Surface Of Monolith Research Articles

Development of a flow reactor incorporating polydopamine-poly(ε-caprolactone) with gold particles

Addressing the significant challenge of dye wastewater pollution, this study introduces a novel solution employing a flow catalytic reactor loaded with gold (Au) particles. The reactor utilizes a porous monolithic material with a Poly(ε-caprolactone) (PCL) matrix as the carrier for Au particles, with polydopamine employed to immobilize the Au onto the surface of the PCL monolith. To assess the catalytic efficiency of the reactor, a model catalytic degradation experiment involving the reaction between methyl orange (MO) and sodium borohydride was conducted. The catalytic reaction was facilitated by a peristaltic pump. The reactor setup involved fixing the monolith within a heat shrinkable tube, and the peristaltic pump ensured the flow catalytic reaction. The protective effect of liquid nitrogen was utilized to confirm that the porous structure of the PCL monolith, with its low melting point, remained intact after being fixed in the heat shrink tube. Catalytic results revealed remarkable efficacy, with the decomposition efficiency of MO reaching 98.54%. This flow reactor enables continuous operation, making it more practical for real-world applications compared to traditional batch methods. Furthermore, even after 5 cycles, the sample maintained a catalytic efficiency exceeding 90%, demonstrating the excellent reusability of the reactor.

Cellulose/GO monolith covered with Pd–Pt bimetallic nanocrystals for continuous-flow catalytic reduction of hexavalent chromium

Cellulose monolith materials have interconnected open porous structures with very high porosity, making them attractive structures for use as support materials in heterogeneous catalysis applications. In this study, we developed a highly efficient and reusable continuous-flow reactor for Cr(VI) remediation by combining the advantageous features of cellulose monoliths with suitable reinforcement techniques. We fabricated a porous monolithic cellulose/graphene oxide (GO) composite with a continuous three-dimensional skeletal framework using the thermally induced phase separation technique. Pd nanocrystals were synthesized in situ on the surface of the composite monolith, and then converted to porous Pd–Pt bimetallic nanocrystals through a galvanic replacement reaction. This approach eliminated the need for additional reductants and stabilizers, making the process simpler and more environmentally friendly. Under carefully optimized conditions, the cellulose/GO/Pd–Pt nanocomposite monolith exhibited outstanding performance in continuous-flow reactions for Cr(VI) reduction, achieving a maximum conversion rate of 98 %. Moreover, the nanocomposite monolith-based heterogeneous catalyst exhibited remarkable long-term stability, maintaining its catalytic activity even after extended periods of storage in the dried state. These findings highlight the potential of cellulose-based composite monoliths as versatile and robust support materials for heterogeneous catalysis.

Effect of the surface composition of MnOX-CeOX 3D-printed monolithic catalysts toward total oxidation of toluene.

Successful fabrication of Mn-based 3D-printed monoliths by stereolithography (SLA) is reported for the first-time in this work. The catalytic performances, as function of the surface composition, of the developed monoliths were evaluated by the total oxidation of toluene. The monolith with a surface composition of Mn0.7Ce0.3 showed the highest catalytic efficiency (98%) with a T90 value of 322 °C and acceptable catalytic stability after a second reaction cycle. By changing space velocity values, the T90 value can decrease to 311 °C. Microstructural and surface characterizations confirm the formation of Mn2O3 and Ce species on Mn sites and the homogeneous dispersion of Mn and Ce species on the surface of the 3D-printed monoliths. For comparison purposes, a single MnOX and CeOX monoliths were also synthesized and tested by toluene total oxidation, which confirms the cooperative effect between the oxygen storage capacity of Ce and the redox ability of Mn species observed in Mn0.7Ce0.3 monolith catalyst, giving rise to the highest catalytic activity. These results pointed out the promising catalytic properties of the developed Mn-based 3D-printed monolith catalysts for the total oxidation of volatile organic compounds at a low cost, which is an interesting alternative to mitigating atmospheric emissions.

Highly efficient and recyclable monolithic bioreactor for interfacial enzyme catalysis

HypothesisBiocatalysts are key to the realization of all bioconversions in nature. However, the difficulty of combining the biocatalyst and other chemicals in one system limits their application in artificial reaction systems. Although some effort, such as Pickering interfacial catalysis and enzyme-immobilized microchannel reactors, have addressed this challenge an effective method to combine chemical substrates and biocatalysts in a highly efficient and re-usable monolith system is still to be developed. ExperimentsA repeated batch-type biphasic interfacial biocatalysis microreactor was developed using enzyme-loaded polymersomes in the void surface of porous monoliths. Polymersomes, loaded with Candida antarctica Lipase B (CALB), are fabricated by self-assembly of the copolymer PEO-b-P(St-co-TMI) and used to stabilize oil-in-water (o/w) Pickering emulsions as a template to prepare monoliths. By adding monomer and Tween 85 to the continuous phase, controllable open-cell monoliths are prepared to inlay CALB-loaded polymersomes in the pore walls. FindingsThe microreactor is proven to be highly effective and recyclable when a substrate flows through it, which offers superior benefits of absolute separation to a pure product and no enzyme loss. The relative enzyme activity is constantly maintained above 93% in 15 cycles. The enzyme is constantly present in the microenvironment of the PBS buffer ensuring its immunity to inactivation and facilitating its recycling.

Incorporation of metal-organic framework MOFs-5 into the polymer monolith via the surface covalent immobilization method for enhanced capillary liquid chromatographic separation of benzene homologues

In this study, metal organic framework material MOFs-5 was immobilized covalently on the surface of polymer monolith to improve the separation efficiency of small molecular compounds in the mode of capillary liquid chromatography (cLC) firstly. Scanning electron microscopy, fourier transform infrared spectroscopy and flow-through property test were applied to characterize the novel [email protected] monolith, confirming that MOFs-5 was effectively immobilized on the surface of polymer monolith via covalent reactions. More importantly, Benzene homologues (benzene and phenol) which could be separated by the commercialized C18 packed chromatographic column have been well separated via the [email protected] monolith. By contrast, there wasn't any separation between benzene and phenol via the original polymer monolith. Moreover, the relative standard deviation was less than 2.2 % for run-to-run. These results showed that the [email protected] monolith is a kind of potential commercialized material for small molecular compound separation in the mode of cLC.

Modification of Monolith for Simultaneous SO2 /NO x Removal from Flue Gas

The aggressive acid treatment creates a wealth of oxygen-containing functional groups (-OH, C=O, C-O) on the surface of an adsorbent and acts as binding sites for catalyst support therefore, in this study, the surface of monolith (ACM) was oxidized via the acid modification and high temperature activation. Various types of catalysts from the precursors of cerium nitrate (CeO2 /ACM), copper nitrate (CuO/ACM) and cobalt nitrate (Co3 O4 /ACM) using the deposition precipitation synthesis method. The catalyst activity tests were investigated in a fixed bed reactor by passing a stream of flue gas generated by burning coal. The breakthrough study of SO2 /NOx and the experimental results showed that for CeO2 /ACM catalyst the adsorption capacity of SO2 was 24.3 and 18.5 mg/g for NOx and for CuO/ACM catalyst they were 27.0 and 32.8mg/g and for Co3 O4 /ACM catalyst, values obtained were 10.6 and 49.7mg/g. FTIR, BET and FESEM analysis were performed. This investigation depicts the development of highly efficient adsorbent for flue gas treatment.

Degradation of cotton stalk lignin by carbon dots loaded copper oxide synergistic emulsion system

Based on the realization of efficient utilization of cotton stalk lignin, the degradation of cotton stalk lignin by a CDs/CuO synergistic emulsion system was investigated. Copper oxide (CuO) nanoparticles with monoclinic crystal structure were prepared and carbon dots (CDs) synthesized by microwave method was combined with CuO. Under visible light, water and n-butanol were used to construct a water–oil (W/O) emulsion reaction system to achieved depolymerisation of lignin into small molecule compounds. The involvement of hydrogen peroxide (H2O2) makes the degradation of lignin in this system even more effective. The final high value-added monophenolic compound of 57.70 mg g−1 was obtained, among which the most abundant were six monophenolic compounds such as vanillin, eugenol and vinyl guaiacol and so on. The results of GC-MS and FTIR characterization indicated that H-type monomers were the main products of lignin degradation in this system. The process conditions for lignin hydrogenolysis in this system were optimized and the best ratio of CDs/CuO was obtained by product analysis. There were characterized by SEM, TEM, XRD, XPS, FTIR, and US–vis. The results show that CDs/CuO aggregates into flower clusters, in which CDs are uniformly distributed on the surface of rhomboidal CuO monoliths. The analysis shows that the doping of CDs improves the absorption efficiency of CuO in the visible region, while reducing the complexation of CuO photogenerated electrons and holes, which achieves the purpose of improved photocatalytic activity of CuO.

Robust Dual-Biomimetic Titanium Dioxide-Cellulose Monolith for Enrichment of Phosphopeptides.

Metal oxide affinity chromatography (MOAC) is considered to be one of the most effective methods for phosphopeptide enrichment. However, most of the materials used in the method are powder; frequent centrifugation is necessitated during the enrichment process, and potential risks of loss of peptides and materials and clogging of the column employed for liquid chromatography-mass spectrometry (LC-MS) arise. Moreover, the reusability of these materials to achieve sustainability was hardly investigated. To overcome these limitations, herein, inorganic titanium dioxide (TiO2) was coated onto the skeletal surface of the organic cellulose monolith (CM) material with a coral-like structure via a sol-gel method. This produced an organic-inorganic hybrid TiO2-CM material, which contained a combination of organic and inorganic substances, making it mimic the mollusk shell in terms of composition. The prepared TiO2-CM material as monolith exhibited excellent mechanical strength and did not break during the enrichment process; thus, the tedious implementation of multiple centrifugation cycles was prevented, thereby streamlining the experimental procedure and avoiding the loss of peptides and materials. Moreover, a large amount of TiO2 was introduced onto the surface of the CM material, and thus, the resultant TiO2-CM material exhibited a large surface area. As a result, the fabricated TiO2-CM material was successfully applied to the enrichment of phosphopeptides obtained from the tryptic digests of a BSA/β-casein (mass ratio, 500/1) mixture. The results were superior to those achieved for commercial TiO2 beads, confirming that TiO2-CM has excellent selectivity for phosphopeptides and reusability. Furthermore, 9287 unique phosphopeptides derived from the 2661 phosphoproteins were successfully identified from two milligrams of tryptic digests of Hela cell exosomes obtained through five independent replications after enriching using the TiO2-CM material. The results indicated that the material has good application prospects in the analysis of protein phosphorylation. Furthermore, TiO2-CM consists of green and cheap cellulose as the skeleton, and its synthesis process is environment-friendly, simple, and inexpensive.

Coating Process of Honeycomb Cordierite Support with Ni/Boehmite Gels

This study presents the development of a method for the washcoating of Ni/boehmite gels, prepared by the sol–gel process, onto the surface of a commercial ceramic monolith. Indeed, a cordierite monolith in a honeycomb shape was used as the substrate for the Ni/Al2O3 deposition. An experimental assembly was made in order to apply the coating on the cordierite surface. Different suspensions were used with various viscosities, and multiple coating parameters were tested as the withdrawal speed, or the number of impregnations. It was observed that the simple deposition of the Ni/boehmite gel led to the formation of coating. Different morphologies were observed, and defects were highlighted as cracks, coating-free areas or aggregates. Among the various parameters studied, the pH of the sol appeared to play a role even more important than the viscosity. Indeed, the sol acidified with nitric acid showed a coating which was almost free of cracks or of large aggregates. Moreover, the use of a slurry mix of calcined alumina particles and colloidal boehmite appeared also as an interesting path. The beneficial influence of the slurry was attributed to a better resistance of the coating against the stresses induced during drying, and a deviation of the cracks in the gels by slurry grains.

Chromoionophoric ligand impregnated mesoporous polymeric optical sensors for the colorimetric quantification of Cu2+ in water samples

In this work, we demonstrate the use of simple, low-cost, benign, and portable solid-state optical sensor material constructed through direct immobilization of chromoionophoric probe onto a porous polymer monolithic template. The fabricated polymer template depicts superior sensing properties such as a high surface area with uniform porous networks, which is suitable for the homogenous dispersion of chromoionophoric probe onto the voluminous cavity of the polymer template. The surface morphological features and the structural analysis of the polymer template are characterized using p-XRD, TEM, SEM, SAED, EDAX, XPS, and N2 isotherm analysis. The impregnation of the probe, 2-(4-(dimethylamino)benzylidene)-N-phenylhydrazine-1-carbothioamide (DABNC) onto the pore surface of the polymer monolith renders superior sensing performance in capturing ultra-trace concentration of Cu2+ ions, which is inferred from a series of visual color transitions (dull white to sap green). The selective naked-eye color recognition is associated with the formation of stable charge-transfer complexes with the chelating sites of the probe molecules with Cu2+ ions. To ensure the effectiveness of ion-sensing, analytical parameters such as solution pH, probe concentration, sensor dosage, temperature, response kinetics, and ion-selectivity amidst matrix ions are systematically optimized. The range of linear response signal is found to be 0–100 μg/L, with a limit of detection and quantification values of 0.15 and 0.56 μg/L, respectively. The used sensor material can be regenerated to its original state, without any loss of its sensing efficacy, up to six regenerative cycles. The practical applicability of the developed sensor is tested using various real water samples, and the analytical data obtained are reliable and reproducible (RSD ≤1.12%, n = 3).

Hydroxyapatite surface-functionalized monolithic column for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid

To date, hydroxyapatite (HAP) based monoliths were mainly fabricated by directly doping of HAP, which suffered from less effective coverage of HAP. Herein, a HAP surface-functionalized monolithic column (HAP@PDA@UF) has been prepared by in-situ biomineralization and applied as sorbent for selective in-tube solid phase microextraction of zoleronic acid and risedronic acid. A polydopamine coating was first generated on the surface of the parent urea-formaldehyde resin monolith; and then HAP microcrystals were further grew on the polydopamine coating to achieve this preparation. SEM, EDAX, FTIR, XPS and mercury intrusion method were utilized for the characterization of the HAP@PDA@UF monolith, and provided evidences of this successful preparation. The selective extraction mechanism of the HAP@PDA@UF monolith was investigated by the optimization of methanol percentage in the sampling solution, phosphate concentration in the eluent. Other crucial factors, including sampling and elution flow rate, and collection time span, were also optimized for the desired SPME performance. Under the optimal conditions, the proposed method showed low LODs of 0.1 μg/mL, satisfactory recoveries of 79.6%-92.5% with RSDs less than 2.7%, and good reproducibility with RSD less than 6.9%, which demonstrated the excellent application of the HAP@PDA@UF monolith, and its potential as a promising selective sorbent for bisphosphonates.

Dry Reforming of CH4 /CO2 by Stable Ni Nanocrystals on Porous Single-Crystalline MgO Monoliths at Reduced Temperature.

Dry reforming of CH4 /CO2 provides a promising and economically feasible route for the large-scale carbon fixation; however, the coking and sintering of catalysts remain a fundamental challenge. Here we stabilize single-crystalline Ni nanoparticles at the surface of porous single-crystalline MgO monoliths and show the quantitative production of syngas from dry reforming of CH4 /CO2 . We show the complete conversion of CH4 /CO2 even only at 700 °C with excellent performance durability after a continuous operation of 500 hours. The well-defined and catalytically active Ni-MgO interfaces facilitate the reforming reaction and enhance the coking resistance. Our findings would enable an industrially and economically viable path for carbon reclamation, and the "Nanocrystal On Porous Single-crystalline Monoliths" technique could lead to stable catalyst designs for many challenging reactions.

Identifying and Engineering Active Sites at the Surface of Porous Single-Crystalline Oxide Monoliths to Enhance Catalytic Activity and Stability

Identifying and engineering active sites play a key role in many catalytic reactions. Herein, we create well-defined surface structures through the growth of porous single-crystalline Mn3O4 and Mn2...

Visible-light-driven efficient photocatalytic abatement of recalcitrant pollutants by centimeter-length MoO3/SiO2 monoliths with long service life

The alarming challenge of water-pollution can be effectively dealt with by using easy-to-recover monolithic-photocatalysts. Herein, MoO3/SiO2 monoliths have been prepared by wet-impregnation route. The crystallinity of the catalyst and oxidation-state of elements were revealed by XRD and XPS analyses, while EDS and color-mapping confirmed the uniform dispersal of elements in the catalyst. FESEM and HRTEM analyses revealed the highly porous surface of monolith and small particle size whereas BET-analysis revealed its pore-size (~15.05 nm) and excellent surface-area (~202m2/g). The optical properties disclosed that MoO3/SiO2 monoliths were visible-light-active having band-gap ~2.58 eV and a low recombination-rate. The photoactivity of the catalyst was checked through photodegradation of model dye rhodamine-B (Rh-B) and antibiotic metronidazole (MZ). The effects of catalyst-concentration, pH, pollutant-concentration, and illumination-area were investigated. Under visible-light-irradiation, and at natural-pH, excellent efficiency was obtained for Rh-B (88.6%; 0.0129min−1) and MZ-degradation (67.4%; 0.0054min−1). Similar experiments in sunlight manifested better efficiency. High reusability of catalyst (~9%-reduction in efficiency after 4-runs) was justified by post-photocatalytic characterization-results. The trapping-experiments displayed that holes had primary involvement in the degradation. The intermediate products of MZ after photodegradation were identified by GC–MS analysis. The photocatalytic treatment of real wastewater (without physicochemical-treatment) showed ~64% COD-removal and 57% TOC-removal. The current study along with a comparison with literature demonstrates the potential of the MoO3/SiO2 monoliths for the eradication of recalcitrant-contaminants from a real-world-perspective.

High-performance 7-channel monolith supported SSZ-13 membranes for high-pressure CO2/CH4 separations

Continuous SSZ-13 zeolite membranes were reproducibly synthesized on the inner surface of 7-channel monolith supports for the first time. Packing density and mechanical strength were much greater than those using normal tubular and disc membranes. The membrane in the central channel of monolith was thinner than these of the side channels. The best monolith supported SSZ-13 membrane (with spacers) showed a CO2/CH4 selectivity of 72 and a CO2 permeance of 163 × 10-8 mol/(m2 s Pa) at pressure drop of 2.0 MPa and feed flow rate of 20 standard L/min for an equimolar CO2/CH4 mixture. Such separation performance was higher than most of zeolite membranes prepared on single-channel tubes or discs. The effects of temperature, pressure drop and fluid state on separation performance of the membranes were investigated. The extent of concentration polarization through monolith supported membrane was modelled by the concentration polarization index (CPI). Increasing feed flow rate and inserting spacers into the channels were effective ways to reduce the negative influence of concentration polarization. The latter way was more effective for our monolith supported membranes than the former because the dead volume was reduced greatly. Carbon dioxide permeance and CO2/CH4 selectivity increased by 24% and 85%, respectively, when the CPI increased from 0.79 (without spacer) to 0.89 (with spacer) at feed flow rate of 20 standard L/min.

Facile joining of SiC ceramics with screen-printed polycarbosilane without pressure

Joining of SiC ceramics was successfully achieved at a relatively low temperature of 1500 °C without any pressure using pure polycarbosilane (PCS) as the joining material, which was distributed homogenously on the surface of SiC monolith through a screen printing method. The XRD pattern shows that the pyrolysis product of PCS is single-phase SiC. The interlayer thickness of the SiC joint is approximately 2 μm. This ultra-thin interlayer with lower possibility of the existence of defects contributes to the average shear strength of 105.8 ± 10.4 MPa, higher than that of other works using other preceramic polymers to the best of our knowledge. Due to the simplicity, low cost and high joining strength, the screen printing method using PCS as the joining material has good practicality in SiC ceramics joining.

Incorporation of silver stearate nanoparticles in methacrylate polymeric monoliths for hemeprotein isolation

AbstractA unique method was used to synthesize extremely stable silver stearate nanoparticles (AgStNPs) incorporated in an organic-based monolith. The facile strategy was then used to selectively isolate hemeproteins, myoglobin (Myo) and hemoglobin (Hb). Ethyl alcohol, silver nitrate, and stearic acid were, respectively, utilized as reducing agents, silver precursors, and capping agents. The color changed to cloudy from transparent, indicating that AgStNPs had been formed. AgStNP nanostructures were then distinctly integrated into the natural polymeric scaffold. To characterize the AgStNP–methacrylate polymeric monolith and the silver nanoparticles, energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), and Fourier-transform infrared (FT-IR) spectroscopy were used. The results of the SEM analysis indicated that the AgStNP–methacrylate polymeric monolith’s texture was so rough in comparison with that of the methacrylate polymeric monolith, indicating that the extraction process of the monolith materials would be more efficient because of the extended surface area of the absorbent. The comparison between the FT-IR spectra of AgStNPs, the bare organic monolith, and AgStNP–methacrylate polymeric monolith confirms that the AgStNPs were immobilized on the surface of the organic monolith. The EDX profile of the built materials indicated an advanced peak of the Ag sequence which represented an Ag atom of 3.27%. The results therefore established that the AgStNPs had been successfully integrated into the monolithic materials. Extraction efficiencies of 92% and 97% were used to, respectively, recover preconcentrated Myo and Hb. An uncomplicated method is a unique approach of both fabrication and utilization of the nanosorbent to selectively isolate hemeproteins. The process can further be implemented by using other noble metals.

Robust immobilized enzyme reactor based on trimethylolpropane trimethacrylate organic monolithic matrix through “thiol-ene” click reaction

A novel immobilized enzyme reactor (IMER) based on trimethylolpropane trimethacrylate (TRIM) organic monolith was prepared by “thiol-ene” click reaction. The IMERs were made by fabricating TRIM monolith core in advance. There were residual double bonds on the surface of TRIM monolith, in which click reaction can be performed with the free thiol groups of trypsin at room temperature to bond the trypsin on the monolithic column without additionally introducing an active functional group. The enzyme activity was characterized by kinetic parameters Km and Vmax and determined by off-line chromatography. The performance of the IMERs was evaluated by digesting standard protein BSA and compared with in-solution digestion method. By using IMER 5 min, the sequence coverage rate of BSA was 79.41%, which was similar to that in-solution digestion for 12 h (82.7%). The applicability of the IMERs in complex samples was assessed by digesting crude protein extracts from egg white and mouse liver, identifying 28 (104 peptides) and 843 (3916 peptides) proteins, respectively. All results indicated that the IMERs have great potential in high-throughput proteomics analysis.

Noble metal catalysts growing on polyurethane foam monoliths by electroless plating deposition method for formaldehyde purification at room temperature

A series of monolithic catalysts were prepared by growing noble metals of Pt and Pd on polyurethane foam (PUF) monoliths via electroless plating deposition method. The as-prepared Pt-Pd/PUF monolithic catalysts can preserve the same size, shape and macroporous network of the pristine PUF monoliths. And the noble metal active components of Pt and Pd nanoparticles were uniformly dispersed on the surface of PUF monoliths. Therefore, compared to the low formaldehyde conversion of 14% over pristine PUF monolith, the obtained Pt-Pd/PUF monolithic catalysts exhibited excellent formaldehyde purification activity at room temperature: the formaldehyde conversion can reach as high as 66%.

Mercapto-Functionalized Porous Organosilica Monoliths Loaded with Gold Nanoparticles for Catalytic Application.

Porous organosilica monoliths have attracted much attention from both the academic and industrial fields due to their porous structure; excellent mechanical property and easily functionalized surface. A new mercapto-functionalized silicone monolith from a precursor mixture containing methyltrimethoxysilane; 3-mercaptopropyltrimethoxysilane; and 3-mercaptopropyl(dimethoxy)methylsilane prepared via a two-step acid/base hydrolysis–polycondensation process was reported. Silane precursor ratios and surfactant type were varied to control the networks of porous monolithic gels. Gold nanoparticles were loaded onto the surface of the porous organosilica monolith (POM). Versatile characterization techniques were utilized to investigate the properties of the synthesized materials with and without gold nanoparticles. Scanning electron microscopy was used to investigate the morphology of the as-synthesized porous monolith materials. Fourier transform infrared spectroscopy was applied to confirm the surface chemistry. 29Si nuclear magnetic resonance was used to investigate the hydrolysis and polycondensation of organosilane precursors. Transmission electron microscopy was carried out to prove the existence of well-dispersed gold nanoparticles on the porous materials. Ultraviolet–visible spectroscopy was utilized to evaluate the high catalytic performance of the as-synthesized Au/POM particles