Permeate Flux Values Research Articles

Thorium Recovery with Crown Ether–Polymer Composite Membranes

Thorium is a weak radioactive element, but the control of its concentration in natural aqueous systems is of great interest for health, because it is a toxic heavy metal. The present paper presents the recovery of thorium from diluted synthetic aqueous systems by nanofiltration. The membranes used for the nanofiltration of systems containing thorium species are composites containing 4′-Aminobenzo-15-crown-5 ether (ABCE) and sulfonated poly–etherether–ketone (sPEEK). The composite membranes (ABCE–sPEEK) were characterized by scanning electron microscopy (SEM), energy-dispersive X–Ray spectroscopy (EDAX), thermal analysis (TG and DSC), and from the perspective of thorium removal performance. To determine the process performance, the variables were the following: the nature of the composite membrane, the concentration of thorium in the aqueous systems, the rotation speed of the stirrer, and the pressure and the pH of the thorium aqueous system. When using pure water, a permeate flux value of 12 L·m−2 h−1 was obtained for the sPEEK membrane, and a permeate flux value of up to 15 L·m−2 h−1 was obtained for the ABCE–sPEEK composite membrane. The use of mechanical stirring, with a propeller stirrer, lead to an increase in the permeate flux value of pure water by about 20% for each of the studied membranes. Depending on the concentration of thorium and the pH of the feed solution, retentions between 84.9% and 98.4% were obtained. An important observation was the retention jump at pH 2 for the ABCE–sPEEK composite membrane. In the paper, a thorium ion retention mechanism is proposed for the sPEEK membrane and the ABCE–sPEEK composite membrane.

Membrane fouling in integrated forward osmosis and membrane distillation systems – A review

With the increase in water consumption, especially by the industrial and agricultural sectors, more strategies capable of increasing the recovery and reuse of water resources have been sought. An example of technology that assists in this challenge is membrane separation processes. However, systems that use this type of separation may be limited by the phenomenon of fouling. Integrated systems such as forward osmosis (FO) with membrane distillation (MD) have several advantages, such as obtaining a high-quality permeate from raw wastewater, the constant regeneration of the draw solution, which assists in continuous operation, and the possibility of association with biological tanks that enable nutrients recovery. However, these systems face limitations related to low flux values caused by membrane fouling. Therefore, the present review seeks to study fouling in integrated FO-MD systems to understand the main challenges of applying this technology and achieving higher permeate flux values. From the most recent studies, many strategies are being evaluated, such as different membrane materials, deposition of antifouling materials on membrane surface, feed temperature, draw solution substances, concentration and temperature, use of spacers and new modules configurations. That way, the low flux from those systems may be bypassed, enabling FO-MD systems scale up.

Preparation and characterization of oxygen‐functionalized graphene‐doped polyvinylidene fluoride ultrafiltration membranes

AbstractTo separate the oil/water mixtures, polyvinylidene fluoride (PVDF) nanofiber mats were produced using electrospinning. Additionally, PVDF films were made using the solvent evaporation method, and the effectiveness of their separation was evaluated against that of nanofiber mats. By choosing oxygen‐functionalized graphene (with HNO3) as a nano reinforcement, the hydrophobic properties of the PVDF materials made using both techniques were transformed into hydrophilic ones. It has been determined how the characteristics of the solution (viscosity, conductivity, molecular weight, surface tension, and contact angle) relate to the diameter of the nanofiber. Fourier transform infrared spectroscopy‐attenuated total reflection (FT‐IR/ATR), x‐rays diffraction (XRD), scanning electron microscope, thermogravimetric analyses (TGA)/DTG, and differential scanning calorimetric (DSC) have been used to study the chemical and crystal structures, morphology, and thermal behavior of PVDF materials. The addition of oxygen‐functionalized graphene was found to cause a peak in the PVDF composites' FT‐IR/ATR spectrum, roughly in the wavenumber 1400 cm−1, which was identified as the C‐OH bending vibration. Together with the shift in peak strengths, the lack of a discernible shift in the PVDF peak location in the XRD patterns indicates that the addition of oxygen‐functionalized graphene has caused a phase transition in the PVDF in the semi‐crystal structure. Surface hydrophobicity has also been measured using contact angle measurements. The addition of oxygen‐functionalized graphene has been seen to decrease the PVDF's contact angle, resulting in the development of a hydrophilic characteristic. These PVDF‐based materials' oil/water separation capabilities have also been evaluated. PVDF composite films were not as effective as PVDF nanofiber mats with oxygen‐functionalized graphene in the studies to separate the oil/water mixtures. The permeate flux value was determined to be 240 Lm−2 h−1, and the oil/water separation efficiency of nanofibers containing 10% (m/m) PVDF534000 combined with oxygen‐functional graphene was found to be 99%.

Surface Modification of a Zeolite Microfiltration Membrane: Characterization and Application to the Treatment of Colored and oily Wastewaters

Membrane-based technologies used for water treatment can be an excellent alternative to handle wastewater including both conventional and emerging pollutants as they can provide technological (e.g., high quality of treated water) and economic (e.g., small footprint and low unit cost of production) advantages over other water treatment processes. Recently, low cost ceramic membranes fabricated from natural resources like kaolinitic clay, bentonite clay, phosphate are increasingly used owing to their low-cost starting materials, low sintering temperature and their excellent additional properties. Moreover, the modification of the surface by grafting process provides membranes appropriate for low UF process (dp < 10 nm) and suitable for micropollutants removal at relatively high permeate flux value which can be maintained during filtration due to antifouling characteristics of the UF active layer. In this work, the surface of microfiltration membranes made from natural zeolite was chemically modified by grafting with 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane molecule named PFAS. Various characterization methods and techniques, including scanning electron microscopy (SEM), mercury porosimetry, FTIR, TGA, and contact angle, were used to check the properties of the membranes surface before and after grafting. The grafted membranes pore size and porosity were reduced, as proved by SEM images. The determination of the water permeability shows a reduction from 1218 L.h−1.m−2.bar −1 to 204 L.h−1.m−2.bar −1 which confirm the surface densification. The application of the grafted membrane to the treatment of Indigo Blue (IB) colored solution and oily wastewater was investigated to evaluate the performances of this membrane in terms of permeate flux and pollutants retention. The filtration results revealed a good retention of color and oil, exceeding 95% for both parameters. Therefore, it is interesting to recommend this new low-cost membrane for the treatment of industrial wastewater containing recalcitrant pollutants such as color. The study of the effect of the treated colored solution on plant growth, shows that the presence of some residual nutrients required for crops growth, might make the IB treated water beneficial for irrigation purposes.

Multi-dimensional parametric study for enhancing Brackish Water Reverse Osmosis membrane performance suited for desalination of low salinity feeds.

Reverse osmosis (RO) effectively provides clean drinking water. Different RO membrane types are tailored to treat saline water feeds with varying characteristics. In the context of low brackish water feeds, the objective is to remove only a minimal excess of salinity through the membrane. Our study introduces a method of membrane post-treatments capable of achieving controlled salt rejection while concurrently enhancing permeate flux, which is vital for achieving effective and energy-efficient desalination of low brackish water. The post-treatments were conducted on our in-house-developed membranes using aqueous solutions of N,N-Dimethylformamide and glycerol for different drying times at the coupon level. The process was scaled up at the module level, allowing us to assess its potential for commercial application. At the coupon level, the permeate flux increased significantly from 3.7 ± 0.9 to 10.6 ± 0.2L/m2·h·bar, while the salt rejection decreased from 95.6 ± 1% to 70.5 ± 1% when measured with a feed of 2,000 ppm NaCl concentration. At the module level, we observed a higher flux of 12.8L/m2·h·bar, alongside a salt rejection of 55.5% with a similar feed. Varying post-treatment parameters at the coupon level allowed us to attain the desired salt rejection and permeate flux values. Physical changes in both pristine and post-treated membranes, including polymer swelling, were observed without chemical alterations, enhancing our understanding of the post-treatment effect and its potential for broader commercial use. PRACTITIONER POINTS: Post-treatment of RO membranes enhances flux. Physical structuring through polymer swelling was observed with the chemical structure unaltered. Post-treatment of RO opens doors for broader energy-efficient desalination application.

Development of metakaolin-based geopolymeric asymmetric membrane for oil-in-water emulsion microfiltration

This study investigated the potential application of geopolymeric material for the separation of oil-in-water emulsions in wastewater treatment. For the first time, an asymmetric membrane made of geopolymers was developed for this specific separation process. The performances of the geopolymeric membrane in oil separation were compared with those obtained by a commercial ceramic membrane. The study also aimed at exploring the effects of emulsion formulation and emulsion properties (surfactant type and concentration, pH, and zeta potential) and membrane parameters (surface charge and material) on permeate volumetric flux and chemical oxygen demand (COD) rejection. Emulsions were prepared using 3% (w/v) dodecane oil in distilled water, with surfactant concentrations of 1x and 10x critical micelle concentration (CMC) and three surfactants of different nature (Oleth-10, Brij 76, and CTAB) at pH values of 2, 5, and 8. Results showed that for the best operating conditions of the geopolymeric membrane, initial and final permeate flux values of 42 and 26 L h−1 m−2, respectively, were achieved. COD rejection values ranged from 95.0 to 99.4% using the geopolymeric membrane thus indicating a very similar behavior between geopolymeric and ceramic membranes. These findings suggest that geopolymers are promising to produce membranes for oil-in-water emulsion microfiltration, promoting an interesting alternative for the treatment of industrial wastewater more sustainable in terms of environmental effects and costs compared to ceramic membranes.

Equivalence assessment of creams with quali-quantitative differences in light of the EMA and FDA regulatory framework

EMA and FDA are upgrading guidelines on assessing the quality and the equivalence of topically applied drug products for developing copies of originator products and supporting post-marketing variations. For topical products having remarkably similar composition, both EMA and FDA accept the equivalence on the bases of the comparison of rheological properties and in vitro drug release constant (k) and skin permeation flux (J) values, instead of clinical studies. This work aims to evaluate the feasibility to expand this approach to variations of the composition of complex semi-solid preparations. Ibuprofen (IB) creams at two different strengths (i.e., 1 % and 10 %) were used as a model formulation. Two formulative changes were performed: (a) the addition of the humectant to simulate a minor post-marketing variation; (b) the substitution of the emulsifying system to simulate a major one. These variations impacted only in 1 % IB formulations where both the equivalences of rheological data and J-values failed. At the highest concentration, the presence of IB crystals broke down the differences in rheological patterns and lead the IB thermodynamic activity at the maximum figuring out an overlapping of the J-values. Such data suggest the combination of these studies, which are thought mainly for the development of copies, could be also applied to the management of post-marketing variations that involve product composition.

CdO-Nanografted Superhydrophobic Hybrid Polymer Composite-Coated Cotton Fabrics for Self-Cleaning and Oil/Water Separation Applications.

The current study presents a simple and cost-competitive method for the development of high-performance superhydrophobic and superoleophilic cotton fabrics coated with cadmium oxide/cerotic acid (CdO/CE)-polycaprolactone (PCL)- and cadmium oxide/stearic acid (CdO/ST)-polycaprolactone-grafted hybrid composites. X-ray powder diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy are used to characterize the CdO/CE-PCL and CdO/ST-PCL and polycaprolactone-modified cotton fabrics. Using an optical contact angle meter, the wetting behavior of corrosive liquids such as coffee, milk, tea, water dyed with methylene blue, strong acids (HCl), strong alkali (NaOH), and saturated salt solution (NaCl) on the CdO-CE/ST/PCL-modified cotton fabrics is assessed as well as the durability of CdO-CE/ST/PCL-modified cotton fabrics in corrosive liquids. Data obtained from the oil-water separation experiment indicate remarkable separation efficiency with oil purity values of ≥99.97 wt %, and high permeation flux values of up to 11,700 ± 300 L m-2 h-1 are observed for surfactant-stabilized water-in-oil emulsions via a gravity-driven technique. From the data obtained, it is concluded that the nano-CdO-grafted superhydrophobic hybrid polymer composite-coated cotton fabrics (CdO-ST/(CE)/PCL/CFs) can be utilized for self-cleaning and oil/water separation applications.

Effects of the Applied Potential on the Performance of Polysulfone Membranes Functionalized with Sulfonated Polyether Ether Ketone Polymers.

The global water crisis growth has led to a tremendous increase in membrane technology research. Membranes are favored over many other technologies for water treatment because, in principle, they require no chemical additives and can be used isothermally at low temperatures. Membranes that can reject contaminants and salts, produce adequate permeate flux values, and require minimal cleaning are highly demanded. However, most synthesized membranes on the market have associated problems, such as membrane fouling; inverse relationships between flux and solute rejection; and the high cost of synthesis, operation, and maintenance. Therefore, there is a continuied need to produce membranes with properties that make them able to sustain flux and selectivity over time. This research study focused on increasing the surface charge and hydrophilicity of polysulfone (PSf) membranes by incorporating sulfonate-functionalized poly-ether-ether-ketone (SPEEK) into PSf/N-Methyl-2-pyrrolidone (PSf/NMP) membranes. The sulfonation of the PEEK provided a net increase in negative charge on the surface of the membranes that enabled charge repulsion to take place, thus increasing the rejection of ions. In this project, the effect of the applied potential on the performance of SPEEK: PSf/NMP membranes was evaluated. The characterization of the as-synthesized membranes was carried out using the surface's structure and morphology, contact angle, and zeta potential. Furthermore, a voltage of 1.5 V was applied to the membranes in the presence of various salts (sodium chloride, calcium chloride, and potassium chloride salts) to evaluate the effects of the applied potential on solute rejection. It was found that both the permeability and the selectivity of the membranes increased when the voltage was applied. The obtained results indicate that incorporating SPEEK into PSf/NMP membranes increased the hydrophilicity of the membranes, and under the applied voltage, the incorporation allowed it to function as an electrodialysis process that is capable of removing ions from water bodies by utilizing the charge repulsion of ions.

Removal of Cr(VI) from tanning wastewater using chitosan-SDS complexes in PEUF: Optimization and analysis via response surface methodology

In this study, we addressed the removal of hexavalent chromium (Cr(VI)), a highly toxic and soluble anionic heavy metal, using enhanced ultrafiltration (UF). The objective was to eliminate Cr(VI) species with molecular weights beyond the retention capability of standard UF membranes and achieve their retention through the incorporation of polymers and polymer-surfactant complexes within the UF membrane. Chitosan, a cationic polymer, and sodium lauryl sulfate (SDS), an anionic surfactant, were used in this context. The Cr(VI) solution was subjected to ultrafiltration in a laboratory-scale membrane cell, and its removal was assessed spectrophotometrically. Polymer and surfactant structures were characterized using turbidity, electrical conductivity, SEM-EDX, and FTIR analyses. Experimental studies were conducted using the face-centered central composite design (CCD) of the response surface methodology (RSM) to determine optimal removal and permeate flux values, as well as to unveil the relationships between the studied factors and the resulting responses.The results revealed that 100 % of the Cr(VI) species were removed from wastewater in the chitosan-based polymer-enhanced ultrafiltration (PEUF) study. With the chitosan-SDS complex, a removal efficiency of 98.33 % was achieved in synthetic wastewater. The PEUF study employing chitosan and the chitosan-SDS complex yielded permeate flux values of 30.73 L/h/m2 and 53.89 L/h/m2, respectively. The optimized conditions obtained from the models were then applied to real wastewater obtained from a leather industry tanning process. In the case of chitosan and the chitosan-SDS complex, the Cr(VI) removal efficiencies in the real wastewater were 4.40 % and 98.33 %, respectively.

Using the Log Mean Temperature Difference (LMTD) and ε-NTU Methods to Analyze Heat and Mass Transfer in Direct Contact Membrane Distillation.

In direct contact membrane distillation (DCMD), heat and mass transfers occur through the porous membrane. Any model developed for the DCMD process should therefore be able to describe the mass transport mechanism through the membrane, the temperature and concentration effects on the surface of the membrane, the permeate flux, and the selectivity of the membrane. In the present study, we developed a predictive mathematical model based on a counter flow heat exchanger analogy for the DCMD process. Two methods were used to analyze the water permeate flux across one hydrophobic membrane layer, namely the log mean temperature difference (LMTD) and the effectiveness-NTU methods. The set of equations was derived in a manner analogous to that employed for heat exchanger systems. The obtained results showed that the permeate flux increases by a factor of approximately 220% when increasing the log mean temperature difference by a factor of 80% or increasing the number of transfer units by a factor of 3%. A good level of agreement between this theoretical model and the experimental data at various feed temperatures confirmed that the model accurately predicts the permeate flux values for the DCMD process.

Investigation of Different Pre-Treatment Techniques and 3D Printed Turbulence Promoter to Mitigate Membrane Fouling in Dairy Wastewater Module.

This study investigates the enhancement of dairy wastewater treatment using chemical and physical pre-treatments coupled with membrane separation techniques to reduce membrane fouling. Two mathematical models, namely the Hermia and resistance-in-series module, were utilized to comprehend the mechanisms of ultrafiltration (UF) membrane fouling. The predominant fouling mechanism was identified by fitting experimental data into four models. The study calculated and compared permeate flux, membrane rejection, and membrane reversible and irreversible resistance values. The gas formation was also evaluated as a post-treatment. The results showed that the pre-treatments improved UF efficiency for flux, retention, and resistance values compared to the control. Chemical pre-treatment was identified as the most effective approach to improve filtration efficiency. Physical treatments after microfiltration (MF) and UF showed better fluxes, retention, and resistance results than ultrasonic pre-treatment followed by UF. The efficacy of a three-dimensionally printed (3DP) turbulence promoter was also examined to mitigate membrane fouling. The integration of the 3DP turbulence promoter enhanced hydrodynamic conditions and increased the shear rate on the membrane surface, shortening filtration time and increasing permeate flux values. This study provides valuable insights into optimizing dairy wastewater treatment and membrane separation techniques, which can have significant implications for sustainable water resource management. The present outcomes clearly recommend the application of hybrid pre-, main- and post-treatments coupled with module-integrated turbulence promoters in dairy wastewater ultrafiltration membrane modules to increase membrane separation efficiencies.

Evaluation of a Hybrid Moving Bed Biofilm Membrane Bioreactor and a Direct Contact Membrane Distillation System for Purification of Industrial Wastewater.

Integrated wastewater treatment processes are accepted as the best option for sustainable and unrestricted onsite water reuse. In this study, moving bed biofilm reactor (MBBR), membrane bioreactor (MBR), and direct contact membrane distillation (DCMD) treatment steps were integrated successively to obtain the combined advantages of these processes for industrial wastewater treatment. The MBBR step acts as the first step in the biological treatment and also mitigates foulant load on the MBR. Similarly, MBR acts as the second step in the biological treatment and serves as a pretreatment prior to the DCMD step. The latter acts as a final treatment to produce high-quality water. A laboratory scale integrated MBBR/MBR/DCMD experimental system was used for assessing the treatment efficiency of primary treated (PTIWW) and secondary treated (STIWW) industrial wastewater in terms of permeate water flux, effluent quality, and membrane fouling. The removal efficiency of total dissolved solids (TDS) and effluent permeate flux of the three-step process (MBBR/MBR/DCMD) were better than the two-step (MBR/DCMD) process. In the three-step process, the average removal efficiency of TDS was 99.85% and 98.16% when treating STIWW and PTIWW, respectively. While in the case of the two-step process, the average removal efficiency of TDS was 93.83% when treating STIWW. Similar trends were observed for effluent permeate flux values which were found, in the case of the three-step process, 62.6% higher than the two-step process, when treating STIWW in both cases. Moreover, the comparison of the quality of the effluents obtained with the analysed configurations with that obtained by Jeddah Industrial Wastewater Treatment Plant proved the higher performance of the proposed membrane processes.

Improved Subcutaneous Delivery of Ketoconazole Using EpiDerm and HSPiP Software-Based Simulations as Assessed by Cell Viability, Cellular Uptake, Permeation, and Hemolysis In Vitro Studies.

Ketoconazole (KETO) is the drug of choice to control local, systemic, and resistant types of fungal infections. Subcutaneous (sub-Q) delivery offers several benefits. The present study investigated the sub-Q delivery of KETO using HSPiP software based on optimized concentrations of dimethylacetamide (DMA) in binary solvents (DMA + water), in vitro cellular uptake (J774A.1) assays, cellular toxicity (L929), and in vitro hemolysis studies. Results showed that the estimated permeation coefficient (9.6 × 10-3 cm/h) and diffusion coefficient (3.9 × 10-3 cm2/h) of KETO (22.3 mg) in KF3 (300 mg of DMA + water) across EpiDerm were relatively higher as compared to the other formulations [KF1 (11.2 and 150 mg as KETO and DMA, respectively) and KF2 [(22.3 and 300 mg as KETO and DMA, respectively)] due to the increased content of DMA and KETO. HSPiP simulated and predicted the impact of constant and variable diffusion coefficients on the percent drug absorption across EpiDerm and the time needed to achieve equilibrium. The concentration-dependent diffusion coefficient fed into HSPiP predicted that the drug absorption and permeation values were linearly dependent on the square root of time. The HSPiP predicted permeation flux values from KF3, KF2, and KF1 across the EpiDerm were 4.07 × 10-6, 4.01 × 10-6, and 1.1 × 10-6 g/cm2/s, respectively, at respective D range values. The selected K30G (324 mOsm/Kg) showed an optimal pH (6.9) and minimum drug loss (0.01%) over a period of 1 month at room temperature. KG30 was found to be less toxic to normal L292 cells and caused maximum cytotoxicity to candida cells residing within infected macrophage cells (J774A.1 incubated for 24 h), which was attributed to the slow diffusion of K30G compared to DS (the drug solution with an equivalent concentration). KG30 elicited substantial internalization with candida albicans (MTCC 4748) compared to the control group (24 h). Lastly, in vitro hemolysis studies (1 and 5 μg/mL) corroborated the safety of K30G for sub-Q delivery. Therefore, this new formulation and approach for delivering KETO is a promising alternative to conventional products to control fungal infections and, thus, should be further studied in vivo.

Anti‐fouling performance of polyamide microfiltration membrane modified with surfactants

AbstractFouling is the main limitation in membrane separation processes. This phenomenon occurs by the adsorption/deposition of particles, colloids, or biomolecules on the membrane surface and it pores. This process can severely affect membrane performance due to the decrease in permeate flux, lifetime reduction, and selectively and separability changes. Studies have concluded that physicochemical superficial characteristics of membranes is a key for understanding and mitigating fouling. In this study, the surface of a commercial microfiltration membrane (MF) was modified with commercial surfactants and a biosurfactant to reduce fouling and improve its performance. Coated (MF‐SDS, MF‐CTAB, MF‐Tween80, and MF‐Rha) and uncoated membranes were characterized by Fourier‐transform infrared spectroscopy (FT‐IR), contact angle, and zeta potential. Microfiltration tests were performed by using Saccharomyces cerevisiae yeast suspensions as model fouling agent at different transmembrane pressures and feed flow rates. Interfacial analysis indicated that the adsorption of surfactants on the membranes' surface is responsible for significant changes in the membrane's hydrophilicity and superficial charges. Considering filtration of the model suspensions, the permeate flux values were increased for all coated membranes compared to the uncoated one. Long‐term experiments showed a high stability of the rhamnolipid adsorption on the membrane surface, proving its effectiveness in fouling reduction.

Use of ultrafiltration ceramic membranes as a first step treatment for olive oil washing wastewater

Olive oil is a food product in great demand throughout the world, its production generating large volumes of wastewater with a high organic load, where phenolic compounds are present. These compounds have outstanding antioxidant characteristics, so their recovery is of great interest. In this way, the treatment of these wastewaters should be based on reusing water and, at the same time, on recovering valuable compounds. Ultrafiltration with ceramic membranes (5, 15 and 50 kDa) is proposed as a first treatment step for olive oil washing wastewater (OOWW) from the continuous two-phase centrifugation process. The effect of cross flow velocity and transmembrane pressure was evaluated against permeate flux values and the removal of turbidity, colour, chemical oxygen demand (COD), sugars and the phenolic compounds recovery. The CFV had a great influence on the removal of colour and turbidity. COD rejection increased with increasing TMP, being the highest rejection obtained under the most extreme conditions. The rejection of phenolic compounds and sugars did not show great variation between conditions. The 50 kDa membrane was the one that presented the largest permeate flux decline and the lowest permeability recovery after the cleaning, confirming the great fouling that this membrane suffered. The 15 kDa membrane at the operating conditions of 3 m.s-1 and 3 bar was observed as a good option to eliminate much of the colour (72%) and turbidity (99%) and to reduce considerably the organic load (54%) without greatly affecting the concentration of phenolic compounds (rejection of 21%) for future recovery.

Kenics Static Mixer Combined with Gas Sparging for the Improvement of Cross-Flow Microfiltration: Modeling and Optimization.

The use of membrane filtration as a downstream process for microbial biomass harvesting is hampered due to the low permeate flux values achieved during the microfiltration of fermentation broths. Several hydrodynamic methods for increasing permeate flux by creating turbulent flow patterns inside the membrane module are used to overcome this problem. The main goal of this study was to investigate the combined use of a Kenics static mixer and gas sparging during cross-flow microfiltration of Bacillus velezensis IP22 cultivation broth. Optimization of the microfiltration process was performed by using the response surface methodology. It was found that the combined use of a static mixer and gas sparging leads to a considerable increase in the permeate flux, up to the optimum steady-state permeate flux value of 183.42 L·m−2·h−1 and specific energy consumption of 0.844 kW·h·m−3. The optimum steady-state permeate flux is almost four times higher, whilst, at the same time, the specific energy consumption is almost three times lower compared to the optimum results achieved using gas sparging alone. The combination of Kenics static mixer and gas sparging during cross-flow microfiltration is a promising technique for the enhancement of steady-state permeate flux with simultaneously decreasing specific energy consumption.

A comparative study of community reverse osmosis and nanofiltration systems for total hardness removal in groundwater

In this research, the efficiency of reverse osmosis (RO) and nanofiltration (NF) treatment methods installed in the dry zone (Sri Lanka) were examined as a function of operation parameters, feed and product water quality, membrane type, user maintenance, and wastes handling. The quality of the feedwater varies as electrical conductivity (265–1329 mg/L), total hardness (97–318 mg/L as CaCO3) and fluoride (0.58–2.93 mg/L), often exceeding WHO or SLS tolerance limits. About 77% of the feedwater contains dissolved organic carbon (DOC) above 4.00 mg/L that requires control to avoid membrane fouling and other harmful effects. The salt rejection ratio, pressure flux and transmembrane pressure of the RO/NF membranes vary widely with the feedwater quality. The operation parameters of the membrane plants vary significantly; eight RO plants use low-pressure (0.5–1.0 MPa) similar to the NF pressure requirement, but they desalinate water at 95% salt rejection efficiency. Most RO membranes deviate (>50%) from the recommended transmembrane pressure and specific permeate flux values. However, such deviations are not observed in NF treatment plants. RO membranes remove solutes excessively, but post mineralization step is currently not practiced in the study area. The water recovery by the NF membranes is highest (>60%) compared to RO plants. The wastewater resulting from the NF plants is handled satisfactorily compared to RO-generated wastes. In the area examined, the salinity occurs due to water's permanent hardness. Therefore, NF membrane-based technology is suitable to desalinate groundwater in the dry zone (Sri Lanka).

Membrane-based Operations for the Fractionation of Polyphenols and Polysaccharides From Winery Sludges

The present work investigated the impact of ultrafiltration (UF) and nanofiltration (NF) membranes on the recovery and fractionation of polyphenolic compounds and polysaccharides from Sangiovese and Cabernet Sauvignon wine lees. A laboratory-made flat-sheet membrane in cellulose acetate (CA400-38) was used in the UF treatment of Sangiovese wine lees; three laboratory-made flat-sheet membranes in cellulose acetate (CA316, CA316-70, CA400-22) and a polyamide commercial membrane (NF90) were used in the NF treatment of Cabernet Sauvignon wine lees. All membranes were characterized in terms of hydraulic permeability and rejection toward references solutes; the performances of the membranes were measured in terms of productivity, fouling index, cleaning efficiency and retention toward target compounds.Experimental results indicated that all UF and NF membranes were effective in separating target compounds rejecting more than 92% of polysaccharides with polyphenols preferentially permeating through the membrane. The UF membrane rejected more than 40% of total polyphenols; rejections toward non-flavonoids and flavonoids were less than 25% and 12.5%, respectively.The laboratory-made NF membranes exhibited higher permeate flux values (of the order of 11–12 L/m2h) in comparison with the commercial NF membrane, despite the observed differences in the retention of specific solutes. Among the prepared membranes the CA316 showed a total rejection toward most part of non-flavonoids and flavonoids.The experimental results support the use of UF and NF processes in a sequential design to fractionate and refine phenolic compounds from winery sludge for the production of concentrated fractions with high antioxidant activities.

Chemical and mechanical stability of BCZY-GDC membranes for hydrogen separation

This work investigates, for the first time, the hydrogen permeation of BaCe0.65Zr0.20Y0.15O3-δ-Ce0.8Gd0.2O2-δ (BCZY-GDC) asymmetric membranes for 100 h, using wet 15% CO2 in Ar as sweep gas. In the same frame, ex-situ aging tests were performed for 100 h exposure at 750 °C in different atmospheres (H2, CO2, H2 + CO2), to evaluate the phase, microstructure, and mechanical long-term stability of this system. The thermal aging in H2-atmosphere leads to lower flexural strength caused by a microstructure embrittlement of the BCZY-GDC asymmetric membrane, due to chemical expansion/contraction of the GDC cell after the aging cycle. Indeed, micro-cracking of GDC grains, that decreases the composite hardness, is observed in symmetric (pressed pellet) membranes. The aging in CO2 causes a slightly increase in flexural strength values due to the formation of sub-micrometric Zr-doped ceria-BaCO3 phases at the expense of the perovskite. Higher hardness values related to the emerging of BaCO3 islands on the symmetric membrane surface were also recorded. In H2 + CO2 atmosphere (real testing condition), the membrane shows a slight decrease in flexural strength and hardness while no evident morphological or structural changes (except the BaCO3 formation in traces) were observed. This study highlights that promising and stable hydrogen permeation flux values can be recorded using the asymmetric configuration for 100 h, using wet 15% CO2 in Ar as sweep gas. Neither structural nor morphological modification of the membrane were detected after the testing.