Photocatalityc membrane reactor for CO2 conversion

Global warming is considered to be one of the principal environmental problems and CO2, being a greenhouse gas, largely contributes to the global climate change. Owing to this problem, an increasing concern has brought the scientific community to devote huge efforts towards CO2 reduction and/or valorization through a sustainable process. In this contest, photocatalytic membrane technologies can be a promising and innovative way to pursue CO2 conversion into value-added products.1 To this purpose, Carbon Nitride (C3N4) photocatalyst was prepared and characterized by FTIR and IR-ATR, DRS and XRD analyses. The preliminary reactivity experiments were carried out in a batch reactor (V = 120 mL) filled with humid CO2 and irradiated in a solar box (65°C). CH4 and CO were the main reduction products detected. This catalyst was then dispersed to obtain catalytic mixed matrix Nafion membranes. Comprehensive structural and morphological analyses by DRS, FT-IR, ATR-IR, SEM and N2 and CO2 permeability measurements were performed. The photocatalytic membranes were then used for the same reaction under UV-Vis irradiation in a membrane reactor operating in continuous mode, as already done with TiO2-Nafion catalytic membranes2. Different H2O/CO2 molar ratios and residence times were used. MeOH, EtOH and HCHO were the main products detected. Under the best experimental conditions, methanol and ethanol were identified as the main products with a productivity of 23 and 25 mol g-1 h-1, respectively. References. 1. R. Molinari, A. Caruso, L. Palmisano, Photocatalytic Membrane reactor in the conversion or degradation of organic compounds, in E. Drioli et L. Giorno (Eds.) Membrane Operations, innovative Separation and transformations, Chapter 15, 335-361, 2009, Wiley-Vch Verlag GmbH & Co. KGaA, Weinheim (Germany). 2. M. Sellaro, M. Bellardita, A. Brunetti, E. Fontananova, L. Palmisano, E. Drioli, G. Barbieri, “CO2 conversion in a photocatalytic continuous membrane reactor”, RSC Advances, 2016, 6, 67418 – 67427

Graphene Oxide Membranes for Reverse Electrodialysis Applications

Graphene Oxide Membranes for Reverse Electrodialysis Application

Probing membrane and interface properties in concentrated electrolyte solutions

This study deals with the membrane and interface electrical properties investigation by electrochemical impedance spectroscopy (EIS). The EIS is a powerful technique for characterizing electrical behavior of systems in which coupled electrical processes occur at different rates.A systematics tudy on the effect of solution concentration,temperature and velocity, on the electrical resistance of anion-and cation- exchange membranes (AEMs and CEMs) and their interfaces (electrical double layer and diffusion boundary layer), was carried out. At the best of our knowledge, for t he first time electrolyte concentrations up to 4 M were used for the study of membranes and interface by EIS. Moreover, Pulsed Gradient Spin Echo Nuclear Magnetic Resonance (PGSE-NMR)technique was used to measure the water self-diffusion coefficients in swelled membrane as a function of the solution concentration and temperature.These measurements gave additional important insights about the effect of the electrolyte solution and fixed charges concentration in membrane,on membrane microstructure and its transport and electrical properties. & 2014TheAuthors.PublishedbyElsevierB.V.ThisisanopenaccessarticleundertheCCBY This study deals with the membrane and interface electrical properties investigation by electrochemical impedance spectroscopy (EIS)

An Overview on Exploitation of Graphene-Based Membranes: From Water Treatment to Medical Industry, Including Recent Fighting against COVID-19

Graphene and its derivatives have lately been the subject of increased attention for different environmental applications of membrane technology such as water treatment and air filtration, exploiting their antimicrobial and antiviral activity. They are interesting candidates as membrane materials for their outstanding mechanical and chemical stability and for their thin two-dimensional (2D) nanostructure with potential pore engineering for advanced separation. All these applications have evolved and diversified from discovery to today, and now graphene and graphene derivatives also offer fascinating opportunities for the fight against infective diseases such as COVID-19 thanks to their antimicrobial and antiviral properties. This paper presents an overview of graphene-based 2D materials, their preparation and use as membrane material for applications in water treatment and in respiratory protection devices

Development of new polymeric functional membranes for applications in catalysis and fuel celles

Dottorato di Ricerca in Ingegneria Chimica e dei Materiali, XX Ciclo,a.a. 2006-2007Università degli Studi della Calabri

Photocatalytic Membranes in Photocatalytic Membrane Reactors

The present work gives a critical overview of the recent progresses and new perspectives in the field of photocatalytic membranes (PMs) in photocatalytic membrane reactors (PMRs), thus highlighting the main advantages and the still existing limitations for large scale applications in the perspective of a sustainable growth. The classification of the PMRs is mainly based on the location of the photocatalyst with respect to the membranes and distinguished in: (i) PMRs with photocatalyst solubilized or suspended in solution and (ii) PMRs with photocatalyst immobilized in/on a membrane (i.e., a PM). The main factors affecting the two types of PMRs are deeply discussed. A multidisciplinary approach for the progress of research in PMs and PMRs is presented starting from selected case studies. A special attention is dedicated to PMRs employing dispersed TiO2 confined in the reactor by a membrane for wastewater treatment. Moreover, the design and development of efficient photocatalytic membranes by the heterogenization of polyoxometalates in/on polymeric membranes is discussed for applications in environmental friendly advanced oxidation processes and fine chemical synthesis

Development of Tailored Hydrogel Composite Membranes for Application in Membrane Contactors

Dottorato di Ricerca in Scienze ed Ingegneria dell'Ambiente, delle Costruzioni e dell'Energia (SIACE). Ciclo XXIXThis work was performed during the period from November 2013 to May 2015 in the Institute on Membrane Technology (ITM-CNR) at the University of Calabria (UNICAL), under supervision of Prof. Efrem Curcio, Dr. Gianluca Di Profio and Dr. Enrica Fontananova, from May 2015 to December 2015 at Universidade Nova de Lisboa (UNL), under supervision of Prof. Joao Crespo and from March 2016 to September 2016 at the University of Chemistry and Technology (ICT) Prague, under supervision of Dr. Eng. Vlastmil Fila. The main objective of this study was to design and develop tailored hydrogel composite membranes for application in membrane contactors, in particular, membrane distillation and membrane crystallization. Among various methods for membrane surface functionalization, surface photo-initiated graft polymerization technique (at UNICAL) and surface coating by incorporating nanoparticles (at UNL) were investigated to fabricate tailored hydrogel composite membranes In the first year at the University of Calabria, various hydrogel composite membranes were prepared by using photo-initiated polymerization method. The possibility of fine tuning the porosity and the chemical nature of hydrogels, were implemented with the preparation of composites containing diverse hydrogel components (monomer and cross-linker) and ratio among them. The selection of hydrogel components was based on the possibility to obtain homogeneous and stable composites by using specific polymeric porous membranes as supports. The resulting composite membranes were characterized by electron scanning microscopy, surface chemistry analysis, swelling degree, ion exchange capacity and water contact angle measurements Furthermore, virgin and hydrogel composite membranes were used in membrane distillation and crystallization experiments and the performance improvement was evaluated. As a result, higher water-transfer flux and enhanced ion rejection than traditional MD membranes was observed in MD treatment of saline solutions. When such HCMs used in membrane assisted crystallization of carbonate calcium (biomineralization), a wide range of crystal morphologies, most of them displaying a polycrystalline or mesocrystalline structure, was obtained in a great variety of experimental conditions. We demonstrated that this composite provides the opportunity to fine control the delivery of additives to the gel network through the porous structure of both support membrane and hydrogel layer, thus affecting crystallization kinetics, and crystal morphologies In the second year of the study at Universidade Nova de Lisboa, hydrogel composite membranes with tailored surface roughness and patterning were designed to examine the influence of the topography of such composite membranes on the growth of protein crystals. Iron oxide nanoparticles (NPs) were used as topographical designers providing a good control of membrane surface roughness and patterning. Surface morphology and topography of the prepared membranes were characterized using electron scanning microscopy, profilometry analysis and contact angle measurements. Finally, their performance was evaluated in the crystallization of Lysozyme used as a model protein and the effect of surface chemistry and topography on the heterogeneous nucleation of lysozyme crystals was investigated. We demonstrated that roughness influences crystallization, but we also show that excessive roughness may be deleterious, since it increases the number of crystals formed at the expenses of crystal size. Therefore, there is an optimum value of roughness for the formation of a low number of well-faced crystals with a larger size In the third year at the University of Chemistry and Technology Prague, the modeling of membrane crystallization was studied. The main goal of this work was to develop general model of membrane crystallization process. The development of this model involved the fundamental theories and models in membrane process and crystallization engineering, especially the models described the mass and heat transfers in membrane module and the crystal size distribution (CSD) determined by both nucleation and crystal growth processes based on the concept of the population balance equation. The experimental results of this study, allows to achieve new insight to fabricate and develop the novel hydrogel composite membranes with proper properties and novel functionality for application in membrane distillation and membrane crystallization processesUniversità della Calabria

Green H₂ Production by Water Electrolysis Using Cation Exchange Membrane: Insights on Activation and Ohmic Polarization Phenomena

Low-temperature electrolysis by using polymer electrolyte membranes (PEM) can play an important role in hydrogen energy transition. This work presents a study on the performance of a proton exchange membrane in the water electrolysis process at room temperature and atmospheric pressure. In the perspective of applications that need a device with small volume and low weight, a miniaturized electrolysis cell with a 36 cm2 active area of PEM over a total surface area of 76 cm2 of the device was used. H2 and O2 production rates, electrical power, energy efficiency, Faradaic efficiency and polarization curves were determined for all experiments. The effects of different parameters such as clamping pressure and materials of the electrodes on polarization phenomena were studied. The PEM used was a catalyst-coated membrane (Ir-Pt-Nafion™ 117 CCM). The maximum H2 production was about 0.02 g min−1 with a current density of 1.1 A cm−2 and a current power about 280 W. Clamping pressure and the type of electrode materials strongly influence the activation and ohmic polarization phenomena. High clamping pressure and electrodes in titanium compared to carbon electrodes improve the cell performance, and this results in lower ohmic and activation resistances

Hybrid Photocatalytic Membranes Embedding Decatungstate for Heterogeneous Photooxydation

Photocatalytic membranes have been prepared by incorporation of decatungstate into polymeric films with a high thermal, chemical and mechanical stability (PVDF, PDMS, Hyflon). Surface spectroscopy techniques including transmittance and reflectance UV-Vis and FT-IR have been used to assess the photocatalyst integrity within the polymeric support

Preparation of mixed matrix membranes for water treatment

Dottorato di Ricerca in Scienze ed Ingegneria dell'Ambiente, delle Costruzioni e dell'Energia. Ciclo XXIXThe treatment of wastewater and its reuse is a very important topic in industrial processes. This because not only avoids drawing on natural resources, but also enables a significant reduction in the amount of wastewater discharged into the natural environment. Wastewater can also be used for various purposes where drinking water quality is not mandatory, including agricultural irrigation, the cleaning of industrial equipment, the watering of green spaces, and street maintenance, etc. In fact, the water reuse has become essential in all areas in the world that suffer from water shortages [1]. Different methods are used for wastewater treatment. These processes can be to divide in: primary, secondary and tertiary treatment. Primary treatment (screening, filtration, centrifugation, sedimentation, coagulation, gravity and flotation method) includes preliminary purification processes of a physical and chemical nature while secondary treatment deals with the biological treatment of wastewater. In tertiary treatment process wastewater is converted into good quality water that can be used for different types of purpose, i.e. drinking, industrial, medicinal etc. supplies [2]. The complexity of industrial processes, the variety of pollutants and the limitation of a single operation, has led to the need for more complex processes and especially to a combination of processes. Membranes technologies falls on the tertiary water treatment technologies and are actually the most effective separation processes and they are still in rapid development creating new prospects of their applications in clean technologies [3]. The utilization of membrane operations as hybrid systems, i.e. in combination with other conventional techniques or integrated with different membrane operations is considered the way forward for more rationale applications [4]. The possibilities of redesigning various industrial cycles by combining various membrane operations have been studies and in some case realized with a low environmental impact and a low energy consumption [5]. Different processes can be used in various steps of a hybrid system, depending from the size of the pollutants to be removed. Microfiltration (MF) and ultrafiltration (UF) membrane processes, can be used as pre-treatment, while nanofiltration (NF) and reverse osmosis (RO) can used in the final step of the integrated system to remove particles with smaller dimensions (Chapter 1) The membranes have different morphological characteristics that affect their performance. The study of all the conditions which modulate these characteristics is a crucial point in the choice of membranes to be used in the various separation processes. Therefore, it is important to investigate about new materials and new types of membranes, like as mixed matrix membrane (MMM). MMM is a heterogeneous membrane consisting of inorganic fillers embedded in a polymeric matrix and can be made into flat sheets and hollow-fiber. Nevertheless, the selection of membrane configuration is greatly dependent on the application and therefore the production of MMMs in useful configuration is undoubtedly a crucial point in membrane development [6]. Also, the selection of inorganic fillers depends of desired membrane performance and their use. More attention was focus on the interesting characteristic of carbonanotubes (CNTs) (chapter 2). CNTs themselves have remarkable electrical, thermal, and mechanical properties. These nanotubes have the structure of a rolled-up graphene sheet with smaller diameter. Multiwalled carbonanotube (MWCNTs) were used to prepare MMMs for wastewater treatment. Different compounds, as additives in the polymeric membranes were used in high percentage; in the case of MWCNTs was observed as a low amount can change the membrane morphologies, mechanical and transport properties. A crucial point was the choice of membrane materials. Two type, hydrophilic poly(imide) (PI) and hydrophobic poly(vinylidenfluoride) (PVDF) were choose for membrane materials to produce MMMs. Another important point in this study was the use of functionalized MWCNTs that provide a good dispersion in the casting solution first, and in the polymeric matrix after phase separation. The main limitation in the use of CNTs is their poor dispersion in the main solvents used for the preparation of membranes. The functionalization has been proven an efficient method to overcome this limitation improving the compatibility with the polymer matrix. The presence of polar groups on the carbon nanotubes can reduces their tendency to aggregate by van der Waals interactions, while forming hydrogen bonds and electron donor/acceptor interactions with the polymer. Low percentages of CNTs were used for the preparation of membranes. These percentages were sufficient to improve better performance to modified membranes. PI was select as polymeric materials because combine easy processability in the form of membranes, with a high chemical and thermal stability, over a wide range of operative conditions. Three different PI polymers were used to prepared porous asymmetric membrane by non-solvent induced phase separation (NIPS): a homopolymer (Matrimid) and two co-polymers (Lenzing P84 and Torlon). The effect of membrane preparation conditions on the membrane morphology and transport properties, were investigate. Moreover, mixed matrix based on co-polyimide P84 and functionalized multiwalled carbon nanotubes (oxidized and aminated MWCNTs) were prepared. The different polymeric membranes were compared in the rejection of organic dyes, as model of organic pollutant present in wastewater (chapter 3). To investigate about the influence of functional groups on the MWCNTs for their interaction with polymeric matrix, three different type of functionalized MWCNTs (oxidized, amined and aminated) were dispersed also in polymeric hydrophobic PVDF membranes. PVDF was selected as polymeric materials of its outstanding properties: excellent chemical resistance and hydrolytic stability; high mechanical strength and stability over a broad pH range; polymorphism (main crystalline phases are: α, β, γ, δ and ε) [7]. The aim was to tailor the interactions with the polymeric matrix in order to realize high performing composite film with improved performance. Bovine serum albumin (BSA) protein was select as compound to evaluate the membrane performance. In particular, the antifouling properties and the permeation flux of mixed matrix membranes, were evaluate as well as thermal and structural and mechanical properties (chapter 4).Università della Calabria