Impact of Sub-Ambient Temperature on Aging Rate and Gas Separation Properties of Polymers of Intrinsic Microporosity

Aging in polymers of intrinsic microporosity has slowed exploitation due to a decay in performance over time since densification makes them unsuitable for industrial applications. This work aimed to study the impact of the operation and storage temperature on the gas separation properties and aging rates of PIM-1 self-standing films. The permeability, diffusivity, and solubility of the tested membranes were monitored through permeation tests for pure carbon dioxide and nitrogen at a maximum upstream pressure of 1.3 bar for temperatures ranging from −20 °C to 25 °C. This study found significant benefits in the operation of glassy polymeric membranes at low temperatures, resulting in a favourable trade-off in separation performance and a reduction in the aging rate by three orders of magnitude. This brings new opportunities for the industrial application of PIMs in innovative carbon capture processes

CO2 sorption modelling in humidified Polyvinyl amine (PVAm) with PC-SAFT

Carbon dioxide emissions represent one of the main environmental issue of our time. The greenhouse gases atmospheric loading, due to anthropogenic activities, are causing a continue rise of global temperature. In the field of CO2 capture from gas streams, membrane technologies are promising alternative to the more common operations. Among these, Facilitated Transport Membranes show high performances in terms of CO2 permeabilities and selectivities even at low pressures by coupling a simple solution diffusion transport mechanism and a reversible chemical reaction with a carrier agent. Polyvinyl amine (PVAm) binds one primary amino group for each monomer along the chain, showing high hydrophilicity and affinity to CO2. In this work we use the PC-SAFT [1] Equation of State to model the H2O uptake and the solubility of CO2 in the ternary system of PVAm / H2O / CO2

Modelling water sorption in Facilitated Transport Membranes with PC-SAFT Equation of State: the case of Polyvinyl amine

Facilitated transport membranes have great potential for carbon dioxide removal. By coupling the solution diffusion mechanism and the facilitation effect of the chemical reaction, CO2 transport in such systems is substantially higher compared to other gases, like nitrogen and methane. The presence of water is needed in the membrane to activate the reaction mechanism, and affects the sorption and diffusion of all the gases in the membrane. The present work focuses on the modelling of water sorption in purified Lupamin\uae (polyvinylamine (PVAm)), with the PC-SAFT Equation of State (EoS) (Gross and Sadowski, 2001). The work is aimed at finding the best parameters and association schemes to model the water sorption in PVAm with the PC-SAFT model, in order to use it to model more complex situations such as the multicomponent sorption in the system

Mixed Matrix Membranes based on PPO and graphene for gas separation

Novel composite Mixed Matrix Membranes (MMM) were fabricated by dispersion of different loadings of graphene nanoparticles (from 0.3 to 15 % weight percentage) in a dense permeable glassy polymer, poly (2,6-dimethyl-1,4-phenylene oxide), PPO, by solvent casting procedure. The permeability, selectivity and diffusivity of helium, nitrogen and carbon dioxide have been measured at two different temperatures, 35° and 65°C and the effect of graphene loading was studied. (R. Rea et al. 2018)

Permeability and Selectivity of PPO/Graphene Composites as Mixed Matrix Membranes for CO2 Capture and Gas Separation

We fabricated novel composite (mixed matrix) membranes based on a permeable glassy polymer, Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), and variable loadings of few-layer graphene, to test their potential in gas separation and CO2 capture applications. The permeability, selectivity and diffusivity of different gases as a function of graphene loading, from 0.3 to 15 wt %, was measured at 35 and 65 \u25e6C. Samples with small loadings of graphene show a higher permeability and He/CO2 selectivity than pure PPO, due to a favorable effect of the nanofillers on the polymer morphology. Higher amounts of graphene lower the permeability of the polymer, due to the prevailing effect of increased tortuosity of the gas molecules in the membrane. Graphene also allows dramatically reducing the increase of permeability with temperature, acting as a \u201cstabilizer\u201d for the polymer matrix. Such effect reduces the temperature-induced loss of size-selectivity for He/N2 and CO2/N2, and enhances the temperature-induced increase of selectivity for He/CO2. The study confirms that, as observed in the case of other graphene-based mixed matrix glassy membranes, the optimal concentration of graphene in the polymer is below 1 wt %. Below such threshold, the morphology of the nanoscopic filler added in solution affects positively the glassy chains packing, enhancing permeability and selectivity, and improving the selectivity of the membrane at increasing temperatures. These results suggest that small additions of graphene to polymers can enhance their permselectivity and stabilize their propertie

Modelling facilitated transport in Polyvinyl amine membranes for CO2 capture: insights from Molecular Dynamics and PC-SAFT EoS.

In the context of CO2 removal from gas streams, the project NANOMEMC2 (www.nanomemc2.eu) focuses on Facilitated Transport (FT) membranes based on Polyvinyl mine (PVAm). Such materials bear amine groups that, in presence of humidity, promote reactions that boost the transport of CO2 while not affecting the other gases. A possible reaction route is shown in Figure 1. Very few modelling studies are present in the literature concerning these fixed sites FT membranes despite their selectivity comparable to the most common absorption processes. Aim of the present work is to provide a detailad deep investigation on the transport properties of PVAm, to partially fill this lack, for the ternary system of CO2/H2O/PVAm. Molecular Dynamics (MD) and PC-SAFT1 Equation of State (EoS) were used to achieve a reliable interpretation of the physical sorption process of CO2 in such a complex, strongly polar environment

Modelling facilitated transport in Polyvinyl amine membranes for CO2 capture: insights from Molecular Dynamics and PC-SAFT EoS.

The removal of CO2 from flue gas in power plants or energy-intensive industries is one of the main ways to reduce the increasing CO2 atmospheric levels, that cause global warming. Among the various technologies identified for this aim, such as solvent absorption and adsorption, membrane separation is considered as the most flexible and environmentally friendly option. For this reason the project NANOMEMC2 (www.nanomemc2.eu) aims at developing innovative membranes with improved CO2 capture ability, which can make the capture less costly. The project focuses on Facilitated Transport (FT) membranes, that are endowed with higher selectivity values with respect to conventional ones. Such materials bear amine groups that, in presence of humidity, promote reactions that boost the transport of CO2 while not affecting the other gases

Modelling facilitated transport in Polyvinyl amine membranes for CO2 capture: insights from Molecular Dynamics and PC-SAFT EoS.

In the context of CO2 removal from gas streams, the project NANOMEMC2 (www.nanomemc2.eu) focuses on Facilitated Transport (FT) membranes based on Polyvinyl mine (PVAm). Such materials bear amine groups that, in presence of humidity, promote reactions that boost the transport of CO2 while not affecting the other gases. A possible reaction route is shown in Figure 1. Very few modelling studies are present in the literature concerning these fixed sites FT membranes despite their selectivity comparable to the most common absorption processes. Aim of the present work is to provide a detailad deep investigation on the transport properties of PVAm, to partially fill this lack, for the ternary system of CO2/H2O/PVAm. Molecular Dynamics (MD) and PC-SAFT1 Equation of State (EoS) were used to achieve a reliable interpretation of the physical sorption process of CO2 in such a complex, strongly polar environment

A magnetar giant flare in the nearby starburst galaxy M82

Giant flares, short explosive events releasing up to 10$^{47}$ erg of energy in the gamma-ray band in less than one second, are the most spectacular manifestation of magnetars, young neutron stars powered by a very strong magnetic field, 10$^{14-15}$ G in the magnetosphere and possibly higher in the star interior. The rate of occurrence of these rare flares is poorly constrained, as only three have been seen from three different magnetars in the Milky Way and in the Large Magellanic Cloud in about 50 years since the beginning of gamma-ray astronomy. This sample can be enlarged by the discovery of extragalactic events, since for a fraction of a second giant flares reach peak luminosities above 10$^{46}$ erg/s, which makes them visible by current instruments up to a few tens of Mpc. However, at these distances they appear similar to, and difficult to distinguish from, regular short gamma-ray bursts (GRBs). The latter are much more energetic events, 10$^{50-53}$ erg, produced by compact binary mergers and originating at much larger distances. Indeed, only a few short GRBs have been proposed, with different levels of confidence, as magnetar giant flare candidates in nearby galaxies. Here we report the discovery of a short GRB positionally coincident with the central region of the starburst galaxy M82. Its spectral and timing properties, together with the limits on its X-ray and optical counterparts obtained a few hours after the event and the lack of an associated gravitational wave signal, qualify with high confidence this event as a giant flare from a magnetar in M82.Comment: Submitted version. New figures. Accepted for publication in Nature with minor modification

Radiation techniques for acromegaly

Radiotherapy (RT) remains an effective treatment in patients with acromegaly refractory to medical and/or surgical interventions, with durable tumor control and biochemical remission; however, there are still concerns about delayed biochemical effect and potential late toxicity of radiation treatment, especially high rates of hypopituitarism. Stereotactic radiotherapy has been developed as a more accurate technique of irradiation with more precise tumour localization and consequently a reduction in the volume of normal tissue, particularly the brain, irradiated to high radiation doses. Radiation can be delivered in a single fraction by stereotactic radiosurgery (SRS) or as fractionated stereotactic radiotherapy (FSRT) in which smaller doses are delivered over 5-6 weeks in 25-30 treatments. A review of the recent literature suggests that pituitary irradiation is an effective treatment for acromegaly. Stereotactic techniques for GH-secreting pituitary tumors are discussed with the aim to define the efficacy and potential adverse effects of each of these techniques