Making and Comparing the Performance of Zeolite Membranes

Zeolite membranes NaA, ZSM-5, Mordenite, NaX and NaY grown onto seeded mullite supports. Separation performance of zeolite membranes were studied for water-dimethylhydrazine mixtures using pervaporation (PV). The best Flux and separation factor of the membranes were 0.62 kg/m2.h and 52000, respectively, for NaA zeolite membrane. Strong electrostatic interaction between ionic sites and water molecules (due to its polar nature) makes the zeolite NaA membrane very hydrophilic. Zeolite NaA membranes are thus well suited for separating liquid-phase mixtures by pervaporation. In this study, experiments were conducted with various dimethylhydrazine –water mixtures (1–20 wt. %) at 25. Total flux for UDMH–water mixtures was found to vary from 0.331 to 0.241 kg/m2.h with increasing UDMH concentration from 1 to 20 wt.%. Ionic sites of the NaA zeolite matrix play a very important role in water transport through the membrane. Surface diffusion of water occurs in an activated fashion through these sites. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with UDMH concentration. Keywords: nanopore; pervaporation; zeolite membranes; Stephan Maxwell mode

Preparation of Nanopore Hydroxysodalite Zeolite Membranes by Dry Gel Method

Hydroxysodalite (HS) Zeolite membrane was prepared onto seeded mullite supports using a new crystallization method called ‘Dry Gel Conversion Technique’. Molar composition of the starting gel of HS zeolite membrane was SiO2/Al2O3=1.0, Na2O/Al2O3=65, and H2O/Al2O3=1000. X-ray diffraction (XRD) patterns of the membranes exhibited peaks corresponding to the support and the zeolite. The crystal species were characterized by XRD and morphology of the supports subjected to crystallization was characterized by Scanning electron microscopy (SEM). Separation performance of HS zeolite membranes was studied for water-Ethanol mixtures using pervaporation (PV). The membranes showed good selectivity towards water in the water-Ethanol mixtures. Water permeates faster because of its preferential adsorption into the nano-pores of the hydrophilic zeolite membrane. In PV of water-Ethanol mixtures, the membrane exhibits a hydrophilic behavior, with a high selectivity towards water and a good flux. The best Flux and separation factor of the membranes were 2.05 kg/m2.h and 10000, respectively. In addition, these membranes used for hydrogen separation from CH4 and It shown high selectivity and permeability ratio to zeolite membrane preparated by conventional method. Keywords: nanopore, hydroxysodalite, pervaporation, dry gel, zeolite, membran

Use of Polymer Membranes for Modeling Desulfurization in the Process of Pervaporation through Artificial Neural Network

The present study considered the amount of thiophene_alkane separation within the process of pervaporation by use of-of membrane polyethylene glycol and polydimethylsiloxane-polyacrylonitrile with the help of Artificial Neural Network Modeling. In this research, the effects of such parameters as Volumetric flow rate and temperature, as well as feedstuff properties (separation factor and flux) on the Desulfurization process efficiency were evaluated, and the Multi Layers Perceptron (MLP) neural network feed forward along with Propagation learning algorithm and Levenberg-Marquardt function with inputs and outputs were implemented. Tansig activation algorithm was used for the hidden layer, and Purelin algorithm was utilized for the output layer. Furthermore, 5 neurons were defined for the hidden layer. After processing the data, 70 percent were allocated for learning, 15% were allocated for validity, and the remaining 15% was allocated for the experience. The achieved results with the aforementioned method had a suitable accuracy. The graphs of the error percentage for the actual values of the separation factor and flux outputs were compared to the achieved values from modeling through related membranes for evaluating the efficiency of pervaporation process in a separation of ethanol, Acetone, and butanol from the water. Finally, the graphs were drawn. Keywords: Modeling, desulfurization, artificial neural networks, polyethylene glyco

Synthesis, Evaluation, Modeling and Simulation of Nanopore NaA Zeolite Membranes for Application in Ethanol Separation

Zeolite membranes have uniform and molecular-sized pores that separate molecules based on the differences in the molecules’ adsorption and diffusion properties. Strong electrostatic interaction between ionic sites and water molecules (due to its highly polar nature) makes the zeolite NaA membrane very hydrophilic. Zeolite NaA membranes are thus well suited for the separation of liquid-phase mixtures by pervaporation. In this study, experiments were conducted with various ethanol–water mixtures (1–20 wt. %) at 25 °C. Total flux for ethanol–water mixtures was found to vary from 0.331 to 0.229 kg/m2.h with increasing thanol concentration from 1 to 20 wt.%. Ionic sites of the NaA zeolite matrix play a very important role in water transport through the membrane. These sites act both as water sorption and transport sites. Surface diffusion of water occurs in an activated fashion through these sites. The precise Nano-porous structure of the zeolite cage helps in a partial molecular sieving of the large solvent molecules leading to high separation factors. A comparison between experimental flux and calculated flux using Stephan Maxwell (S.M.) correlation was made and a linear trend was found to exist for water flux through the membrane with ethanol concentration. A comprehensive model also was proposed for the ethanol-water pervaporation by Finite Element Method (FEM). The 2D model was masterfully capable of predicting water concentration distribution within both the membrane and the feed side of the pervaporation membrane module. Keywords: nanopores, pervaporation, ethanol separation, zeolite NaA membrane, FEM simulatio

CFD simulation of pervaporation of organic aqueous mixture through silicalite nano-pore zeolite membrane

Nanopore silicalite type membranes were prepared on the outer surface of a porous-mullite tube by in situ liquid phase hydrothermal synthesis. The hydrothermal crystallization was carried out under an autogenously pressure, at a static condition and temperature of 180 °C with tetrapropylammonium bromide (TPABr) as a template agent. The molar composition of the starting gel of silicalite zeolite membrane was: Na2O/SiO2=0.287-0.450, H2O/SiO2 = 8-15, TPABr/SiO2 = 0.01-0.04. The zeolites calcinations were carried out in air at 530 °C, to burn off the template (TPABr) within the zeolites. X-ray diffraction (XRD) patterns of the membranes consisted of peaks corresponding to the support and zeolite. The crystal species were characterized by XRD, and morphology of the supports subjected to crystallization was characterized by scanning electron microscopy (SEM). Performance of silicalite nanoporous membranes was studied for separation of water-unsymmetrical dimethylhydrazine (UDMH) mixtures using pervaporation (PV). Finally, a comprehensive steady state model was developed for the pervaporation of a water-UDMH mixture by COMSOL Multiphysics software version 5.2. The developed model was strongly capable of predicting the effect of various dimensional factors on concentration and velocity distribution within the membrane module. The best silicalite zeolite membranes had a water flux of 3.34 kg/m2.h at 27 °C. The best PV selectivity for Silicalite membranes obtained was 53

Cleaning of ultrafiltration membranes fouled with BSA by means of saline solutions

In this work, four ultrafiltration (UF) membranes with molecular weight cut-offs (MWCOs) of 5, 15, 30 and 50 kDa, respectively, were fouled with 1% BSA aqueous solutions and cleaned with different saline solutions. The influence of MWCO, membrane material and operating conditions on the cleaning effi- ciency was investigated. Saline solutions were able to clean the 5, 15 and 30 kDa membranes, but not the 50 kDa membrane. NaCl, NaNO3, NH4Cl and KCl were the most effective salts. The cleaning tests demonstrated that the higher the temperature of the saline solution was, the higher the cleaning efficiency was also. In addition, an increase in the crossflow velocity resulted in an increase in the hydraulic cleaning efficiency (HCE). However, there was an optimum value of salt concentration to clean the membrane effectively. Response Surface Methodology was used to investigate the relationship between salt concentration and temperature in the cleaning process.The authors of this work wish to gratefully acknowledge the financial support from the Spanish Ministry of Science and Innovation through the project CTM2010-20186 and the Generalitat Valenciana through the program "Ayudas para la realizacion de proyectos I+D para grupos de investigacion emergentes GV/2013".Corbatón Báguena, MJ.; Alvarez Blanco, S.; Vincent Vela, MC. (2014). Cleaning of ultrafiltration membranes fouled with BSA by means of saline solutions. Separation and Purification Technology. 125(7):1-10. https://doi.org/10.1016/j.seppur.2014.01.035S110125

Salt cleaning of ultrafiltration membranes fouled by whey model solutions

In this work, three ultrafiltration (UF) membranes were fouled with whey model solutions that contained BSA (1% w/w) and CaCl2 (0.06% w/w). These membranes were cleaned with NaCl solutions. Temperature, crossflow velocity and concentration were varied. The membranes considered were a polyethersulfone (PES) membrane, a ceramic ZrO2–TiO2 membrane and a permanently hydrophilic polyethersulfone (PESH) membrane. Their molecular weight cut-offs (MWCOs) are 5, 15 and 30 kDa, respectively. The cleaning efficiency was related to the MWCO, membrane material and operating conditions. The results obtained demonstrated that NaCl solutions were able to clean the membranes tested. In addition, the higher the temperature and the crossflow velocity of the cleaning solution, the higher the cleaning efficiency was. However, there was an optimum value of NaCl concentration to clean the membranes effectively. When concentration was higher than the optimum, the cleaning efficiency decreased. The relationship between the cleaning efficiency and the operating conditions was obtained with statistical and optimization analysis.The authors of this work wish to gratefully acknowledge the financial support from the Spanish Ministry of Science and Innovation through the project CTM2010-20186 and the Generalitat Valenciana through the program "Ayudas para la realizacion de proyectos I+D para grupos de investigacion emergentes GV/2013".Corbatón Báguena, MJ.; Alvarez Blanco, S.; Vincent Vela, MC. (2014). Salt cleaning of ultrafiltration membranes fouled by whey model solutions. Separation and Purification Technology. 132:226-233. https://doi.org/10.1016/j.seppur.2014.05.029S22623313

Fouling mechanisms of ultrafiltration membranes fouled with whey model solutions

In this work, three ultrafiltration (UF) membranes with different molecular weight cut-offs (MWCOs) and made of different materials were fouled with several whey model solutions that consisted of bovine serum albumin (BSA) (1% w/w), BSA (1% w/w) and CaCl2 (0.06% w/w in calcium) and whey protein concentrate (WPC) with a total protein content of 45% w/w at three different concentrations (22.2, 33.3 and 44.4 g·L− 1). The influence of MWCO and membrane material on the fouling mechanism dominating the UF process was investigated. Experiments were performed using two flat-sheet organic membranes and a ceramic monotubular membrane whose MWCOs were 5, 30 and 15 kDa, respectively. Hermia's models adapted to crossflow UF, a combined model based on complete blocking and cake formation equations and a resistance-in-series model were fitted to permeate flux decline curves. The results demonstrated that permeate flux decline was accurately predicted by all the models studied. However, the models that fitted the best to permeate flux decline experimental data were the combined model and the resistance-in-series model. Therefore, complete blocking and cake formation were the predominant mechanisms for all the membranes and feed solutions tested.The authors of this work wish to gratefully acknowledge the financial support of the Spanish Ministry of Science and Innovation through the project CTM2010-20186.Corbatón Báguena, MJ.; Alvarez Blanco, S.; Vincent Vela, MC. (2015). Fouling mechanisms of ultrafiltration membranes fouled with whey model solutions. Desalination. 360:87-96. https://doi.org/10.1016/j.desal.2015.01.019S879636