Francesco Galiano

Bromide ion exchange with a Keggin polyoxometalate on functionalized polymeric membranes: a theoretical and experimental study.

Noncovalent interactions between the polyoxometalate [PMo12O40](3-) and acryloyloxyundecyltrimethyl ammonium bromide surfactant, used during membrane preparation, were evaluated in the frame of density functional theory. The electronic solvation energy of [PMo12O40](3) and bromide anions was also evaluated, at the same level of theory, in order to predict a probable exchange on the polymeric surface between these anions at the water/polymer interface. Energy balances were theoretically assessed, showing that the bromide cannot be exchanged with this nanosized polyanion in large extent. In order to validate this theoretical conclusion, ad hoc and accurate measurements were carried out by using homemade polymeric membranes and by dipping them in an ca. 0.4 mM solution of Na3[PMo12O40] for 4 days. The Br(-) concentration, released in a polyoxometalate solution, was followed at different times during the test period by gravimetrical analysis. The agreement between the theoretical prediction and experimental data was remarkable, as the quantum calculations correctly accounted for the short-range intermolecular interactions involved in this phenomenon. Bearing in mind that the achieved conclusion is based on an ab initio quantum approach, the findings of this study can be considered rather general and then exploitable for other similar systems.

Mixed matrix membranes (MMMs) for ethanol purification through pervaporation: current state of the art

Abstract Over the last few decades, different polymers have been employed as materials in membrane preparation for pervaporation (PV) application, which are currently used in the preparation of mixed matrix membranes (MMMs) for ethanol recovery and ethanol dehydration. The ethanol-water and water-ethanol mixtures are, in fact, the most studied PV systems since the bioethanol production is strongly increasing its demand. The present review focuses on the current state of the art and future trends on ethanol purification by using MMMs in PV. A particular emphasis will, therefore, be placed on the enhancement of specific components transport and selectivity through the incorporation of inorganic materials into polymeric membranes, mentioning key principles on suitable filler selection for a synergistic effect toward such separations. In addition, the following topics will be discussed: (i) the generalities of PV, including the theoretical aspects and its role in separation; (ii) a general overview of the methodologies for the preparation of MMMs; and (iii) the most recent findings based on MMMs for both ethanol recovery and ethanol dehydration for better evolution in the field. From the last decade of literature inputs, the poly(vinyl alcohol) has been the most used polymeric matrix targeting ethanol dehydration, while the zeolites have been the most used embedded materials. Today, the latest developments on MMM preparation declare that the future efforts will be directed to the chemical modification of polymeric materials as well as the incorporation of novel fillers or enhancing the existing ones through chemical modification.

Novel low-fouling membranes from lab to pilot application in textile wastewater treatment

A novel antifouling coating based on the polymerization of a polymerisable bicontinuous microemulsion (PBM) was developed and applied for commercially available membranes for textile wastewater treatment. PBM coating was produced by polymerizing, on a polyethersulfone (PES) membrane, a bicontinuous microemulsion, realized by finely tuning its properties in terms of chemical composition and polymerization temperature. In particular, the PBM was prepared by using, as the surfactant component, inexpensive and commercially available dodecyltrimethylammonium bromide (DTAB). The coating exhibited a more hydrophilic and a smoother surface in comparison to uncoated PES surface, making the produced PBM membranes more resistant and less prone to be affected by fouling. The anti-fouling potential of PBM membranes was assessed by using humic acid (HA) as a model foulant, evaluating the water permeability decrease as an indicator of the fouling propensity of the membranes. PBM membrane performances in terms of dye rejection, when applied for model textile wastewater treatment, were also evaluated and compared to PES commercial ones. The PBM membranes were finally successfully scaled-up (total membrane area 0.33 m2) and applied in a pilot membrane bioreactor (MBR) unit for the treatment of real textile wastewater.

Novel Photocatalytic PVDF/Nano-TiO2 Hollow Fibers for Environmental Remediation

Polyvinylidene difluoride (PVDF) mixed matrix membranes loaded with inorganic TiO2 nanoparticles have received increasing attention in the last few years as self-cleaning membranes for possible application in wastewater treatment and seawater filtration. These novel membranes show increased hydrophilicity, stability and catalytic activity under UV-A irradiation. In this work, PVDF-TiO2 hollow fibers were prepared by employing new strategies for enhancing the stability of the TiO2 dispersion, reducing particle agglomeration and improving their distribution. The spinning conditions for producing ultrafiltration hollow fiber membranes from PVDF material and nano-TiO2 were investigated. Finally, the optimized fibers have been characterized and tested for methylene blue (MB) degradation in water and salty seawater, revealing good permeability, long-term stability under UV-A irradiation, and photo-catalytic activity in both test solutions.

Methanol Separation From Liquid Mixtures Via Pervaporation Using Membranes

Abstract Pervaporation (PV) is considered an efficient and indispensable membrane process in liquid separation and in particular for breaking azeotropes of liquid mixtures. It is based on the use of a polymeric or inorganic membrane located at the interface between a liquid feed mixture to be treated and the vapor phase (permeate). This membrane technology ranges over numerous applications including the dehydration of an organic solvent, organic/organic separation, and the removal of volatile organic compounds (VOCs) from water. In the first part of the chapter, an introduction on PV, reporting the fundamentals and the transport mechanism of the process, is reported. The application of PV in organic/organic separation is also illustrated. The second part of the chapter deals with the PV separation of methanol/organic and methanol/aqueous mixtures.

A novel Ru–polyethersulfone (PES) catalytic membrane for highly efficient and selective hydrogenation of furfural to furfuryl alcohol

A novel catalytic membrane has been synthesised, characterised and evaluated for the selective hydrogenation of furfural to furfuryl alcohol. Unlike conventional methods, involving high pressure and high H2 : feed ratios, this work proposes an innovative ruthenium based Catalytic Membrane Reactor (CMR) to overcome mass transfer limitations, resulting in low H2 requirements, high catalytic activity and high selectivity towards furfuryl alcohol. A UV-curable hydrophilic anionic monomer acrylic acid was used as a coating material on a commercial PES membrane and subsequently Ru nanoparticles were added. The hydrogenation of furfural was carried out in a customised catalytic membrane reactor under mild conditions: 70 °C and 7 bar, exhibiting high catalytic activity towards furfuryl alcohol (selectivity >99%) with turnover frequency (TOF) as high as 48 000 h−1, 2 orders of magnitude higher than those obtained so far.

Tailoring PES membrane morphology and properties via selected preparation parameters

Abstract Polyethersulfone (PES) is among the most interesting materials for membranes preparation, thanks to its outstanding properties, coupled to compatibility with several additives and the facility to be solubilized in several solvents. In this work, flat sheet membranes were prepared by the non-solvent induced phase separation (NIPS) technique, using PES as polymer and polyvinyl pyrrolidone (PVP, 10 kDa) as additive. Preparation and casting conditions were varied and membranes with tailored morphology and properties were obtained. The main objective was to investigate the relationship between selected preparation conditions and membrane features. This may help to understand how to tailor membrane morphology and properties depending on the desired application.