Nanofiltration Range Research Articles

Conductive polyelectrolyte multilayers PANI membranes synthesis for tunable filtration ranges

Polyaniline membrane tends to swell and brittle when it undergoes excessive acid doping upon increasing its conductivity and hydrophilicity properties. Therefore, modification was done by introducing polyelectrolyte layers on polyaniline membrane surface with the aim to produce nanofiltration range membrane. Modification of PANI membrane with layer-by-layer polyelectrolyte is a new method for modifying PANI membrane; thus, the effect of doping time with number of polyelectrolyte bilayers with the membrane properties was investigated. From the results, the optimum doping time was 120 min to maximally increase the membrane’s hydrophilicity and conductivity. Next, introduction of polyelectrolyte layers on the membranes’ surface via layer-by-layer coating has found to decrease the porosity of the membranes top layer up to 10 times from ultrafiltration to nanofiltration ranges. Their surface hydrophilicity and negativity has also increased significantly while having a similar conductivity increment trend upon measured in wet condition (similar to water filtration condition). Furthermore, the permeability of the modified PANI membranes before and after back-flushing was performed for membranes cleaning process was seen to have no significant difference. Thus, it can be concluded that the presence of polyelectrolyte multilayers on the membrane surface has successfully formed a stable nano-range membrane with the same desired permeability even after back-flushing.

Facile preparation of polyacrylonitrile-co-methylacrylate based integrally skinned asymmetric nanofiltration membranes for sustainable molecular separation: An one-step method

While polyacrylonitrile (PAN) has been widely used to prepare membranes, it is still not handy to prepare PAN integrally skinned asymmetric (ISA) nanofiltration (NF) membrane via direct immersion precipitation phase inversion method. Herein, a low-cost and commercial polyacrylonitrile-co-methylacrylate, P(AN-co-MA), was demonstrated to prepare ISA NF membranes via a one-step immersion precipitation phase inversion process. It was found that increasing P(AN-co-MA) concentration in NMP can shift the membranes from ultrafiltration (UF) to NF range. The addition of a co-solvent in dope could further improve dye rejection. Effects of solvent (NMP or DMF)/co-solvent (THF and 1,4-dioxane) type and mass ratio in dope solution on membrane separation performance were further investigated. The membrane prepared from a 20% polymer concentration and a NMP/1,4-dioxane ratio of 3:1 showed 87.4% methyl orange (MO) rejection and 98.3% rose bengal (RB) rejection, and simultaneously a relatively high water permeance of 55.22 L m−2 h−1 bar−1. Increase in the content of co-solvent in solvent/co-solvent mixture would depress the formation of macrovoids, lead to a dense top layer and contribute to high dye rejections. The low-cost and one-step process to prepare P(AN-co-MA) ISA NF membranes disclosed in this study paved a new way for sustainable molecular separation.

Nanofiltration range desalination by high flux graphene oxide impregnated ultrafiltration hollow fiber mixed matrix membrane

In this work, a novel graphene oxide impregnated ultrafiltration grade hollow fiber membrane was prepared having capability of salt rejection in the range of nanofiltration. Sodium sulfate showed higher rejection (40%–50%) than the other salts, magnesium sulfate and sodium chloride. Charge-charge interaction is the major salt retention mechanism. Optimum operating conditions were identified as 55 kPa transmembrane pressure drop and 5 L/h cross-flow rate. Increasing the solution pH from 5 to 9 augmented the rejection of sodium sulfate from 43% to 51% at relatively high permeate flux 0.25 L/m2.h.kPa. In case of filtration of actual sea water, the permeate flux is lowered to 0.20 L/m2.h.kPa due to presence of other fouling agents. Rejection of total dissolved solids was 30% for seawater. Beyond 11 h (breakthrough time) the rejection decreases due to screening of charge effects of the membrane surface. Pretreatment by activated carbon delayed the breakthrough time to 14 h and improved permeate flux 0.22 L/m2.h.kPa. Thus, ultrafiltration grade hollow fiber mixed matrix membrane offers equivalent salt rejection of nanofiltration membrane at a much higher throughput.

Streaming potential properties of ceramic nanofiltration membranes – Importance of surface charge on the ion rejection

The aim of the present research is the electrokinetic determination of the inner surface centercharges of ceramic nanofiltration membranes under varying electrochemical conditions and their influences on the filtration properties especially on salt/ion rejection. Ceramic microporous nanofiltration membranes of TiO2 with pore size of 0.9 nm were characterized. The membrane charge was determined under real filtration conditions at different salt solutions, concentrations and pH-values using flow-through streaming potential measurement. In the case of liquid saturated oxide ceramic membranes a surface charge results from protonated und deprotonated surface groups and specifically adsorbed ions. The charge properties of the amphoteric titania nanofiltration membrane significantly depending on the pH value of the feed. The specific adsorption of multivalent ions modifies additionally the membrane charge and shifts the isoelectric point. Depending on the valence and art of the ions and the pH value/range of the solution the membrane charge is shielded or increased. Using magnitude and sign of the measured streaming potential at different salt solution, concentration and pH-values the salt/ion rejection can be predicted. This could be checked by cross-flow filtration experiments. Single and multivalent ion separation in the nanofiltration range does not only result from a sieving effect/steric exclusion of the pore structure but is strongly influenced by the surface charge characteristics of the pore/channel walls. When the membrane is charged, the ions are retained, and when shielded, the ions pass through the membrane. The investigations show the possibility for adjusting the separation characteristic up to a nearly complete salt rejection by choosing the appropriate pH-value, concentration and the kind of the salt solution. The measurement of the streaming potential during real filtration processes supports in the simplest way the optimization and monitoring of desalination processes with charged nanofiltration membranes.

Influence of contaminants in glycerol/water mixtures during post-treatment on physicochemical properties and separation performance of air-dried membranes

Membranes for water treatments always have a glycerol/water post-treatment before air-drying to maintain their microporous structure during and after air-drying. However, the presence of trace amounts of impurities in glycerol/water mixtures may have big effects on both pore size and pure water permeability (PWP) of the treated membranes, especially when the membranes have a pore size near or in the nanofiltration (NF) range. By investigating the effects of different contaminants to membranes, this article may provide new guidance for membrane scientists and engineers to study the science and engineering on how to properly post-treat membranes before and after the air-drying process.

Iron oxide (FeO) nanoparticles embedded thin-film nanocomposite nanofiltration (NF) membrane for water treatment

This research work investigated the usage of pre-seeding interfacial polymerization method using iron oxide (FeO) nanoparticles on the polyethersulfone (PES) support membrane for water treatment. The two different concentrations (low (0.05 wt%) and high (2 wt%) of FeO nanoparticles were used as the membrane surface modification parameter. Surface modified membranes were characterized by several characterizations methods. Membrane surface charge was calculated qualitatively by using Grahame equation with the help of contact angle measurements. Synthesized membranes showed 90% rejection with polyethylene glycol (PEG) with M.W. 1500 Da, which was fitted in the range of nanofiltration. The membrane performance towards salt rejection, flux (at different pressure) and anti-fouling activity was evaluated using a various salt solution like CaCl2, MgCl2, C6H5Na3O7, Na2SO4, NaCl with an initial concentration of 2000 mg/L, saltwater (collected from Suvali beach, Surat, India). With the increase in the concentration of FeO nanoparticles, hydrophilic nature (84.7 to 49.6°), surface charge (−6.27 to −14.21 mC/m2) and flux (27.46 to 36.85 L/m2h) of the nanocomposite membranes were effectively enhanced, and also showed the high salt rejections (>90%). Anti-fouling activity of the membrane with saltwater was analyzed by flux recovery ratio that showed FeO nanoparticles embedded membrane notably reduced the fouling.

Interfacial Polymerization of Zwitterionic Building Blocks for High-Flux Nanofiltration Membranes.

A simple scalable strategy is proposed to fabricate highly permeable antifouling nanofiltration membranes. Membranes with a selective thin polyamide layer were prepared via interfacial polymerization incorporating building blocks of zwitterionic copolymers. The zwitterionic copolymer, poly(aminopropyldimethylaminoethyl methacrylate)- co-poly(sulfobetaine methacrylate) with an average molecular weight of 6.1 kg mol-1, was synthesized in three steps: (i) polymerization of dimethylaminoethyl methacrylate to yield the base polymer by atom transfer radical polymerization (ATRP), (ii) fractional sulfobetainization via quaternization, and (iii) amination via quaternization. The effect of the zwitterionic polymer content on the polyamide surface characteristics, fouling resistance, and permeance is demonstrated. The zwitterion-modified membrane becomes more hydrophilic with lower surface roughness, as the zwitterionic polymer fraction increases. The excellent fouling resistance of the zwitterion-modified membrane was confirmed by the negligible protein adsorption and low bacteria fouling compared to a pristine membrane without zwitterionic segments. In addition, the zwitterion-modified membranes achieve a water permeation around 135 L m-2 h-1bar-1, which is 27-fold higher than that of the pristine membrane, along with good selectivity in the nanofiltration range, confirmed by the rejection of organic dyes. This permeance is about 10 times higher than that of other reported loose nanofiltration membranes with comparable dye rejection. The newly designed membrane is promising as a highly permeable fouling resistant cross-linked polyamide network for various water treatment applications.

Thin porphyrin composite membranes with enhanced organic solvent transport

Extending the stability of polymeric membranes in organic solvents is important for applications in chemical and pharmaceutical industry. Thin-film composite membranes with enhanced solvent permeance are proposed, using porphyrin as a building block. Hybrid polyamide films are formed by interfacial polymerization of 5,10,15,20-(tetra-4-aminophenyl)porphyrin/m-phenylene diamine (MPD) mixtures with trimesoyl chloride. Porphyrin is a non-planar molecule, containing a heterocyclic tetrapyrrole unit. Its incorporation into a polyamide film leads to higher free volume than that of a standard polyamide film. Polyamide films derived from porphyrin and MPD amines with a fixed total amine concentration of 1 wt% and various porphyrin/MPD ratios were fabricated and characterized. The porphyrin/MPD polyamide film was complexed with Cu(II), due to the binding capacity of porphyrin to metal ions. By coupling scanning transmission electron microscopy (STEM) with electron energy-loss spectroscopy (EELS), Cu mapping was obtained, revealing the distribution of porphyrin in the interfacial polymerized layer. By using porphyrin as amine-functionalized monomer a membrane with thin selective skin and enhanced solvent transport is obtained, with good dye selectivity in the nanofiltration range. For instance, an ultra-fast hexane permeance, 40-fold increased, was confirmed when using 0.5/0.5 porphyrin/MPD mixtures, instead of only MPD as amine monomer. A rejection of 94.2% Brilliant Blue R (826 g/mol) in methanol was measured.

Durable pressure filtration membranes based on polyaniline–polyimide P84 blends

A pressure filtration membrane from conducting polymer polyaniline (PANI) is known to possess low mechanical strength and thermal stability. Therefore, it is believed that the properties of the membrane can be enhanced by blending PANI with a conventional polymer like polyimide (PI), which possesses high mechanical strength and thermal stability. A thermal analysis revealed that polymer chain of blend membranes started to break beyond the melting temperature of pure PANI membrane indicating that the addition of PI hindered the degradation of PANI and thus slowed down the decomposition process. Mechanical tests further showed that PANI/PI membrane had a tensile strength that was 60% higher than pure PANI membrane. Furthermore, the surface hydrophilicity and negativity of the blend membrane increased as it was doped in acid, thereby reflecting the exploitation of advantages of both polymers. Rejection at various molecular ranges of PEGs showed that PANI/PI membrane was initially in the ultrafiltration (UF) range, but later fell into the nanofiltration (NF) range when an acid dopant was introduced to the membrane. According to the long‐term filtration performance, the PANI/PI membrane was able to sustain a rejection of up to 99% in Congo red solution with just a slight reduction in flux. POLYM. ENG. SCI., 59:E82–E92, 2019. © 2018 Society of Plastics Engineers

Fabrication and characterization of novel antimicrobial thin film nano‐composite membranes based on copper nanoparticles

AbstractBACKGROUNDCopper nanoparticles (CuNPs) are studied for the design of advanced nanocomposite membranes owing to their highly antimicrobial properties, specific catalytic and chemical activities, abundancy and low cost. In this work, thin film nanocomposite membranes (TFN) containing CuNPs in the polyamide (PA) layer were designed via a facile interfacial polymerization method. The nanoparticles were incorporated into an aqueous solution containing piperazine monomers which is poured on the top surface of the polyethersulfone ultrafiltration membrane followed by adding trimesoyl chloride to form a polymerized PA film.RESULTSThe results show that the surface morphological structure investigated by scanning electron microscopy and atomic force microscopy images is subject to visible changes of surface morphology, with a rougher net‐like structure while analysis of the chemical structure using attenuated total reflection–Fourier transform infrared spectroscopy confirms that the introduction of CuNPs did not impede the structure of the PA layer.The effect of addition of inorganic functionalized nanomaterials on the overall membrane performance was significant. The water flux was greatly increased (twice the original water permeability), while maintaining high retention of Na2SO4, demonstrating good performance in the range of nanofiltration (NF). Furthermore, the TFN membranes exhibited a specific antibacterial effect, reducing the number of living bacteria (Escherichia coli) by 94.0%.CONCLUSIONInorganic functionalization using CuNPs in the aqueous phase strongly enhanced membrane performance and provided the membrane surface with antimicrobial properties. This study suggests a new approach to TFN membrane research for the design of NF membranes for water treatment. © 2018 Society of Chemical Industry

Effect of polyacid dopants on the performance of polyaniline membranes in organic solvent nanofiltration

Abstract Polyaniline (PANI) has been widely explored as a promising membrane material, but the trade-off between porosity and stability limits its widespread application in organic solvent nanofiltration (OSN). Here we present a simple approach to prepare PANI membranes with excellent chemical stability and rejection performance in OSN by employing polyacids as PANI dopants for the first time. The PANI membranes were doped with two polyacids with different molecular weights (MW) and acid dissociation constants (pKa): namely poly(4-styrenesulfonic acid) (PSSA, MW: 75000 g mol−1, pKa: 0.94) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA, MW: 800000 g mol−1, pKa: 0.87), and were compared with a small acid (HCl) doped PANI membrane. The polyacid doped membranes, PANI-PSSA and PANI-PAMPSA, obtained dense structures with increased hydrophilicity due to strong intermolecular interactions between the PANI and the polyacids. Stability tests showed that the PANI-PSSA and PANI-PAMPSA were stable in a wide range of polar and nonpolar solvents, while the undoped PANI and PANI-HCl had poor stability in these solvents. The swelling degree and permeance of the doped membranes decreased with the increase of the dopant MW. The PANI-PAMPSA membrane exhibited a molecular weight cut-off (MWCO) in the nanofiltration (NF) range of 400 g mol−1 in methanol and isopropanol, while the PANI-HCl and PANI-PSSA membranes were in the ultrafiltration (UF) range. This study demonstrates that polyacid doping can make stable and nanoporous PANI membranes for OSN applications without the need for crosslinking. This simple approach can be used to design new classes of OSN membranes for challenging separation processes in the future.

Cerium oxide nanoparticles embedded thin-film nanocomposite nanofiltration membrane for water treatment

In this paper, a new approach to synthesize thin-film nanocomposite membranes using cerium oxide (CeO2) nanoparticles (NPs) by pre-seeding interfacial polymerization method was reported. Prepared membranes were examined using contact angle, molecular weight cut-off (MWCO), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and scanning probe microscopy (SPM) to observe its hydrophilicity, pore size, morphology, surface chemistry, and roughness, respectively. Surface charges of the prepared membranes were also qualitatively calculated with the help of contact angle measurements by using the Grahame equation. MWCO studies revealed >90% polyethylene glycol (M.W. 1500 Da) rejection, which was fitted in the range of nanofiltration. By increasing the concentration of CeO2 NPs, flux (33.12 to 41.28 L/m2h), hydrophilicity (77.3 to 51.1°) and surface charges (−7.58 to −13.39 mC/m2) of the membranes was successfully improved, and also showed the high (>90%) salt rejections. The CeO2 embedded membrane was also found out in successful prevention from the attack of bacteria (Escherichia coli) compared to pure polyamide (PA) membrane and confirmed through SEM and viable cell count method. The membrane performances were also evaluated using seawater for fouling study and found that CeO2 embedded surface increased the rejection of hydrophobic contaminants, and notably reduced the fouling.

Interfacial polymerization: A facile technique for developing solvent resistant nanofiltration (SRNF) membrane

Interfacial polymerization (IP) is recently evolved method to fabricate solvent resistant nanofiltration (SRNF) membrane. Herein the preparation of SRNF is presented which involves the polymerization of piperazine (PIP) and trimesoyl chloride (TMC) on the surface of inert support i.e. Celgard 2400. The extent of interfacial polymerization (IP) on Celgard 2400 membrane was examined afterwards by different analytical techniques including atomic force microscopy (AFM), scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR). Their outcome revealed obvious surface modification of Celgard 2400 with thin and homogenous polyamide layer. Furthermore, the sugar (dextrose, sucrose and raffinose) solutions were passed from SRNF membranes to calculate the molecular weight cutoff (MWCO). Based on sugar rejection, the value of MWCO of SRNF membranes come in the range of nanofiltration (> 300 Da). An economical, chemical resistant, homemade NF Cell was fabricated to conduct permeation study through these membranes. Effect of various reaction conditions i.e. monomer concentrations, curing temperature and reaction time on the synthesis of SRNF membranes was optimized. Bromothymol blue (BTB) was selected dye in ethanol to permeate across SRNF membranes. The rise in monomer concentrations augments the rejection of BTB thereby declining ethanol flux, owing to more even surface coverage of Celgard 2400 membrane. Moreover, the reaction time and curing temperature affect the BTB rejection and ethanol flux in the same way. The pore size in SRNF membranes was estimated theoretically by Hagen-Poiseuille as ~0.59 nm. In conclusion, PIP-TMC monomeric system synthesized stable, homogenous and effective SRNF membranes with distinct rejection and flux values.

Effect of polycation structure on the fabrication of polyelectrolyte multilayer hollow fiber membranes for loose nanofiltration applications

Abstract Polyelectrolyte multilayer (PEM) membranes were fabricated by using a polycation with a long pendant group in order to prepare loose nanofiltration membranes. Poly(2-methacryloxyethyltrimethylammonium bromide)/poly(styrene sulfonate) multilayer membranes were prepared on the lumen side of polyethersulfone hollow fiber membranes with a dynamic coating method and compared to identically prepared poly(diallyldimethylammonium chloride)/poly(styrene sulfonate) multilayer membranes to observe how the different polycation structures affect membrane properties. Both membranes were evaluated in terms of their water permeability, rejection of MgSO4, rejection of neutral polyethylene glycol model compounds, and stability against sodium hypochlorite at pH 8.0. Poly(2-methacryloxyethyltrimethylammonium bromide)-based membranes with loose nanofiltration properties and high water permeability were successfully fabricated. However, they degraded rapidly under sodium hypochlorite treatment, whereas the poly(diallyldimethylammonium chloride)-based membranes showed no significant degradation until after 50,000 ppm·h of sodium hypochlorite treatment. Despite the rapid degradation of poly(2-methacryloxyethyltrimethylammonium bromide)-based multilayers under the sodium hypochlorite treatment, the results show that choosing polyelectrolytes with appropriate side group structures can be attractive when designing PEM membranes with membrane properties in the loose nanofiltration range.

Fabrication of nanofiltration membranes via stepwise assembly of oligoamide on alumina supports: Effect of number of reaction cycles on membrane properties

This study presents the preparation procedure and the properties of nanofiltration membranes fabricated by step-by-step assembly on ultrafiltration supports. This procedure allows the covalent binding of molecular layers of alternating monomers, trimesoyl chloride and m-phenylenediamine, to control film growth and surface chemical functionality. The molecular layers are attached directly onto aminated alumina supports, obtained by functionalization of the supports using an aminosilane reagent, for the first time without the need of an anchoring polymeric layer. The membranes are fabricated by performing different numbers of reaction cycles between the two monomers and are characterized along the various cycles 2–6.5 reaction cycles). Surface analyses demonstrate the development of the layered assembly and the attained functionalizations as a function of exposed moiety. Electron microscopy proves that low number of cycles allows achievement of a smooth film, while layer thickness and heterogeneity increase above five step reactions. The water permeance and the salt rejection capabilities of the fabricated membranes are in the range of nanofiltration, with observed rejections of 20–80% and 20–95% for NaCl and MgSO4, respectively. The transport properties correlate well with the number of reaction cycles, thus allowing tuning of the membrane permeance and selectivity by adjusting the total number of layers in the assembly.

Parametric optimisation for the fabrication of polyetherimide-sPEEK asymmetric membranes on a non-woven support layer

Abstract Casting of a novel polyetherimide-sulfonated poly (ether ether ketone) membrane onto a non-woven support layer to improve mechanical strength and robustness of the resulting membrane is studied. The resultant membrane performance is optimised by considering the phase inversion parameters of polymer concentration, casting thickness, casting speed, evaporation time and coagulation bath temperature. Performance analysis was measured by membrane flux and rejection of PEG 10,000, along with structural characterisation of the membrane by SEM. Polymer concentration and coagulation bath temperature had the greatest influence on the final rejection properties of the membrane; increasing rejection from 0.72 to 0.96 when increasing from 16 wt% to 28 wt% and decreasing rejection from 0.95 to 0.60 when increasing the temperature from 3 °C to 50 °C respectively. Increasing the polymer concentration had the adverse effect of significantly reducing the permeation rate of the membrane from 50 LMH/bar to 1 LMH/bar when increasing from 16 wt% to 28 wt%. Using defined control of the phase inversion parameters the membrane was changed from an open pore ultrafiltration membrane with a molecular weight cut-off of >10 kDa to a much narrower pore size membrane in the nanofiltration range with a molecular weight cut-off of ∼3000 Da. The fabrication process for the optimised membrane is far more robust than the original process and is suitable for membrane mass production.

Solvent resistant nanofiltration for acetonitrile based feeds: A membrane screening

A range of commercially available and lab-made membranes was screened for use in feeds containing acetonitrile (ACN). ACN was selected as it is one of the most widely used solvents in pharmaceutical industry and surprisingly absent in earlier studies on solvent resistant nanofiltration (SRNF). The selected membranes ranged from the tight nanofiltration range to the lower end ultrafiltration range, prepared from different membrane chemistries and with different membrane preparation methods. Multiple dyes were tested as probe molecules to study the retention behavior of the membranes in ACN. Gel content measurements were conducted on the membranes and interaction parameters with ACN, the dyes and the membranes were calculated to link physico-chemical properties to separation performances. ACN was found to be a very appropriate solvent for SRNF applications, as most membranes reached high fluxes and retentions, comparable to those obtained in most other solvents. As most membrane polymers did not dissolve in ACN, membrane crosslinking is not even strictly necessary to ensure stability of the membranes when applied in these feeds. This study thus showed that for ACN-based solutions, many different types of SRNF membranes can potentially be selected to achieve the aimed separations.

Effects of polyethersulfone membrane substrate on the separation performance of thin film composite membrane in biorefinery

This study was aimed to develop a customised thin film composite (TFC) membrane for the separation in biorefinery. After the biomass hydrolysis stage, sugars component (i.e. glucose and xylose) need further refinement to remove any inhibitor (i.e. acetic acid) that can decrease the yield of the product during the fermentation stage. Substrate layer properties and the condition of thin film formation during interfacial polymerisation (IP) influenced the performance of the TFC membrane. Not much attention is given on the effects of substrate membrane properties asmost support membranes were purchased commercially. Polyethersulfone (PES) membrane substrate was fabricated in the current study at different PES concentration range of 15 wt% to 23 wt%. IP was performed using the piperazine and trimesoyl chloride monomers. As the PES concentration in the membrane substrate increased, the pure water permeability (PWP) decreased. The PWP of the membrane substrate prepared from 15 % PES and 23 % PES were 231.67 ± 16.59 L/m2.h.bar and 24.49 ± 6.54 L/m2.h.bar. After the IP, the PWP decreased to the range of nanofiltration. The PWP value were 28.07 ± 5.42 L/m2.h.bar and 3.94 ± 1.21 L/m2.h.bar for the TFC membrane prepared using 15 % PES and 23 % PES membrane support. TFC membrane prepared using 23 % PES showed the rejection value 24.07 ± 5.96 % of xylose, 47.56 ± 1.99 % of glucose and 2.67 ± 1.05 % of acetic acid. This is corresponding to the ideal separation factor of 1.45 ± 0.06 for xylose/glucose, 1.86 ± 0.05 for acetic acid/glucose and 1.29 ± 0.09 for acetic acid/xylose.

INTEGRATION OF POLYETHERSULFONE AND HYDROXYAPATITE NANOFILTRATION MEMBRANE FOR VANILLIC ACID SEPARATION

In this work, the integration of polyethersulfone and hydroxyapatite was studied for vanillic acid separation. The polyethersulfone membranes were modified with hydroxyapatite via in-situ approach in order to enhance the performance of the membrane. The membranes were further characterized concerning permeability, morphology, membrane structural details, porosity and contact angle. The addition of hydroxyapatite in mixed matrix membrane increased the permeation rate from 19.05 L/m2.hr up to 95.76 L/m2.hr due to the increasing of hydrophilicity. The membrane permeability coefficients lie in the range of 1.909 – 10.05 L/m2.hr.bar which were nanofiltration range. The performances of the membrane exhibited higher rejection which showed the vanillic acid rejection up to 69.88% for modified membrane.

Membranes prepared by self-assembly and chelation assisted phase inversion

We combine self-assembly in solution, complexation with metallic salts and phase separation induced by solvent-non-solvent exchange to prepare nanostructured membranes for separation in the nanofiltration range. This method was applied to prepare membranes from newly synthesized poly(acrylic acid)-b-polysulfone-b-poly(acrylic acid) copolymers dissolved in a selective solvent mixture and immersed in aqueous Cu2+ or Ag+ solutions.