investigated. Different adsorption models and different kinetic models were used, respectively to define the equilibrium data and the kinetics of adsorption. Adsorption data was seen to fit the Langmuir isotherm and the pseudo-second-order kinetic model. In addition, MCM-48 was found to be very successful for the removal of the BR29 dye model solutions, even at an initial dye concentration of 500 mg/L for which the removal efficiency was above 97%.

Application of MCM-48 with large specific surface area for VOCs elimination: synthesis and hydrophobic functionalization for highly efficient adsorption

MCM-48 molecular sieve with a large specific area (1470.87 m²/g) was hydrothermally synthesized for VOCs elimination by the adsorption method. The dynamic adsorption behaviors of toluene on this material were evaluated via breakthrough curves under both dry and wet conditions. A high toluene adsorption capacity of 171.13 mg/g was observed under dry conditions; however, in the presence of water vapor (20% RH), the adsorption capacity greatly decreased to 58.88 mg/g due to the competitive occupation of adsorption sites between water molecules and toluene molecules. To improve the affinity to toluene, functionalized MCM-48 materials were obtained by the co-condensation method and grafting method, respectively. It was found that co-M48(1:5)-100/48 sample by co-condensation method presents the highest dynamic adsorption capacity at both dry condition (194.62 mg/g) and 20% RH (122.42 mg/g), which has a significant advantage in the same type of adsorbent. This could be ascribed to the conjugated π-electrons effect between aromatic rings of phenyl groups uniformly distributed in MCM-48 skeleton and toluene molecules, which was qualitatively confirmed by FTIR. Moreover, cycle tests confirmed that this adsorbent possesses superior stability. The Yoon-Nelson model was successfully employed to describe the dynamic adsorption behavior of toluene over the organofunctionalized MCM-48 adsorbents, and the adsorption force of toluene was explained. Finally, a diagram describing the effect of different functionalization methods on the hydrophobicity and organophilicity of MCM-48 was given for a better understanding.

Rosaniline Hydrochloride Encapsulated MCM-48: Fluorescent and Electrochemical Sensor for Dopamine

The dye Rosaniline hydrochloride (RANH) has been successfully incorporated in MCM-48 (designated as RANH@MCM-48) and characterized by various spectroscopic methods including FT-IR, SEM, EDX and N₂ adsorption-desorption isotherm. RANH@MCM-48 in aqueous medium acts as fluorescence "on" sensor for neurotransmitter dopamine (DA) in presence of its main biological interfering agent ascorbic acid or vitamin c (AA) along with Glucose, Cholesterol and Uric acid (UA). The limits of detection (LOD) were found to be 65 nM and 51 nM respectively in absence and in presence of AA. The interaction of DA to RANH@MCM-48 is found to be reversible with respect to EDTA^2-. The fluorescence intensity vs. pH plot shows a narrow fluorescence window of 7.2 to 8.8. RANH@MCM-48 has been successfully applied for DA detection in artificial cerebrospinal fluid (ACF) and bovine serum albumin (BSA) with LOD values 27 nM and 22.5 nM respectively. Platinum disc electrode has been modified with RANH@MCM-48 which showed distinct oxidation peaks with a separation of 0.188 V in cyclic voltammetry (CV). The LOD for DA in presence of AA determined from oxidation current is 77.5 nM. The voltammetric detection of DA is found to be free from common interfering species Na⁺, K⁺, Ca²⁺, Fe²⁺, UA, Cholesterol and Glucose. RANH@MCM-48 has been found to be a very effective fluorescence and voltammetric sensor for DA with very low  LOD.

In Situ Calb Enzyme Immobilization in Mesoporous Material Type MCM-48 Synthesis Using Ionic Solid [C14MI]Cl as Structure-Directing Agent

MCM-48 mesoporous support was synthesized with the ionic solid 1-tetradecyl-3-methylimidazolium chloride ([C₁₄MI]Cl) as a structure-directing agent for in situ immobilization of Candida antarctica B (CALB). The MCM-48[C₁₄MI]Cl support showed characteristics of mesoporous material of interest, with a pore size of 20.30 and 73.41 A for the support without and with the enzyme, respectively. The elongation of the carbonic chain of the ionic solid directly influenced the increase in the specific area and pore volume of the material. In addition, the decrease in the specific area and pore volume for support with the enzyme showed the effectiveness of immobilization in situ. It was possible to obtain the ideal levels for the best activities of esterification of the enzyme with optimization of a mathematical model. The optimized variables were 0.31 g of enzyme and 3.35% of ionic solid with a maximum esterification activity of 392.92 U/g and 688% of yield. The support showed residual activity above 50% when stored under refrigeration for 75 days. At 60 and 80 °C, the enzyme immobilized on the support retained more than 80 and 40% of its residual activity, respectively. In addition, the support presented the possibility of reuse for up to 10 cycles with residual activity of approximately 50%. The support synthesized in the present study presents a great industrial opportunity for the immobilization and use of the CALB enzyme.

Facile Preparation of Mesoporous MCM-48 Containing Silver Nanoparticles with Fly Ash as Raw Materials for CO Catalytic Oxidation

An environmentally friendly method was proposed to prepare mesoporous Mobil Composition of Matter No.48 (MCM-48) using fly ash as the silica source. Silver nanoparticles were infiltrated on MCM-48 facilely by an in situ post-reduction method and evaluated as an effective catalyst for CO oxidation. The as-prepared MCM-48 and Ag/MCM-48 nanoparticles were characterized by XRD, N₂ adsorption/desorption, and TEM. Investigations by means of XPS for Ag/MCM-48 were performed in order to illuminate the surface composition of the samples. Studies revealed the strong influence of the loading of Ag nanoparticles on catalysts in the oxidation of CO. CO conversion values for Ag/MCM-48 of 10% and 100% were achieved at temperatures of 220 °C and 270 °C, respectively, indicating that the Ag-decorated MCM-48 catalyst is extremely active for CO oxidation.

Insight into chitosan/mesoporous silica nanocomposites as eco-friendly adsorbent for enhanced retention of U (VI) and Sr (II) from aqueous solutions and real water

The chitosan chains were integrated with MCM-48 mesoporous silica in an eco-friendly composite (CH/MCM-48) of enhanced adsorption capacity. The prepared CH/MCM-48 composite was applied in systematic retention of U (VI) as well as Sr (II) ions from water as the commonly detected radioactive pollutants. It displayed promising retention capacities of 261.3 mg/g and 328.6 mg/g for U (VI) and Sr (II) considering the equilibrium time interval that was identified after 420 min. The composite showed the kinetic behavior of the Pseudo-First order model and the isotherm properties of the Langmuir assumption. The thermodynamic assessment of the reactions validated the retention of both U (VI) and Sr (II) ions by spontaneous, favorable, and exothermic reactions. Based on the theoretical values of entropy (-5.94 kJ mol^-1 (U (VI)) and -2.93 kJ mol^-1 (Sr (II))), Gibbs free energy (less than 20 kJ mol^-1), and Gaussian energy (5.77 kJ mol^-1 (U (VI)) and 4.56 kJ mol^-1 (Sr (II))) the uptake processes are related to physical adsorption reactions. The CH/MCM-48 composite is of significant recyclability and showed considerable affinities for the studied radioactive ions even in the presence of other metal ions (Cd (II), Pb (II), Zn (II), and Co (II)).

Micelles of Mesoporous Silica with Inserted Iron Complexes as a Platform for Constructing Efficient Electrocatalysts for Oxygen Reduction

Iron, N-codoped carbon materials (Fe-N-C) are promising electrocatalysts toward oxygen reduction reactions due to their high atom utilization efficiency and intrinsic activity. Nanostructuring of the Fe-N-C materials, such as introducing porosity into the carbon structure, would be conducive to further increasing the exposure of active sites as well as improving the mass transfer. Herein, we explore the potential of iron complex-functionalized micelles of mesoporous SiO₂ as a platform for constructing porous Fe-N-C materials. The classical three-dimensional MCM-48 was selected as a proof-of-concept example, which was utilized as the hard template, and cetyltrimethylammonium bromide micelles inside it played the role of the main carbon source. Fe-N_x sites were derived from Fe-1,10-phenanthroline complexes in the micelles introduced by in situ incorporation of 1,10-phenanthroline and post Fe²⁺ insertion in an aqueous solution. After thermal annealing in a nitrogen atmosphere and subsequent removal of the MCM-48 framework, a carbon material that possesses porous structural features with uniformly dispersed Fe-N_x sites (MPC@PhFe) was obtained, which shows superior ORR activity in a 0.1 M KOH solution and great potential for Zn-air battery applications as well. This work demonstrates the feasibility as well as the effectiveness of turning micelles of mesoporous SiO₂ into porous carbon structures and might offer a universal strategy for manufacturing carbon materials for future application in energy storage and conversion.

Preparation and characterization of MCM-48/nickel oxide composite as an efficient and reusable catalyst for the assessment of photocatalytic activity

Mesoporous silica (MCM-48) was synthesized and used as a catalyst for supporting the nickel oxide photocatalyst. The loading of nickel oxide on MCM-48 results in a considerable reduction in the bandgap energy to 2.4 eV. MCM-48 was used as a catalyst and back-supporter for the nickel oxide to enhance its photocatalytic properties along with adsorption capacity. Therefore, the adsorption capacity of MCM-48/Ni₂O₃ was enhanced by 17.5% and 32.2% compared to Ni₂O₃ and MCM-48, respectively. Furthermore, the percentage of photocatalytic degradation was improved by approximately 68.2% relative to the free-standing Ni₂O₃. The MCM-48/Ni₂O₃ proved the chemisorption adsorption mechanism that happens in multilayer form through the heterogeneous surface. This through fixing such Ni₂O₃ particles over the nanoporous topography to provide more exposed hot adsorption and photocatalytic sites for the incident light photons. Therefore, supporting Ni₂O₃ catalytic particles onto MCM-48 produces a new category of photocatalytic systems with promising active centers for the efficient degradation of Congo red dye molecules.

Surfactant-Triggered Molecular Gate Tested on Different Mesoporous Silica Supports for Gastrointestinal Controlled Delivery

In recent decades, the versatility of mesoporous silica particles and their relevance to develop controlled release systems have been demonstrated. Within them, gated materials able to modulate payload delivery represent great advantages. However, the role played by the porous matrix in this kind of systems is scarce. In this work, different mesoporous silica materials (MCM-41, MCM-48, SBA-15 and UVM-7) are functionalized with oleic acid as a molecular gate. All systems are fully characterized and their ability to confine the entrapped cargo and release it in the presence of bile salts is validated with release assays and in vitro digestion experiments. The cargo release profile of each synthesized support is studied, paying attention to the inorganic scaffold. Obtained release profiles fit to Korsmeyer–Peppas model, which explains the differences among the studied supports. Based on the results, UVM-7 material was the most appropriate system for duodenal delivery and was tested in an in vivo model of the Wistar rat. Payload confinement and its complete release after gastric emptying is achieved, establishing the possible use of mesoporous silica particles as protection and direct release agents into the duodenum and, hence, demonstrating that these systems could serve as an alternative to the administration methods employed until now.

Investigation of in vitro permeability and in vivo pharmacokinetic behavior of bare and functionalized MCM-41 and MCM-48 mesoporous silica nanoparticles: a burst and controlled drug release system for raloxifene

In the present work, MCM-41 and MCM-48 type of nanoparticles were successfully engineered. Effect of nanosize and amine functionalization on drug release, in vitro intestinal absorption and in vivo pharmacokinetic behavior was investigated in a comprehensive manner. The tailor-made bare and surface decorated MCM-41 and MCM-48 were synthesized and evaluated for their mesoporous skeleton, pore size, particle size, surface area, zeta potential, etc. by nitrogen sorption, DLS, TEM, etc. Incorporation of raloxifene (RLF) was affirmed using optimized immersion-solvent evaporation technique and its success confirmed by DSC, IR, and XRD analysis. TGA analysis revealed higher %grafting of amine groups on the exterior and larger RLF encapsulation into mesoporous derivate. The detailed in vitro release study revealed SGF to be the most compatible media for RLF showing an initial burst release from pristine nanoparticles and a delayed release from surface coated nanoparticles. Furthermore, release kinetics model data demonstrated Weibull and Higuchi as the best fit models for bare and amine-functionalized nanoparticles respectively. Moreover, an in vitro permeability study on Caco-2 cell line revealed higher absorption by engineered nanoparticle as compared to pure RLF and its marketed formulation. The supremacy in the in vivo pharmacokinetic parameters of RLF-41 and RLF-48 was demonstrated with 3.33 and 3.50 times enhancement in the bioavailability of RLF with respect to RLF suspension. To sum up, the results obtained were superior and promising for synthesized nanoparticles and more precisely for MCM-48 amongst them.

Electrochemical Detection of Dopamine at a Gold Electrode Modified with a Polypyrrole⁻Mesoporous Silica Molecular Sieves (MCM-48) Film

A gold electrode modified with a polypyrrole–mesoporous silica molecular sieves (polypyrrole—MCM-48) nanostructure film was used for the electrochemical determination of small concentrations of dopamine (DA) by cyclic voltammetry and square-wave voltammetry techniques. This electrode showed good electrocatalytic activity for the oxidation of dopamine. The oxidation potential of dopamine was decreased significantly compared with that obtained at the bare gold electrode. The observed linear range for the determination of the dopamine concentration, without interferents through cyclic voltammetry measurements, was from 10 μM to 1.2 mM (R² = 0.9989) for the gold electrode modified with the polypyrrole—MCM-48 nanostructure, with a detection limit of 2.5 μM. In the case of square-wave voltammetry, the linear range was 2–250 μM, with a correlation coefficient of 0.9996, and the detection limit was estimated to be 0.7 μM. The effects of interferents, such as ascorbic acid (AA) and uric acid (UA), on the electrochemical detection of dopamine were also examined. The modified electrode can successfully separate the oxidation potentials for ascorbic acid and dopamine, shifting the oxidation peak potential of ascorbic acid to a more positive potential, and significantly decreasing the peak current. The presence of ascorbic acid increased the sensitivity of dopamine determination at the modified electrode, and the detection limit was estimated to be 0.5 μM with 0.1 mM ascorbic acid to imitate physiological solutions. Additionally, studies showed that the presence of uric acid does not affect the electrochemical detection of dopamine. The modified electrode can be successfully applied for the quantitative analysis of dopamine both with and without interferents.

Synthesis and characterization of MCM-48/hydroxyapatite composites for drug delivery: Ibuprofen incorporation, location and release studies

MCM-48 is crystalline, mesoporous silicate used in catalysis and for adsorption various molecules to create useful materials for chemistry, pharmacy and medicine. In this work, the MCM-48 silicate has been coated with nanohydroxyapatite (HA) to design a new drug delivery system. The MCM-48/hydroxyapatite composite was synthesized using a new method involving precipitation of HA onto the earlier prepared MCM-48. The method gives an interesting mesoporous material capable of adsorbing drugs on its external surface and on the internal surface in mesopores. This was shown using ibuprofen (Ibu). The MCM-48/HA composites and MCM-48/HA/Ibu conjugates have been thoroughly characterized using various physicochemical methods. It was concluded that the MCM-48/HA composite offers a significant potential for controlled drug delivery systems involving small API molecules.

Photocatalytic removal of Congo red dye using MCM-48/Ni2O3 composite synthesized based on silica gel extracted from rice husk ash; fabrication and application

MCM-48 mesoporous silica was successfully synthesized from silica gel extracted from rice husk ash and loaded by nickel oxide (Ni₂O₃). The resulted composite was characterized using X-ray diffraction, scanning electron microscope, and UV-vis spectrophotometer. The role of MCM-48 as catalyst support in enhancing the photocatalytic properties of nickel oxide was evaluated through the photocatalytic degradation of Congo red dye under visible light source. MCM-48 as catalyst support for Ni₂O₃ shows considerable enhancement in the adsorption capacity by 17% and 29% higher than the adsorption capacity of MCM-48 and Ni₂O₃, respectively. Additionally, the photocatalytic degradation percentage increased by about 64% relative to the degradation percentage using Ni₂O₃ as a single component. The adsorption mechanism of MCM-48/Ni₂O₃ is chemisorption process of multilayer form. The using of MCM-48 as catalyst support for Ni₂O₃ enhanced the adsorption capacity and the photocatalytic degradation through increasing the surface area and prevents the nickel oxide particles from agglomeration. This was done through fixing nickel oxide particles throughout the porous structure which providing more exposed active adsorption sites and active photocatalyst sites for the incident photons. Based on the obtained results, supporting of nickel oxide particles onto MCM-48 are promising active centers for the degradation of Congo red dye molecules.

Performance assessment of MCM-48 ceramic composite membrane by separation of AlCl3 from aqueous solution

Three dimensional ordered mesoporous MCM-48 membrane was fabricated on a circular shaped ceramic support by in-situ hydrothermal method. The synthesized MCM-48 powder and MCM-48 ceramic composite membrane were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). The porosity and pore size of the composite membrane are reduced considerably by the deposition of MCM-48 on the support. The formation of MCM-48 is verified by the XRD analysis. Three stepwise mechanisms for surfactant removal are observed by TGA analysis. FESEM images clearly signify the deposition of MCM-48 on the ceramic support. The pure water flux of the support and MCM-48 composite membrane is found to be 3.63×10^-6 and 4.18×10^-8m³/m²skPa, respectively. The above prepared MCM-48 ceramic composite membrane is employed for the removal of AlCl₃ from aqueous solution and the highest rejection of 81% is obtained at an applied pressure of 276kPa with salt concentration of 250ppm.

Cross flow ultrafiltration of Cr (VI) using MCM-41, MCM-48 and Faujasite (FAU) zeolite-ceramic composite membranes

This work describes the removal of Cr (VI) from aqueous solution in cross flow mode using MCM-41, MCM-48 and FAU zeolite membranes prepared on circular shaped porous ceramic support. Ceramic support was manufactured using locally available clay materials via a facile uni-axial compaction method followed by sintering process. A hydrothermal technique was employed for the deposition of zeolites on the ceramic support. The porosity of ceramic support (47%) is reduced by the formation of MCM-41 (23%), MCM-48 (22%) and FAU (33%) zeolite layers. The pore size of the MCM-41, MCM-48 and FAU membrane is found to be 0.173, 0.142, and 0.153 μm, respectively, which is lower than that of the support (1.0 μm). Cross flow ultrafiltration experiments of Cr (VI) were conducted at five different applied pressures (69-345 kPa) and three cross flow rates (1.11 × 10(-7) - 2.22 × 10(-7) m(3)/s). The filtration studies inferred that the performance of the fabricated zeolite composite membranes is optimum at the maximum applied pressure (345 kPa) and the highest rejection is obtained with the lowest cross flow rate (1.11 × 10(-7) m(3)/s) for all three zeolite membrane. The permeate flux of MCM-41, MCM-48 and FAU zeolite composite membranes are almost remained constant in the entire duration of the separation process. The highest removal of 82% is shown by FAU membrane, while MCM-41 and MCM-48 display 75% and 77% of Cr (VI) removal, respectively for the initial feed concentration of 1000 ppm with natural pH of the solution at an applied pressure of 345 kPa.

Spherical V-Fe-MCM-48: The Synthesis, Characterization and Hydrothermal Stability

Spherical MCM-48 mesoporous sieve co-doped with vanadium and iron was successfully synthesized via one-step hydrothermal method. The material was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherms, inductively coupled plasma (ICP), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis spectra, and X-ray photoelectron spectra (XPS) techniques. Results indicated that the V-Fe-MCM-48 showed an ordered 3D cubic mesostructure with spherical morphology, narrow pore size distribution and high specific surface area. Most of vanadium and iron atoms existing as tetrahedral V⁴⁺ and Fe³⁺ species were co-doped into the silicate framework. The particle sizes of V-Fe-MCM-48 were smaller and the specific area was much higher than those of of V-MCM-48. Additionally, the synthesized V-Fe-MCM-48 exhibited improved hydrothermal stability compared with the pure MCM-48.