Performance evaluation of polyvinylchloride/polyacrylonitrile ultrafiltration blend membrane

Polyvinylchloride (PVC) membranes were modified by blending with polyacrylonitrile (PAN) as a second polymer. The miscibility of PVC/PAN blend was examined using an incompressible regular solution (CRS) model in no need to make a membrane. The results showed that the PVC/PAN blend was immiscible for all compositions at a temperature range of ?25 to 225 °C. Furthermore, the prediction of the phase behavior of a PVC/PAN/DMF ternary system showed that the blend of two polymers was highly incompatible even in their common DMF solvent. However, this incompatibility led to a remarkable increase in the porosity of the blend membrane and pure water flux compared to those for pure PVC membrane. The pure water flux of the PVC membrane (37.9 ± 1.5 L/m² h) increased about 41 and 76% by adding 10 and 20 wt% PAN, respectively. The blend membranes also showed an enhanced flux recovery ratio (FRR) compared to a pure PVC membrane, although the PVC membrane rejection for Bovine serum albumin (BSA) was decreased after blending with PAN. The PVC/PAN (90/10) blend membrane was subjected to hydrolysis with NaOH alkaline solution at three different concentrations and contact times to further enhance its performance. The membrane, which was hydrolyzed with a 0.5 mol/L NaOH solution for 0.5 h, showed a highest pure water flux of 75.6 ± 7.2 L/m² h due to its increased hydrophilicity. This membrane also revealed an improved FRR and better thermal and mechanical properties compared to an unmodified membrane.     

β-SiAlON ceramic membranes modified with SiO2 nanoparticles with high rejection rate in oil-water emulsion separation

Porous ceramic membranes with high mechanical strength are suitable for oil-water emulsion separation. Nonetheless, it is difficult to prepare ceramic membranes with a small pore size and a good antifouling ability. In this work, SiO₂ nanoparticles were used to modify β-SiAlON ceramic membranes, which were successfully utilized to remove small oil droplets from oil-water emulsion. The modified membranes displayed a narrow pore size (the average pore size decreased from 1.05?µm, in the unmodified membrane, to 0.65?µm), and gas and water fluxes which are suitable for oil-water separation. Oil rejection rate was always higher than 90% under various pressures (1.0–2.0?bar) and flow velocities (1.0?3.0?L?min^?1) tested, which is considerably higher (60%) than the rejection rate of the unmodified membrane (which was 39.8%). Moreover, the modified membranes exhibited a good antifouling ability, since flux declined by only 7.0% after three recoveries via a simple ultrasonic treatment, over a total running period of 10?h. Accordingly, the produced membranes can be qualified for further consideration in oily wastewater treatment.     

Dehydration of 2‐Butanol by Pervaporation Through Blend Membranes of Chitosan and Hydroxy Ethyl Cellulose

Abstract

Blend membranes of chitosan (CS) and hydroxyethylcellulose (HEC) were synthesized and cross‐linked with glutaraldehyde for the separation of 2‐butanol/water mixtures. The blends were characterized by fourier transform infrared (FTIR) spectroscopy and wide‐angled X‐ray diffraction (WAXD) to assess the intermolecular interactions and occurrence of cross‐linking, respectively. The pervaporation performance was evaluated by varying experimental parameters such as feed composition, membrane thickness, and permeate pressure and found to be promising. Sorption studies were conducted to evaluate affinity and degree of swelling of both the unmodified and cross‐linked blend membranes in pure as well as binary mixtures of the two liquids. The blends were found to have good potential for breaking the aqueous azeotrope of 2‐butanol (77 wt.%). Upon cross‐linking, the blend membranes exhibited a substantial improvement in performance. Amongst the various blend combinations used for the dehydration studies, the membrane constituting 70 wt.% of CS and 30 wt.% HEC yielded a flux of 2.1 kg/m² · h · 10 µm and a selectivity of 554, which was optimum.     

Pervaporation performance of surface-modified zeolite/PU mixed matrix membranes for separation of phenol from water

Polyurethane (PU) is a kind of promising pervaporation membrane material and silica-rich zeolite is a potential modifier to PU, but the pristine zeolite particles suffer from the bad dispersion in the polymer. This work presents a new route to modify zeolite (ZSM-5) particles via bridging with isocyanate to prepare a membrane for the recovery of phenol from the water. Zeolite ZSM-5 particles were successfully grafted by TDI, β-cyclodextrin, and oleyl alcohol, consecutively. The corresponding zeolites filled PU membranes were prepared and characterized by FTIR, TGA and SEM techniques. The effects of the grafted structures on the pervaporation performances of the zeolites/PU membranes were investigated in the recovery of phenol from the water. The results showed that the modified ZSM-5 particles had a good dispersion in PU, while the pristine ones demonstrated an obvious sedimentation. The modified zeolite/polyurethane membranes achieved better comprehensive separation performance than the neat PU and pristine ZSM-5 modified PU membranes. Depending on the good affinity of the β-cyclodextrin to phenol, ZSM-5 particles grafted by toluene diisocyanate and β-cyclodextrin (ZSM-TC) showed the optimal separation performance with the flux of 46.03 kg μm m^?2 h^?1 and the separation factor of 15.64 for the 0.3 wt% aqueous phenol solution at 80 °C. With the increase in the zeolite loading from 5 to 25%, ZSM-5/PU membrane showed the decreased separation factor and flux comparing to the neat PU. However, ZSM-TC/PU membrane showed higher flux and better selectivity than the neat PU and pristine ZSM-5 filled PU membranes.     

Enhanced desalination performance and arsenate removal using semi-aromatic polyamide-based pervaporation membranes by modifying with amino-acids via interfacial polymerization

In this study, the semi-aromatic polyamide membranes were synthesized by the interfacial polymerization between piperazine (PIP) monomers in the water phase and Benzene-1,3,5-tricarbonyl chloride in the organic phase. To further modify the semi-aromatic pervaporation membrane, the two amino acids, glycine, and l -lysine, were mixed with PIP monomers for interfacial polymerization. The morphology and physicochemical properties of the synthesized membranes were analyzed using Fourier transform infrared (FTIR), field emission scanning electron microscope (FE-SEM), atomic force microscope (AFM), and contact angle measurements. The results show that the semi-aromatic polyamide membranes modified by the two amino acids possess a higher hydrophilic surface and lower thickness compared to the unmodified membrane. Additionally, the permeation flux of the semi-aromatic polyamide membranes was improved by 18.6% and 38.5% as modified with glycine and l -lysine, respectively, at the operating temperature of 70°C when the rejection of both NaCl and arsenic are higher than 99.8%. Furthermore, the operating temperature significantly influenced the permeation flux, while the salt rejections were insignificantly affected. The permeation flux increases by 3.2- and 4.0-folds for glycine and lysine-modified membranes, respectively, when elevating the feed temperature from 40°C to 70°C. The highest permeation flux of 29.5 kg m⁻² h⁻¹ with a 5 wt% NaCl rejection of 99.8% was obtained at 70°C by using 0.3 wt% l -lysine modified polyamide (PA) membrane. For elimination of 1.5 mg L⁻¹ As solution at the feed temperature of 70°C, such l -lysine modified PA membrane exhibited the permeation flux of 30.5 kg m⁻² h⁻¹ and As rejection of 99.6%, respectively. This work provides a cost-saving, facile, and eco-friendly preparation method for effectively improving the permeation flux while not sacrificing the high rejection of salts of the modified membranes.     

Microfiltration of Milk with Third Generation Ceramic Membranes

The objective of this study was to compare the behavior of different ceramic membranes during skimmed milk microfiltration. Permeate flow rates, protein rejection, and decimal reduction of bacteria were compared for three different 1.4-µm pore size ceramic membranes, one of which was considered traditional (ceramic multichannel membrane) while the other two had a modified structure (on either the macroporous support or the filtering layer). Permeate flux ranged from 400 to 530 Lm^?2h^?1 at 0.5 bar of transmembrane pressure. Protein rejection values between 0.8 and 2.9% were obtained. Temperature (21–45°C) did not have a significant effect. Membranes showed decimal reduction in total bacterial count between 3.5 and 5.2, with Isoflux® membranes showing higher values. The lifespan of microfiltered milk was extended to 10 days in the absence of heat treatment.     

Polypropylene membranes modified with interpenetrating polymer networks for the removal of chromium ions

Polypropylene (PP) membranes incorporating poly[(ar‐vinylbenzyl) trimethylammonium chloride] P(ClVBTA), and poly[sodium (styrene sulfonate)] P(SSNa) were modified via an “in situ” radical polymerization synthesis. Two methods were used for impregnation of the reactive solution: pressure injection and plasma superficial activation with argon gas. The following conditions were varied: the monomer concentrations, number of injections, and cross‐linked concentration. The modified polypropylene membranes were then characterized using scanning electron microscopy/energy dispersive X‐ray spectroscopy, Fourier transform‐infrared spectroscopy, electrokinetic potential, and Donnan dialysis for the chromium ions transport. The modified membranes exhibited a hydrophilic character with a water uptake capacity between 15% and 20% and a percent modification between 2.5% and 4.0%. This was compared with the results of an unmodified polypropylene membrane as the blank and the mentioned polypropylene membrane has not the capacity to uptake water because this kind of material is highly hydrophobic. Hexavalent chromium ions were efficiently transported by the modified membranes containing P(ClVBTA) via a plasma method and it achieved 59.2% extraction at pH 9.0 using a 1‐mol L^?1 NaCl extraction agent. Therefore, unmodified polypropylene membrane shows an extraction percentage close to 10% from the hexavalent chromium ions at pH 9.0. In the same way, the trivalent chromium transport using membranes modified with P(SSNa) achieved 49.0% extraction at pH 2.0 using 1 × 10^?1 mol L^?1 HNO₃ and 1 mol L^?1 NaCl as the extraction agents. Moreover, the unmodified polypropylene membrane reached a value close to 10% from the trivalent chromium ions using 1 × 10^?1 mol L^?1 HNO₃ and 1 mol L^?1 NaCl. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41953.     

Polypropylene composite hollow fiber ultrafiltration membranes with an acrylic hydrogel surface by in situ ultrasonic wave-assisted polymerization for dye removal

In this study, polypropylene composite hollow fiber membrane with an acrylic hydrogel layer was fabricated successfully by in situ ultrasonic wave-assisted polymerization. The ultrasonic irradiation can significantly improve the grafting efficiency of acrylic acid on the membrane surface. The modified membranes were characterized on the basis of physicochemical characteristics, permeation performance and antifouling property. The results revealed that the pure water flux of modified membranes was significantly increased when the graft density was lower than 0.82 mg cm⁻², due to the improvement of hydrophilicity. Interestingly, the optimized membrane PPM1.49 could efficiently remove organic dyes from aqueous solution, showing retentions of 99.5 and 98.7% to Congo red and methylthionine chloride, respectively. Meanwhile, its flux recovery ratio was elevated from 68.0 to 92.0% using bovine serum albumin aqueous solution as a foulant compared with the pristine membrane. These promising results indicate that modified membranes developed in this study are potentially applicable for dye removal from wastewater. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47099.     

Membrane functionalization using bisamide-based organic frameworks for molecular weight cutoff reduction

Functional polymers or copolymers have been added to separations membranes by incorporating them in the membrane dope prior to casting, by in situ polymerization, and by postsynthesis surface modification of existing membranes. Here, a postsynthesis membrane functionalization that targeted decreasing the molecular weight cutoff (MWCO) and increasing the hydrophilicity without significantly decreasing the operating flux was studied. Hybrid bisamide molecules with added amine and carboxylic acid functionalities as end groups were synthesized to form a selective layer on membrane surface via covalent attachment to the membrane. Fourier transform infrared spectroscopy analysis showed the functional groups corresponding to bisamide molecules were present on modified membranes. Furthermore, modified membranes displayed MWCO of 400 Da as compared to 1000 Da MWCO of unmodified membranes, along with an increase in the hydrophilicity of modified membranes. Modified membranes showed an improvement in divalent salt rejection and percent flux recovered after reverse-flow filtration as compared to unmodified membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48327.     

Structure and ionic conductivity of a series of di‐o‐butyrylchitosan membranes

Di‐o‐butyrylchitosan was prepared by reacting chitosan with butyric acid anhydride in the presence of perchloric acid as a catalyst. ¹³C‐NMR and IR spectra of the modified chitosan suggested that both hydroxyl groups, at the C‐6 and C‐3 positions, in the chitosan molecules were substituted. The maximum degree of substitution was found to be less than 28%. The results of X‐ray diffractograms revealed that, in comparison with the unmodified chitosan membrane, the crystallinity of di‐o‐butyrylchitosan membranes was remarkably decreased. Meanwhile, it was also observed that the swelling indices of modified membranes were increased significantly in direct proportion to the degree of substitution. Thermogravimetric analysis indicated that the modified membranes exhibited a slightly increased thermal stability compared to the unmodified membrane. The ionic conductivity of di‐o‐butyrylchitosan membranes after hydration was investigated using impedance spectroscopy. Compared to the unmodified chitosan membrane, the hydrated di‐o‐butyrylchitosan membrane with a relatively high degree of the substitution showed an increased ionic conductivity of more than one order of magnitude. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2309–2323, 2004     

Influence of metal salts in reaction medium on performance enhancement of novel aliphatic–aromatic-based polyamide thin-film composite osmosis membranes

In this study, we report an easy and novel way to develop high flux aliphatic–aromatic-based thin-film composite (TFC) polyamide osmosis membranes by addition of inorganic metal salts with amine reactants in the reaction system of polyethylene imine (PEI) and 1,3-benzene dicarbonyl chloride. Inorganic metal salts like CuSO₄, NiSO₄, MgSO₄, and Al₂(SO₄)₃ added to block some of the amine groups of PEI through complexation which in turn changes the polycondensation reaction kinetics of amine acid chloride reaction. The prepared membranes were characterized using water contact angle and atomic force microscopy studies and the performances were evaluated both in reverse osmosis and forward osmosis mode. In presence of metal salts in reaction interface, the performance of TFC membranes was greatly enhanced and the optimum metal salt concentration was identified for individual metal salts for maximum performance enhancement. The effects of different anions for same metal ion and different molecular weight of PEI were evaluated on composite polyamide membrane performances. Water permeability (flux) of 63.48 L m^?2 h^?1 was achieved upon inorganic salt addition compared to the unmodified TFC membranes with flux of 42.1 L m^?2 h^?1 at similar salt rejection of ~95%. Based on the new findings, a conceptual model was proposed to explain the role of metal ion in amine solution on the resulting characteristics of aromatic–aliphatic type polyamide–polysulfone composite membrane.     

Fouling control in sugarcane juice ultrafiltration with surface modified polysulfone and polyethersulfone membranes

Commercial 50 and 100 kD polyethersulfone (PES) and polysulfone (PS) ultrafiltration membranes were surface modified by UV photografting of poly(ethylene glycol) methacrylate (PEGMA) monomer. The modified membranes were characterized by the degree of grafting, water flux and molecular weight cutoff (MWCO) rating. The flux and fouling of the modified and unmodified membranes were examined with sugarcane juice and its polysaccharide fraction. Under the conditions of this study, the modified membranes displayed a low degree of grafting (26-36 μg/cm²), which was independent of the UV exposure duration; however, both membrane water flux and MWCO rating were affected by the irradiation time. In the best case, the modified membranes exhibited lower fouling with sugarcane juice; furthermore, the propensity to foul also decreased. More significantly, juice flux recovery was almost complete for successive UF-cleaning cycles.     

Recovery of microbial polysaccharides from fermentation broths by microfiltration on ceramic membranes

This paper investigates the extraction of microbial polymers (polysaccharides) from fermentation broths of Sinorhizobium meliloti M5N1CS using crossflow filtration through ceramic membranes of various pore sizes from 0.1 to 0.8 µm. The duration of fermentation was set at 70 h in order to maximize the production of high molecular weight polysaccharides (average 2 × 10⁵ Da). The 0.1 µm membrane underwent rapid fouling and was found inadequate for this application. For the other membranes, the sieving coefficients decreased from 95% to about 20% in 90 min, at a slower rate than the permeate flux. The largest permeate and mass fluxes were obtained with the 0.5 µm membrane (18.5 × 10⁻⁶ m s⁻¹ and 20 × 10⁻⁶ gm⁻²s⁻¹). Increasing the fluid velocity from 3 to 6 m s⁻¹ increased both the permeate flux and sieving coefficients, while raising the transmembrane pressure from 50 kPa to 100 kPa increased the flux slightly but decreased the sieving coefficient. Polysaccharide extraction will be maximized by operating at high velocities and low transmembrane pressure (TMP) which may require cocurrent recirculation of the permeate. Experiments with cell‐free solutions showed that the permeate flux is mostly limited by the bacterial layer deposited on the membrane while the presence of cells has a positive effect on the sieving coefficient. Irreversible fouling due to polymer adsorption on the membrane decreased with increasing pore size and velocity but increased strongly with TMP. © 1999 Society of Chemical Industry     

Crosslinked PVDF-HFP-based hydrophobic membranes incorporated with CNF for enhanced stability and permeability in membrane distillation

Over the past decades, numerous materials have emerged as promising amenities for the fabrication of novel membranes. The current study gives insight into a modest and effective method to fabricate a crosslinked poly-vinylidene fluoride-co-hexafluoropropylene membrane with better mechanical properties and permeability for desalination. Poly-vinylidene fluoride-co-hexafluoropropylene membrane was grafted with crosslinked collagen to enhance direct contact membrane distillation used for desalination. Stiffness, rigidity and mechanical properties of the membrane were intensified by incorporating collagen (extracted from eggshells) into the membrane matrix, with glutaraldehyde crosslinkers. Furthermore, to improve water vapor diffusion, immobilized carbon nanofibers (CNF) were integrated in the membrane, casted via phase inversion technique with an optimized controlled approach. The permeate flux of CNF incorporated membrane was as high as 8 LMH, 18% higher than the unmodified poly-vinylidene fluoride-co-hexafluoropropylene membrane at 60 °C, besides minimal salt leakage. The properties of the modified membrane were characterized from its contact angle, morphological structure, surface roughness, dynamic mechanical properties, and water flux. The overall performance of the modified membranes was better than the virgin membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48021.     

Treatment of Oily Waste Water Using Low-Cost Ceramic Membrane: Flux Decline Mechanism and Economic Feasibility

Abstract

This work addresses the applicability of different membrane pore blocking models for the prediction of flux decline mechanisms during dead end microfiltration (MF) of stable oil-in-water (o/w) emulsions using relatively low-cost ceramic membranes. Circular disk type membranes (52.5 mm diameter and 4.5 mm thickness) were prepared by the paste method using locally available low-cost inorganic precursors such as kaolin, quartz, calcium carbonate, sodium carbonate, boric acid, and sodium metasilicate. Characterization of the prepared membrane was done by SEM analysis, porosity determination, and pure water permeation through the membrane. Hydraulic pore diameter, hydraulic permeability, and hydraulic resistance of the membrane was evaluated as 0.7 µm, 1.94 × 10^?6 m³/m²·s·kPa and 5.78 × 10¹¹ m²/m³, respectively. The prepared membrane was used for the treatment of synthetic stable o/w emulsions of 40 and 50 mg/L crude oil concentration in batch mode with varying trans-membrane pressure differentials ranging from 41.37 to 165.47 kPa. The membrane exhibited 96.97% oil rejection efficiency and 21.07 × 10^?6 m³/m²·s permeate flux after 30 min of experimental run at 165.47 kPa trans-membrane pressure for 50 mg/L oil concentration. Different pore blocking, models such as complete pore blocking, standard pore blocking, intermediate pore blocking and cake filtration were used to gain insights into the nature of membrane fouling during permeation. The observed trends for flux decline data convey that the decrease in permeate flux was initially due to intermediate pore blocking (during 1 to 10 minutes of experimental run) followed with cake filtration (during 10 to 30 minutes of experimental run). Based on retail prices of the inorganic precursors, the membrane cost was estimated to be 130 $/m². Finally, preliminary process economic studies for a single stage membrane plant were performed for the application of the prepared membrane in industrial scale treatment of o/w emulsions. A process economics study inferred that the annualized cost of the membrane plant would be 0.098 $/m³ feed for treating 100 m³/day feed with oil concentration of 50 mg/L.     

Plasma Polymerization Modified Polyvinylidene Fluoride (PVDF) Membrane Development and Characterization for Degumming of Soybean Oil

Unmodified and surface‐modified polyvinylidene fluoride (PVDF) membranes were tested for their ability to degum soybean crude oil and crude oil miscellas. The membrane was modified with 1,1,1,3,3,3‐hexafluoro‐2‐propanol or hexamethyldisiloxane (HMDSO) by radio‐frequency plasma polymerization at 10–100 W glow discharge power and 1–30 min contact time. The membranes were characterized by contact angle measurements, attenuated total reflectance Fourier transform infrared spectroscopy, atomic force microscopy, and scanning electron microscopy. Modification of the PVDF membrane with HMDSO at 60 W power for 5 min increased the interfacial free energy between water and solid surface from 30 ± 2 to 64 ± 2 mJ/m². This membrane was tested for permeate flux and phospholipid rejection with crude oil and different concentrations of miscella. Although formation of the polymer film on the membrane tended to decrease membrane pore size, the modified membrane had an oil flux as good as the unmodified membrane did. In addition, the modified‐membrane improved the phospholipid rejection and removed 76 % of the phospholipids from the crude oil and 81–90 % of the phospholipids from crude oil miscellas.     

Fabrication of antifouling membranes by blending poly(vinylidene fluoride) with cationic polyionic liquid

Membrane fouling problem is now limiting the rapid development of membrane technology. A newly synthesized cationic polyionic liquid (PIL) [P(PEGMA-co-BVIm-Br)] was blended with poly(vinylidene fluoride) (PVDF) to prepare antifouling PVDF membranes. The PVDF/P(PEGMA-co-BVIm-Br) exhibited an increased surface hydrophilicity, the water contact angle was reduced from 77.8° (pristine PVDF) to 57.9°. More porous membrane structure was obtained by adding PIL into the blending polymers, as high as 478.0 L/m²·h of pure water flux was detected for the blend PVDF membrane in comparison with pristine PVDF (17.2 L/m²·h). Blending of the cationic PIL with PVDF gave a more positive surface charge than pristine PVDF membrane. Blend membranes showed very high rejection rate (99.1%) and flux recovery rate (FRR, 83.0%) to the positive bovine serum albumin (BSA), due to the electrostatic repulsion between the membrane surface and proteins. After three repeated filtration cycles of positive BSA, the blend PVDF membranes demonstrated excellent antifouling performance, the permeation flux of the membranes was recovered very well after a simple deionized water washing, and as high as 70% of FRR was obtained, the water flux was maintained at above 350 L/m²·h. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48878.     

Preparation and characterization of carbon microfiltration membrane applied to the treatment of textile industry effluents

Two tubular carbon microfiltration membranes have been prepared using mineral coal powder under similar conditions onto graphite supports made from carbon powder of 25 and 44 µm and having a porosity and mean pore diameter of 34% and 37% and 1.7 and 3.0 µm, respectively. The mean pore diameters were of 0.5 and 0.8 µm, respectively.

The performances depend on the membrane pore diameter. Particularly, the membrane presenting the largest pore size reached a stabilized permeate flux at 1 bar of 150 L/h.m² against 4.5 L/h.m² for the membrane of 0.5 µm. However, both membranes showed similar efficiency in term of pollutant removal, which was found independent of transmembrane pressure.     

Effects of simultaneous chemical cross-linking and physical filling on separation performances of PU membranes

The novel modified polyurethane (PU) membranes were prepared by β-cyclodextrin (CD) cross-linking and SiO₂/carbon fiber filler, simultaneously. The structures, thermal stabilities, morphologies, and surface properties were characterized by FTIR, TGA, SEM, and contact angle. The results showed that the addition of inorganic particles increased the thermal stabilities of PU membranes. The modified PU membranes possessed more hydrophobic surfaces than pure PU. In the swelling investigation, PU and its modified membranes were swelled gradually with increasing phenol content in the mixture. The membranes modified by CD cross-linking (PUCD) demonstrated the highest swelling degree. Pervaporation (PV) performances were investigated in the separation of phenol from water. Three kinds of modified membranes obtained better permeability and selectivity than PU membranes. With the feed mixture of 0.5 wt% phenol at 60 °C, the modified PU membrane by CD cross-linking and SiO₂ filler (PUCD-S) obtained the total flux of 5.92 kg μm m^?2 h^?1 which was above doubled that of PU (2.90 kg μm m^?2 h^?1). The modified PU membrane by CD cross-linking and carbon fiber filling (PUCD-C) obtained the separation factor of 51.31 which was nearly tripled that of PU (17.72). The PUCD membranes showed both better permeability and selectivity than the pure PU membranes. The increased phenol content induced an increased separation factor of PUCD and PU, but a decreased selectivity of PUCD-S and PUCD-C. The methods of CD cross-linking and inorganic particle filling were effective to develop the overall separation performances, greatly.     

CRITICAL FLUX DETERMINATION IN ULTRAFILTRATION OF WASTEWATER FROM A FOOD INDUSTRY BY OPTIMIZATION METHOD

Two ultrafiltration membranes with different geometries (spiral polymeric and tubular ceramic) but similar cutoffs were used to treat wastewater from a food industry. Hydrodynamic conditions were optimized by statistical methods as a strategy to get more accurate values of the critical parameters and then to produce higher water flux and minimization of membrane fouling. The validation of the optimization method was obtained by experimental critical flux determination at critical parameters. Membrane fluxes revealed significant differences during filtration. The polymeric membrane showed an optimal flux of 45.60 Lh^?1 m^?2 at 3.21 bar while operating at a stable time of 11.61 h, whereas optimal flux of the ceramic membrane was 32.43 Lh^?1 m^?2 at 3.98 bar for 16.03 h. Experimental critical flux values were only slightly lower than optimal fluxes for both membranes, showing the validity of the statistics models applied. Negligible osmotic pressure was found on the two membranes at critical flux parameters, indicating irreversible fouling for both cases. The polymeric membrane revealed strong fouling behavior and the ceramic membrane showed a weak form; the flux decline occurred first in the polymeric membrane, whereas the ceramic membrane exhibited high stability during the filtration operations. A high degree of purification of wastewater was obtained by this membrane at critical flux conditions.