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Clinical and immunological assays of white blood cells (WBCs) in human peripheral blood are of significance for disease diagnosis and immunological studies. However, separating WBCs from blood with high recovery and high purity remains challenging. In this study, by incorporating a pair of linearly tapered filter arrays, a crossflow filtration-based microfluidic chip was designed and fabricated for separation of WBCs from blood. The implementation of the linearly tapered filter arrays not only ensures a minimal and consistent flow through each sieve, but also achieves a high filtration ratio (~ 19). The validity and robustness of this straightforward design were substantiated through theoretical analysis, simulations, and model microparticle tests. The microfluidic chip achieved an almost perfect (> 99.2%) recovery and a ~ 20-fold enrichment of the targeted 8 μm particles (as surrogates for WBCs) from undesired 2 μm particles (as substitutes for red blood cells, RBCs) at flow rates ranging from 50 to 200 μL/min, irrespective of the filter array length and particle concentration. When applied to a twenty times diluted blood sample, the chip achieved a 96.6% recovery and 19.7-fold enrichment of WBCs, as well as a 95.0% removal of RBCs, at the optimal flow rate of 100 μL/min. With its simple design, cost-effectiveness, high recovery, substantial enrichment ratio, and considerable throughput, this chip offers an alternative solution that is potentially applicable to scenarios involving the separation of WBCs as well as other particles/cells. [ABSTRACT FROM AUTHOR]

The removal of persistent organic micropollutants (OMPs) from secondary effluent in wastewater treatment plants is critical for meeting water reuse standards. Traditional treatment methods often fail to adequately degrade these contaminants. This study explored the efficacy of a hybrid ozonation membrane filtration (HOMF) process using CeO2 and CeTiOx-doped ceramic crossflow ultrafiltration ceramic membranes for the degradation of OMPs. Hollow ceramic membranes (CM) with a 300 kDa molecular weight cut-off (MWCO) were modified to serve as substrates for catalytic nanosized metal oxides in a crossflow and inside-out operational configuration. Three types of depositions were tested: a single layer of CeO2, a single layer of CeTiOx, and a combined layer of CeO2 + CeTiOx. These catalytic nanoparticles were distributed uniformly using a solution-based method supported by vacuum infiltration to ensure high-throughput deposition. The results demonstrated successful infiltration of the metal oxides, although the yield permeability and transmembrane flow varied, following this order: pristine > CeTiOx > CeO2 > CeO2 + CeTiOx. Four OMPs were examined: two easily degraded by ozone (carbamazepine and diclofenac) and two recalcitrant (ibuprofen and pCBA). The highest OMP degradation was observed in demineralized water, particularly with the CeO2 + CeTiOx modification, suggesting O3 decomposition to hydroxyl radicals. The increased resistance in the modified membranes contributed to the adsorption phenomena. The degradation efficiency decreased in secondary effluent due to competition with the organic and inorganic load, highlighting the challenges in complex water matrices. [ABSTRACT FROM AUTHOR]

Key unresolved questions about particle separation mechanisms in suspensionfeeding fishes are identified and discussed, focusing on areas with the potential for substantial future discovery. The published hypotheses that are explored have broad applicability to biological filtration and bioinspired improvements in commercial and industrial crossflow microfiltration processes and microfluidics. As the first synthesis of the primary literature on the particle separation mechanisms of marine, estuarine, and freshwater suspension-feeding fishes, the goals are to enable comparisons with invertebrate suspension-feeding processes, stimulate future theoretical and empirical studies, and further the development of biomimetic physical and computational fluid dynamics models. Of the eight particle separation mechanisms in suspension-feeding fishes, six have been proposed within the past twenty years (inertial lift and shear-induced migration, reduction of effective gap size by vortices, cross-step filtration, vortical flow along outer faces of gill raker plates, ricochet filtration, and lateral displacement). The pace of discovery is anticipated to continue accelerating. Multidisciplinary collaboration and integration among biologists and engineers (including chemical, mechanical, biomedical, and filtration engineering) will result in new perspectives to identify patterns and potential unifying mechanisms across the breadth of suspension-feeding fish taxa, morphology, and function. [ABSTRACT FROM AUTHOR]

Treatment processes have been proposed that will utilize crossflow filtration to concentrate sludge waste streams at the Department of Energy's Hanford Site. Challenges associated with solid–liquid separation of the waste streams drive a necessary evaluation of available Hanford high level waste (HLW) filtration data. Limiting flux conditions during crossflow filtration are elucidated with the formation of a cake layer on the membrane surface. A mass transfer coefficient between the gel and bulk concentrations plays a critical role in determining filter flux. A correlation between the gel concentration and mass transfer coefficient is made to assist in determining filter performance of select HLW streams. As a process alternative to crossflow filtration, gravity settling of waste streams may be deployed as a solid–liquid separation technique. However, this results in a contrasting performance with the centrifuged solids concentration. A method was developed to estimate expected filtration and settling performance based on physical characterization data for Hanford tank waste samples. By assessing the estimated processing performance of HLW, technical support can be provided during flowsheet planning. [ABSTRACT FROM AUTHOR]

Key unresolved questions about particle separation mechanisms in suspension-feeding fishes are identified and discussed, focusing on areas with the potential for substantial future discovery. The published hypotheses that are explored have broad applicability to biological filtration and bioinspired improvements in commercial and industrial crossflow microfiltration processes and microfluidics. As the first synthesis of the primary literature on the particle separation mechanisms of marine, estuarine, and freshwater suspension-feeding fishes, the goals are to enable comparisons with invertebrate suspension-feeding processes, stimulate future theoretical and empirical studies, and further the development of biomimetic physical and computational fluid dynamics models. Of the eight particle separation mechanisms in suspension-feeding fishes, six have been proposed within the past twenty years (inertial lift and shear-induced migration, reduction of effective gap size by vortices, cross-step filtration, vortical flow along outer faces of gill raker plates, ricochet filtration, and lateral displacement). The pace of discovery is anticipated to continue accelerating. Multidisciplinary collaboration and integration among biologists and engineers (including chemical, mechanical, biomedical, and filtration engineering) will result in new perspectives to identify patterns and potential unifying mechanisms across the breadth of suspension-feeding fish taxa, morphology, and function.

From food- to analytical-grade products, the commercial exploitation of phycocyanin (PC) strongly depends on its degree of purity. In this study, we utilized a pilot-scale system (100 L working volume), based on serial tangential flow micro- and ultra-filtration (cut size 0.2 μm and 50 kDa, respectively) for the concentration and purification of PC extracted from a commercial strain of Arthrospira platensis. The process resulted in a PC recovery of around 54%, whilst the resulting solution had a concentration of 1.1 ± 0.2 mgPC mL−1, purity of 1 ± 0.2, and antioxidant activity of 84 ± 6 ppmascorbic-acid-equivalent. Various preservatives were evaluated in order to enhance the stability of aqueous PC solution at room temperature. The addition of 0.4% citric acid had no effect (half-life ~ 7 days), while the addition of 2.5% sodium chloride or 20% sucrose significantly increased half-life up to ~ 250 days. PC solutions underwent either spray- or freeze-drying, either with or without carrier (trehalose) addition. The obtained PC powders had up to twofold higher color values compared to a commercial sample. The spray-drying process negatively affected the purity and yield of the final product (10% and 50% less than freeze-drying, respectively). In summary, our results suggest that tangential flow filtration followed by freeze-drying has huge potential for the production of food-grade phycocyanin. [ABSTRACT FROM AUTHOR]

Robust cell retention devices are key to successful cell culture perfusion. Currently, tangential flow filtration (TFF) and alternating tangential flow filtration (ATF) are most commonly used for this purpose. TFF, however, suffers from poor fouling mitigation, which leads to high filtration resistance and product retention, and ATF suffers from long residence times and cell accumulation. In this work, we propose a filtration system for alternating tangential flow filtration, which takes full advantage of the fouling mitigation effects of alternating flow and reduces cell accumulation. We have tested this novel setup in direct comparison with the XCell ATF® as well as TFF with a model feed comprising yeast cells and bovine serum albumin as protein at harsh permeate to feed flow conditions. We found that by avoiding the dead‐end design of a diaphragm pump, the proposed filtration system exhibited a reduced filtration resistance by approximately 20% to 30% (depending on feed rate and permeate flow rate). A further improvement of the novel setup was reached by optimization of phase durations and flow control, which resulted in a fourfold extension of process duration until hollow fiber flow channel blockage occurred. Thus, the proposed concept appears to be superior to current cell retention devices in perfusion technology. [ABSTRACT FROM AUTHOR]

Research on the suspension-feeding apparatus of fishes has led recently to the identification of novel filtration mechanisms involving vortices. Structures inside fish mouths form a series of ‘backward-facing steps' by protruding medially into the mouth cavity. In paddlefish and basking shark mouths, porous gill rakers lie inside ‘slots’ between the protruding branchial arches. Vortical flows inside the slots of physical models have been shown to be important for the filtration process, but the complex flow patterns have not been visualised fully. Here we resolve the three-dimensional hydrodynamics by computational fluid dynamics simulation of a simplified mouth cavity including realistic flow dynamics at the porous layer. We developed and validated a modelling protocol in ANSYS Fluent software that combines a porous media model and permeability direction vector mapping. We found that vortex shape and confinement to the medial side of the gill rakers result from flow resistance by the porous gill raker surfaces. Anteriorly directed vortical flow shears the porous layer in the centre of slots. Flow patterns also indicate that slot entrances should remain unblocked, except for the posterior-most slot. This new modelling approach will enable future design exploration of fish-inspired filters.

Computational fluid dynamics (CFD) was used to study hydrodynamics and mass transfer in a conventional circular bench-scale membrane testing device, and improved geometry of the device was proposed. The conventional and modified geometries were fabricated for experimental validation of the simulation results. It was observed that the modified cell outperformed the conventional cell in terms of distribution of mass transfer coefficient and shear stress on the membrane surface. Further, the ranges of average shear stress and mass transfer coefficient in the modified membrane testing cell for crossflow rates between 25 and 60 L/h overlaped with the corresponding ranges observed in a spacer-filled membrane channel. Hence, the modified geometry is a better choice for membrane testing and can also be extended to study the performance of antifouling membranes.

Although interest in the use of membranes for the concentration of microalgal biomass has steadily been growing, little is known regarding the phenomena of membrane fouling. In addition, more attention has been given to polymeric membranes compared to ceramic membranes, which have a longer life that is associated with a higher resistance to aggressive chemical cleaning. In this study, microfiltration (MF) and ultrafiltration (UF) of two microalgae species, Chlorella vulgaris and Monoraphidium contortum, were carried out using tubular crossflow ceramic membranes. Permeate flux was measured, resistance was calculated, and dissolved organic carbon (DOC) was determined. The flux reduction during the first 10 min of filtration was higher for MF than UF (>70% and <50%), and steady-state permeate fluxes were <5% (for MF) and <25% (for UF) of initial (in m3 m−2 s−1) 6.2 × 10−4 (for MF) and 1.7 × 10−4 (for UF). Total resistances (in m−1) were in the ranges of 4.2–5.4 × 1012 (UF) and 2.6–3.1 × 1012 (MF) for M. contortum and C. vulgaris, respectively. DOC reduction was higher for UF membrane (>80%) than for MF (<66%) and DOC concentrations (mg C L−1) in permeates following MF and UF were about five and two, respectively. In conclusion, we demonstrated: (i) higher irreversible resistance for UF and reversible resistance for MF; (ii) permeate flux higher for UF and for M. contortum; (iii) the significant role of dissolved organic compounds in the formation of reversible resistance for MF and irreversible resistance for UF. [ABSTRACT FROM AUTHOR]

Textile industries emit contaminated waste water (dyes) to the environment. Elimination of dye (methylene blue (MB)) in an aqueous solution over the uncoated, and coated membrane (media) with three layers, two layers of titanium dioxide (TiO2), and one layer of natural clay was investigated. The solutions of TiO2 and natural clay were coated on the media through the dip-coating method. In addition, the filtration performance of the clay media was assessed using cross flow filtration of Methylene blue solutions containing 50 ppm under 3 bar pressure. Total Dissolved solids (TDS) can't remove by using uncoated and TiO2 coated media since the concentration of TDS after filtration was less than that of the initial but 28% of TDS can remove by one layer of clay coated media. 67% of MB color can eliminate by two layers of TiO2 coated media, as well as 97% of MB, can eliminate by clay coated media at the maximum wavelength of 665 nm. The media permeability of uncoated media is 1843 L/m2h, two layers of TiO2 coated media is 389 L/m2h, two layers of TiO2 coated media is 223 L/m2h, and one layer of clay coated media is 1.6 L/m2h separately at TMP 3 Bar. [ABSTRACT FROM AUTHOR]

Lignin is a polyphenolic biopolymer present in large amounts in black liquor (BL). This work investigated the recovery of lignin from BL (pre-filtered by ultrafiltration (UF)) by nanofiltration (NF). For the NF tests, laboratory-made mixed matrix membrane (MMM) prepared with 0.1% activated carbon (AC) nanoparticles were used in crossflow filtration mode. The effect of pressure (6–15 bar) and volume reduction (VR) (~65%) were analyzed, and the filtration performance was evaluated in terms of permeate flux, lignin rejection rate, and flux reduction. The lignin rejection rate varied in the range of 67–80% with the pressure, however, the highest increases in flux and rejection were observed at 12 bar, which was found to be the optimum pressure. At a VR of ~65%, the permeate flux decreased by ~55% and the lignin rejection rate increased from 78% to 86%. In addition, an economic evaluation was performed for the preparation of UF and NF MMM. The minimum-to-maximum price range was estimated considering the costs of the laboratory and commercial grade regents. It showed a difference of ~10-fold and ~14-fold for UF and NF membranes, respectively. The results of the laboratory-scale study were used to evaluate the economic feasibility of the process for recovering lignin- and hemicellulose-rich retentate streams.

Particle deposition during crossflow filtration is significantly influenced by the operating conditions, in particular the permeate flux and crossflow velocity. However, there is a lack of detailed knowledge about how deposit layer structures and distributions depend on operating parameters. This study uses a microfluidic visualisation filtration system to examine the influence of operating conditions on the deposition process during crossflow ultrafiltration from a microscopic perspective. Increasing the permeate flux caused an increasing amount of deposition and a thicker deposit layer. Higher crossflow velocities reduced the extent of deposition. The degree of deposition varied over a range of operating conditions due to the altered hydrodynamic forces exerted on the particles, which can be examined by the deposition probability according to an existing model. Building on this, an empirical correlation between the deposition probability and volume of deposition as a function of filtration time was developed, which gave good agreement with experimental results. The effect of solution conditions was also involved in this correlation as a interaction energies. This could be useful for predicting the dynamic deposition process during crossflow filtration over a range of operating and solution conditions. [ABSTRACT FROM AUTHOR]

Treating oily wastewater streams such as produced water has a huge potential to resolve the issue of wastewater disposal and generate useful water for reuse. Among different techniques employed for oily wastewater (oil-in-water; O/W emulsion) treatment, membrane-based separation is advantageous owing to its lower energy consumption, recycling, ease of operation, and wider scope of tuning the active layer chemistry for enhanced performance. In line with the possibilities of enhancing the performance of the membranes for efficient O/W emulsion separation, the current work is designed to yield five different variants of polyaniline (PANI) active layers with special surface wettability features (superhyrophilic and underwater superoleophobic) on a ceramic alumina support. To achieve variants of PANI on ceramic alumina supports, emulsion polymerization was carried out, and different concentrations of initiator ammonium persulfate (APS) were applied to lead to PANI-A@Aluminum Oxide membrane, PANI-B@Aluminum Oxide membrane, PANI-C@Aluminum Oxide membrane, PANI-D@Aluminum Oxide membrane, and PANI-E@Aluminum Oxide membrane corresponding to 0.15, 0.25, 0.35, 0.5, and 1.0 M concentrations of initiator. The variation in initiator concentration resulted in different PANI growth patterns; hence, the resultant membranes showed different structural, physical, and performance features. Different characterization techniques including 1 H NMR, SEM, FE-TEM, AFM, water contact angle, XRD, EDX, and ATR-FTIR confirmed a more uniform and continuous growth of PANI (PANI-B) using a 0.25 M initiator concentration. The resultant PANI-B@Aluminum Oxide membrane showed an excellent surfactant stabilized crude O/W emulsion separation reaching >99% with a permeate flux of 2154 L m -2 h -1 (LMH) at 4 bar using a 100 ppm surfactant stabilized crude oil-in-water emulsion. The fouling and cleaning cycles revealed that the membrane can be reused with a 70% recovery of the initial permeate flux.

To assess potential filtration mechanisms, scanning electron microscopy was used in a comprehensive quantification and analysis of the morphology and surface ultrastructure for all five branchial arches in the ram suspension‐feeding fish, American shad (Alosa sapidissima, Clupeidae). The orientation of the branchial arches and the location of mucus cells on the gill rakers were more consistent with mechanisms of crossflow filtration and cross‐step filtration rather than conventional dead‐end sieving. The long, thin gill rakers could lead to a large area for the exit of water from the oropharyngeal cavity during suspension feeding (high fluid exit ratio). The substantial elongation of gill rakers along the dorsal‐ventral axis formed d‐type ribs with a groove aspect ratio of 0.5 and a Reynolds number of approximately 500, consistent with the potential operation of cross‐step filtration. Mucus cell abundance differed significantly along the length of the raker and the height of the raker. The mucus cell abundance data and the observed sloughing of denticles along the gill raker margins closest to the interior of the oropharyngeal cavity suggest that gill raker growth may occur primarily at the raker tips, the denticle bases, and the internal raker margins along the length of the raker. These findings will be applied in ongoing experiments with 3D‐printed physical models of fish oral cavities in flow tanks, and in future ecological studies on the diet and nutrition of suspension‐feeding fishes. Research Highlights: The morphology of American shad mouths is consistent with models of crossflow and cross‐step filtration rather than dead‐end sieving. The rib‐and‐groove arrangements of gill rakers in herrings and sardines may function as filtration engineering structures. [ABSTRACT FROM AUTHOR]

A novel cellulose acetate-based monophasic hybrid skinned amine-functionalized CA-SiO2-(CH2)3NH2 membrane was synthesized using an innovative method which combines the phase inversion and sol-gel techniques. Morphological characterization was performed by scanning electron microscopy (SEM), and the chemical composition was analyzed by Fourier transform infrared spectroscopy in attenuated total reflection mode (ATR-FTIR). The characterization of the monophasic hybrid CA-SiO2-(CH2)3NH2 membrane in terms of permeation properties was carried out in an in-house-built single hemodialysis membrane module (SHDMM) under dynamic conditions. Permeation experiments were performed to determine the hydraulic permeability (Lp), molecular weight cut-off (MWCO) and the rejection coefficients to urea, creatinine, uric acid, and albumin. SEM confirmed the existence of a very thin (2-(CH2)3NH2 membrane were 66.61 kg·h−1·m−2·bar−1 and 24.5 kDa, respectively, and that the Lp was 1.8 times higher compared to a pure CA membrane. Furthermore, the CA-SiO2-(CH2)3NH2 membrane fully permeated urea, creatinine, and uric acid while completely retaining albumin. Long-term filtration studies of albumin solutions indicated that fouling does not occur at the surface of the CA-SiO2-(CH2)3NH2 membrane.

Fouling mitigation using chaotic advection caused by herringbone-shaped grooves in a flat membrane module is numerically investigated. The feed flow is laminar with the Reynolds number (Re) ranging from 50 to 500. In addition, we assume a constant permeate flux on the membrane surface. Typical flow characteristics include two counter-rotating flows and downwelling flows, which are highly influenced by the groove depth at each Re. Poincaré sections are plotted to represent the dynamical systems of the flows and to analyze mixing. The flow systems become globally chaotic as the groove depth increases above a threshold value. Fouling mitigation via chaotic advection is demonstrated using the dimensionless average concentration (c¯w*) on the membrane and its growth rate. When the flow system is chaotic, the growth rate of c¯w* drops significantly compared to that predicted from the film theory, demonstrating that chaotic advection is an attractive hydrodynamic technique that mitigates membrane fouling. At each Re, there exists an optimal groove depth minimizing c¯w* and the growth rate of c¯w*. Under the optimum groove geometry, foulants near the membrane are transported back to the bulk flow via the downwelling flows, distributed uniformly in the entire channel via chaotic advection.

Oil droplet stability and electrical charge, and membrane's affinity for oil govern droplet attachment to a membrane surface. Moderate droplet-surface affinity encourages surface coalescence and removal of droplets to help maintain the membrane relatively oil-free. Droplet attachment onto model nanofiltration membranes was studied, in situ and in real time, using the Direct Observation Through the Membrane method. Optically transparent nanofiltration membranes were designed by forming polyelectrolyte multilayer films, with either positively or negatively charged surfaces, on Anopore ultrafilters. Crossflow across the membrane surface employed hexadecane-in-water emulsions stabilized by an anionic surfactant (sodium dodecylsulfate) in model sea water or aqueous solutions containing NaCl or MgSO 4. Moderate affinity between oil and the polyelectrolyte-coated surface promotes crossflow controlled coalescence to remove droplets larger than a critical size, d drop crit , in the crossflow shear. The torque balance on a sessile oil droplet in a linear shear field overpredicted d drop crit pointing to a need for more accurate estimates of lift and drag forces on a droplet. In the presence of divalent cations, lower electrostatic repulsion between droplets facilitated droplet-droplet adhesion and led to rapid coalescence that resulted in membrane fouling. The most significant fouling appeared in tests with positively charged and less oleophobic coatings. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Polymerized titanium salts were proposed for municipal wastewater pretreatment. • PTC has superior coagulation performance for particles, organics and P removal. • PTC produces larger flocs and flocs sedimentation can be completed in 1 min. • PTC produces flocs with high-shear-resistance and strong re-aggregation capability. • Direct filtration of PTC effluent is alternative way for reclaimed wastewater reuse. Abstract Research concerning polymerized titanium salts for preliminary treatment of municipal wastewater remains limited. We proposed the pre-coagulation of municipal wastewater with polymerized titanium based coagulants, followed by direct crossflow ultrafiltration for water reuse by avoiding biological treatment. Compared with polymerized aluminum chloride (PAC), polymerized ferric sulfate (PFS) and polymerized titanium sulfate (PTS), the polymerized titanium chloride (PTC) achieved higher coagulation efficiency, with chemical oxygen demand (COD) and total phosphorus (TP) removal reached 80.5% and 99.1%, respectively. Besides, PTC produced larger flocs (median equivalent diameter of 1408.1 μm) with better settling ability (flocs sedimentation in 1 min), higher shear resistance (strength factor reached 95.87%) and stronger re-aggregation capability (recover factor of 225.13%). The subsequent direct crossflow ultrafiltration of primary settled municipal wastewater could achieve complete suspended solids and P removal, being accompanied by additional 10–15% of organics removal. Specifically, ultrafiltration of PTC effluent obtained larger permeate flux up to 499.5 L m−2 h−1 and the reused water having higher quality (COD removal of 90.4%). Current study demonstrated the feasibility and superiority of utilizing polymerized titanium salts (especially PTC) for preliminary treatment of municipal wastewater. The resultant high-quality effluent through direct ultrafiltration provides alternative schemes for the demanding reclaimed wastewater reuse. [ABSTRACT FROM AUTHOR]

Abstract The Cry4AaCter tag is a pull-down tag which promotes the formation of inclusion bodies (IBs) that can be resolubilized in an alkaline buffer. Here, we used the Cry4AaCter tag to create a platform for the production of antimicrobial peptides (AMPs) in Escherichia coli featuring a uniform resolubilization process independent of the peptide fused to the pull-down tag. The Cry4AaCter tag conserves the bioactivity of fusion proteins and thus allows the purification of simple AMPs and more complex AMPs stabilized by disulfide bonds. We developed a downstream process (DSP) for the purification of IBs containing the mutated Galleria mellonella insect metalloprotease inhibitor IMPI(I38V), which has a globular structure stabilized by five disulfide bonds. IMPI(I38V) is a potent inhibitor of the M4 metalloproteases used as virulence factors by several human pathogens. We used a single crossflow filtration for the washing and resolubilization of the Cry4AaCter-induced IBs and obtained bioactive IMPI(I38V) after tag removal. We achieved a 68-fold higher protein yield using our IB system compared to an alternative DSP approach in which a GST-fusion strategy was used to produce soluble IMPI(I38V). The Cry4AaCter-based process was transferable to gloverin (another G. mellonella AMP) and the visible marker green fluorescent protein, which accumulated in fluorescent IBs, confirming it is a broadly applicable strategy for the recovery of functional proteins. Highlights • The Cry4AaCter tag promotes inclusion body formation with native protein structures. • Washing and resolubilization of inclusion bodies was achieved in a crossflow unit. • Resolubilization was pH dependent but independent of the fusion protein. • A platform technology for recombinant AMP production in E. coli was established. • An active protease inhibitor was purified from Cry4AaCter-induced inclusion bodies. [ABSTRACT FROM AUTHOR]

This study investigated the impact of implanting TiO2-NPs within a membrane to minimize the influence of long-term operation on the membrane characteristics. Four poly vinyle chloride-titanium oxide (PVC-TiO2-NPs) membranes were prepared to create an ultrafiltration membrane (UF) that would effectively treat actual refinery wastewater. The hypothesis of this work was that TiO2-NPs would function as a hydrophilic modification of the PVC membrane and excellent self-cleaning material, which in turn would greatly extend the membrane’s lifetime. The membranes were characterized via Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), atomic force microscope (AFM), and scanning electron microscope (SEM). The removal efficiency of turbidity, total suspended solid (TSS), oil and grease, heavy metals and chemical oxygen demand (COD) were investigated. Contact angle (CA) reduced by 12.7% and 27.5% on the top and bottom surfaces, respectively. The PVC membrane with TiO2-NPs had larger mean pore size on its surface and more holes with larger size inside the membrane structure. The addition of TiO2-NPs could remarkably enhance the antifouling property of the PVC membrane. The pure water permeability (PWP) of the membrane was enhanced by 95.3% with an increase of TiO2 to 1.5 gm/100gm. The PWP after backwashing was reduced from 22.3% for PVC to 10.1% with 1.5 gm TiO2-NPs. The long-term performance was improved from five days for PVC to 23 d with an increase in TiO2-NPs to 1.5 gm. The improvements of PVC-TiO2-NPs long-term were related to the enhancement of the hydrophilic character of the membrane and increase tensile strength due to the reinforcement effect of TiO2-NPs. These results clearly identify the impact of the TiO2-NPs content on the long-term PVC/TiO2-NPs performance and confirm our hypothesis that it is possible to use TiO2-NPs to effectively enhance the lifetime of membranes during their long-term operation.

Graphical abstract Abstract The need to determine the onset of dislodgment of an oil droplet pinning over a membrane surface is important in order to determine the critical conditions at which oil droplets detach. Although, previous studies considered this case in relation to an oil droplet pinning over a single pore, in reality, relatively larger size droplets pin over multitude of pore openings. In other words, droplets contact the surface over an area large enough to render the torque balance, which was devised previously to determine critical velocity, inaccurate. Another framework based on force balance is developed in this study from which critical velocity for the dislodgment of pinned droplet may be estimated. A friction force is assumed to balance the drag force due to crossflow field. The friction force is proportional to the resultant normal force that applies on pinned droplet. The proportionality factor is a friction coefficient that is determined as the ratio of the drag force due to crossflow and the resultant normal force. In this work, we determine these forces in addition to the crossflow velocity required to dislodge pinned droplet through computational fluid dynamic study (CFD). This analysis may be applicable to systems in which the deformation of the droplet is not large enough. In this case the resultant component of surface forces along the surface may be considered small. In this study a rectangular domain is considered with a 9 × 9 vertical tubes representing a pattern of pore openings. An oil droplet is released closer to the surface, where the permeation flux carries the droplet to reside on the membrane surface. The pressure inside the domain is adjusted such that it is less than the critical entry pressure and therefore, the droplet will not permeate. We seek to determine the velocity at the top surface that is barely enough to dislodge the droplet. This velocity, in addition to permeation flux, is used to determine the different hydrodynamic forces required to determine the friction force. In this study a number of droplets of different diameters are considered, namely 8, 10 and 12 microns. A base scenario is considered to determine the friction factor when no pores exist. A formula is suggested to estimate the friction factor for the more complex multipored system using that obtained when no pores exist. The numerical work is validated against the data exist in literature and excellent qualitative and quantitative match are obtained, which builds confidence in the numerical approach. [ABSTRACT FROM AUTHOR]

This work aimed to characterize the impact of high shear rate generated by crossflow microfiltration on the particles size, the rheological behavior and the overall fouling propensity of fruit juices. To this end, two orange juices, with different characteristics, were circulated during a defined duration (until 120 min) under a high shear rate (22,270 s −1 ) in a side-stream membrane unit, without filtration. Results showed that this shearing condition was likely to induce significant changes concerning at the same time the particles size distribution (with a possible particles fractionation) and the rheological properties of the fruit juices (with a potential increase of energy of cohesion between the particles). The fouling propensity of the juices, estimated through lab-scale filtration test, was also modified by the shear rate, showing that new foulant components could be released during the circulation in the filtration loop. Industrial relevance Crossflow microfiltration is successfully applied to stabilize and clarify fruit juices or to concentrate their pulpy fraction. This work aimed to characterize for the first time the impact of high shear rate applied during crossflow microfiltration on the particles size distribution, the rheological behavior and the overall fouling propensity of fruit juices. This work showed for the first time that it is important to consider the impact of high shear rates on the particles size fractionation and the release of foulant compounds when carrying-out fruit juices microfiltration under high crossflow velocities. Crossflow microfiltration of fruit juices under high crossflow velocity may not be, in some cases, the most appropriate strategy to reduce membrane fouling. According to the juice characteristics, specific industrial strategies such as enzymatic treatment or mechanical actions (e.g. back-pulsing) would be more useful than crossflow velocity to enhance the overall performance of microfiltration. [ABSTRACT FROM AUTHOR]

The detailed structures and distributions of the deposit layer formed during cross-flow filtration of 0.4 µm polystyrene particles has been investigated. A new filtration system was used to directly visualize particle deposition on the membrane surface in a filtration channel in real time. High-resolution and time sequenced images were obtained as well as 3D views of the filtration channel. The structural differences of the deposit layer over a range of solution conditions (pH, ionic strength, and feed concentration) were determined to yield new insight into the fouling mechanism. The time-dependent deposition behaviour was characterized on the basis of surface coverage, deposition volume and normalised deposition volume. The initial deposition process was primarily governed by membrane-particle interactions, while the characteristics of the fully developed deposition layers were mainly affected by particle-particle interactions. [ABSTRACT FROM AUTHOR]

The filtration characteristics of drilling fluids were evaluated by dynamic filtration under cross flow geometry. Crossflow (tangential flow) filtration by using a rotating cylinder geometry occurs when the mud is being circulated radially by inner rotating cylinder and permeates tangentially through the outer wall filter media. Dynamic filtration tests under cross flow represent more realistic conditions compared to static tests. The growth of the filter cake and filtrate flow are controlled by the blocking and erosive action of the mud stream. Dynamic HPHT ® Filtration System Model 90 which operates at high temperature and high pressure, manufactured by Fann Instrument Company™ is the most commonly used device to evaluate fluid loss and filtration characteristics of drilling fluids. However, according to its equipment manual, there are no standard methods for interpreting the dynamic filtration data. Here, the fluid loss data of drilling mud formulations were modelled based on the kinetics of filtration and plugging of through filtration media by drilling muds. The total volume loss, V as a function of time under crossflow filtration was expressed by writing ordinary differential equation of the flux which decreases due to pore plugging and cake forming and increases due to cake erosion. The differential equation was solved and the experimental data were analyzed by stating spurt loss volume as an initial value. The solution of derived differential equation which we called as Boluk-Balavi dynamic filtration equation expressed the dynamic filtration data of muds perfectly well. The fittings of experimental results to the equation gave us the direct evaluation of spurt loss volume, initial rate of fluid volume loss (flux), filter blocking and cake erosion. [ABSTRACT FROM AUTHOR]

Tubular ceramic microfiltration membranes were prepared by extruding thermally treated clay (TC) and raw clay to form a porous tubular membrane with the addition of cationic manioc starch and toasted manioc flour. The influence of an applied thermal treatment on the proprieties of the clay and the microfiltration membranes was characterized by measuring the particle size distribution, pore size distribution, and mechanical strength and by conducting X-ray fluorescence analysis, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and differential scanning calorimetry. The membranes were used for microfiltration of Acutodesmus obliquus microalgae with various applied pressures in the range of 2 × 10 4 –1 × 10 5 Pa with a volumetric flow rate of 6.94 × 10 − 5 m 3 ·s − 1 at a temperature of 10 ± 5 °C. The efficiency of each of the ceramic membranes was evaluated in terms of the permeate flux for water and microalgae and the microalga retention. The addition of TC to the membrane resulted in an optimal microalga permeate flux of 3.24 × 10 − 2 kg·m − 2 ·s − 1 and a microalga retention of 98.3% at 4 × 10 4 Pa and had positive impacts on the other proprieties measured. Overall, these results demonstrate a potential application of TC in ceramic membranes for crossflow microfiltration processes. [ABSTRACT FROM AUTHOR]

Ram suspension-feeding fishes swim with an open mouth to force water through the oral cavity and extract prey items that are too small to be pursued individually. Recent research has indicated that, rather than using a dead-end mechanical sieve, American paddlefish (Polyodon spathula) employ vortical cross-step filtration. In this filtration mechanism, vortical flow that is generated posterior to the branchial arches organizes crossflow filtration processes into a spatial structure across the gill rakers. Despite the known impact of locomotor kinematics on fluid flow around the bodies of swimming fish, the effects of locomotor kinematics on filtration mechanisms in ram suspension feeders are unknown. Potential temporal organization of filtration mechanisms in ram suspension-feeding fish has not been studied previously. We investigated the effects of locomotor kinematics associated with undulatory swimming on intraoral flow patterns and food particle transport. A mechanized model of the oral cavity was used to simulate the swimming kinematics of suspension-feeding paddlefish. We recorded fluctuations of flow speed and pressure within the model, which occurred at a frequency that corresponded with the frequency of the model's strides. Using the mechanized model in a flow tank seeded with Artemia cysts, we also showed that swimming kinematics aided the transport of this simulated food to the posterior margins of the gill slots, although the time scale of this transport is expected to vary with prey parameters such as size and concentration. Dye stream experiments revealed that, although stable vortical flow formed because of flow separation downstream of backward-facing steps in control trials, vortical flow structures in mechanized trials repeatedly formed and shed. These findings suggest strong integration between locomotor and feeding systems in ram suspension-feeding fishes. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) has been continuously demonstrated as promising membrane for water purification due to its excellent hydrophilic surface properties and special interconnected 2D nanofluidic channels for ion/molecule transport. In this work, to resolve the membrane fouling problem for GO membrane, GO/TiO 2 membrane with the multifunction of concurrent water filtration and photodegradation for pollutants was successfully fabricated by a one-step facile approach. Crossflow filtration was applied to evaluate the separation performance by simulating the real industrial process. The as-prepared GO/TiO 2 membrane exhibited remarkable ability on photocatalytic degradation of Methylene Blue under UV light, 92% of MB could be degraded after 110 min irradiation with 4 mg of photocatalyst. The membrane fouling could be effectively alleviated with UV light irradiation, resulting in a high flux recoverability of 96% after 100 min. Furthermore, the mechanism of membrane fouling processes for GO/TiO 2 membrane under crossflow filtration was analyzed based on Darcylaw model. The result showed adsorption and cake layer which accounted for 46.3% and 46.0% of membrane resistance were main factors that cause GO/TiO 2 membrane fouling. The excellent performance of GO/TiO 2 membrane provided valuable insight for its industrial application in clean water production field. [ABSTRACT FROM AUTHOR]

The development of novel and high-tech solutions for rapid, accurate, and non-laborious microbial detection methods is imperative to improve the global food supply. Such solutions have begun to address the need for microbial detection that is faster and more sensitive than existing methodologies (e.g., classic culture enrichment methods). Multiple reviews report the technical functions and structures of conventional microbial detection tools. These tools, used to detect pathogens in food and food homogenates, were designed via qualitative analysis methods. The inherent disadvantage of these analytical methods is the necessity for specimen preparation, which is a time-consuming process. While some literature describes the challenges and opportunities to overcome the technical issues related to food industry legal guidelines, there is a lack of reviews of the current trials to overcome technological limitations related to sample preparation and microbial detection via nano and micro technologies. In this review, we primarily explore current analytical technologies, including metallic and magnetic nanomaterials, optics, electrochemistry, and spectroscopy. These techniques rely on the early detection of pathogens via enhanced analytical sensitivity and specificity. In order to introduce the potential combination and comparative analysis of various advanced methods, we also reference a novel sample preparation protocol that uses microbial concentration and recovery technologies. This technology has the potential to expedite the pre-enrichment step that precedes the detection process. [ABSTRACT FROM AUTHOR]

The paper presents results of a direct visualization study of membrane fouling by hexadecane-in-water emulsions (0.1% v/v) stabilized by sodium dodecyl sulfate (SDS; 0.1 mM or 3 mM) in the presence of divalent counterions (Mg 2+ ; 0 mM, 6.7 mM, or 42.6 mM). Direct Observation Through the Membrane (DOTM) tests were performed using an ultrafiltration membrane (Anopore; d pore =0.02 µm) and low wettability by hexadecane (contact angle, θ , in 3 mM aqueous solution of SDS is ~164°). Three emulsions employed in DOTM tests had different values of interfacial tension and surface charge and exhibited distinctly different behaviors of oil droplets on the membrane surface. In addition to decreasing the solubility of SDS, MgSO 4 had two opposing effects on emulsion stability wherein both interfacial tension and ζ -potential of oil droplets decreased; the overall effect of MgSO 4 was a more facile droplet coalescence that was further promoted by permeate flux and concentration polarization of oil. The dominant fouling mechanism was cake filtration with multilayer and sub-monolayer coverages observed for different conditions. Because of the relative oleophobicity of the membrane, the attached oil did not form contiguous oil films. Under conditions of extensive coalescence (high MgSO 4 ), oil droplets reached a critical size and were then removed by the crossflow resulting in minimal membrane fouling. [ABSTRACT FROM AUTHOR]

Advances in the design of membranes and membrane modules have led to a variety of new configurations with enhanced separation performance. In order to study the performance of membrane systems with novel geometries, the flow field of the continuum phase must be known. In this study an approximate approach is used to obtain the solution for steady state flow fields in several crossflow membrane filtration systems with cylindrical symmetry. The analytical solutions are presented for a single channel tubular membrane, a tubular membrane with a co-axial solid cylinder at its center, a tubular membrane located at the center of a channel with impervious walls, and a configuration with two tubular co-axial membranes. The results are compared to numerical solutions. The analytical solutions for both velocity and pressure distributions are in agreement with the results of numerical modeling. [ABSTRACT FROM AUTHOR]

A fundamental study of microfiltration membrane fouling by emulsified oil was conducted using a combination of real-time visualization, force balance on a droplet, and permeate flux analysis. The model 0.1% v/v hexadecane-in-water emulsions contained sodium dodecyl sulfate (0.1 mM, 0.4 mM, or 0.8 mM) to regulate interfacial tension. Direct Observation Through the Membrane tests with Anopore ( d pore =0.2 µm) and track-etch ( d pore =5 µm) membranes revealed three characteristic stages of membrane fouling: (1) droplet attachment and clustering, (2) droplet deformation, and (3) droplet coalescence. In qualitative agreement with visualization results, the force balance predicted that droplets ≲ 36–40 µm would remain pinned at d pore =5 µm pores while larger droplets would be swept off the surface by the crossflow drag. In a separate set of constant pressure crossflow filtration tests with track-etch membranes, the average oil rejection was ≥98% while the permeate flux decreased to a pseudo-steady-state ~10% of the initial value. The results indicate that membrane fouling by emulsified oil is controlled by droplet coalescence and crossflow shear: the transport of oil to the membrane surface by the permeate flow is balanced by the shear-induced removal of the droplets that coalesce to exceed a critical size. [ABSTRACT FROM AUTHOR]

Particle depositions on patterned membrane surface were experimentally measured and compared with those of non-patterned membranes. Prism patterns introduced to membrane surface significantly reduced particle deposition. A larger pattern was less effective against particle deposition than a smaller pattern under low Reynolds number, but was very successful in mitigating particle deposition under high Reynolds number at faster crossflow velocity. The particle deposition and anti-fouling mechanisms were analyzed using computational fluid dynamics simulation. A vortex was formed in the valley region between prism patterns, proposing that particles entering the valley region because of permeation drag had a chance to return back to bulk crossflow stream during flowing along with the vortex. The distance between the vortex and bulk stream was shorter under high Reynolds number than under small Reynolds number, suggesting that the return of particles in the valley region into the bulk stream was quite enhanced by increasing crossflow velocity. To further mitigate particle deposition on the valley region, new patterns were developed by introducing intervals to prism patterns and showed much improvement in antifouling ability by enhancing the vortex and reducing the portion of permeation stream in the valley region. [ABSTRACT FROM AUTHOR]

The long-time (>100 h of operation) flux was measured for a set of five tests where nuclear waste slurry simulant was separated and continuously recycled using a stainless steel crossflow filter. The tests were conducted at various constant axial velocities and transmembrane pressures. In all five tests, the filter flux continued to decay at long times and did not reach a steady-state value. The long-time slope of the flux decay was unaffected by the axial velocity, but a larger transmembrane pressure resulted in a larger slope. Post-test examination of the filter did not show evidence of significant depth fouling. The experimental results are compared to theoretical predictions of the time to initiate cake formation and the time to reach steady-state predicted by models from the literature, both of which do not imply long-time phenomena would be expected. A more reasonable match between theory and experiment was achieved using a model based on the principles of dead-end filtration. [ABSTRACT FROM AUTHOR]

This paper is devoted to preparation of low-cost microfiltration (MF) membranes using lixiviated phosphate powder crushed at 50 μm. The filtering layer was coated on phosphate tubular support with 10 μm pore diameter and 43% porosity. The preparation of this ceramic layer was performed by the slip-casting method. A deflocculated slip was obtained by mixing mineral powder, polyvinyl alcohol, and water with dispersant. After drying at room temperature for 24 h, the MF layer was heated to 800°C for consolidation. Scanning electron microscopy observation showed homogeneous layers without cracks with an average pore diameter of 0.35 μm for the active layer, the thickness is approximately 10 μm. Water permeability obtained is about 700 L/h m2 bar. The membranes have been tested to treat wastewater of phosphate industry, to clarify synthetic solutions of lime and aluminum hydroxide, and to remove bacteriological pollution present in water wells. The experiments carried out show that elaborated MF membrane is very efficient for the reduction of turbidity, total phosphorus, and number of bacterial germs with almost the same performances than that obtained with a commercial α-alumina membrane. [ABSTRACT FROM PUBLISHER]

The performance of a liquid–liquid separation process based on an axially rotating tubular ceramic membrane operated in a crossflow regime is studied numerically with oil–water dispersions used as a model mixture. Internal hydrodynamics are explored using computational fluid dynamics simulations to obtain the velocity field in the continuous phase (water) and predict the separation efficiency with respect to the dispersed phase (oil). A discrete phase model is used to estimate trajectories of dispersed oil droplets within the membrane channel. The separation performance of the process is evaluated in terms of the droplet cutoff size. Effects of the Reynolds and Swirl numbers on velocity and pressure fields, shear stress, droplet cutoff size, and separation efficiency are investigated. The increased shear stress on the membrane surface due to the angular and the crossflow velocities decreased the accumulation of droplets on the membrane while increasing the separation efficiency. The droplet cutoff size is observed to decrease with an increase in the Reynolds and Swirl numbers. The separation efficiency strongly depends on the Swirl and Stokes numbers but only weekly on the Reynolds number. By increasing the Swirl number of the flow, it may be possible to remove very fine droplets by centrifugal force only and avoid membrane fouling. [ABSTRACT FROM AUTHOR]