Effect of non-solvent additives on the structure and performance of PVDF hollow fiber membrane contactor for CO2 stripping

Microporous polyvinylidene fluoride (PVDF) hollow fiber membranes with various non-solvent additives, i.e. lithium chloride, glycerol, polyethylene glycol (PEG-400), methanol and phosphoric acid, were fabricated for CO2 stripping via membrane contactors. The membranes were characterized in terms of liquid entry pressure, contact angle, gas permeation and morphology analysis. CO2 stripping performance was investigated by using an in-house made stainless steel module with CO2-preloaded aqueous diethanolamine as the liquid absorbent. Hydrophobicity and gas permeability of the membranes reduced with the addition of a non-solvent additive in the polymer dope but increase in liquid entry pressure was observed as more sponge-like structures developed in the inner layer of the fibers. It was found that PVDF/PEG-400 membrane produced the highest stripping flux of 4.03×10-2 mol m-2 s-1 which can be correlated to its high gas permeation and high effective surface porosity. The result of long-term stripping operation indicated an approximatly 80% stripping flux reduction which can be related to the interaction of polymer membrane and amine solution at high temperature

Development of Porous Asymmetric Polyamide–Imide Torlon® Membranes for Physical CO2 Absorption and Separation

Porous flat-sheet polyamide–imide (PAI) membranes were prepared via a phase inversion method to evaluate CO2 absorption performance in the gas-liquid membrane contactors. Different amounts of polyethylene glycol (PEG-600) were introduced into the polymer solution to investigate the structure and performance of resulted membranes. The membranes were characterized in terms of gas permeation, contact angle measurement and CO2 absorption flux. By introducing 6 wt.% PEG into the polymer dope, N2 permeance of the membrane was significantly improved from 482 to 1320 GPU. Mean while, the effect of PEG on the measured water contact angle was in significant. From CO2 absorption test, the developed membrane presented about 90% higher CO2flux compared to the plain membrane at water flow rate of 70 ml/min. In conclusion, by introducing a polymeric non-solvent additive into the polymer dope, it is possible to enhance surface porosity (permeability) of PAI membranes, which is a key factor for CO2 absorption test

Material design for teaching citations skills in scientific writing

Citations are important rhetorical devices that when properly and strategically employed, allow writers to promote their current research findings persuasively and efficiently. As knowledge construction is progressive and cumulative, specifically in scientific disciplines, it is evident that acquiring skills for adequate and effective application of citations is essential for success. Scientific writers are required to possess advanced academic literacy skills in order to ably position their study within the framework of existing knowledge, and strategically employ citations to advance the acceptability of their research findings. This paper endeavors to propose materials for teaching the rhetorical functions of citations in advanced academic writing courses. The tasks are designed specifically to raise students’ awareness of citation norms, especially in their own specific disciplines. Since the practice of citing the work of others ethically is highly challenging for emerging research writers, materials suggested in this paper can be beneficial to instructors who are involved in developing advanced discipline-specific writing courses, or short-term academic writing workshops

Mass transfer analysis of CO2 capture by PVDF membrane contactor and ionic liquid

Post-combustion processes based on ionic liquids (ILs) and membrane contactors are attractive alternatives to traditional systems. Here, a gas stream composed of 15% CO2 and 85% N2 flowed through the lumen side of a hollow-fiber membrane contactor containing poly(vinylidene fluoride)-IL (PVDF-IL) fibers. The IL 1-ethyl-3-methylimidazolium acetate [emim][Ac] served as an absorbent due to its high chemical absorption and CO2 solubility. The overall mass transfer coefficient (Koverall), activation energy (Ea), and resistances of the hollow-fiber membrane were quantified. The Koverall value was one order of magnitude higher than those reported in previous works with conventional solvents, and the Ea was lower than formerly stated values for other solvents. A theoretical simulation was conducted to estimate the operational parameters required for 90% CO2 capture and to quantify intensification effects related to CO2 absorption in a packed column.This research was funded by the Spanish Ministry of Economy and Competitiveness (Projects CTQ2013-48280-C3-1-R and CTQ2016-76231-C2-1-R). The authors thank Dr. J. C. Remigy (Laboratoire de Genie Chimique, UPS, Toulouse, France) for the preparation of 1AQ2-PVDF fibers

Liquid-Liquid Extraction of Penicillin-G from Pharmaceutical Wastewater Via a Developed Polysulfone Hollow Fiber Membrane Contactor

The presence of pharmaceutical wastewater can pose significant challenges to the environment. Since conventional wastewater treatment processes are not efficient for the complete separation of drug materials, solvent extraction through a hollow fiber membrane contactor could be a promising alternative. In this study, a developed polysulfone (PSF) hollow fiber membrane was fabricated using a non-solvent phase separation (NIPS) method to extract penicillin G from aqueous solutions in the membrane contactor system. From the characterization experiments, the prepared polysulfone membrane demonstrates an outer surface contact angle of 69.6°, critical water entry pressure (CEPw) of 250 kPa, total porosity of 72.2%, and collapsing pressure of 500 kPa. The extraction of penicillin G from the aqueous phase was performed with a 5% w/w solution of Aliquat 336. The effect of the operating parameters on the extraction flux of penicillin G was investigated using the response surface method (RSM). The optimum penicillin G flux of 1.46×10-3 kg/m2s was found at an operating pressure of 100 kPa, an aqueous phase flowrate of 70.5 ml/min, and an organic phase flowrate of 200 ml/min. Therefore, the developed PSF hollow fiber membrane contactor can be considered a proper choice to remove antibiotics (penicillin G) from aqueous solutions

Trace ammonium removal by liquid-liquid membrane contactors as water polishing step of water electrolysis for hydrogen production from a wastewater treatment plant effluent

© 2016 Society of Chemical Industry. BACKGROUND: This work evaluates hollow fiber liquid-liquid membrane contactors (HFMC) as a polishing step for the removal of low levels of ammonium from water purified by (or being supplied to) a membrane distillation unit in order to fulfil the conductivity requirements of hydrogen production by water electrolysis. RESULTS: The influence of the operating conditions (flow, pH, ammonium concentration, buffer capacity) were evaluated under a closed-loop setup in order to achieve a reduction of total ammonia concentration in water, from 15 to 1mgL-1 to assure the production of water in the membrane distillation with a conductivity lower than 1 µS cm-1. These values were used to validate a numerical algorithm describing the system performance. In order to reach the ammonia concentration requirements and considering the low concentration of bicarbonate (low pH buffer capacity) in the treated water a buffer agent was added to the working solution. CONCLUSIONS: HFMC technology is a suitable solution to remove low levels of ammonium from water to values as low as 1mgL- 1NH3 through appropriate control of pH. The ammonium removal efficiency of the HFMC was improved by raising the pH or the flow rate. Finally, the model proposed provides a good description of the membrane contactor performance with minimal deviations when compared with experimental results.Peer ReviewedPostprint (published version

Clinical Study Endovascular Treatment of Intracranial Artery Dissection: Clinical and Angiographic Follow-Up

Background. Intracranial artery dissections are rare and many controversies exist about treatment options. The aim of this study was to evaluate the efficacy and safety of the endovascular approach in patients with an intracranial dissection presenting with different symptoms. Methods. We prospectively evaluated the clinical features and treatment outcomes of 30 patients who had angiographically confirmed nontraumatic intracranial dissections over 4 years. Patients were followed up for 17 months, and their final outcomes were assessed by the modified Rankin Score (mRS) and angiography. Results. Sixteen (53.3%) patients had a dissection of the anterior circulation, whereas 14 (46.7%) had a posterior circulation dissection. Overall, 83.3% of the patients suffered a subarachnoid hemorrhage (SAH). Grade IV Hunt and Hess score was seen in 32% of the SAH presenting cases. Parent artery occlusion (PAO) with coil embolization was used in 70% of the cases. The prevalence of overall procedural complications was 23.3%, and all were completely resolved at the end of follow-up. No evidence of in-stent occlusion/stenosis or rebleeding was observed in our cases during follow-up. Angiography results improved more frequently in the PAO with coil embolization group (100%) than in the stent-only-treated group (88.9%) ( = 0.310) and the unruptured dissection group (5/5, 100%) in comparison with the group that presented with SAH (95.8%) ( = 0.833). Conclusion. Favorable outcomes were achieved following an endovascular approach for symptomatic ruptured or unruptured dissecting aneurysms. However, the long-term efficacy and durability of these procedures remain to be determined in a larger series