Mesoporous Membranes Research Articles

A laboratory-based electrochemical NAP-XPS system for operando electrocatalysis studies

During electrocatalytic reactions, the electrode, adsorbates, electrolyte ions, and solvent molecules at the electrode-electrolyte interface each play an important role. Electrochemical X-ray photoelectron spectroscopy (XPS) holds great promise for deciphering these roles, providing the oxidation state or bonding environment of every element present at the interface. However, combining the vacuum required for XPS with the wet environment needed for electrochemistry constitutes a technical challenge, requiring purpose-built instrumentation and spectro-electrochemical cell design. Here, we present a laboratory-based electrochemical XPS instrument optimized for operando studies on nano-structured electrocatalysts. The core of the system is a 3D printed spectro-electrochemical cell containing a membrane-electrode-graphene assembly. We show that this design enables us to probe the electrode surface, interfacial water, and interfacial ions under well-defined potential control. Meanwhile, the introduction of a mesoporous membrane into the assembly enables the transport of any molecular or ionic reactant towards the working electrode, opening the way to study any aqueous phase electrocatalytic system using laboratory-based electrochemical XPS. We exemplify this for the oxygen reduction reaction.

Mesoporous Silica-Based Membranes in Transdermal Drug Delivery: The Role of Drug Loss in the Skin.

Compared to other forms of drug administration, the use of Transdermal Drug Delivery Systems (TDDSs) offers significant advantages, including uniform drug release profiles that contribute to lower side effects and higher tolerability, avoidance of direct exposure to the gastrointestinal tract, better patient compliance due to their non-invasive means of application and others. Mesoporous silica membranes are of particular interest in this regard, due to their chemical stability and their tunable porous system, with adjustable pore sizes, pore volumes and surface chemistries. While this allows for fine-tuning and, thus, the development of optimized TDDSs with high loading capacities and the desired release profile of a given drug, its systemic availability also relies on skin penetration. In this paper, using a TDDS based on mesoporous silica membranes in Franz cell experiments on porcine skin, we demonstrate surprisingly substantial drug loss during skin penetration. Drug passage through porcine skin was found to be dependent on the age and pre-treatment of the skin. pH and temperature were major determinants of drug recovery rates as well, indicating drug loss in the skin by enzymatic metabolization. Regarding the TDDS, higher loading obtained by SO3H surface modification of the mesoporous silica membranes reduced drug loss. Still, high loss rates in the skin were determined for different drugs, including anastrozole, xylazine and imiquimod. We conclude that, beyond the fine-tuned drug release profiles from the mesoporous silica membrane TDDS, remarkably high drug loss in the skin is a major issue for achieving desired skin penetration and, thus, the systemic availability of drugs. This also poses critical requirements for defining an optimal TDDS based on mesoporous silica membranes.

Morphological Transitions of Block Copolymer Micelles: Implications for Mesoporous Materials Ordering

AbstractThe design of block‐copolymer‐based functional materials, including mesoporous membranes and nanoparticles, requires a comprehensive understanding of the hierarchical assembly of block copolymers in selective solvents into micelles and subsequent ordered phases. It is hypothesized that micellar ordering and characteristic assembly can be described using a set of phase parameters that account for entropic and enthalpic interactions. Dissipative particle dynamics (DPD) simulations are used to systematically investigate the self‐assembly of semidiluted block copolymers, resembling isoporous membrane preparation conditions. The effect of Flory–Huggins interaction parameters, block lengths, and concentration on the morphology and polydispersity of the micelles is evaluated. The interaction parameters are mapped into Flory–Huggins theory by considering the block's conformation. These results reveal the effect of polymer concentration and solvent affinity on the morphological transition of the aggregates, in agreement with existing experimental evidence. It is identified that monodisperse‐spherical micelles in solution are fundamental to stabilize ordered states. Weak solvent segregation of the largest block, curvature of the core‐corona interface, and stretching of the corona‐forming one are found to be key to stabilize monodisperse assemblies. These conditions can be predicted using spherical‐micelles packing considerations and a global phase parameter from the Flory–Huggins theory. This study provides valuable insights into the self‐assembly of diblock copolymers and offers a potential way to optimize the preparation of mesoporous ordered structures and micelle ordering in semidiluted systems.

Unipolar Ionic Diode Nanofluidic Membranes Enabled by Stepped Mesochannels for Enhanced Salinity Gradient Energy Harvesting.

Developing ionic diode membranes featuring asymmetric structures is in high demand for salinity gradient energy harvesting. These membranes offer benefits in mitigating ion concentration polarization, thereby promoting ion permeability. However, most reported works focus on the role of heterogeneous charge-based bipolar ionic diode membranes for ion concentration polarization suppression, with comparatively less attention given to maintaining ion selectivity. Herein, unipolar ionic diode nanofluidic mesoporous silica membranes featuring stepped mesochannels were developed via a micellar sequential oriented interfacial self-assembly strategy as a salinity gradient energy harvester. Due to the asymmetric mesochannels and unipolar structure (both sides carry negative charge), the ionic diode membranes exhibit a strong rectification ratio of ∼15.91 to facilitate unidirectional ion transport while maintaining excellent cation selectivity (cation transfer number of ∼0.85). Besides, the vertically aligned mesochannels significantly reduce ion transport resistance, generating a high ionic flux. Consequently, the unipolar ionic diode nanofluidic membranes demonstrate a power output of 5.88 W/m2 between artificial sea and river water. The unipolar feature gives notable enhancements of 296% and 144% in power output compared to the symmetric membrane and bipolar ionic diode membrane, respectively. This work opens up new routes for designing ionic diode membranes for salinity gradient energy harvesting.

Probing Ion Diffusion and Ion Sieving through Hollow Porous Silica Shells by Imaging the Mobility of Colloids Inside the Shells

AbstractIonic transport through porous membranes and porous materials has received enormous attention due to its importance to many applications. An innovative methodology is proposed to study ion diffusion and ion sieving through mesoporous silica membranes (shells). The mobility of fluorescently labeled core particles within a hollow porous shell, filled with an index‐matched electrolyte solution, is observed using confocal laser scanning microscopy. The core motion range, i.e., the area explored by the core within the hollow compartment, sensitively changed depending on the local ionic concentration. Monitoring transitions in the core motion range is a practical way to detect which ions can migrate through the shells and on what timescale. For instance, lithium and chloride ions easily diffused through the porous silica shells, resulting in a core motion range that changed relatively quickly upon change of the ion concentrations outside of the shell. However, the motion range changed significantly slower upon changing to a bigger cation (tetraoctylammonium ion). This proof of principle experiment can be explained by the Gibbs‐Donnan effect, revealing that the detection of core motion ranges is a good probe to measure both ion diffusion and ion sieving through porous membranes.

Carbonic anhydrase immobilized on Zn(II)-geopolymer membrane for CO2 capture

Inorganic membranes are widely used in water filtration and gas separation due to their many advantages. In this work, we proposed an innovative approach for enzyme immobilization using a geopolymer based tubular inorganic membrane (GM) as a carrier. The GM has abundant mesopores, excellent mechanical strength and strong stability for continuous flow systems in biocatalysis field, and carbonic anhydrase (CA) was successfully loaded into this mesoporous membrane using adsorption-crosslinking method, relying on the excellent ion exchange capacity of geopolymers and large number of hydroxyl groups naturally present in the membrane's mesopores. The results of the immobilization experiments showed that the immobilized enzyme composite membrane (GZnM-CA) could achieve 63.7% enzyme recovery. This is a significant improvement over the enzyme recoveries obtained on organic membranes which are typically less than 50%. In stability tests, the membrane retained more than 90.0% relative activity after 10 consecutive uses. In the CO2 capture assay, the CO2 capture efficiency developed dramatically under the catalytic of GZnM-CA. To our delight, the membrane has excellent separation capability for CO2 gas mixtures, especially at low CO2 concentrations, achieving 99.90% CO2 removal rate, and this result can be maintained for a long period of time in a pH = 8.0 environment.

High-performance separation for ultra-low concentration nanoparticles with mesoporous silica thin membrane

Mesoporous silica thin film membrane (MSTF) emerges as an ideal ultrafiltration membrane for the removal of nanoparticles, ensuring the production of particle-free water. This is mainly ascribed to its uniform and narrow pore size distribution, having vertical nanochannels with low tortuosity, and being ultrathin, which helps enhance its selectivity and permeability. In this study, we demonstrated the potential of MSTF overlayed on macroporous anodic aluminum oxide (AAO) support for separating gold nanoparticles even at a very low concentration. Moreover, with the addition of pore-expanding agents, E-MSTF⊥AAO (pore size 3.12 nm) and D-MSTF⊥AAO (pore size 5.26 nm) membranes are formed, and both membranes indeed showed high rejection efficiency towards 150 ppb gold nanoparticles of sizes 10 nm and 5 nm, ∼99 %, and ∼96 %, respectively. It is also worth noting that as compared to the state-of-the-art conventional UF membranes, the E-MSTF⊥AAO membrane showed significantly high permeance of 114.1 ± 12.76 L m−2 h−1 bar−1 and 104.1 ± 50.6 L m−2 h−1 bar−1 while efficiently separating 150 ppb and 50 ppb 5 nm gold nanoparticles, respectively. Moreover, the promising long-term stability and chemical stability of the MSTF⊥AAO membrane paved a promising path for applying mesoporous silica membranes for effective nanoparticle separation in wastewater treatment and particle-free water production in industries.

Gel-casting of mesoporous silica electrolyte membranes loaded with phosphoric acid for protonic electrolyte cells

Proton conducting membranes that operate at temperatures above 100 °C are highly sought after for use in energy devices such as fuel cells owing to the high catalytic activity of electrodes induced by elevated temperature and no requirement for water management. In the present study, novel mesoporous silica membranes were prepared by a gel-casting process using commercial colloidal silica and subsequent sintering. These membranes served as the scaffold for phosphoric acid-based electrolytes. Well-interconnected mesopores with uniform pore sizes was effective for hosting phosphoric acid (PA), and the tunable pore sizes (5.9–32.0 nm) were achieved by tuning the sintering temperature from 500 to 725 °C. High porosity (about 50%) and high hydrophilicity of silica membranes are beneficial to reach high phosphoric acid loading by an impregnation process. The PA-loaded membrane sintered at 700 °C achieved a high protonic conductivity of 0.11 S cm−1 and a peak power density of 287.3 mW cm−2 in hydrogen fuel cells at 160 °C. The conductivity is 1 order of magnitude higher than that of the pressed meso-silica membranes and comparable to that of PA-mesoporous silica spheres. This study has demonstrated a new method to construct high-temperature protonic electrolyte membranes.

Active Dendrite Suppression by Ferroelectric Membrane Separators in Rechargeable Batteries.

Anodic dendrite formation is a critical issue in rechargeable batteries and often leads to poor cycling stability and quick capacity loss. Prevailing strategies for dendrite suppression aim at slowing down the growth rate kinetically but still leaving possibilities for dendrite evolution over time. Herein, we report a complete dendrite elimination strategy using a mesoporous ferroelectric polymer membrane as the battery separator. The dendrite suppression is realized by spontaneously reversing the surface energetics for metal ion reduction at the protrusion front, where a positive piezoelectric polarization is generated and superimposed as the protrusion compresses the separator. This effect is demonstrated first in a Zn electroplating process, and further in Zn-Zn symmetric cells and Zn-NaV3O8·1.5H2O full cells, where the dendritic Zn anode surfaces are completely turned into featureless flat surfaces. Consequently, a substantially longer charging/discharging cycle is achieved. This study provides a promising pathway toward high-performance dendrite-free rechargeable batteries.

Mesoporous silica-grafted deep eutectic solvent-based mixed matrix membranes for wastewater treatment: Synthesis and emerging pollutant removal performance

Abstract Nano-enhanced membrane technology and deep eutectic solvents (DESs) have demonstrated effectiveness in addressing emerging environmental pollutants. This research centers on purifying water by removing heavy metals employing membranes enhanced with mesoporous silica and DES. Various DESs, including hexanoic acid, octanoic acid, and decanoic acid, were synthesized using tetrabutylammonium bromide (TBABr) as a base. The study combined a polysulfone-based membrane with mesoporous silica, aiming for efficient indigenous crafting to remove heavy metals. Mesoporous silica was blended with the synthesized DES solution, creating diverse membranes for heavy metal separation. The study characterized these membranes using various techniques such as scanning electron microscopy, atomic force microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and contact angle measurements. Surface mapping confirmed the integration of silicon-based DES, reducing the membrane surface roughness from 4 to 1.4 nm. By adjusting the carboxylic acid chain length with TBABr and adding mesoporous silica, leaching ratios were reduced from 4.2 to 2.3%. Silica-grafted DES-based membranes exhibited a progressive increase in flux from 2.6 to 26.67 L/m2 h. The synthesized silicon-based membranes demonstrated outstanding performance, achieving rejection rates exceeding 80% for chromium and arsenic, maintaining an impressive 90% flux recovery ratio even at high flux rates. This study will envision the potential of nano-enhanced membrane technology utilizing DES for sustainable water purification and wastewater treatment applications to achieve the sustainable development goal (SDG) of clean water and sanitation (SDG-6).

Long-lifespan Zinc-ion Capacitors Enabled by Anodes Integrated with Interconnected Mesoporous Chitosan Membranes through Electrophoresis-driven Phase Separation.

The advancement of highly secure and inexpensive aqueous zinc ion energy storage devices is impeded by issues, including dendrite growth, hydrogen evolution and corrosion of zinc anodes. It is essential to modify the interface of zinc anodes that homogenizes ion flux and facilitates highly reversible zinc planarized deposition and stripping. Herein, by coupling zinc ion coordination with acid-base neutralization under the driving of electrophoresis, manageable mesoscopic phase separation for constructing chitosan frameworks was achieved, thereby fabricating interconnected mesoporous chitosan membranes based heterogeneous quasi-solid-state electrolytes integrated with anodes. The framework is constructed by twisted chitosan nanofiber bundles, forming a three-dimensional continuous spindle-shaped pore structure. With this framework, the electrolyte provides exceptional ion conductivity of 25.1 mS cm-1 , with a puncture resistance strength of 2.3 GPa. In addition, the amino groups of chitosan molecule can make the surface of the framework positively charged. Thus, reversible zinc planarized deposition is successfully induced by the synergistic effect of stress constraint and electrostatic modulation. As a result, as-assembled zinc ion capacitor has an excellent cycle life and sustains the capacity by over 95 % after 20000 cycles at a current density of 5 A g-1 . This research presents a constructive strategy for stable electrolytes-integrated zinc anodes.

Long‐lifespan Zinc‐ion Capacitors Enabled by Anodes Integrated with Interconnected Mesoporous Chitosan Membranes through Electrophoresis‐driven Phase Separation

AbstractThe advancement of highly secure and inexpensive aqueous zinc ion energy storage devices is impeded by issues, including dendrite growth, hydrogen evolution and corrosion of zinc anodes. It is essential to modify the interface of zinc anodes that homogenizes ion flux and facilitates highly reversible zinc planarized deposition and stripping. Herein, by coupling zinc ion coordination with acid‐base neutralization under the driving of electrophoresis, manageable mesoscopic phase separation for constructing chitosan frameworks was achieved, thereby fabricating interconnected mesoporous chitosan membranes based heterogeneous quasi‐solid‐state electrolytes integrated with anodes. The framework is constructed by twisted chitosan nanofiber bundles, forming a three‐dimensional continuous spindle‐shaped pore structure. With this framework, the electrolyte provides exceptional ion conductivity of 25.1 mS cm−1, with a puncture resistance strength of 2.3 GPa. In addition, the amino groups of chitosan molecule can make the surface of the framework positively charged. Thus, reversible zinc planarized deposition is successfully induced by the synergistic effect of stress constraint and electrostatic modulation. As a result, as‐assembled zinc ion capacitor has an excellent cycle life and sustains the capacity by over 95 % after 20000 cycles at a current density of 5 A g−1. This research presents a constructive strategy for stable electrolytes‐integrated zinc anodes.

Ultra-Stable Inorganic Mesoporous Membranes for Water Purification.

Thin, supported inorganic mesoporous membranes are used for the removal of salts, small molecules (PFAS, dyes, and polyanions) and particulate species (oil droplets) from aqueous sources with high flux and selectivity. Nanofiltration membranes can reject simple salts with 80-100% selectivity through a space charge mechanism. Rejection by size selectivity can be near 100% since the membranes can have a very narrow size distribution. Mesoporous membranes have received particular interest due to their (potential) stability under operational conditions and during defouling operations. More recently, membranes with extreme stability became interesting with the advent of in situ fouling mitigation by means of ultrasound emitted from within the membrane structure. For this reason, we explored the stability of available and new membranes with accelerated lifetime tests in aqueous solutions at various temperatures and pH values. Of the available ceria, titania, and magnetite membranes, none were actually stable under all test conditions. In earlier work, it was established that mesoporous alumina membranes have very poor stability. A new nanofiltration membrane was made of cubic zirconia membranes that exhibited near-perfect stability. A new ultrafiltration membrane was made of amorphous silica that was fully stable in ultrapure water at 80 °C. This work provides details of membrane synthesis, stability characterization and data and their interpretation.

Cellulose-based mesoporous membrane co-engineered with MOF for high-safety lithium-ion batteries

At present, the commercial polyolefin membranes for lithium-ion battery (LIBs) usually have poor thermal stability, poor wettability and high cost. Herein, we developed a sustainable mesoporous membrane with good anionic grabbing effect based on the biomass cellulose co-engineered with the metal–organic frameworks (MOFs). The abundant oxygen-containing functional groups in cellulose can enhance the affinity of the membrane with the electrolyte. And the coordination of the metal ions in MOFs with the functional groups in cellulose not only prevents the aggregation of the cellulose to form uniform porous structure, but also enhances the mechanical strength of the membrane. More importantly, the MOFs has appropriate mesopore size and strong cationic site, which can crab the PF6- anions in the electrolyte, thus promoting the fast transfer of Li+, thereby inhibiting the growth of lithium dendrite. In summary, this work put forward a simple and efficient strategy for designing the membrane with fast Li+ transfer, high safety and thermal stability and for LIBs.

Chemical surface modification of mesoporous SiO2-based membranes for fine-tuning of drug loading and release properties

Transdermal Drug Delivery Systems (TDDS) show significant advantages over other forms of drug application. Despite their clinical use for decades, these drug delivery devices have yet to reach their full potential. While polymer matrices are most commonly used as transdermal patches so far, inorganic carriers like mesoporous silica membranes offer several advantages, including chemical stability and their tunable porous system, with adjustable pore sizes, pore volumes and surface chemistries. In this study, we chemically modified high and low porosity mesoporous silica membranes by post-synthetic methods and compared the effects of different surface modifications on loading efficacies and release profiles of different pharmacologically relevant drugs with different chemical properties. Drug loading capacities and release profiles were substantially affected by pore structure and surface modifcations with strongly acidic SO3H groups or hydrophobic methyl groups, while weakly acidic COOH groups or nitrile groups showed little effects. SO3H modification of low porosity (LP) membranes led to markedly increased loading capacity and a more sustained release profile of anastrozole. The latter was also observed for xylazine, but associated with lesser drug loading. Likewise, the SO3H modification also slowed down the release of imiquimod or flunixin. Increasing LP membrane hydrophobicity by methyl modification essentially abolished anastrozole drug loading. In high porosity (HP) membranes, effects of chemical surface modifications were overall weaker. This led to particularly slow anastrozole or xylazine release profiles from methyl-modified membranes. Biocompatibility studies showed some cell-inhibitory effects of CN functionalization, but full biocompatibility of SO3H functionalized membranes as indicated by efficient cell attachment and high viability. Both parameters, pore structure and chemical surface modifcations, drug-dependently affect drug loading and release properties. Since they can be precisely fine-tuned in mesoporous silica membranes, this allows for the development of optimized TDDS providing high drug loading and the desired release profile of a given drug. Our results presented here indicate that the SO3H modification is particularly useful in this regard.

Preparation of chitosan mesoporous membrane/halloysite composite for efficiently selective adsorption of Al(III) from rare earth ions solution through constructing pore structure on substrate

The removal of impurity Al(III) from rare earth ion solution by selective adsorption method was one of the challenging tasks. Herein, calcination and acid dissolution treatment were used to construct the pore structure for the halloysite substrate (Hal-650-H) and provide conditions for the formation of the chitosan mesoporous membrane to prepare composite (Hal-H-2CS). The selective adsorption properties and mechanism of the Hal-H-2CS for Al(III) in the rare earth ion solution were studied. The results showed that the formation of mesoporous structures for chitosan provided abundant sites for the adsorption of Al(III). Hal-H-2CS showed remarkable selective adsorption properties for Al(III) in a wide pH range and the binary mixtures with high content of Al(III) or La(III). The maximum adsorption capacity of Al(III) was 106 mg/g, while the adsorption capacity of La(III) was only 1.41 mg/g at pH 4.0. In addition, the Hal-H-2CS exhibited excellent regeneration and structural stability. The remarkable selective properties of Hal-H-2CS was achieved by the synergistic effect between chitosan mesoporous membrane and Hal-650-H, the main adsorption sites were the OH, NH2, CONH2 of chitosan and the oxygen sites of the Hal-650-H. This work provides a new strategy for the design and preparation of outstanding selective adsorbent for Al(III).

Development of mesoporous ceramic membranes of diatomite/TiO2/Nb2O5 nanocomposites for the treatment of contaminated water

There is an urgent need for low cost and efficient methods for the treatment of contaminated water; in this regard the combination of natural minerals for the preparation of sieves is of special interest. The aim of this work is to develop mesoporous composite ceramic membranes using low-cost minerals: diatomite, niobium pentoxide (Nb2O5) and titanium dioxide (TiO2) powders. The multilayer samples were prepared by the tape casting technique. Initially, four tapes with different relative amounts of the minerals are prepared (diatomite %/ TiO2 %/ Nb2O5 %); the samples are A (1/0/0), B (0.9/0.1/0), C (0.9/0.05/0.05) and D (0.9/0/0.1). These tapes were cut, arranged in a multilayer, pressed, and calcined at 500 °C in presence of air. Then, these multilayers were sintered at 1200 °C in presence of argon to form the ceramic membranes (CM): CM-A, CM-B, CM-C and CM-D. A fifth ceramic membrane CM-E was prepared by combining tapes B and D. The X-ray diffraction characterization identified the phases cristobalite, quartz, anatase, rutile, and H-Nb2O5. The three-point bending test demonstrated a 225 % increase in strength after the incorporation of Nb2O5 and TiO2 particles to the diatomite matrix. For instance, the CM-A and CM-C membranes showed 4.28 and 13.90 MPa, respectively. The monolithic ceramic membranes showed high surface area, the BET analysis indicated a narrowing of pore sizes when are added Nb2O5 and TiO2 particles to diatomite; and showed surface areas of up to 6.161 m2 g-1. The composites presented band gap energies in the range of 3.19–3.70 eV. The ability of the ceramic membranes in the photodegradation of methylene blue in aqueous solutions was tested, the results showed a degradation of up to 87.3 % of the dye.

Composite Silica-Based Films as Platforms for Electrochemical Sensors.

Sol-gel-derived silica thin films generated onto electrode surfaces in the form of organic-inorganic hybrid coatings or other composite layers have found tremendous interest for being used as platforms for the development of electrochemical sensors and biosensors. After a brief description of the strategies applied to prepare such materials, and their interest as electrode modifier, this review will summarize the major advances made so far with composite silica-based films in electroanalysis. It will primarily focus on electrochemical sensors involving both non-ordered composite films and vertically oriented mesoporous membranes, the biosensors exploiting the concept of sol-gel bioencapsulation on electrode, the spectroelectrochemical sensors, and some others.

Cu-doped mesoporous TiO2 photocatalyst for efficient degradation of organic dye via visible light photocatalysis

A solvothermal method was used to synthesize the mesoporous TiO2, (1-3w %) Cu-doped mesoporous TiO2 membrane with the help of a bioreactor. To understand the physicochemical composition of all synthesized nanomaterials, the structure, morphology and crystallinity of the materials were studied using X-ray diffractometer (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform-infrared (FTIR), Energy dispersive X-ray spectroscopy (EDS) and cyclic voltammetry (CV). Under artificial light source (500 W mercury bulb) irradiations, the nano catalysts' catalytic effectiveness was examined for the azo dyes, namely Congo red. Cu-doping causes a shift in the light absorption of mTiO2 from the ultraviolet to the visible region. The 3w% Cu-doped mTiO2 photocatalyst exhibits lower band gap energy (2.6eV) than TiO2 which is 3.2 eV to efficiently utilize solar energy. As a result, the light absorption was shifted towards the visible spectrum. The recommended mTiO2 and (1, 2, 3) w% Cu-doped mTiO2 photocatalysts were used to photodegrade Congo red and methylene blue. For the degradation of CR, the mTiO2 photocatalyst exhibited 61% and 3w% Cu-doped mTiO2 demonstrated 99% photocatalytic performance after 50 min. A variety of scavengers were also utilized to distinguish the active species by catching the radicals and holes created during the process of photocatalytic degradation. CV indicates the presence of Cu2+ and Cu1+ in Cu-doped mTiO2. Oxygen vacancies and the electronegative surface of Cu1+ seem to perform the photocatalytic reduction of CR.

Mesoporous SiC-Based Photocatalytic Membranes and Coatings for Water Treatment.

Photocatalytically active silicon carbide (SiC)-based mesoporous layers (pore sizes between 5 and 30 nm) were synthesized from preceramic polymers (polymer-derived ceramic route) on the surface and inside the pores of conventional macroporous α-alumina supports. The hybrid membrane system obtained, coupling the separation and photocatalytical properties of SiC thin films, was characterized by different static and dynamic techniques, including gas and liquid permeation measurements. The photocatalytic activity was evaluated by considering the degradation efficiency of a model organic pollutant (methylene blue, MB) under UV light irradiation in both diffusion and permeation modes using SiC-coated macroporous supports. Specific degradation rates of 1.58 × 10-8 mol s-1 m-2 and 7.5 × 10-9 mol s-1 m-2 were obtained in diffusion and permeation modes, respectively. The performance of the new SiC/α-Al2O3 materials compares favorably to conventional TiO2-based photocatalytic membranes, taking advantage of the attractive physicochemical properties of SiC. The developed synthesis strategy yielded original photocatalytic SiC/α-Al2O3 composites with the possibility to couple the ultrafiltration SiC membrane top-layer with the SiC-functionalized (photocatalytic) macroporous support. Such SiC-based materials and their rational associations on porous supports offer promising potential for the development of efficient photocatalytic membrane reactors and contactors for the continuous treatment of polluted waters.