Performance evaluation of the different nano-enhanced polysulfone membranes via membrane distillation for produced water desalination in Sert Basin-Libya

A Polysulfone-Polyethylene glycol (PS/PEG) flat sheet membrane was prepared by phase inversion technique. Dimethyl Formamide (DMF) was utilized as a solvent and deionized water was utilized as the coagulant. Polyethylene glycol (PEG) of a various dose of PEG 2000 was utilized as the polymeric improvers and as a pore-forming agent in the casting mixture. The single-walled carbon nanotube (SWCNTs), multi-walled carbon nanotube (MWCNTs), aluminum oxide (Al₂O₃) and copper oxide (CuO) nanoparticles (NPs) were utilized to improve the PS/PEG membrane performances. The characterizations of the neat PS, PS/PEG, PS/PEG/Al2O3 (M1) PS-PEG/CuO (M2), PS-PEG/SWCNTs (M3) and PS/PEG/MWCNTs (M14) nanocomposite (NC) modified membranes were acquired via Fourier-transform infrared analysis (FTIR), water contact angle estimation (WCA), scanning electron microscope (SEM), dynamic mechanical analyzer (DMA) and thermogravimetric analysis (TGA). Enhanced Direct contact membrane distillation (EDCMD) unit was used for estimating the efficiency of the performance of the synthesized NC membranes via 60 °C feed synthetic water and/or saline oil field produced water samples containing salinities 123,14 mg/L. Adjusting the operational procedures and water characteristics confirmed a high salt rejection of 99.99% by the synthesized NC membranes. The maximum permeate flux achieved in the order of SWCNTs (20.91) > Al₂O₃ (19.92) > CuO (18.92) > MWCNT (18.20) (L/m².h) with adjusted concentration of 0.5, 0.75, 0.75, 0.1 wt% compared with PS weight, i.e. 16%. The optimum operational circumstances comprised feed and permeate temperatures 60 °C and 20 °C, respectively. The achieved flux was 5.97 L/m².h, using brine oil field produced water, via PS/PEG/SWCNTs membrane with 0.5 wt% of SWCNTs. Moreover, the membrane indicated sustaining performance stability in the 480 min continuous desalination testing, showing that the synthesized PS/PEG/SWCNTs NC modified membrane may be of magnificent potential to be activated in EDCMD procedure for water desalination.     

Performance improvement of polysulfone ultrafiltration membrane by blending with polyaniline nanofibers

Polyaniline (PANI) nanofibers were used to improve hydrophilic property and permeability of polysulfone (PS) membrane. PS membrane and PS/PANI nanofibers blended membranes with different PANI–PS mass ratios (1, 5, 10, and 15 wt.%) were prepared by phase inversion process. The blended membranes showed similar bovine serum albumin (BSA) and albumin egg (AE) rejections to PS membrane. The blended membranes had larger porosity and better hydrophilic property than PS membrane, which caused the improvement of their permeability. Pure water fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 1.6 and 2.4 times that of PS membrane, respectively. During the filtration of BSA solution, the blended membranes had slower flux decline rate than PS membrane. Moreover, stable permeate fluxes of the blended membranes with PANI–PS mass ratios of 1 and 15 wt.% were 2.0 and 2.5 times that of PS membrane, respectively. Compared with PS membrane, mechanical property and thermal stability of the blended membranes with less PANI–PS mass ratio, e.g. 1 wt.%, had no obvious change. For the blended membrane with PANI–PS mass ratio of 15 wt.%, breaking strength increased 28% and elongation at break decreased 30.6%.     

pH stimuli-responsive and fouling resistance PES membrane fabricated by using photochromic spiropyran and spironaphthoxazine nanofillers for pesticide removal

New fouling resistance and stimulus–responsive nanofiltration membranes were fabricated by adding photochromic spiropyran (SPO) and spironaphthoxazine (SNO) nanofillers to the polyethersulfone (PES) matrix via the phase inversion method. The effect of SPO and SNO, as novel photoresponsive molecule nanofillers, were evaluated in terms of membrane morphology, porosity, wettability, pure water flux (PWF), antifouling resistance, and stimulus–responsive properties. All the modified membranes indicated better performance compared to the bare PES. The membrane PWF was notably enhanced from 7.7 kg/m²h for the bare PES up to 18.68 and 20.58 kg/m²h for the 0.1 wt.% SPO and SNO blended membranes, respectively. Also, the 0.1 wt.% of SNO-based PES membrane indicated the best flux recovery ratio compared to the other membranes. The photo stimulus–responsive assessment showed a color change for both SPO and SNO photochromic in membranes. In the case of variable effect investigation, the response surface methodology at three levels (pressure: 4, 5, 6 bar and flow rate: 50, 100, and 150 L/h) was applied. A suitable flux (23.39 kg/m² h) and high removal efficiency (more than 90%) was achieved at optimum conditions. Also, the modified membranes by photochromic materials were sensitive to environmental variables such as acidic and alkaline conditions by changing their color.     

Polyphenylsulfone/multiwalled carbon nanotubes mixed ultrafiltration membranes: Fabrication,characterization and removal of heavy metals Pb2+, Hg2+, and Cd2+ from aqueous solutions

Polyphenylsulfone/multiwalled carbon nanotubes/polyvinylpyrrolidone/1-methyl-2-pyrrolidone mixed matrix ultrafiltration flat-sheet membranes were fabricated via phase inversion process to inspect the heavy metals separation efficacy from aqueous media. Fabricated membranes cross-sectional morphological changes and the topographical alterations were assessed with Scanning electron microscopy (SEM) and atomic force microscopy (AFM). Particularly, MWCNTs assisted membranes exhibited better permeability ability as well as heavy metal removal enactment than virgin membrane. The dead-end filter unit was engaged in current research to examine the permeability and heavy metal removal competence of membranes. With the continuous enhancement of MWCNTs wt% in a polymer matrix, significant enhancement was observed with pure water flux study, from 41.69 L/m² h to >185 L/m² h as well as with the heavy metals separation study. Added additive MWCNTs can impact the pore sizes in membranes. The heavy metal separation results achieved, the membrane with 0.3 wt% of MWCNTs (PCNT-3) exhibited >98%, >76% and >72% for Pb²⁺, Hg²⁺ and Cd²⁺ ions, respectively. Overall, MWCNTs introduced PPSU membranes exposed best outcomes with heavy metals contained wastewater treatment.     

Cross-linked polyimide membranes for solvent resistant nanofiltration in aprotic solvents

Solvent stable nanofiltration membranes were prepared through the chemical cross-linking of asymmetric Matrimid^®-based polyimide membranes with p-xylylenediamine. The influence of this straightforward post-treatment on membrane stability, morphology and performance in dimethylformamide (DMF), N-methylpyrrolidinone (NMP), dimethylacetamide (DMAc) and dimethylsulfoxide (DMSO) was thoroughly investigated. With permeabilities up to 5.4 l/m² bar h and rejections up to 98% for low molecular weight dyes in these demanding solvents, optimally performing, truly solvent resistant nanofiltration membranes were obtained. Nanozeolite-filled membranes were prepared in parallel to study the effect of an inorganic filler on the cross-linking reaction and performance in aprotic solvents. The outstanding stability and performance of these membranes and their easy preparation clearly offer vast potential for applications in harsh solvent environments.     

Fabrication of the polyethersulfone/functionalized mesoporous carbon nanocomposite nanofiltration membrane for dyes and heavy metal ions removal: Experimental and quantum mechanical simulation method

The presence of industrial pollutants, especially salts, heavy metals ions, and dyes in water and wastewater is considered a serious environmental issue. To eliminate these pollutants, a high-performing nanofiltration (NF) membrane was prepared by blending the functionalized mesoporous carbon CMK-5 (F-CMK-5) nanofiller. This membrane was synthesized by introducing the active groups of sulfonyl and amide to the surface of mesoporous carbon CMK-5 through covalent functionalization. Characterizations were conducted to study the membranes' physical properties and separation performance in terms of antifouling properties and rejection of salts, heavy metal ions, and dyes. The interactions between the active sites of the nanocomposite membrane and the studied solutes, including dyes and heavy metal ions in aqueous solutions, were studied by the density functional based tight binding method and structural optimization was carried out. Insertion of the F-CMK-5 nanofiller was eventuated in a remarkable increase in surface hydrophilicity, pure water flux, and antifouling properties. For all membranes, the lowest and the highest salt rejection was obtained for NaCl and Na₂SO₄, respectively, exhibiting the characteristics of NF membranes. Moreover, M_0.3 with 0.3 wt% nanofiller showed the highest rejection for heavy metal ions (Fe²⁺ = 99.9%, Zn²⁺ = 99.9%, Cu²⁺ = 99.7%, and Pb²⁺ = 99.2%) and dyes (RB5 = 99.21, DR16 = 98.87, and MB = 98.12%), as well as high separation performance for filtration of multipollutant solutions. The reusability and 144 h uninterrupted filtration experiments for M_0.3 confirmed the stability of the membrane. The findings suggest that the PES/F-CMK-5 nanocomposite NF membrane is a promising candidate for water and wastewater treatment.     

Removal of dithioterethiol (DTT) from water by membranes of cellulose acetate (AC) and AC doped ZnO and TiO2 nanoparticles

Dithioterethiol (DTT) is a typical example of substances that contain sulfur with adverse effects on human health. Membranes-based cellulose acetate is used for the separation processes of thiols after the addition of ZnO and TiO₂ nanoparticles. The measurement of permeability allows us to estimate the efficiency of membrane cleaning. The permeability increases from 8.82 L.h^?1.m^?2.bar^?1 for CA membrane to 20.77 L.h^?1.m^?2.bar^?1 for CA-TiO₂ and 21.96 L.h^?1.m^?2.bar^?1 for CA-ZnO membranes. For the permeability values of DTT, we noted that the CA-ZnO membrane has the highest permeability (50.66 L.h^?1.m^?2.bar^?1). The CA-ZnO membrane changes from nanofiltration to ultrafiltration membrane. On the other hand, for the CA-TiO₂ modified membrane, the permeability decreases to 6.00 L.h^?1.m^?2.bar^?1. The CA-TiO₂ membrane is in the category of reverse osmosis membranes. This variation is explained by the interaction between nanoparticles and DTT. The contact angles of the incorporated membranes decrease progressively with the addition of TiO₂ or ZnO-NPs. The low contact angle with water means high hydrophilicity, indicated that the addition of TiO₂ and ZnO improved the hydrophilicity of the membranes. The CA membrane had the highest contact angle with water of 92.64 ± 1.5°. After the addition of 0.1 g of TiO₂ or ZnO, the contact angle of CA-TiO₂ and CA-ZnO was reduced to 86.7 ± 0.2° and 70.51 ± 1.5°, respectively. Both TiO₂ and ZnO caused strong hydrophilicity of membranes. From the elimination rates of DTT, it is concluded that there are optimal conditions of (1) Pressure P = 2 bars, (2) pH = 10 and (3) DTT concentration = 2 mM.     

Nanostructured polyethersulfone membranes for dye and protein separation: Exploring antifouling role of holmium (III) molybdate nanosheets

Nanostructured polymer membranes are nowadays of crucial importance in achieving antifouling properties. Nanomaterials with tunable composition, size, and morphology, surface modification and functionality offer unprecedented opportunities for efficient wastewater treatment. In this work, the effect of holmium (III) molybdate (Ho₂MoO₆) nanomaterial as a new nanofiller on preparation of nanostructured polyethersulfone (PES) mixed matrix membranes was examined in terms of hydrophilicity, membrane morphology, permeability, dye and protein separation and antifouling property. The Ho₂MoO₆ nanosheets were synthesized and characterized by FTIR, XRD, and FESEM and used in different amounts in PES matrix. The pore size and the membrane porosity increased with Ho₂MoO₆ loading. The nanocomposite membranes showed enhancement in hydrophilicity, antifouling properties, dye rejection and permeability. The remarkably pure water flux (195 L/m²h at 3 bar) and 92.3% flux recovery after bovine serum albumin (BSA) filtration were obtained for the membrane mixed with 2 wt% Ho₂MoO₆ compared to 95 L/m²h and 75.2% obtained for the bare PES, respectively. Moreover, significantly high rejection of Acid Red 125 (95 ± 1%) was achieved. Thus, the experimental results established the potential efficiency of the novel nanocomposite membrane for the separation applications.     

Enhancing the performance of TFC nanofiltration membranes by adding organic acids in polysulfone support layer

Throughout this study, the effect of certain organic acids, methacrylic acid, lactic acid and tartaric acid, doped in polysulfone (PSF) casting solution onto the performance of nanofiltration (NF) membranes was investigated. Different NF membranes have been prepared from m-phenylenediamine and trimesoylchloride onto the top surface of the acid-modified PSF membranes through regulating the concentration and contact time of the conventional interfacial polymerization process. The study of scanning electron microscopy (SEM) was used to investigate the influence of acids on the morphology of membranes and cross-sectional structures. The functional groups, hydroxyl and carboxylic acid, of the acids have resulted in a significant increase in membrane thickness, porosity and hydrophilicity, with a decrease in macrovoid capacity of the PSF layer. The acid-modified PSF/TFC membranes showed higher rejection of salt, with an increment in water flux compared to the neat membrane. Water flux and salt rejection (R_s %) of the control membrane was 7.6 L/m² h and 65.4%, whereas polysulfone/methacrylic acid (PSF/MAAc), polysulfone/tartaric acid (PSF/TAc), and polysulfone/lactic acid (PSF/LAc) were 16.8, 18.5, and 20.2 L/m² h and 88, 88.2 and 94.1%, respectively. Efficiency of prepared NF membranes under various inlet pressures and specific salts was investigated with selectivity and salt rejection. The salt rejection of a mixed salt solution was found to meet the order of R_s % CaSO₄ ≥ R_s % Na₂SO₄ ˃ R_s % MgSO₄ ˃ R_s MgCl₂ ˃ Rs % NaCl.     

Hydrophilic nanofiltration membranes with self-polymerized and strongly-adhered polydopamine as separating layer

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions,a novel hydrophilic nanofiltration（NF） membrane was fabricated by simply dipping polysulfone（PSf） ultrafiltration（UF） substrate in dopamine solution.The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy（FTIR-ATR）,X-ray photoelectron spectroscopy（XPS）,scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane.The surface hydrophilicity of membranes was evaluated through water contact angle measurements.It was found that membrane hydrophilicity was significantly improved after coating a polydopamine（pDA） layer,especially after double coating.The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue,congo red and methyl orange with a pure water flux of 83.7 L/（m²·h） under 0.6 MPa.The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process.The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment.It was demonstrated that the salts rejections followed the sequence:NaCl2SO₄422,and the rejection to CaCl₂ reached 68.7%.Moreover,the composite NF membranes showed a good stability in water-phase filtration process.     

The formation of ultrafine polyamide 6 nanofiber membranes with needleless electrospinning for air filtration

Particulate matter (PM) is a major air pollutant, which has a significant impact on public health. Filtration of PM through filters is a common method to protect the environment. However, the effective removal of PM with conventional filters still remains a challenge because of its small sizes. Here, we reported the formation of ultrafine polyamide 6 (PA‐6) nanofiber membranes formed with needleless electrospinning, in which both relative humidity condition and electrode type were included in the discussion. The PA‐6S nanofibers formed by using spiral electrode as a spinneret at 60% RH had the diameter of 33 nm, while the PA‐6C nanofibers formed by using cylindrical electrode had the diameter of 120 nm. With the integration of fine diameter, small pore size, and high porosity, the resultant PA‐6S nanofiber membrane exhibits high filtration efficiency of 99.42% and low pressure drop of 85.5 Pa under a face velocity of 85 L/min. Besides, it took only 10 minutes to reduce the concentration of PM_2.5 from 999 to 34.1 μg/m³ when used to filter real PM particles.     

Development of a new styrene copolymer membrane for recycling of polyester fibre dyeing effluent

A new ultra-filtration membrane has been developed using indigenously available polymer, low cost solvents and a simple casting technique. The performance evaluation of the developed membrane in terms of pure water permeability (PWP), flux and rejection as compared to commercially available national and international membranes was carried out. It is observed that the newly developed membranes show acceptable performance both in terms of flux and rejection. The compressibility characteristic of the new membrane shows an improvement after suitable chemical modification through cross-linking reactions. The application perspectives of the membranes developed in our laboratory have been evaluated for the selective separation of dyes from typical textile waste stream of polyester fibre dyeing units with an aim to recover and recirculate the auxiliary chemicals and water in the process house. The rejection of dyes >98% and the permeate flux (0.8–1.0 m³/m² per day) values obtained for a specific type of textile effluent is of acceptable standards.The membranes were characterised for pore size and pore size distribution using molecular weight cut-off, combined bubble pressure and solvent permeability method. Membrane morphology has been studied using scanning electron microscopy (SEM). The other features of the developed membrane are its resistance to temperature and adverse chemical environment.     

Improved microfiltration and bacteria removal performance of polyethersulfone membranes prepared by modified vapor‐induced phase separation

Polyethersulfone (PES) microfiltration membranes were fabricated by a combined vapor‐induced phase separation and wet phase separation method. The effect of different non‐solvent additives in casting solution, ie, acetone, diethylene glycol, and triethylene glycol (TEG) was investigated on the membrane morphology and performance. Scanning electron microscopy images showed that the membrane containing TEG additive had a skinless symmetric structure with well interconnected pores. The permeability of the PES/PVP/TEG membranes increased by decreasing PES and TEG and increasing PVP concentration. Bacteria removal performance of the prepared membranes was investigated by the filtration of E. coli suspension. The membrane made from casting solution containing 15 wt.% PES, 16 wt.% PVP, and 20wt.% TEG showed a pure water flux of ~ 5370 L/m² h at low transmembrane pressure of 10 psi and 100% bacteria removal efficiency. The results of in vitro cytotoxicity test and cell viability assay showed non‐toxic nature of the prepared membranes.     

Separation of cells and proteins from fermentation broth in a shear-enhanced cross-flow ultrafiltration module as the first step in the refinement of lactic acid

A shear-enhanced, cross-flow ultrafiltration module was used to separate cells and proteins from the fermentation broth. Three (fermented) media were studied: rich medium, rich medium with hydrolytic enzymes added after fermentation, and wheat flour hydrolysate. To find a membrane with as high a flux as possible, but still capable of separating cells and proteins from the lactic acid containing broth, the performance of three hydrophilic membranes of varying cutoffs (10,000, 20,000, and 30,000) and one hydrophobic membrane (cutoff 25,000) was investigated. The proteins produced by the lactic acid bacteria during fermentation and the hydrolytic proteins were retained by the hydrophilic membrane with a cutoff of 20,000, whereas wheat flour proteins were detected in the permeate. In the permeates from the hydrophobic membrane (cutoff 25,000), almost no proteins were detected. The flux of the whole-wheat flour hydrolysate was significantly lower than that of rich medium, for both the hydrophilic and the hydrophobic membranes. The flux was, in all cases, higher for the hydrophilic membrane (12–85 L/[m²·h], depending, on which medium was treated) than for the hydrophobic one (8–45 L/[m²·h]), even though the nominal cutoffs of the hydrophobic and hydrophilic membranes were almost the same. However, the difference in flux was smaller when the whole-wheat flour hydrolysate was processed (12 vs 8 L/[m²·h]) than when the rich medium was processed (85 vs 45 L/[m²·h]). Protein retention was higher for the hydrophobic membrane than for the hydrophilic membrane (cutoff 20,000) owing to blocking of the pores by proteins adsorbed on to the hydrophobic membrane surface.     

Investigating the effect of PEG200 and two-dimensional h-BN on PVDF membrane performance for membrane distillation–crystallization

Although water supplies are prominently dependent on desalination technology, desalination plant facing severe issues of discharged brine concentrate. Membrane distillation crystallization is an emerging synergistic technology that resolves the issue of brine concentrate by recovering clean water and value-added minerals simultaneously. In the present study, properties of polyvinylidene fluoride (PVDF) membrane were modified by incorporation of exfoliated fillers of hexagonal boron nitride and polyethylene glycol. The changes in morphology, surface roughness, hydrophobicity, thermal stability, and chemical composition of the prepared membranes were evaluated by scanning electron microscopy, atomic force microscopy, contact angle, thermogravimetric analysis, Fourier-transform infrared spectroscopy, respectively. Membrane distillation crystallization experiments were conducted to observe the effect of modified membranes on the permeate flux and salts recovery at different feed temperatures. The results showed a significant improvement in the permeate flux with modified membranes compared with pure PVDF membrane. It was found that hexagonal boron nitride/polyethylene glycol200 incorporated PVDF membrane gave the higher permeate flux (3.41 kg/m² h for K₂SO₄ and 2.62 kg/m² h for KNO₃) at a temperature of 80 °C along with higher salts recovery than pure PVDF membranes. A 100 h long run test was conducted on modified membranes, which showed consistency in permeate flux with a marginal increase in conductivity.     

Selective water‐permeable channels induced by polystyrene brushes within hairy nanocellulose/cellulose acetate membrane

Hairy nanocellulose (NC) was prepared by in‐situ admicellar polymerization of styrene on NC surface in the presence of cetyltrimethylammonium bromide through a stepwise fashion. It was also tried to achieve three hairy NCs with different polystyrene (PS) brush contents (i.e. 40, 50, and 80%) through altering monomer initial concentration. Then, NC and three hairy NCs were separately added into cellulose acetate (CA) solutions to fabricate membranes via the phase inversion technique. Transmission electron microscope images show that NC and three hairy NCs are spherical‐shaped nanoparticles. Results of Fourier transform infrared spectra provide clear evidence of PS brush being attached to the NC surfaces. Thermal gravimetric analysis confirms that increasing styrene initial concentration leads to enhanced PS content of hairy NCs. Results also elucidate that dispersions of prepared hairy NCs are highly stable even at high loading levels. It was found that incorporation of 1 wt% hairy NC with optimum brush content of 50% within CA membranes results in the increasing membrane water permeability from 7 to 40 l/m² hr with no change in its selectivity. Indeed, new interactions induced by PS brushes at hairy NC/CA interfaces result in the creation of connected channels at the interfaces which facilitate water transport through the membrane. This study provides insights into the key role that PS brushes play in overcoming the dispersion problems of NC in nonpolar media and offers guidelines to tailor channels within hairy NC/CA membrane for enhanced filtration performance. Copyright © 2017 John Wiley & Sons, Ltd.     

Hydrophilic modification of polypropylene ultrafiltration membrane by air‐assisted polydopamine coating

Coating by a mussel inspired polydopamine (PDA) is a simple and promising strategy to modify the hydrophilicity of polymer membrane surfaces. In this work, PDA coating was used to modify polypropylene (PP) ultrafiltration hollow fiber membrane. PDA coating parameters, ie, solution concentration and coating time were varied, and the effect of those parameters on membrane morphology, porosity, water contact angle, and pure water flux was investigated. In addition, air‐assisted PDA coating process was also conducted by channelling the air through PP membrane to avoid pore blocking and prevent water flux decline. The results showed that PDA coating successfully improved the hydrophilicity of PP membrane indicated by the decrease of water contact angle from 110° to 67° after coated by 3 g/L of PDA solution for 3 hours. The addition of air permeation on membrane lumen also increased pure water flux up to 511.2 L/m².h, a 270% increase from unmodified PP membrane. It might be associated to the pore blocking prevention that has been proven by SEM image and the membrane porosity that was increased about 4%.     

Nanofiltration-like forward osmosis membranes on in-situ mussel-modified polyvinylidene fluoride porous substrate for efficient salt/dye separation

Here, polyvinylidene fluoride (PVDF) membranes were fabricated via non-solvent induced phase separation (NIPS) using dopamine (DA) and polyethyleneimine (PEI) as the hydrophilic additives, which has a loose surface and somewhat improved hydrophilicity. Then nanofiltration (NF)-like thin-film composite forward osmosis (TFC FO) membrane with a loose polyamide (PA) active layer on the blend membrane was synthesized via the interfacial polymerization. The as-prepared NF-like TFC FO membrane exhibited a high water flux (J_w) of 29.98 L m⁻² h⁻¹ and a much low specific salt flux (J_s/J_w) of 0.018 g/L, when 0.6 M NaCl was used as draw solution (DS). It had a superior rejection of malachite green (99.6% ± 0.1%) and a low rejection of NaCl (27.4% ± 4.2%), when filtrated malachite green/NaCl mixture solution in active layer-facing draw solution (AL-FS) mode. The results provide new insights on the design and preparation of FO membranes of selective separation for dyes from salty water.     

New low-cost tubular ceramic microfiltration membrane based on natural sand for tangential urban wastewater treatment

In wastewater treatment, the development of low-cost separation methods is of significant importance. Low-cost membranes based on natural materials have become a highly active research topic in recent years. Herein, using low-cost natural Moroccan sand, new ceramic supports have been developed and characterized using different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), along with scanning electron microscope (SEM). Plastic paste (average particle size ≤125 µm) was blended with organic additives and water, then the obtained paste was extruded into porous tubular supports. The support had a porosity of 43%, water permeability of 1928 L/h m² bar, excellent chemical and mechanical properties and an average pore diameter in the range of 8–15 µm after firing at 950 °C/2 h. As per SEM analysis, the tubular supports had a smooth and crack-free surface. The slip casting process was used to create a microfiltration layer from the same natural sand powder (average particle size ≤63 µm) using a mixture of powder sand, water, and polyvinyl alcohol solution. The water permeability of the microfiltration membrane sintered at 950 °C/2 h was 1052 L/h m² bar, the average pore size diameter was about 0.90 µm and 82% of pores had a diameter ≤1.00 µm. The obtained microfiltration membrane was tested for the treatment of urban wastewater. The membrane showed excellent separation performance in turbidity removal and chemical oxygen demand.     

Biogas upgrading with novel cellulose nano-crystals and polyvinyl amine nanocomposite membranes

A novel crystalline nano cellulose (CNC) and polyvinyl amine (PVAm) based nanocomposite membranes were synthesized and evaluated for biogas upgrading. Different concentrations of CNC was incorporated in 3 wt % PVAm solution on commercial polysulfone (PSf) sheet using dip coating method. The effect of feed pressure (5, 10 and 15 bar) was investigated for the CO₂/CH₄ separation. The incorporation of CNC increased the crystallinity of membranes. The thickness of selective layer enhanced to 2.16 μm from 1.5 μm with increasing concentration of CNC. However, degree of swelling reduced from 75.88% to 68.93 with CNC concentration at 1.5 wt%. The best results were shown by PVAm membrane with 1 wt % CNC concentration i.e. CO₂ permeance of 0.0216 m³(STP)/m².bar.hr and selectivity (CO₂/CH₄) of 41.The permeance decreased approximately 1.8 folds for PVAm/1CNC membrane with the increase in pressure from 5 to 15 bar. However, selectivity dropped from 41 to 39 for formulated membranes.