Manufacturing, characterisation and mechanical analysis of PAN membranes

In recent years, usage of membranes is quite common in water and wastewater treatment. Polyacrylonitrile (PAN) is a polymeric material used in membrane production. To investigate the effect of Polyvinylpyrrolidone (PVP) addition and consequently porosity, two different sets of membranes are manufactured, since PVP is a widely used poring agent which has an impact on the mechanical properties of the membrane material. The first set (PAN 1) includes PAN and the necessary solvent while the second set (PAN 2) is made of PAN and PVP. These membranes are put through several characterisation processes including tensile testing. The obtained data are used to model the static behaviour of the membranes with different geometries, but similar loading and boundary conditions that represent their operating conditions. This modelling process is undertaken by using finite element method. The main idea is to investigate how geometry affects the load-carrying capacity of the membranes. Alongside membrane modelling, their materials are modelled with representative elements (RE) to understand the impact of porosity on the mechanical properties.</jats:p

Manufacturing and characterization of polymeric membranes for water treatment and numerical investigation of mechanics of nanocomposite membranes

In this study, polyethersulfone (PES) and polyvinylidene fluoride (PVDF) microfiltration membranes containing polyvinylpyrrolidone (PVP) with and without support layers of 130 and 150 μm thickness are manufactured using the phase inversion method and then experimentally characterised. For the characterisation of membranes, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and pore size analysis are performed, the contact angle and water content of membranes are measured and the tensile test is applied to membranes without support layers. Using the results obtained from the tensile tests, the mechanical properties of the halloysite nanotube (HNT) and nano-silicon dioxide (nano SiO2) reinforced nanocomposite membranes are approximately determined by the Mori–Tanaka homogenisation method without applying any further mechanical tests. Then, plain polymeric and PES and PVDF based nanocomposite membranes are modelled using the finite element method to determine the effect of the geometry of the membrane on the mechanical behaviour for fifteen different geometries. The modelled membranes compared in terms of three different criteria: equivalent stress (von Mises), displacement, and in-plane principal strain. Based on the data obtained from the characterisation part of the study and the numerical analysis, the membrane with the best performance is determined. The most appropriate shape and material for a membrane for water treatment is specified as a 1% HNT doped PVDF based elliptical membrane

Speciation of Cr(III) and Cr(VI) after column solid phase extraction on Amberlite XAD-2010

A speciation procedure for Cr(III) and Cr(VI) based on column solid phase extraction on Amberlite XAD-2010 and flame atomic absorption spectrometry combination. Cr(VI) was quantitatively recovered on Amberlite XAD-2010 resin at pH range of 2.0-3.0 as its diethyldithiocarbamate complex, while the recoveries of Cr(III) was below 5%. The influences of the various parameters including amounts of the reagents, eluent type and its volume, sample volume, etc., on the quantitative recoveries were examined. The interference of matrix and coexistent elements for method were studied. The detection limit (corresponding to three times the standard deviation of the blank) and the enrichment factor for Cr(VI) were found to be 1.28 mu g/L and 25, respectively. To verify the accuracy of the method, drinking water certified reference material (CRM-TMDW-500) was analyzed and the results obtained were in good agreement with the certified value. The proposed method has been successfully applied to the speciation of Cr(III) and Cr(VI) in water samples and preconcentration of total chromium in environmental samples. (C) 2006 Elsevier B.V. All rights reserved

A Multicenter Study of 1144 Patients with Cerebral Venous Thrombosis: The VENOST Study

Background Based on a number of small observational studies, cerebral venous sinus thrombosis has diverse clinical and imaging features, risk factors, and variable outcome. In a large, multicenter cerebral venous thrombosis (VENOST) study, we sought to more precisely characterize the clinical characteristics of Caucasian patients. Methods All data for the VENOST study were collected between the years 2000 and 2015 from the clinical follow-up files. Clinical and radiological characteristics, risk factors, and outcomes were compared in terms of age and sex distribution. Results Among 1144 patients 68% were women, and in older age group (>50 years) male patients were more prevalent (16.6% versus 27.8%). The most frequent symptoms were headache (89.4%) and visual field defects (28.9%) in men, and headache (86.1%) and epileptic seizures (26.8%) in women. Gynecological factors comprised the largest group in women, in particular puerperium (18.3%). Prothrombotic conditions (26.4%), mainly methylenetetrahydrofolate reductase mutation (6.3%) and Factor V Leiden mutation (5.1%), were the most common etiologies in both genders. 8.1% of patients had infection-associated and 5.2% had malignancy-related etiology that was significantly higher in men and older age group. Parenchymal involvement constitutively hemorrhagic infarcts, malignancy, and older age was associated with higher Rankin score. Epileptic seizures had no effect on prognosis. Conclusions Clinical and radiological findings were consistent with previous larger studies but predisposing factors were different with a higher incidence of puerperium. Oral contraceptive use was not a prevalent risk factor in our cohort. Malignancy, older age, and hemorrhagic infarcts had worse outcome. © 2017 National Stroke Associatio