Siavash Darvishmanesh | KU Leuven (original) (raw)

Papers by Siavash Darvishmanesh

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Chemphyschem, 2010

The understanding of polymer–solvent interactions is highly important for the development of tail... more The understanding of polymer–solvent interactions is highly important for the development of tailored membrane manufacturing procedures and for the prediction of membrane performance from transport mechanisms. This study examines the permeation performance of organic solvents through state-of-the-art polyimide membranes (STARMEM, Membrane Extraction Technology Ltd.). Solvents are systematically selected to allow investigation of the effects of key physicochemical transport parameters by keeping constant all other parameters thought to be relevant. The effect of the solubility parameter, polarity (dielectric constant), surface tension, and viscosity are studied in detail. Dead-end permeation experiments are carried out at 20 bar with STARMEM 122 and STARMEM 240 membranes. Results for the selected solvents show higher permeation rates for ketones over alcohols and aromatics as well as for acids. It is suggested that the viscosity and polarity have a greater influence than the other parameters. The effect of solvent molar volume is also investigated. Transport of solvents with high molar volume, independent of their polarity and compatibility with the membrane material, is slower in all cases than for solvents with smaller molar volume. The solubility parameter does not show any significant effect on transport phenomena.

Chemical Engineering Journal, 2011

Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), p... more Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), particularly in high pressure and temperature conditions, resulting in a cumbersome water-acetic acid separation. When acetic acid is to be recycled in process conditions in a hybrid pervaporation approach, the PV membrane may experience these conditions of high temperatures and pressures. This study explores the potential of dehydrating acetic acid using pervaporation with novel polyphenylsulfone (PPSU) membranes. These membranes were tested for PV dehydration of mixtures of acetic acid-water with 80 and 90 wt.% acetic acid in the temperature range between 30 and 80 • C. In addition to that, an experimental study of membrane stability was performed at high concentration of HAc and high temperatures.

Separation and Purification Technology, 2009

In this work, permeation of a number of different classes of solvents through commercial TiO2 and... more In this work, permeation of a number of different classes of solvents through commercial TiO2 and ZrO2 ceramic nanofiltration membranes was measured. A wide variety in permeate flux levels were observed. Solvent permeation was found to be a function of solvent characteristics (viscosity, surface tension, effective molecular diameter and dielectric constant) along with membrane characteristics (surface tension, average pore size

Journal of Membrane Science, 2009

The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltrati... more The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltration (SRNF) has already been demonstrated extensively. A new semi-empirical model based on the traditional solution diffusion with imperfection model has been developed. In the newly developed model solvent permeability was found to be dependent on viscosity, and two new defined non-dimensional parameters. These parameters reflect the surface tension and dielectric constant. The permeation of a homologous series of six primary alcohols through hydrophobic polymeric membrane (Solsep-030505) has been measured. The experimental results have been used to validate the new model. The result of the model fitting was well satisfactory. The model was also validated for a broad range of solvents using additional filtration experiments. The permeation of various solvents from different chemical families through a hydrophobic polymeric membrane (MPF 50) and a hydrophilic ceramic membrane (HITK 275) has been measured. The permeability values calculated with the new model showed a very high correlation over the entire range of solvents used. The modelling results confirm the assumption of convective-diffusive transport in SRNF.

Fuel and Energy Abstracts, 2011

In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow ... more In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow fiber membranes (HFM) was carried out. PPSU is a polysulfone with better solvent resistance than Polysulfone (PSf) and poly(ether sulfone) (PES), which makes investigation of its potential use in solvent resistant nanofiltration (SRNF) membranes interesting. The membranes were prepared via the dry wet spinning method with three different

Fuel and Energy Abstracts, 2011

In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (... more In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (PPSU) was investigated. A synthesis method based on phase inversion with three different compositions of PPSU (17 wt.%, 21 wt.% and 25 wt.%) in dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP) and a mixture of dimethylformamide (DMF) and NMP was employed. Scanning electron microscopy (SEM) was used to investigate the morphological characteristics and the structure of the membranes, which were found to have a typical asymmetric structure with a dense skin top layer and a porous substructure. The pore size was estimated by measuring the permeation rate of N 2 when different pressures are applied, ranging from 15 nm to 40 nm, depending on the manufacturing method. An increasing amount of macrovoids was observed in the membrane substructure when the polymer concentration is decreased.

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Industrial & Engineering Chemistry Research, 2010

ABSTRACT

Chemphyschem, 2010

The understanding of polymer–solvent interactions is highly important for the development of tail... more The understanding of polymer–solvent interactions is highly important for the development of tailored membrane manufacturing procedures and for the prediction of membrane performance from transport mechanisms. This study examines the permeation performance of organic solvents through state-of-the-art polyimide membranes (STARMEM, Membrane Extraction Technology Ltd.). Solvents are systematically selected to allow investigation of the effects of key physicochemical transport parameters by keeping constant all other parameters thought to be relevant. The effect of the solubility parameter, polarity (dielectric constant), surface tension, and viscosity are studied in detail. Dead-end permeation experiments are carried out at 20 bar with STARMEM 122 and STARMEM 240 membranes. Results for the selected solvents show higher permeation rates for ketones over alcohols and aromatics as well as for acids. It is suggested that the viscosity and polarity have a greater influence than the other parameters. The effect of solvent molar volume is also investigated. Transport of solvents with high molar volume, independent of their polarity and compatibility with the membrane material, is slower in all cases than for solvents with smaller molar volume. The solubility parameter does not show any significant effect on transport phenomena.

Journal of The American Oil Chemists Society

The extraction stage of edible oil in the oil industry is commonly performed by using toxic solve... more The extraction stage of edible oil in the oil industry is commonly performed by using toxic solvents (e.g. hexane) and processes with high energy consumption (e.g. distillation, evaporation) to recover the solvent, which represents around 70–75 wt% in the oil–solvent mixture. In this paper, a membrane-based extraction method using nanofiltration (NF) membranes is presented. Commercial nanofiltration membranes made of different polymers (Desal-DK-polyamide NF from GE-osmonics®, NF30 polyethersulfone NF from Nadir®, STARMEMTM122 polyimide from MET® and SOLSEP NF030306 silicone base polymer SOLESP®) were selected and tested to recover the solvent from soybean oil/solvent (10–20–30% w/w oil) mixtures at various separation pressures and constant temperature in a dead-end filtration set up. The selection of the solvent was made in order to compare solvents obtainable from renewable resources, such as ethanol, iso-propanol and acetone, with solvents traditionally used in the industry (i.e. cyclohexane and n-hexane). The structural stability of the membranes towards the different solvents used in this work was verified visually, by the variation of the membrane area and by means of permeate flux assessments. Desal-DK and NF30 showed poor filtration performance and even visible defects after exposure to acetone but a good performance was obtained for the nanofiltration membranes STARMEMTM122 and SOLSEP NF030306 with ethanol, iso-propanol and acetone. For example, considering a mixture with 30% edible oil in acetone, STARMEMTM122 shows a flux and oil rejection of 16.8 L m−2 h and 70%, respectively. For the same conditions, SOLSEP NF030306 exhibited a flux of 4.8 L m−2 h with 78% rejection, which shows the potential application of nanofiltration membranes in the oil industry.

Chemical Engineering Journal, 2011

Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), p... more Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), particularly in high pressure and temperature conditions, resulting in a cumbersome water-acetic acid separation. When acetic acid is to be recycled in process conditions in a hybrid pervaporation approach, the PV membrane may experience these conditions of high temperatures and pressures. This study explores the potential of dehydrating acetic acid using pervaporation with novel polyphenylsulfone (PPSU) membranes. These membranes were tested for PV dehydration of mixtures of acetic acid-water with 80 and 90 wt.% acetic acid in the temperature range between 30 and 80 • C. In addition to that, an experimental study of membrane stability was performed at high concentration of HAc and high temperatures.

Separation and Purification Technology, 2011

In this paper the McCabe-Thiele method, previously used for the design of gas separation membrane... more In this paper the McCabe-Thiele method, previously used for the design of gas separation membrane cascades, was adapted for membrane cascades for solute-solute separations. This method was applied here on three different sugar separations: raffinose-sucrose, fructose-glucose and xylose-glucose. The state of the art for all these separations is simulated moving bed (SMB) chromatography. For all separations a membrane cascade could be designed to reach the same specifications as the reference SMB. This is especially remarkable for the very challenging glucose-fructose separation where starting from 50% fructose purity a 94% fructose purity could be reached. Due to the high number of required stages, for this separation the cascade cost was several times higher than the cost of the reference SMB. However, for the raffinose-sucrose and glucose-xylose separation the cascade cost was similar or lower than the cost of the SMB. Moreover from the raffinose-sucrose separation and purification it could be concluded that the competitiveness of membrane cascades over SMB chromatography increases with the plant size. Also if the purity requirement becomes less stringent the competitiveness increases as could be seen from the glucose-xylose separation. As a result membrane cascades seem most promising for large scale continuous processes for producing pure but depending on the selectivity not ultrapure products. A hybrid membrane cascade SMB process could be envisaged to also cover the ultrapure products range in a cost effective way.

Separation and Purification Technology, 2009

In this work, permeation of a number of different classes of solvents through commercial TiO2 and... more In this work, permeation of a number of different classes of solvents through commercial TiO2 and ZrO2 ceramic nanofiltration membranes was measured. A wide variety in permeate flux levels were observed. Solvent permeation was found to be a function of solvent characteristics (viscosity, surface tension, effective molecular diameter and dielectric constant) along with membrane characteristics (surface tension, average pore size

Chemical Engineering Science, 2009

The solvent flux was measured in binary mixtures of ethanol and n-hexane for nine solvent-stable ... more The solvent flux was measured in binary mixtures of ethanol and n-hexane for nine solvent-stable polymeric membranes in range of reverse osmosis (RO) to ultrafiltration (UF) (GE AK Osmonics, Dow 102326, GE DK Osmonics, MPF-34, STARMEM™ 122, STARMEM™ 240, NF30, NTR7450, NF-PES-010). GC-analyses of feed and permeate samples showed a separation factor close to 1, which indicates the solvent transport occurs by convection or by coupled diffusion through the membranes. The effect of viscosity, surface tension, di-electric constant and solubility parameter of solvent on permeation rate was studied for four categories of membranes, i.e. RO membranes, dense nanofiltration (NF) membranes, semi-porous NF membranes and micro-porous NF membranes. While viscosity seems to be a main transport parameter (similar composition of feed and permeate), higher fluxes of ethanol compared to n-hexane (with lower viscosity) confirmed that the transport may occur through coupled diffusion. The influences of the solvent–membrane interaction parameters such as surface tension, polarity and solubility parameters of solvent and membranes for dense membranes were investigated. The effect of solvent membrane interaction by means of solubility parameters was more pronounced compared to surface tension since the respective surface tensions of solvents are close to one another (γethanol=21.9,γn‐hexane=17.9). Partial permeabilities were studied as well to evaluate the influence of each component on permeation of the other. Unexpected results were observed for MPF-34, NF30 and NTR7450. Further investigation confirmed that their polymeric structure changed in contact with the solvents. Hydrophobic STARMEM™ membranes, which are expected to have a higher permeability for apolar solvents showed higher fluxes for ethanol compared to n-hexane. The similar solubility parameter of these membranes and ethanol may increase the permeation rate of ethanol molecules through membranes. For porous membranes viscosity was recognized as the key transport parameter, while affinity between membrane and solvent has a lower effect.

Journal of Membrane Science, 2009

The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltrati... more The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltration (SRNF) has already been demonstrated extensively. A new semi-empirical model based on the traditional solution diffusion with imperfection model has been developed. In the newly developed model solvent permeability was found to be dependent on viscosity, and two new defined non-dimensional parameters. These parameters reflect the surface tension and dielectric constant. The permeation of a homologous series of six primary alcohols through hydrophobic polymeric membrane (Solsep-030505) has been measured. The experimental results have been used to validate the new model. The result of the model fitting was well satisfactory. The model was also validated for a broad range of solvents using additional filtration experiments. The permeation of various solvents from different chemical families through a hydrophobic polymeric membrane (MPF 50) and a hydrophilic ceramic membrane (HITK 275) has been measured. The permeability values calculated with the new model showed a very high correlation over the entire range of solvents used. The modelling results confirm the assumption of convective-diffusive transport in SRNF.

Fuel and Energy Abstracts, 2011

In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow ... more In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow fiber membranes (HFM) was carried out. PPSU is a polysulfone with better solvent resistance than Polysulfone (PSf) and poly(ether sulfone) (PES), which makes investigation of its potential use in solvent resistant nanofiltration (SRNF) membranes interesting. The membranes were prepared via the dry wet spinning method with three different

Fuel and Energy Abstracts, 2011

In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (... more In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (PPSU) was investigated. A synthesis method based on phase inversion with three different compositions of PPSU (17 wt.%, 21 wt.% and 25 wt.%) in dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP) and a mixture of dimethylformamide (DMF) and NMP was employed. Scanning electron microscopy (SEM) was used to investigate the morphological characteristics and the structure of the membranes, which were found to have a typical asymmetric structure with a dense skin top layer and a porous substructure. The pore size was estimated by measuring the permeation rate of N 2 when different pressures are applied, ranging from 15 nm to 40 nm, depending on the manufacturing method. An increasing amount of macrovoids was observed in the membrane substructure when the polymer concentration is decreased.

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Industrial & Engineering Chemistry Research, 2010

ABSTRACT

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Chemphyschem, 2010

The understanding of polymer–solvent interactions is highly important for the development of tail... more The understanding of polymer–solvent interactions is highly important for the development of tailored membrane manufacturing procedures and for the prediction of membrane performance from transport mechanisms. This study examines the permeation performance of organic solvents through state-of-the-art polyimide membranes (STARMEM, Membrane Extraction Technology Ltd.). Solvents are systematically selected to allow investigation of the effects of key physicochemical transport parameters by keeping constant all other parameters thought to be relevant. The effect of the solubility parameter, polarity (dielectric constant), surface tension, and viscosity are studied in detail. Dead-end permeation experiments are carried out at 20 bar with STARMEM 122 and STARMEM 240 membranes. Results for the selected solvents show higher permeation rates for ketones over alcohols and aromatics as well as for acids. It is suggested that the viscosity and polarity have a greater influence than the other parameters. The effect of solvent molar volume is also investigated. Transport of solvents with high molar volume, independent of their polarity and compatibility with the membrane material, is slower in all cases than for solvents with smaller molar volume. The solubility parameter does not show any significant effect on transport phenomena.

Chemical Engineering Journal, 2011

Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), p... more Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), particularly in high pressure and temperature conditions, resulting in a cumbersome water-acetic acid separation. When acetic acid is to be recycled in process conditions in a hybrid pervaporation approach, the PV membrane may experience these conditions of high temperatures and pressures. This study explores the potential of dehydrating acetic acid using pervaporation with novel polyphenylsulfone (PPSU) membranes. These membranes were tested for PV dehydration of mixtures of acetic acid-water with 80 and 90 wt.% acetic acid in the temperature range between 30 and 80 • C. In addition to that, an experimental study of membrane stability was performed at high concentration of HAc and high temperatures.

Separation and Purification Technology, 2009

In this work, permeation of a number of different classes of solvents through commercial TiO2 and... more In this work, permeation of a number of different classes of solvents through commercial TiO2 and ZrO2 ceramic nanofiltration membranes was measured. A wide variety in permeate flux levels were observed. Solvent permeation was found to be a function of solvent characteristics (viscosity, surface tension, effective molecular diameter and dielectric constant) along with membrane characteristics (surface tension, average pore size

Journal of Membrane Science, 2009

The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltrati... more The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltration (SRNF) has already been demonstrated extensively. A new semi-empirical model based on the traditional solution diffusion with imperfection model has been developed. In the newly developed model solvent permeability was found to be dependent on viscosity, and two new defined non-dimensional parameters. These parameters reflect the surface tension and dielectric constant. The permeation of a homologous series of six primary alcohols through hydrophobic polymeric membrane (Solsep-030505) has been measured. The experimental results have been used to validate the new model. The result of the model fitting was well satisfactory. The model was also validated for a broad range of solvents using additional filtration experiments. The permeation of various solvents from different chemical families through a hydrophobic polymeric membrane (MPF 50) and a hydrophilic ceramic membrane (HITK 275) has been measured. The permeability values calculated with the new model showed a very high correlation over the entire range of solvents used. The modelling results confirm the assumption of convective-diffusive transport in SRNF.

Fuel and Energy Abstracts, 2011

In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow ... more In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow fiber membranes (HFM) was carried out. PPSU is a polysulfone with better solvent resistance than Polysulfone (PSf) and poly(ether sulfone) (PES), which makes investigation of its potential use in solvent resistant nanofiltration (SRNF) membranes interesting. The membranes were prepared via the dry wet spinning method with three different

Fuel and Energy Abstracts, 2011

In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (... more In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (PPSU) was investigated. A synthesis method based on phase inversion with three different compositions of PPSU (17 wt.%, 21 wt.% and 25 wt.%) in dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP) and a mixture of dimethylformamide (DMF) and NMP was employed. Scanning electron microscopy (SEM) was used to investigate the morphological characteristics and the structure of the membranes, which were found to have a typical asymmetric structure with a dense skin top layer and a porous substructure. The pore size was estimated by measuring the permeation rate of N 2 when different pressures are applied, ranging from 15 nm to 40 nm, depending on the manufacturing method. An increasing amount of macrovoids was observed in the membrane substructure when the polymer concentration is decreased.

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Industrial & Engineering Chemistry Research, 2010

ABSTRACT

Chemphyschem, 2010

The understanding of polymer–solvent interactions is highly important for the development of tail... more The understanding of polymer–solvent interactions is highly important for the development of tailored membrane manufacturing procedures and for the prediction of membrane performance from transport mechanisms. This study examines the permeation performance of organic solvents through state-of-the-art polyimide membranes (STARMEM, Membrane Extraction Technology Ltd.). Solvents are systematically selected to allow investigation of the effects of key physicochemical transport parameters by keeping constant all other parameters thought to be relevant. The effect of the solubility parameter, polarity (dielectric constant), surface tension, and viscosity are studied in detail. Dead-end permeation experiments are carried out at 20 bar with STARMEM 122 and STARMEM 240 membranes. Results for the selected solvents show higher permeation rates for ketones over alcohols and aromatics as well as for acids. It is suggested that the viscosity and polarity have a greater influence than the other parameters. The effect of solvent molar volume is also investigated. Transport of solvents with high molar volume, independent of their polarity and compatibility with the membrane material, is slower in all cases than for solvents with smaller molar volume. The solubility parameter does not show any significant effect on transport phenomena.

Journal of The American Oil Chemists Society

The extraction stage of edible oil in the oil industry is commonly performed by using toxic solve... more The extraction stage of edible oil in the oil industry is commonly performed by using toxic solvents (e.g. hexane) and processes with high energy consumption (e.g. distillation, evaporation) to recover the solvent, which represents around 70–75 wt% in the oil–solvent mixture. In this paper, a membrane-based extraction method using nanofiltration (NF) membranes is presented. Commercial nanofiltration membranes made of different polymers (Desal-DK-polyamide NF from GE-osmonics®, NF30 polyethersulfone NF from Nadir®, STARMEMTM122 polyimide from MET® and SOLSEP NF030306 silicone base polymer SOLESP®) were selected and tested to recover the solvent from soybean oil/solvent (10–20–30% w/w oil) mixtures at various separation pressures and constant temperature in a dead-end filtration set up. The selection of the solvent was made in order to compare solvents obtainable from renewable resources, such as ethanol, iso-propanol and acetone, with solvents traditionally used in the industry (i.e. cyclohexane and n-hexane). The structural stability of the membranes towards the different solvents used in this work was verified visually, by the variation of the membrane area and by means of permeate flux assessments. Desal-DK and NF30 showed poor filtration performance and even visible defects after exposure to acetone but a good performance was obtained for the nanofiltration membranes STARMEMTM122 and SOLSEP NF030306 with ethanol, iso-propanol and acetone. For example, considering a mixture with 30% edible oil in acetone, STARMEMTM122 shows a flux and oil rejection of 16.8 L m−2 h and 70%, respectively. For the same conditions, SOLSEP NF030306 exhibited a flux of 4.8 L m−2 h with 78% rejection, which shows the potential application of nanofiltration membranes in the oil industry.

Chemical Engineering Journal, 2011

Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), p... more Conventional pervaporation (PV) membranes usually have limited resistance to acetic acid (HAc), particularly in high pressure and temperature conditions, resulting in a cumbersome water-acetic acid separation. When acetic acid is to be recycled in process conditions in a hybrid pervaporation approach, the PV membrane may experience these conditions of high temperatures and pressures. This study explores the potential of dehydrating acetic acid using pervaporation with novel polyphenylsulfone (PPSU) membranes. These membranes were tested for PV dehydration of mixtures of acetic acid-water with 80 and 90 wt.% acetic acid in the temperature range between 30 and 80 • C. In addition to that, an experimental study of membrane stability was performed at high concentration of HAc and high temperatures.

Separation and Purification Technology, 2011

In this paper the McCabe-Thiele method, previously used for the design of gas separation membrane... more In this paper the McCabe-Thiele method, previously used for the design of gas separation membrane cascades, was adapted for membrane cascades for solute-solute separations. This method was applied here on three different sugar separations: raffinose-sucrose, fructose-glucose and xylose-glucose. The state of the art for all these separations is simulated moving bed (SMB) chromatography. For all separations a membrane cascade could be designed to reach the same specifications as the reference SMB. This is especially remarkable for the very challenging glucose-fructose separation where starting from 50% fructose purity a 94% fructose purity could be reached. Due to the high number of required stages, for this separation the cascade cost was several times higher than the cost of the reference SMB. However, for the raffinose-sucrose and glucose-xylose separation the cascade cost was similar or lower than the cost of the SMB. Moreover from the raffinose-sucrose separation and purification it could be concluded that the competitiveness of membrane cascades over SMB chromatography increases with the plant size. Also if the purity requirement becomes less stringent the competitiveness increases as could be seen from the glucose-xylose separation. As a result membrane cascades seem most promising for large scale continuous processes for producing pure but depending on the selectivity not ultrapure products. A hybrid membrane cascade SMB process could be envisaged to also cover the ultrapure products range in a cost effective way.

Separation and Purification Technology, 2009

In this work, permeation of a number of different classes of solvents through commercial TiO2 and... more In this work, permeation of a number of different classes of solvents through commercial TiO2 and ZrO2 ceramic nanofiltration membranes was measured. A wide variety in permeate flux levels were observed. Solvent permeation was found to be a function of solvent characteristics (viscosity, surface tension, effective molecular diameter and dielectric constant) along with membrane characteristics (surface tension, average pore size

Chemical Engineering Science, 2009

The solvent flux was measured in binary mixtures of ethanol and n-hexane for nine solvent-stable ... more The solvent flux was measured in binary mixtures of ethanol and n-hexane for nine solvent-stable polymeric membranes in range of reverse osmosis (RO) to ultrafiltration (UF) (GE AK Osmonics, Dow 102326, GE DK Osmonics, MPF-34, STARMEM™ 122, STARMEM™ 240, NF30, NTR7450, NF-PES-010). GC-analyses of feed and permeate samples showed a separation factor close to 1, which indicates the solvent transport occurs by convection or by coupled diffusion through the membranes. The effect of viscosity, surface tension, di-electric constant and solubility parameter of solvent on permeation rate was studied for four categories of membranes, i.e. RO membranes, dense nanofiltration (NF) membranes, semi-porous NF membranes and micro-porous NF membranes. While viscosity seems to be a main transport parameter (similar composition of feed and permeate), higher fluxes of ethanol compared to n-hexane (with lower viscosity) confirmed that the transport may occur through coupled diffusion. The influences of the solvent–membrane interaction parameters such as surface tension, polarity and solubility parameters of solvent and membranes for dense membranes were investigated. The effect of solvent membrane interaction by means of solubility parameters was more pronounced compared to surface tension since the respective surface tensions of solvents are close to one another (γethanol=21.9,γn‐hexane=17.9). Partial permeabilities were studied as well to evaluate the influence of each component on permeation of the other. Unexpected results were observed for MPF-34, NF30 and NTR7450. Further investigation confirmed that their polymeric structure changed in contact with the solvents. Hydrophobic STARMEM™ membranes, which are expected to have a higher permeability for apolar solvents showed higher fluxes for ethanol compared to n-hexane. The similar solubility parameter of these membranes and ethanol may increase the permeation rate of ethanol molecules through membranes. For porous membranes viscosity was recognized as the key transport parameter, while affinity between membrane and solvent has a lower effect.

Journal of Membrane Science, 2009

The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltrati... more The convective-diffusive nature of the transport mechanism through solvent resistant nanofiltration (SRNF) has already been demonstrated extensively. A new semi-empirical model based on the traditional solution diffusion with imperfection model has been developed. In the newly developed model solvent permeability was found to be dependent on viscosity, and two new defined non-dimensional parameters. These parameters reflect the surface tension and dielectric constant. The permeation of a homologous series of six primary alcohols through hydrophobic polymeric membrane (Solsep-030505) has been measured. The experimental results have been used to validate the new model. The result of the model fitting was well satisfactory. The model was also validated for a broad range of solvents using additional filtration experiments. The permeation of various solvents from different chemical families through a hydrophobic polymeric membrane (MPF 50) and a hydrophilic ceramic membrane (HITK 275) has been measured. The permeability values calculated with the new model showed a very high correlation over the entire range of solvents used. The modelling results confirm the assumption of convective-diffusive transport in SRNF.

Fuel and Energy Abstracts, 2011

In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow ... more In this study, the preparation and extensive characterization of polyphenylsulfone (PPSU) hollow fiber membranes (HFM) was carried out. PPSU is a polysulfone with better solvent resistance than Polysulfone (PSf) and poly(ether sulfone) (PES), which makes investigation of its potential use in solvent resistant nanofiltration (SRNF) membranes interesting. The membranes were prepared via the dry wet spinning method with three different

Fuel and Energy Abstracts, 2011

In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (... more In this work, the preparation of nanofiltration flat sheet membranes based on polyphenylsulfone (PPSU) was investigated. A synthesis method based on phase inversion with three different compositions of PPSU (17 wt.%, 21 wt.% and 25 wt.%) in dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP) and a mixture of dimethylformamide (DMF) and NMP was employed. Scanning electron microscopy (SEM) was used to investigate the morphological characteristics and the structure of the membranes, which were found to have a typical asymmetric structure with a dense skin top layer and a porous substructure. The pore size was estimated by measuring the permeation rate of N 2 when different pressures are applied, ranging from 15 nm to 40 nm, depending on the manufacturing method. An increasing amount of macrovoids was observed in the membrane substructure when the polymer concentration is decreased.

Physical Chemistry Chemical Physics, 2010

The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a ... more The separation performance of solvent resistant nanofiltration (SRNF) membranes was studied in a systematic way to elucidate the complex mechanisms involved in rejection of solutes. Rejection of three dyes (Sudan II, Sudan Black, Sudan 408) from common organic solvents (methanol, ethanol, acetone, methyl ethyl ketone, toluene and n-hexane) through a polyimide based SRNF membrane, STARMEM™122, was studied. It was found that the rejection of the STARMEM™122 membrane was lower than that indicated by the manufacturer. The experimental observations for Sudan II were not promising for the rejection study as they were lower than expected. Sudan Black and Sudan 408, which are larger solutes than Sudan II, provided more interesting insights. The effects of the solvent on the membrane and solute were studied separately. A higher permeation rate of ketones and alcohols was observed, while permeabilities of non-polar solvents were low which shows that this membrane shows higher affinity toward semi-polar solvents (alcohols, ketones). The effect of the solvent on the solute's rejection, based on the results for Sudan Black and Sudan 408, was studied for solvents in the same chemical groups, since the membrane showed a similar separation performance for solvents with similar functional groups (e.g. alcohols). The effect of solvent on solute molecular size was investigated by using simulation with Molecular Dynamics. It was shown that the effective size of a molecule is dependent on the solvent due to solvation and hydration of the solute by the solvent. The size of the solute in the solvent belonging to a similar family was studied separately. It was clear that the rejection was influenced by molecular size of the solute in the same group of solvents. A surprising negative rejection of solutes was achieved for n-hexane. Although solutes in n-hexane have higher volume compared to those in other solvents, the affinity between the solute and membrane increases the solute permeation in the presence of n-hexane. The affinity of solvent and solute for the membrane was investigated by means of solubility parameters for solvents within the same chemical family. In two different systems including two different solvents and one solute (Sudan Black and methanol, Sudan Black and ethanol), lower rejection (in this case for Sudan Black and methanol) was achieved when the solutes have higher affinity toward the solvent. Finally, it was found that in a system comprising the solvent, solute and membrane, interactions between solvent and membrane have much more effect on separation than solvent-solute interactions.

Industrial & Engineering Chemistry Research, 2010

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