Composite Catalytic Membranes Research Articles

Activation of peroxymonosulfate for ciprofloxacin degradation by a novel oxygen-deficient CoTiO3/TiO2NTs/Ti composite catalytic membrane:Electron transfer pathway and underlying mechanism

The technique of activating peroxymonosulfate (PMS) by enriching oxygen vacancies (Vo) in heterogeneous catalysts has gained extensive attentions in the removal of emerging contaminants, e.g., antibiotics from wastewater. In this study, a Vo-CoTiO3/TiO2NTs/Ti (Vo-CTNs) catalytic membrane with rich oxygen vacancies was prepared and employed for the activation of PMS in degrading ciprofloxacin (CIP) in a continuous flow reactor. The averaged degradation efficiency of CIP in the Vo-CTNs/PMS system could reach 97.3 %, significantly higher than that in the CoTiO3/TiO2NTs/Ti (CTNs) system (91.1 %). Quenching experiments and electron paramagnetic resonance analysis collectively confirmed the presence of •OH, SO4•−, O2•− and 1O2 during the CIP degradation process. The results of the electrochemical experiments demonstrated that in the presence of oxygen vacancies, the mutual conversion between Co2+ and Co3+ was facilitated, resulting in a lower transfer resistance. At an initial CIP concentration of 10 mg/L and a membrane flux of 600 LMH, the degradation efficiency and mineralization rate of CIP could reach 95.2 % and 51.1 % after 12 h of operation, respectively. Meanwhile, limited leaching of cobalt ions (52 μg/L) from the catalytic membrane was observed during treatment. Theoretical calculations revealed that Vo engineering can modulate the surface electronic states, thereby enhancing binding energy and electron transfer for PMS activation. The degradation of CIP is mainly achieved through the ring opening reactions in the piperazine, quinolone, and cyclopropyl groups attacked by reactive oxygen species. In this work, we built cobalt-based composite nanomaterials to promote effective electron transfer and minimize leaching of cobalt ions, and providing a new method for activating PMS in a continuous flow system by enriching the oxygen vacancies in the catalytic membrane. This method has potentials to be applied in treating wastewater containing antibiotics such as CIP.

Construction of catalytic pervaporation membrane with structure C/PAN/S to intensify esterification by in-site dehydration and proton providing

Catalytic pervaporation membrane can effectively promote the forward esterification reaction by in-site water removing and proton providing. A catalytic composite membrane (CCM) with structure C/PAN/S was proposed. To reduce the damage that the catalytic layer does to the separation layer, the intermediate support layer was designed between them. Two-dimensional material g-C3N4-SO3H was added to sodium alginate (SA) to improve the separation performance. The impregnation phase inversion method was applied to build a porous catalytic layer. Polyvinylpyrrolidone (PVP) was added as the porogen, which greatly reduced the mass transfer resistance. By introducing Amberlite 732, the membrane was endowed with an efficient and stable catalytic performance. The preparation conditions were investigated for better catalytic performance. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used in this work to characterize the materials and membranes. The flux of the catalytic composite membrane is 582 g·m−2·h−1, and the separation factor is 590. The acetic acid conversion rate reached 97.5%. The acetic acid conversion rate remained at 95.7% after five runs, showing outstanding stability. The separation factor of membranes with structure C/PAN/S increased 10 times. The developed catalytic composite membrane with structure C/PAN/S would have broad prospects in the catalytic membranes field.

A sustainable solution for organic pollutant degradation: Novel polyethersulfone/carbon cloth/FeOCl composite membranes with electric field-assisted persulfate activation

Sulfate radical-based advanced oxidation processes (SR-AOP) and ultrafiltration (UF) membranes have demonstrated effectiveness in treating wastewater. This investigation illuminated a pioneering two-stage procedure for fabricating polyethersulfone/carbon cloth/FeOCl (PES/CC/FeOCl) composite catalytic membranes, exhibiting proficiency in persulfate activation. Evidenced by their distinctively high degradation rates and superior stability, these innovative composite membranes efficaciously obviate tetracycline (TC), showcasing a striking TC degradation rate, with an unparalleled removal ratio peaking at 93% under applied electrical fields. The process underlying persulfate activation and TC degradation was meticulously explored through electron paramagnetic resonance (EPR) and quenching trials. These evaluations unveil that hydroxyl radicals (•OH) and sulfate radicals (SO4•−) primarily drive the eradication of diminutive organic molecules. Subsequent studies emphasized the noteworthy rejection ratio of the PES/CC/FeOCl composite membranes (90%) for sodium alginate (SA), further revealing their exceptional on-line cleansing efficiency in an electrofiltration-associated in-situ oxidation system. In essence, this study proposed a novel approach for the synthesis of composite membranes adept at the catalytic degradation of organic pollutants. This paradigm-shifting research imparted a unique lens to perceive the integration of membrane separation technology, enriching the domain of advanced wastewater treatment strategies.

Construction of CoTiO3/TiO2/Ti composite catalytic membrane for degradation of tetracycline via peroxymonosulfate activation: Reactive oxygen species and electron transfer pathways

The advanced oxidation processes based on peroxymonosulfate (PMS) has shown great promise for the removal of emerging contaminants in water reuse applications. Constructing cobalt-based composite nanomaterials is an effective strategy to achieve electron transfer and reduce the leaching of cobalt ions. Here, a CoTiO3/TiO2/Ti (CTT) catalytic membrane was fabricated using TiO2 nanotubes as both template and reactant, and then was applied to activate PMS for tetracycline (TC) degradation in a continuous flow-through reactor. The CTT/PMS system showed a remarkable TC degradation efficiency of 96.99%, exhibiting anti-interference performance towards Cl−, HCO3– and humic acid in water (>90.00% degradation efficiency). It has been proved that OH, SO4−, and 1O2 existed in the CTT/PMS system, and the CTT membrane served as a medium for mediating the electron transfer from TC to PMS. Density functional theory calculations indicated that the construction of a composite structure of CoTiO3 and TiO2 successfully enhanced the activation of PMS by the electron transfer from Ti atoms of TiO2 to Co sites. We proposed three potential degradation pathways for TC, followed by toxicity analysis of the intermediate products. After being exposed to an initial TC concentration of 20 mg/L and a membrane flux of 600 LMH for 30 hours, the CTT catalytic membrane exhibited a TC degradation rate exceeding 92.23% and mineralization rate surpassing 64.43%. This work supplied a new approach for fabricating cobalt-based catalytic membrane for PMS activation, with potential applications in water reuse.

Preparation and characterization of DA@SA catalytic composite membranes strengthened by two-dimensional MXene nanomaterials

Reasonable design of the separation layer structure in the catalytic composite membrane (CCM) is an effective strategy to improve the performance of catalysis and separation. As for the low permeability and obvious non-selective interface defects of the separation layer, a new nanomaterial MXene (Ti3C2TX) was introduced to enhance the permeability of sodium alginate (SA) polymer matrix membrane and dopamine (DA) acted as the binder to improve the non-selectivity between the filler and the polymer, respectively. The porous catalytic layer was proposed by grafting acid ionic liquids (ILs) onto polyvinyl alcohol (PVA). The experimental results showed that the flux of MXene-DA@SA/PAN separation membrane was up to 1640 g∙m−2 h−1, increasing by 70% compared with the pure SA membrane. And the separation factor arrived at 810, increasing by 30.6% compared with the non-dopamine-modified hybrid membrane. Using the developed ILs-g-PVA/MXene-DA@SA/PAN catalytic composite membrane, the conversion rate of acetic acid reached 96.5% within 12 h. This work provides useful enlightenment for improving the efficiency of catalytic reaction by optimizing the separation layer.

Mussel-inspired in-situ metallization of nano-Ag on ceramic membrane for catalytic degradation of dye wastewater

Catalytic membranes supported with nano-catalysts have been widely used for wastewater treatment. The traditionally catalyst immobilization methods, such as physical blending, chemical deposition and impregnation et al., involve complex preparation steps. Herein, Ag nanoparticles were in-situ immobilized on a ceramic microfiltration substrate by a mussel-inspired facile metallization process. Firstly, dopamine was deposited onto the substrate (∼200 nm) to form a uniform polydopamine coating. Then, Ag nanoparticles were in-situ metalized and immobilized on the polydopamine decorated ceramic membrane. The preparation conditions were relatively simple without sintering. FTIR, XRD, FESEM and EDS characterizations demonstrate the successful immobilization of the Ag nanoparticles. The obtained membrane exhibits good hydrophilicity and permeability (606.08 L m−2 h−1 at 0.1 MPa). The degradation rate of methyl orange achieves ∼95.6% within 20 min. The apparent reaction rate constant reaches the highest value of 568.1 min−1 at 0.5 MPa, which is several orders of magnitude higher than that of the feed side. The composite membrane can degrade mixed dyes. The catalytic membrane also shows excellent stability and antifouling property. In conclusion, this research provides a convenient and effective way for preparing a kind of composite catalytic membrane with high performance, which has potential applications in environmental remediation.

Continuous biodiesel production from acidic oil using a combination of acidic and alkaline composite catalytic membranes in flow-through membrane reactors

A comprehensive process of esterification for online separation transesterification for biodiesel production, with a yield of up to 97.52%.

Porous PVA-g-SPA/PVA-SA Catalytic Composite Membrane via Lyophilization for Esterification Enhancement.

A catalytic composite membrane was developed for the enhancement of esterification by lyophilization for the first time. The catalytic composite membrane was composed of a poly(vinyl alcohol) (PVA)-sodium alginate (SA) separation layer and a spongy porous catalytic layer cross-linked by PVA and 4-sulfophthalic acid (SPA). Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) results indicated the successful synthesis of the catalytic composite membrane. The membrane properties were evaluated by ethanol dehydration and esterification. The conversion rate of acetic acid reached 95.9% after 12 h. Compared with batch reactions, the conversion rate increased by 24.4%. After five cycles, the membrane still maintained outstanding catalytic activity. The resistance of mass transfer was analyzed, and the results showed that the porous structure reduced the catalytic layer resistance to total resistance from 70.27 to 32.88%. The composite membrane with a spongy porous catalytic layer exhibited superior dehydration and catalytic performance.

Facile preparation of nanocellulose/Zn-MOF-based catalytic filter for water purification by oxidation process

Sulfate radical (SO4•-)-based advanced oxidation processes (SR-AOPs) have recently attracted much attention due to their potential in degrading organic pollutants. Metal-organic frameworks (MOFs) have been reported as effective materials to generate SO4•-. However, it is challenging to separate and recover the dispersed MOF particles from the reaction solution when MOFs are used alone. We used cellulose nanofibers (CNFs) as a porous filter template to immobilize Zn-based MOF, zeolitic imidazolate framework-8 (ZIF-8), and obtained a catalytic composite membrane having peroxymonosulfate (PMS) activating function to produce SO4•-. The CNF was effective in holding ZIF-8 nanoparticle and making a durable porous filter. The activated PMS-produced •OH and SO4•- radicals from ZIF-8 play an important role in the catalytic reaction. More than 90% of methylene blue and rhodamine B was degraded by ZIF-8/CNFs composite membrane in the PMS environment within 60min. The ZIF-8/CNFs catalytic filters can be used several times without performance reduction for organic dye degradation. The results show that ZIF-8/CNFs catalytic membrane can be separated from organic pollution system quickly and used for the efficient separation and recovery of MOF particle-based catalytic materials. Therefore, this study provides a new perspective for fabricating the MOFs particles-immobilized catalytic filter by biomass nanocellulose-based materials for water purification. This method can be used for facile fabrication of the cellulose-based porous functional filter and open diverse applications.

A novel catalytic composite membrane with anti-swelling for enhancing esterification of acetic acid with ethanol

Ester have important applications in medicine chemical industry, but esterification is a typical reversible reaction controlled by thermodynamic equilibrium. In the study, a new type of catalytic composite membrane (CCM) with SA-MoS2/PAN as separation layer was reported. By-product water was proposed by pervaporation membrane reactor to improve the conversion rate of acetic acid. In 10 wt% ethanol-water solution, the separation factor of the catalytic composite membrane is 145 and the flux is 547 g m−2 h−1. Under the optimal condition, the acetic acid conversion rate reached 94.3%, which was 29% higher than that of batch reaction. The effects of single-layer catalytic membrane and double-layer catalytic membrane on acetic acid conversion rate were studied, which showed that the double-layer catalytic membrane had higher stability in esterification reaction.It is proved that high crosslinking degree can improve the stability of the membrane and reduce the conversion rate of acetic acid.

A catalytic composite membrane reactor system for hydrogen production from ammonia using steam as a sweep gas

For catalytic reactions involving H2 extraction, the membrane reactor is an attractive option for enhancing the equilibrium and kinetics while eliminating excessive purification steps. In this study, a steam carrier adopted composite membrane reactor system is developed to produce pure H2 (>99.99%) from ammonia with high H2 productivity (>0.35 mol-H2 gcat−1 h−1) and ammonia conversion (>99%) at a significantly reduced operating temperature (<723 K). Coupling of a custom developed palladium/tantalum composite metallic membrane and ruthenium on lanthanum-doped alumina catalysts allowed stable operation of the membrane system with significant mass transfer enhancement. Various reactor assemblies involving as-fabricated membranes and catalysts are experimentally compared to suggest the optimal configuration and operating conditions for future applications. Steam is adopted as a sweep gas, presenting efficient H2 recovery (>91%) while replacing conventionally utilized noble carrier gases that require additional gas separation processes. The steam carrier presents similar membrane reactor performance to that of noble gases, and the water reservoir used for steam generation acts as an ammonia buffer via scrubbing effects. Finally, electricity generation is demonstrated using a commercial fuel cell along with process simulation, substantiating potential of the proposed membrane system in practical applications for H2 production from ammonia and on-site power generation.

Fabrication of ionic liquids-functionalized PVA catalytic composite membranes to enhance esterification by pervaporation

A novel ionic liquids (ILs)-functionalized catalytic composite membrane (CCM), poly(vinyl alcohol)-g-poly(ionic liquids)/poly(vinyl alcohol)-glutaraldehyde (PVA-g-PILs/PVA-GA), was proposed for enhancing the esterification between ethanol and acetic acid in a pervaporation catalytic membrane reactor (PVCMR). The ILs-functionalized catalytic layer was prepared by free radical polymerization reaction between PVA and 1-vinyl-imidazole acidic ILs monomer. Covalent bonds between ILs and PVA were formed, and there were –SO3H groups in PVA-g-PILs copolymer chain after graft polymerization, thus improving the stability of immobilized ILs and ensuring high catalytic activity. The PVA-g-PILs copolymer was investigated by 1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The morphology of ILs-functionalized CCM was characterized by scanning electron microscopy. The separation performance of ILs-functionalized CCM was measured by dehydration of ethanol by pervaporation, and the catalytic performance of ILs-functionalized CCM was evaluated via batch experiments and pervaporation coupling esterification experiments. The result of esterification between acetic acid and ethanol showed that acid conversion reached 93% in 12 h at 75 °C with ILs-functionalized CCM in PVCMR; a conversion enhancement of approximately 19% was achieved, compared to that of an equilibrium conversion in a batch reactor under the same conditions. Moreover, the ILs-functionalized CCM exhibited good reusability and catalytic stability owing to the graft polymerization between PVA and acidic ILs.

Fabrication and modeling of catalytic membrane for removing water in esterification

In this study, homogeneous catalyst “poly(styrenesulfonic acid)” and crosslinking agent “3-amino propyl methyl diethoxy silane” were added into the Polyvinyl alcohol to prepare the catalytic composite membrane (CCM). And the separation layer was prepared by blending polyvinyl alcohol and sodium alginate. Poly(styrenesulfonic acid) (PSSA) loaded CCM have been used to synthesize ethyl propionate in a pervaporation catalytic membrane reactor. The CCM was characterized by the SEM, FTIR and XRD. The pervaporation and catalytic performance of CCM were investigated under varying conditions (mass ratio of PSSA to PVA, 3-amino propyl methyl diethoxy silane content, heat treatment time). When the mass ratio of PSSA to PVA was 5:5, content of SCA-A10F was 20.0% to PSSA, the esterification conversion reached 91.6% after 12 h. The permeation flux and separation factor were 260 g m−2 h−1 and 91 respectively. Then the reaction kinetic model and separation kinetic model were established by Python least square method for the first time. Meanwhile, the theoretical maximum conversion curve and the PV coupling model conversion curve were proposed by combining the two models. It was found that the conversion of the actual coupling reaction was between the two model curves.

High-flux efficient catalytic membranes incorporated with iron-based Fenton-like catalysts for degradation of organic pollutants

A novel composite catalytic membrane is developed by blending silicon oxide coated ferroferric oxide (Fe3O4@SiO2) nanoparticles in polyether sulfone (PES) membrane as Fenton-like catalysts via liquid-induced phase separation (LIPS) method. By introducing Fe3O4@SiO2 nanoparticles in PES membrane matrix, the surface hydrophilicity, porosity and mean pore diameter of as-prepared composite catalytic membranes are improved due to the hydrophilic nature of the SiO2 coating layer on the Fe3O4@SiO2 nanoparticles. The as-fabricated catalytic membrane can filter large particles above ~100 nm and shows a high water flux of 2084 kg m−2 h−1 under 0.1 MPa. Importantly, the composite catalytic membrane shows efficient catalytic performance and satisfactory stability in the degradation of organic pollutants based on the Fenton-like reaction mechanism. The proposed strategy for membrane fabrication and the experimental results in this study provide valuable guidance for developing high-flux catalytic membranes with efficient catalytic performances for treatment of industrial and municipal wastewater.

Fabrication of bilayer catalytic composite membrane PVA-SA/SPVA and application for ethyl acetate synthesis

In this study, a dual-function catalytic composite membrane (CCM) was developed by coating a sulfonated-polyvinyl alcohol (SPVA) casting solution onto a polyvinyl alcohol (PVA)-sodium alginate (SA) membrane. SPVA was synthesized via sulfoisophthalic acid (SIPA) cross-linked PVA. The membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), scanning electron microscopy (SEM), pervaporation and pervaporation coupled esterification experiments, etc. The dehydration of ethanol via pervaporation was studied over the concentration range of 3.5–11 wt% water in ethanol. The conversions of acetic acid in a batch reactor (BR) with CCM, pervaporation catalytic membrane reactor (PVCMR) with CCM and BR with free SIPA were compared. The experimental results showed that the conversion reached 96% in 12 h at 75 °C with 20% molar fraction of catalyst, an initial molar ratio (alcohol/acid) of 2:1 and an S/m ratio of 1.13 cm2 g-1 in PVCMR. With these conditions, the conversion was enhanced significantly by approximately 24% compared to BR. After five successive runs, the membrane still maintained outstanding stability.

Development of stable and active PVA‐PSSA/SA‐PVA catalytic composite membrane for esterification enhancement

ABSTRACTAn active and stable catalytic composite membrane (CCM), poly(vinyl alcohol)–poly(styrene sulfonic acid)/sodium alginate–poly(vinyl alcohol) (PVA‐PSSA/SA‐PVA), was prepared to enhance the esterification of ethanol and propionic acid. The morphologies and crystal structures of the CCMs were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy, and X‐ray diffraction. The effects of catalytic layer thickness, mass ratio of PVA to PSSA, concentration of catalytic layer solution, ratio of reaction volume to membrane area, and molar ratio of propionic acid to ethanol were discussed. The pervaporation results showed that the flux of CCM increased from 118 to 320 g m−2 h−1 compared with the SA‐PVA membrane because of the close affinity and low resistance of PSSA to water. After crosslinking with 3‐aminopropylmethyldiethoxysilane, the CCMs had good catalytic activities. The acid conversion reached 92.8% at 75 °C in 12 h, and the stabilization of the CCM was greatly improved. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46514.

Continuous transesterification to produce biodiesel under HTCC/Na2SiO3/NWF composite catalytic membrane in flow-through membrane reactor

A novel polymer-based alkaline composite catalytic membrane (PACCM) for the transesterification of soybean oil with methanol in a flow-through mode, was prepared with sodium silicate (Na2SiO3) and N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride supported into polypropylene non-woven fabric by nonsolvent induced phase separation. The transesterification with a conversion of above 97.0% was achieved under the PACCMs in a membrane reactor under a molar ratio of methanol/soybean oil of 9:1 and residence time of 3913s at 60°C. External mass-transfer resistance in the PACCM could be neglected when the flow rate was beyond 1.0mlmin−1. The transesterification in the membrane reactor was kinetically controlled. The PACCMs showed a good catalytic activity and stability. And the PACCMs could tolerate less than 3.0wt.% water or less than 1.5wt.% FFA in the feedstock at which the conversion reached above 90%.

Hybrid thin film nano-composite membrane reactors for simultaneous separation and degradation of pesticides

Membrane reactors typically combine chemically reactive pathways with separation opportunities to increase conversion and chemical processes efficiency in liquid effluents treatment. The treatment of industrial bio-products, waste mixed solvents and agro-chemicals with such reactors are however challenging due to the natural affinity of such reactive materials for organic and biological matter leading to surface adsorption and fouling tendencies. Here, hybrid thin film composite catalytic membranes offering superior flow permeation characteristics, extremely high retention of low molecular weight organics and partial salt rejection capabilities were for the first time synthesized. Catalytic silver-metal nano-materials were for the first time homogeneously templated and encapsulated across metal organic frameworks nano-particles and incorporated across the top surface of poly(amide) thin films during interfacial polymerization. These novel materials offer high catalytic/anti-microbial behaviours due to the nano-structure of the metal nano-particles reduced within the metal organic framework template, forming unique hierarchical sub-100nm hybrid nano-structures. These ultra-thin but yet dense membranes were able to simultaneously degrade chemicals and filter contaminants, opening new pathways for the design of the next generation thin film nano-composite membranes. Catalytic properties and homogeneity were evaluated for the Fenton-like heterogeneous catalytic degradation of 2,4-Dichlorophenoxyacetic acid, a waste pesticide contained in agricultural wastewater.

Reactive separation system for effective upgrade of levulinic acid into ethyl levulinate

In this study, the reactive separation system has been designed and operated for fuel bioadditive ethyl levulinate synthesis from ethanol and levulinic acid by using a catalytic composite membrane. The catalytic composite membrane was prepared by coating hydroxyethyl cellulose membrane with a thin layer of sulfated zirconia. The membranes were characterized and the stability of the catalytic composite membrane was confirmed by consecutive experiments. Batch reactor experiments were carried out by using powder sulfated zirconia catalyst. While the levulinic acid conversion was 34.92% in 7h by using the powder sulfated zirconia catalyst in the batch reactor, the conversion reached to a level of 95% in 7h by using sulfated zirconia coated hydroxyethyl cellulose catalytic membrane under the same conditions (reaction temperature 70°C, catalyst concentration 8g/L and initial molar ratio 3:1) in the pervaporation catalytic membrane reactor (PVCMR). Results showed that the conversion in the PVCMR was much higher than those in the batch reactors. The effects of temperature, catalyst concentration and initial molar ratio of ethanol to levulinic acid on the conversion value of levulinic acid were investigated for both batch reactor and the pervaporation catalytic membrane reactor.

A study on composite catalytic membrane manufacturing based on sodium alginate and lipase to be used in a pervaporation reactor

A lipase-immobilized dense sodium alginate membrane was prepared and used for the esterification of ethyl alcohol and lactic acid in a pervaporation reactor (PVR). From the solvent to the polymer, all materials were selected as natural and bio-based. The activity of the immobilized lipase was calculated from the batch reactor data in which the immobilized lipase was used as a heterogeneous catalyst. When the temperature was increased from 303 to 323 K, conversion was enhanced from 0.53 to 0.63 in PVR. The effect of the initial molar ratio on conversion was also investigated. As the molar ratio was increased from 1 to 3, conversion was enhanced from 0.53 to 0.62 in PVR. When the molar ratio continued to increase from 3 to 6, conversion decreased from 0.62 to 0.42. It was essential that the 80 % improvement in conversion had been achieved by using PVR compared to the batch reactor. It was also seen that the immobilized lipase used in PVR preserved its activity during the six experiments without a significant activity loss.