Mesoporous Molecular Sieve MCM-41 Research Articles

Characterization and optimization of biodiesel production from corn oil using heterogeneous MoO3/MCM-41 catalysts

Different types of heterogeneous catalysts have been developed worldwide and tested for biodiesel production from corn oil as a feedstock via the transesterification and esterification reactions. In this study, varying contents of MoO3 were incorporated into the mesoporous molecular sieve MCM-41 using the pore saturation method to form heterogeneous catalysts (MoO3/MCM-41). Characterization results confirmed the formation of the MCM-41 structure and the mesoporous phase filling by molybdenum, along with different surface areas, volume, and pore diameters. The silanol groups impart acidity to the molecular sieve, and a molybdenum content above the optimum reduced the availability of acidic sites on the catalyst surface, filling the micro and mesoporous channels, resulting in lower acidity. Catalytic performance was evaluated using a 22 factorial design with three center points to optimize reaction parameters including MoO3content and temperature. The maximum yield was 87.87 %, achieved with a 3 % catalyst load containing 15 wt% MoO3, at an oil-to-alcohol molar ratio of 1:20 at 150 °C for 3 h. Temperature had the most significant influence on biodiesel yield.

An electrochemical sensor for simultaneous voltammetric detection of ascorbic acid and dopamine enabled by higher electrocatalytic activity of co-modified MCM-41 mesoporous molecular sieve

It is of great value to develop effective methods for accurately and simultaneously detecting ascorbic acid (AA) and dopamine (DA) in the field of biochemistry. This work reports a nonenzymatic electrochemical sensor for the simultaneous detection of AA and DA by employing a Co-modified MCM-41 (CoMCM-41) mesoporous molecular sieve as an efficient electrocatalytic material, which was synthesized by a two-step hydrothermal method. Subsequently, the high structural organization of the CoMCM-41 mesoporous structure was characterized, and the electrocatalytic performance of CoMCM-41 toward AA and DA oxidation was then evidenced by the catalytic effect of different electrodes modified with or without CoMCM-41. By virtue of the superior electrocatalytic activity of the CoMCM-41, a much wider peak potential difference (ΔEpa) of 310 mV was obtained for the oxidation of AA and DA in their mixture solution, and the parameters that influenced the electrochemical signals of the modified electrode were also optimized. Under optimal conditions, a good linear response to AA and DA was observed on the CoMCM-41 modified electrode. For individual detection of AA and DA, the linear ranges were 7 ~ 105 μM and 5 ~ 110 μM respectively, while the linear response range was 20 ~ 100 μM for simultaneous detection of AA and DA. Satisfactory recovery results were obtained when the fabricated sensor was applied to determine AA in orange juice and DA in madopar pill samples.

Beyond the boundaries of organics biosorption: Reusable and cost-effective millet-straw-based carboxylate-functionalized mesoporous MCM-41

In this study, we prepared highly porous citric acid-functionalized mesoporous MCM-41 (C-MCM-41) molecular sieve adsorbent from millet straw agricultural residue, which was used for the effective remediation of wastewater contaminated with methylene blue (MB) and ciprofloxacin (CIP). The two-step synthesis process involved extracting highly pure silica from millet straw as a precursor for the ordered mesoporous silica MCM-41. The MCM-41 was synthesized via surfactant-mediated pore design before calcination, followed by citric acid grafting to improve surface functionality and enhance adsorption efficiency. Characterization techniques including XRD, SEM, HRTEM, FTIR, and zeta potential analysis confirmed the mesophase structure, honeycomb pore architecture, functional groups incorporation, and a more electronegative surface, respectively, due to the incorporated carboxyl moieties. Nitrogen adsorption-desorption studies showed a high surface area, which reduced slightly after functionalization. Adsorption of MB and CIP on the C-MCM-41 was superior to the unmodified MCM-41, and the Langmuir isotherm and pseudo-second-order models fitted the equilibrium and kinetic data, respectively. Reuse and cost analysis revealed that C-MCM-41 maintained over 90 % efficiency after four adsorption-desorption cycles and offers a sustainable and cost-effective alternative to conventional adsorbents, demonstrating higher efficiency in treating real wastewater. SynopsisSustainable and cost-effective silica was sourced from biomass and employed for the synthesis of reusable citric acid-functionalized ordered mesoporous silica which was used for the effective treatment of antibiotics contaminated wastewater

Hybrid Molecular Sieve-Based Interfacial Layer with Physical Confinement and Desolvation Effect for Dendrite-free Zinc Metal Anodes.

The side reactions and dendrite growth at the interface of Zn anodes greatly limit their practical applications in Zn metal batteries. Herein, we propose a hybrid molecular sieve-based interfacial layer (denoted as Z7M3) with a hierarchical porous structure for Zn metal anodes, which contains 70 vol % microporous ZSM-5 molecular sieves and 30 vol % mesoporous MCM-41 molecular sieves. Through comprehensive molecular dynamics simulations, we demonstrate that the mesopores (∼2.5 nm) of MCM-41 can limit the disordered diffusion of free water molecules and increase the wettability of the interfacial layer toward aqueous electrolytes. In addition, the micropores (∼0.56 nm) of ZSM-5 can optimize the Zn2+ solvation structures by reducing the bonded water molecules, which simultaneously decrease the constraint force of solvated water molecules to Zn2+ ions, thus promoting the penetrability and diffusion kinetics of Zn2+ ions in Z7M3. The synergetic effects from the hybrid molecular sieves maintain a constant Zn2+ concentration on the surface of the Zn electrode during Zn deposition, contributing to dendrite-free Zn anodes. Consequently, Z7M3-coated Zn electrodes achieved excellent cycling stability in both half and full cells.

Heteroatom Sr doped MCM-41 molecular sieve for VOC adsorption: Study of the surface functionalization and adsorption performance

Volatile organic compounds (VOCs) are recognized as greater adverse effects on both environment and human health, and adsorption is a simple and effective method. Ordered mesoporous MCM-41 molecular sieve was functionalized with heteroatom Sr to change the pore size and surface property by one-step hydrothermal method and adsorption performance for toluene (C7H8) and formaldehyde (CH2O) was investigated. It is found that Sr doped MCM-41 achieves high static adsorption capacities of 534 mg/g for C7H8 and 388 mg/g for CH2O. The dynamic adsorption of C7H8 follows the Langmuir model over Sr doped and undoped MCM-41 under different process conditions, but the dynamic adsorption capacity is only 21 ∼ 99 mg/g. Sr doped MCM-41 maintains a typical pore structure of MCM-41, with some Sr entering the skeleton to form Sr-O-Si bonds. Sr-M−130 has 857 m2/g of SBET and 0.86 cm3/g of Vtotal, but high hydrothermal temperature (150 °C) causes the sintering of MCM-41 structure. Sr doping decreases surface acidity of MCM-41 and increases surface hydroxyl groups (Si-OH). The kinetic diameter and polarity of the adsorbate cause differences in adsorption performance of Sr doped or undoped MCM-41, meaning that the adsorption behavior of non-polar C7H8 mainly depends on surface area and micropore volume while that of polar CH2O is related to the number of ultra-micropore (<1 nm) and forms chemical adsorption of C = O with Si-OH by hydrogen bonds.

Synthesis of MCM-41 mesoporous molecular sieves based on recycled glass fibers from waste fan blades

The development of clean energy leads to a significant increase in decommissioned wind turbine blades, which have become a new type of solid waste.

Rapid Antibiotic Adsorption from Water Using MCM-41-Based Material

The contamination of antibiotics in the environment has raised serious concerns, impacting both human life and ecosystems. This has led to a growing focus on the development of cost-effective and environmentally friendly adsorbent materials. Mesoporous molecular sieve MCM-41, known for its strong adsorption capacity, low cost, and efficient regenerative properties, holds significant promise for addressing this issue. In this study, we investigated the adsorption behavior of demolded MCM-41 materials in relation to tetracycline, doxycycline, and levofloxacin at different temperatures and pH levels. Our experiments encompassed the adsorption of these three common antibiotics, revealing that a neutral or weakly acidic pH environment promoted adsorption, whereas alkaline conditions hindered it. Utilizing the equilibrium isotherm model, we determined the theoretical maximum adsorption capacities for tetracycline (TC), doxycycline (DOX), and levofloxacin (LFX) as 73.41, 144.83, and 33.67 mg g−1, respectively. These findings underscore the significant potential of MCM-41 in mitigating antibiotic wastewater contamination.

Enhancements on volatile organic compounds (VOCs) adsorption and desorption performance of ZSM-5 by fabricating hierarchical MCM-41.

ZSM-5 zeolite has been considered a promising adsorbent for capturing VOCs. However, its hydrophilicity and narrow micropore structure limit their practical application especially under humid atmospheres. In this study, the pure silica mesoporous molecular sieve MCM-41 was assembled on ZSM-5 zeolite with different SiO2/Al2O3 ratios (SARs) via a surfactant-mediated recrystallization method. Then, its adsorption-desorption behaviors were investigated using n-hexane, toluene, and ethyl acetate as VOC model molecules. The results showed that the hydrophobicity of ZSM-5/MCM-41 composites and their VOC diffusion behaviors were significantly improved. Furthermore, the SARs of the ZSM-5 precursors had a remarkable influence on the adsorption performance of ZSM-5/MCM-41 composites. ZSM-5/MCM-41(130) was the optimum option, and its dynamic adsorption capacity for ethyl acetate (111.30 mg·g-1) was higher than that of the corresponding ZSM-5 zeolites even under statured humidity. Meanwhile, the ratios of dynamic adsorption capacities at humid and dry atmospheres (qs,wet/qs,dry) of ZSM-5/MCM-41(130) for n-hexane, toluene, and ethyl acetate were 84.89%, 61.46%, and 73.81% respectively. The results will provide guidelines for the preparation of hydrophobic adsorbents.

Regulating Solvation Structures Enabled by the Mesoporous Material MCM-41 for Rechargeable Lithium Metal Batteries.

For developing the reversible lithium metal anode, constructing an ideal solid electrolyte interphase (SEI) by regulating the Li+ solvation structure is a powerful way to overcome the major obstacles of lithium dendrite and limited Coulombic efficiency (CE). Herein, spherical mesoporous molecular sieve MCM-41 nanoparticles are coated on a commercial PP separator and used to regulate the Li+ solvation structure for lithium metal batteries (LMBs). The regulated solvation structure exhibits an agminated state with more contact ion pairs (CIPs) and ionic aggregates (AGGs), which successfully construct a homogeneous inorganic-rich SEI in the lithium anode. Meanwhile, the regulated solvation structure weakens the interaction between the solvents and Li+, resulting in low Li+ desolvation energy and uniform Li deposition. Thus, a high CE (∼96.76%), dendrite-free Li anode, and stable Li plating/stripping cycling for approximately 1000 h are achieved in the regulated carbonate-based electrolyte without any additives. Therefore, regulating the Li+ solvation structure in the electrolyte by employing a mesoporous material is a forceful way to construct an ideal SEI and harness lithium metal.

Nanoengineered, magnetically guided drug delivery for tumors: A developmental study.

Fighting against tumors is an ongoing challenge in both medicinal and clinical applications. In recent years, chemotherapy, along with surgery, has significantly improved the situation to prolong life expectancy. Theoretically, and regardless of dosage, we now have drugs that are strong enough to eliminate most tumors. However, due to uncontrollable drug distribution in the body, it is difficult to increase treatment efficiency by simply increasing dosages. For this reason, the need for a drug delivery system that can release “bombs” at the target organ or tissue as precisely as possible has elicited the interest of researchers. In our work, we design and construct a silica-based nanocomposite to meet the above demand. The novel nanocomposite drug carrier can be guided to target tumors or tissue by a magnetic field, since it is constructed with superparamagnetic Fe3O4 as the core. The Fe3O4 core is clad in a mesoporous silica molecular sieve MCM-41 (represented as MS, in this article), since this MS has enormous ordered hexagonal caves providing sufficient space to hold the drug molecules. To modify the magnetically guided carriers so that they become both magnetically guided and light-responsive, benzophenone hydrazone is coupled into the molecular sieve tunnel. When a certain wavelength of light is imposed on the gating molecules, C=N double bonds vibrate and swing, causing the cavity that holds the drug molecules to change size and open the tunnels. Hence, the nanocomposite has the ability to release loaded drugs with light irradiation. The structure, loading abilities, and the size of the nanocomposite are inspected with a scanning electron microscope, a transmission electron microscope, thermogravimetry analysis, N2 adsorption/desorption, and dynamic light scattering The biocompatibility and in vitro drug molecule controlled release are tested with an SMMC-7721 cell line.

(Invited) Oxygen Reduction Reaction in Alkaline Media: The Effect of Carbon Support Crystallinity, Conductivity, and Doping

The rapid development of energy consumption combined with growing environmental awareness is conducive to the wide-ranging search for ecological energy sources. In the recent decade, a significant amount of research has focused on the development of anion-exchange membrane (AEM) fuel cells (AEMFCs), as such approach exhibits faster oxygen reduction reaction (ORR) kinetics in the alkaline environment of the cell [1]. However, to become a serious alternative to the current mainstream acidic fuel cells, alkaline systems should overcome current limitations of performance and stability [2]. The design and synthesis of high-performance electrocatalysts facilitating the slow oxygen reduction reaction (ORR) is, therefore, a key issue in the context of the full commercialization of fuel cells. Transition metal oxides with spinel structure constitute an interesting group of potential catalysts that can replace the widely used materials based on Pt [3, 4]. However, due to the low electrical conductivity and the tendency to undesirable aggregation of spinel nanoparticles, it is important to support them on appropriate carbon carriers. Since the nature of the carbon carrier plays a significant role in the ORR activity, we aimed to comprehensively investigate the influence of the electric conductivity of carbon supports, the role of the surface functional oxygen-bearing groups, and doping with heteroatoms on the performance of the bare and cobalt-manganese spinels deposited on the functionalized carbon supports, acting as ORR electrocatalysts in the alkaline media [5].We investigated commercially available Vulcan XC-72, Printex85, MWCNT, amorphous carbon (C-am.), and carbons synthesized by structural nano-replication using the mesoporous molecular sieves MCM-48 (carbon denoted CMK-1) and the spherical silica calcinated at temperature range 650-1050 oC (SPH-650-1050). To investigate the effect of doping on the ORR catalytical activity the MWCNT was modified by nitrogen and sulfur heteroatoms. Additionally, the doped supports were then treated by plasma to introduce surface oxygen groups. On all investigated carbon supports the nanoparticles of manganese-cobalt spinel were dispersed. They were prepared at 150oC by a microwave-assisted hydrothermal route. Comprehensive physicochemical characterization of carbon support was performed using Raman and UV-Vis spectroscopies, XPS, TPD, XRD, TGA techniques, electron microscopy (TEM), and N2 adsorption (BET) (Figure 1). The relative electric conductivity measurements were performed using the contactless microwave technique. The electrochemical properties of the obtained materials were determined by cyclic voltammetry (CV), whereas the electrocatalytic activity of the obtained materials towards ORR was determined using the RDE and RRDE techniques.It was found that the nature of the carbon carrier plays a triple role in the ORR activity, determining dispersion and faceting of the spinel nanoparticles, as well as the extent of the undesired 2e– reduction pathway, controlled by the fraction of an amorphous component. In the case of SPH samples, it was shown that with the increasing carbonization temperature of the carbon support the electric conductivity increase in parallel to the crystallization extent. The electrocatalytic performance of the carbon carriers and the supported cobalt manganese spinels exhibits a volcano-type shape reaching the maximum for carbon materials obtained at 850°C. Such dependence results from two descriptors changing oppositely with the carbonization temperature: an increasing electric conductivity and a decreasing amount of the carbonyl and quinone groups in the sample. The electric conductivity multiplied by the amount of the carboxyl and quinone groups exhibits the same variation with the carbon calcination temperature as the number of electrons exchanged in ORR, confirming that optimal conjunction of these both properties plays a decisive role in this process. The dispersed spinel active phase favors the direct 4e− pathway of ORR and improves the value of the E onset potential distinctly. To the best of our knowledge, the role of electric conductivity and surface oxygen functionalities in the ORR activity over carbon materials and supported spinel electrocatalysts was disentangled for the first time in this study. Acknowledgments: This work was supported by the Polish National Science Centre (NCN) project OPUS-14, No. 2017/27/B/ST5/01004.

Preparation and Characterization of New Electrospun Poly(lactic acid) Nanofiber Antioxidative Active Packaging Films Containing MCM-41 Mesoporous Molecular Sieve Loaded with Phloridzin and Their Application in Strawberry Packaging.

Health concerns about food safety have increased in recent years. In order to ensure the safety and increase the shelf-life of food, many methods have been used to slow down the oxidation rate of food fat. In order to solve this problem, a new type of antioxidant-active packaging has emerged. Poly(lactic acid) (PLA) films containing phloridzin adsorbed on to an MCM-41 mesoporous molecular sieve were prepared by electrostatic spinning, using PLA as a film-forming substrate, phloridzin as an antioxidant, and MCM-41 as the adsorption and controlled release carrier. The physical properties of the new films—including microscopic structure, water vapor transmission rate, and fresh-keeping effects, as well as the mechanical, thermal, antioxidant, and antibacterial properties—were studied. When the mass ratio of MCM-41 to phloridzin is 1:2, the nanofiber membrane achieves a 53.61% free-radical scavenging rate and better antibacterial performance (85.22%) due to the high content of phloridzin (30.54%). Additionally, when the mass ratio of the molecular sieve to phloridzin is 1:2 and 3:4 (with the best antibacterial performance of 89.30%), the films significantly delay lipid oxidation in the strawberry packaging, allowing the fresh-keeping time to be extended to up to 21 days before mildew appears. In this study, an MCM-41 mesoporous molecular sieve was used to load phloridzin for the first time. The packaging film with phloridzin, MCM-41, and poly(lactic acid) were used as the raw materials and electrospinning technology was used to prepare the packaging film with antioxidant activity. The packaging film was used for the first time in the packaging of strawberries.

Ni-based catalysts with coke resistance enhance by radio frequency discharge plasma for CH4/CO2 reforming

Coke deposition has been considered to be one of the most important reasons hindering the stability of the catalyst during CH4/CO2 reforming. In this study, after the addition of P123 (PEG-PPG-PEG triblock copolymer), Ni2+ can be well-dispersed on the mesoporous molecular sieve MCM-41. And then, the catalysts were prepared by using N2 radio frequency (RF) discharge plasma for different treatment times to reduce the size of Ni particles, improve the anti-coking performance, and thereby improve the stability of the catalyst. The results showed that the catalyst NM-P123-PN2h exhibits superior catalytic properties in the CH4/CO2 reforming. The initial conversions of CH4 and CO2 were 90.80% and 89.60% at 750 °C, respectively. The catalyst NM-P123-PN2h showed highly coke resistance with less carbon deposition (1.12%) at 750 °C after 10 h of continuous reaction, while the carbon deposition of the catalyst NM-C was 37.32%. Compared with the traditional calcination method, the catalyst prepared by plasma treatment has a smaller particle size and better dispersibility of nickel. In particular, the nickel particle size of the catalyst NM-C was 8.37 nm, however, that of the catalyst NM-P123-PN2h was only 1.70 nm, and the nickel particle size was reduced by 5 times. Therefore, it can be concluded that the catalyst prepared under the combined action of P123 and RF plasma-treated can effectively improve the coke resistance of the catalyst and the stability of the CH4/CO2 reforming.

Highly efficient nano-Fe/Cu bimetal-loaded mesoporous silica Fe/Cu-MCM-41 for the removal of Cr(VI): Kinetics, mechanism and performance

Zero valent iron (Fe0) can reduce Cr(VI) in water, where Fe0 and Fe(Ⅱ) are possible electron donors, but passivation and aggregation easily occur to Fe0. To improve the performance of Fe0, a new hybridization strategy of Fe/Cu bimetal and silica-based mesoporous molecular sieve MCM-41 for the removal of Cr(VI) from water has been proposed. The results show that the two-dimensional mesoporous structure of MCM-41 can provide skeleton support for Fe0, improve the mass transfer rate, and overcome the aggregation bottleneck of Fe0. The Cr(VI) removal rate reached 98.98% (pH = 2) after 40 min. The analytical results revealed Cr(VI) removal process: Cr(VI) adsorbed onto Fe/Cu-MCM-41 by electrostatic attraction and other molecular inter-atomic forces. The second metal, Cu, can inhibit the passivation of Fe0 and promote Fe(Ⅱ)through the formation of Fe/Cu battery, thereby promoting the electron transfer. The resulting Cr(Ⅲ) is precipitated as FeCr2O4 and CrxFe1−x(OH)3.

Synthesis and Study on Thermal Stability of PMMA Microspheres by Emulsion Polymerization

Polymethyl methacrylate (PMMA) was prepared by emulsion polymerization using methyl methacrylate (MMA) as monomer, potassium per sulfate as initiator. Polymethyl methacrylate/mesoporous molecular sieve composite (PMMA/MCM-48) was synthesized via the addition of mesoporous molecular sieve MCM-48 silica nanomaterial. The synthesized samples were systematically characterized using XRD, SEM, TEM, FT-IR, and TG. The results showed that PMMA microspheres with a diameter of 80-110 nm were prepared by emulsion polymerization. Compared with pure PMMA, PMMA/mesopores molecular sieve MCM-48 composites have good thermal stability. Pure PMMA microspheres can be completely decomposed at a lower temperature (400°C), and the thermal stability of PMMA/MCM-48 composites were improved by the addition of mesoporous molecular sieves.

Тemplate synthesis of multidimensional porous silica

Isothermal data of superficial tension of solutions of surfactant mixture and low-temperature nitrogen sorption of multidimensional porous silica received by template synthesis prove complementarity of its properties and properties of SAA micelles. The measured isotherms of gas sorption belong to IV Type inherent in mesoporous adsorbents. The BET specific surface area is 600–800 m2/g, and the Gurvich pore volume is 0.7–1.0 cm3/g. With increase in mole fraction of nonionic component these values decrease, the ordered texture of SiO2, characteristic of MCM-48 mesoporous molecular sieve, collapses, d211-spacing becomes &lt; 3.31 nm, and NLDFT distribution is transformed from monomodal to polymodal one.

Synthesis of Nanoporous Titanosilicates and Their Structural Characterization by Physical Nitrogen Adsorption

Mesoporous titanosilicate structures synthesized by the sol–gel method using the cetylpyridinium template at different Ti/Si ratios are characterized by high specific surface areas ABET ≈ 800 m2/g and Aext ≈ 900–1000 m2/g, as well as the shape of the isotherms of physical nitrogen adsorption characteristic of the mesoporous molecular sieve MCM-41 with an adsorption branch rising and a section of reversible capillary condensation at a relative pressure of 0.21 < p/p0 < 0.42. An increase in the Ti/Si ratio and pH values leads to a decrease in the dispersion and surface area of the samples. FTIR spectra confirm the presence of titanium(IV) in the silicate framework. The incorporation of titanium(IV) affects the morphology of titanosilicate samples and reduces the ordering of cylindrical mesopores characteristic of MCM-41.

Composite Si-O-metal network catalysts with uneven electron distribution: Enhanced activity and electron transfer for catalytic ozonation of carbamazepine

Electron-rich center and electron-poor center were formed around Si and metal atom linked via Si-O-metal bonding bridge in the Co-Ce doping mesoporous molecular sieves MCM-48 for catalytic ozonation of carbamazepine (CBZ). The density functional theory (DFT) calculations of Co-Ce-MCM-48 concluded that unique Co-O-Si-O-Si-O-Ce had a much lower energy gap than those of Si-O-Si-O-Si-O-Si, Co-O-Si-O-Si-O-Ce and Co-O-Si-O-Si-O-Ce. The successful immobilization of Co-Ce was verified by X-ray absorption fine-structure (XAFS), Raman and 29Si MAS-NMR spectrum. Co-Ce-MCM-48/O3 process achieved 75.6% mineralization of CBZ at 60 min by generation of reactive oxygen species (ROSs) and enhanced redox behaviors of Ce(Ⅲ)/Ce(Ⅳ) and Co(Ⅱ)/Co(Ⅲ). Two new intermediates (P13 and P14) of CBZ in Co-Ce-MCM-48/O3 were observed by DFT and LCMS/MS results. This study opened a new insight by employing an integration of theoretical and experimental techniques to elucidate the synergistic effect of uneven electrons distribution at Co-O-Si-O-Si-O-Ce and catalytic reaction pathway of CBZ.

Removal of Pb (II) from Aqueous Medium by Nanostructured Mesoporous Material MCM-48: Studies on Equilibrium, Isotherm, Kinetics and Thermodynamics

Background: In recent years, with the progress of human civilization, environmental pollution is aggravating. Among them, heavy metal pollution is one of the greatest harmful water pollution problems. As a global pollution problem, heavy metal pollution, such as lead, has been given more attention by scientists. How to solve this problem, is an interesting issue. Objective: The aims of the current study are to develop the optimized adsorption conditions of Pb2+ by an MCM (Mobil Composition of Matter)-48 mesoporous molecular sieve material and study the properties of this adsorption. Method: First, an MCM-48 mesoporous molecular sieve was prepared by the hydrothermal method by using cetyltrimethylammonium as the template and tetraethyl orthosilicate as the silica source. The prepared sample was characterized by powder X-ray diffraction and scanning electron microscopy. Then, a harmful heavy metal Pb2+ was adsorbed by MCM-48. Effects of acidity, contact time, temperature, the initial concentration of lead(II) and the dosage of adsorbent on the rates of adsorption were studied, and the optimum adsorptive conditions were obtained. Results: The results show that when pH value was 4.5, the temperature was 18 ± 1°C, contact time was 40 min and m(MCM-48): m(Pb2+) = 2.5 (mass ratio), the adsorptive effect was the best, the adsorption rate was 96.71% and the adsorptive capacity was 386.84 mg/g. After the kinetic calculation, it was known that the process of the adsorption of Pb2+ by MCM-48 conforms to the pseudo-secondorder kinetic equation. Thermodynamic calculation shows that the adsorption is an exothermic process. The adsorption obeys the Freundlich adsorption isotherm equation. Nitric acid, hydrochloric acid and acetic acid were used to study the effects of desorption, indicating that the desorptive effect was the best using 0.1 mol/L of nitric acid as a desorptive agent. At the time of desorption 6 h, its desorptive ratio was the highest and reached 71.11%. Conclusion: This method is an alternative for removing harmful substances containing lead, which has a potential for application in processing lead-polluted waters.

Ionic liquid-modified MCM-41-polymer mixed matrix membrane for butanol pervaporation.

Because of the preferential butanol selectivity of some ionic liquids (ILs), an increasing amount of research has appeared regarding their application in butanol separation. In this research, two ionic liquids, namely, 1-ethyl-3-vinylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([EVIM][Tf2N], IL1) and N-octyl-pyridinium bis[(trifluoromethyl)sulfonyl]imide ([OMPY][Tf2N], IL2), were applied to modify a mesoporous molecular sieve MCM-41. The IL-modified MCM-41 samples were characterized by XPS, BET, XRD, SEM and TEM. The ionic liquid-modified MCM-41 was incorporated into the polymer PEBA to prepare mixed matrix membranes to study the influences of the filling of IL-modified MCM-41 and operating conditions on the performance of the mixed matrix membrane for butanol pervaporation. The results indicated that the pervaporation performance of the PEBA membrane was enhanced by the incorporation of IL-modified MCM-41. When the temperature of the feeding liquid was 35°C and the mass fraction of butanol was 2.5 wt%, the 5% MCM-41-IL2-PEBA membrane showed a permeation flux of 421.7 g m−2 h−1 and a separation factor of 25.4. The permeation flux and the separation factor of the membrane increased as the temperature of the feeding liquid increased. The results of the long-period experiment suggested that the 5% MCM-41-IL2-PEBA membrane exhibited high stability within 100 h of operation.