Preparation of porous stainless steel hollow-fibers through multi-modal particle size sintering towards pore engineering

The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm) as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors

Ultra-Selective CMSMs Derived from Resorcinol-Formaldehyde Resin for CO2 Separation

A resorcinol-formaldehyde precursor was synthesized to fabricate the CO2 selective Carbon Molecular Sieve Membranes (CMSMs) developed in this study. The degree of polymerization (DP) was analyzed via Gel Permeation Chromatography (GPC) and its effect on the CO2/N2 perm-selectivity and CO2 permeance was investigated. The membrane that was polymerized at 80 °C (named R80) was selected as the best performing CMSM after a preliminary test. The post treatment with oxidative atmosphere was performed to increase the CO2 permeance and CO2/N2 perm-selectivity on membrane R80. The gas permeation results and Pore Size Distribution (PSD) measurements via perm-porometry resulted in selecting the membrane with an 80 °C polymerization temperature, 100 min of post treatment in 6 bar pressure and 120 °C with an oxygen concentration of 10% (named R80T100) as the optimum for enhancing the performance of CMSMs. The 3D laser confocal microscopy results confirmed the reduction in the surface roughness in post treatment on CMSMs and the optimum timing of 100 min in the treatment. CMSM R80T100 exhibiting CO2/N2 ideal selectivity of 194 at 100 °C with a CO2 permeability of 4718 barrier was performed higher than Robeson’s upper bound limit for polymeric membranes and also the other CMSMs fabricated in this work.The research has been carried out within the TTW Perspectief Program “Microsync” project number P16-10

Three-dimensional reduced graphene oxide decorated with iron oxide nanoparticles as efficient active material for high performance capacitive deionization electrodes

A three-dimensional reduced graphene oxide decorated with iron oxide nanoparticles (3D rGO-Fe2O3) material with a suitable porous structure was synthesised using a one-step hydrothermal process in order to fabricate novel electrodes for capacitive deionization (CDI) water desalination. The morphological and structural properties of the as-synthesised compounds were characterised by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Raman spectroscopy (RS), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The CDI electrodes were electrochemically analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A maximum value of specific capacitance of 345 F g−1 was achieved at 5 mV s−1 scan rate using a NaCl 0.1 mol L−1 solution. The ion removal performance of the CDI electrodes was evaluated with NaCl solutions of different concentrations, showing electrosorption capacities as high as 945 mg g−1 for 11,700 mg L−1 (200 mmol L−1) NaCl solutions, which substantially surpasses results of other carbon-based CDI electrodes.This project has received funding from the European Union’s Horizon 2020 research and innovation programme Graphene Flagship under grant agreement No 881603

Vapor/gas separation through carbon molecular sieve membranes: Experimental and theoretical investigation

The separation of H2O vapor from (hydrogen-rich) gaseous streams is a topic of increasing interest in the context of CO2 valorisation, where the in situ water removal increases product yield and catalyst stability. In this work, composite alumina carbon molecular sieve membranes (Al-CMSM) were prepared from phenolic resin solutions loaded with hydrophilic boehmite (γ-AlO(OH)) nanosheets (0.4–1.4 wt. % in solution) which partially transform to γ-Al2O3 nanosheets upon thermal decomposition of the resin, improving the hydrophilicity and thus the adsorption-diffusion contribution of the H2O permeation. The γ-Al2O3 nanosheets showed no influence on the pore size distribution of the membranes in the range of micropores, but they increased the membrane hydrophilicity. In addition, the use of boehmite in the resin solution causes an increase in the viscosity and thus an increase in the carbon layers thickness deposited on the porous α-Al2O3 support (from 1 to 3.3 μm). Furthermore, the alumina sheets introduce defects in the carbon matrix, increasing the tortuosity of the active layer, as concluded via phenomenological modelling and parametric fitting of the experimental results. As a consequence, the water permeability exhibits a maximum (1.3ꞏ10−6 molꞏs−1 Pa−1 m−1 at 150 °C) with boehmite/alumina content of ca. 0.8 wt. %, as the combined effects of increasing hydrophilicity (which favour H2O permeability) and increasing thickness and tortuosity (which hamper permeability) upon increasing boehmite loading. Similarly, the H2O/gas perm-selectivity is optimum at 1.2 wt. % boehmite loading. We further investigated the H2O permeation mechanism by modelling the mono- and multi-layer adsorption and capillary condensation of water in microporous media, which result as the main transport mechanisms in the explored conditions.This project has received funding from the European Union’s Horizon 2020 research and innovation programme undergrant agreement No 838014 (C2Fuelproject)

Water Adsorption Effect on Carbon Molecular Sieve Membranes in H2-CH4 Mixture at High Pressure

Carbon molecular sieve membranes (CMSMs) are emerging as promising solution to overcome the drawbacks of Pd-based membranes for H2 separation since (i) they are relatively easy to manufacture; (ii) they have low production and raw material costs; (iii) and they can work at conditions where polymeric and palladium membranes are not stable. In this work CMSMs have been investigated in pure gas and gas mixture tests for a proper understanding of the permeation mechanism, selectivity and purity towards hydrogen. No mass transfer limitations have been observed with these membranes, which represents an important advantage compared to Pd-Ag membranes, which suffer from concentration polarization especially at high pressure and low hydrogen concentrations. H2, CH4, CO2 and N2 permeation at high pressures and different temperatures in presence of dry and humidified stream (from ambient and water vapour) have been carried out to investigate the effect of the presence of water in the feed stream. Diffusion is the main mechanism observed for hydrogen, while methane, nitrogen and especially carbon dioxide permeate through adsorption-diffusion at low temperatures and high pressures. Finally, H2 permeation from H2-CH4 mixtures in presence of water has been compared at different temperatures and pressure, which demonstrates that water adsorption is an essential parameter to improve the performance of carbon molecular sieve membranes, especially when working at high temperature. Indeed, a hydrogen purity of 98.95% from 10% H2—90% CH4 was achieved. The main aim of this work is to understand the permeation mechanisms of CMSMs in different operating conditions and find the best conditions to optimize the separation of hydrogen.This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant Agreement no. 700355. This Joint Undertaking receves support from the European Union´s Horizon 2020 research

Carbon molecular sieve membranes for water separation in CO₂ hydrogenation reactions:Effect of the carbonization temperature

Carbon membranes are a potentially attractive candidate for the in-situ removal of water vapor in CO2 hydrogenation reactions. Their hydrophilicity and pore structure can be tuned by properly adjusting the synthesis procedure. Herein, we assess the effect of the carbonization temperature (450–750 °C) on the performance of supported CMSM in terms of vapor/gas separation, in correlation with changes in their surface functionality and porous structure. FTIR spectra showed that the nature of the functional groups changes with the evolution of the carbonization step, leading to a gradual loss in hydrophilicity (i.e., OH stretching disappears at Tcarb ≥ 600 °C). The extent of water adsorption displays an optimum at Tcarb of 500 °C, with the membrane carbonized at 650 °C being the least hydrophilic. We found that the pore size distribution strongly influences the water permeance. At all Tcarb, adsorption-diffusion (AD) is the dominant transport mechanisms. However, as soon as ultra-micropores appear (Tcarb: 600–700 °C) molecular sieving (MS) contributes to an increase in the water permeance, despites a loss in hydrophilicity. At Tcarb ≥ 750 °C, MS pores disappear, causing a drop in the water permeance. Finally, the permeance of different gases (N2, H2, CO, CO2) is mostly affected by the pore size distribution, with MS being the dominant mechanism over the AD, except for CO2. However, the extent and mechanism of gas permeation drastically change as a function of the water content in the feed, indicating that gas/vapor molecules need to compete to access the pores of the membranes.</p

Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Background: Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes. Methods: We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18–85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR)25–75 mL/min per 1·73 m 2 of body surface area, and a urine albumin-to-creatinine ratio (UACR)of 300–5000 mg/g who had received maximum labelled or tolerated renin–angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0·75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders)were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0·75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for ≥30 days)or end-stage kidney disease (eGFR <15 mL/min per 1·73 m 2 sustained for ≥90 days, chronic dialysis for ≥90 days, kidney transplantation, or death from kidney failure)in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials.gov, number NCT01858532. Findings: Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325)or placebo group (n=1323). Median follow-up was 2·2 years (IQR 1·4–2·9). 79 (6·0%)of 1325 patients in the atrasentan group and 105 (7·9%)of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR]0·65 [95% CI 0·49–0·88]; p=0·0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3·5%)of 1325 patients in the atrasentan group and 34 (2·6%)of 1323 patients in the placebo group (HR 1·33 [95% CI 0·85–2·07]; p=0·208). 58 (4·4%)patients in the atrasentan group and 52 (3·9%)in the placebo group died (HR 1·09 [95% CI 0·75–1·59]; p=0·65). Interpretation: Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Funding: AbbVie

Macrocyclic and acyclic ligands and their interactions with ionic and neutral species.

This thesis presents investigations related to interactions of chelating ligands (macrocyclic and acyclic) with neutral and ionic species in solution. Following a brief introduction on coordination chemistry, each topic is presented separately in three chapters. In Chapter I, thermodynamic studies on drug cyclodextrin interactions in water and in chloroform at 298.15 K are discussed in relation to the effect of the macrocycle on the transfer of N1-substituted sulphonamides from water to chloroform. It is concluded that the transfer of the drug in this solvent system is thermodynamically more favoured in the absence than in the presence of cyclodextrin. Chapter II concerns thermodynamic aspects on calixarenes and their ester derivatives. As far as calixarenes are concerned, thermodynamic parameters of complexation of tert-butylamine and p-tert-butylcalix[4]arene in benzonitrile suggest that two processes are involved; the formation of the adduct followed by that of an endo-calix complex. The interaction of alkyl-p-tert-butylcalix[4]arene tetraethanoates with alkali-metal cations in acetonitrile and in benzonitrile at 298.15 K was studied by titration calorimetry. The limitation of this technique to derive stability constant data for highly stable complexes led to the development of a double competitive potentiometric method. Thermodynamic data are discussed in terms of the solvation of host, guest and resulting complex in these solvents. Chapter III discusses synthesis, characterisation and acid-base properties of ethylenedinitrilo-N,N1-diacetic-N,N1-bis(1-phenylethylacetamido) acid (edtamba) and ethylenedinitrilo-N,N1-diacetic-N,N'bis(pyridylacetamidoacetamioe)acid (edtapa) This is followed by the thermodynamics of complexation of these ligands with metal cations (Pb(II), Cd(II), Cu(II), Ni(II), Zn(II) and Co(II) in water at 298.15 K. These results show that unlike EDTA, edtamba and edtapa do not interact selectively with these cations as a result of a remarkable enthalpy-entropy compensation effect. Computer programs written during the course of these investigations are appended

Macrocyclic and acyclic ligands and their interactions with ionic and neutral species.

This thesis presents investigations related to interactions of chelating ligands (macrocyclic and acyclic) with neutral and ionic species in solution. Following a brief introduction on coordination chemistry, each topic is presented separately in three chapters. In Chapter I, thermodynamic studies on drug cyclodextrin interactions in water and in chloroform at 298.15 K are discussed in relation to the effect of the macrocycle on the transfer of N1-substituted sulphonamides from water to chloroform. It is concluded that the transfer of the drug in this solvent system is thermodynamically more favoured in the absence than in the presence of cyclodextrin. Chapter II concerns thermodynamic aspects on calixarenes and their ester derivatives. As far as calixarenes are concerned, thermodynamic parameters of complexation of tert-butylamine and p-tert-butylcalix[4]arene in benzonitrile suggest that two processes are involved; the formation of the adduct followed by that of an endo-calix complex. The interaction of alkyl-p-tert-butylcalix[4]arene tetraethanoates with alkali-metal cations in acetonitrile and in benzonitrile at 298.15 K was studied by titration calorimetry. The limitation of this technique to derive stability constant data for highly stable complexes led to the development of a double competitive potentiometric method. Thermodynamic data are discussed in terms of the solvation of host, guest and resulting complex in these solvents. Chapter III discusses synthesis, characterisation and acid-base properties of ethylenedinitrilo-N,N1-diacetic-N,N1-bis(1-phenylethylacetamido) acid (edtamba) and ethylenedinitrilo-N,N1-diacetic-N,N'bis(pyridylacetamidoacetamioe)acid (edtapa) This is followed by the thermodynamics of complexation of these ligands with metal cations (Pb(II), Cd(II), Cu(II), Ni(II), Zn(II) and Co(II) in water at 298.15 K. These results show that unlike EDTA, edtamba and edtapa do not interact selectively with these cations as a result of a remarkable enthalpy-entropy compensation effect. Computer programs written during the course of these investigations are appended

Reduced graphene oxide films as transparent counter-electrodes for dye-sensitized solar cells

Stand-alone graphene-based films were prepared from graphene oxide (GO) nanoplatelets and their use as counter-electrodes (CEs) indye-sensitized solar cells (DSCs) was investigated. The graphene-based CEs were produced by spray deposition of GO and chemicallyreduced GO, followed by thermal annealing under an inert atmosphere. These GO-based CEs were shown to have similar transparencyas a reference CE made of Pt. Consistent with impedance data from symmetrical half-cells, DSCs assembled with such GO-based CEsexhibited relative efficiencies of ca. 75% comparatively to the reference Pt CE. The possibility of obtaining transparent (transmittancehigher than 80%) and reasonable catalytic films for DSCs (energy conversion efficiency of 2.64%) from GO nanoplatelets was demonstrated.The need for reduction of the graphene oxide nanoplatelets prior to deposition was not observed, allowing for a simplified CEmanufacturing process. However, further work is still needed to equal or surpass the performance of Pt CEs