Dead-end Cell Research Articles

Protein Adsorption Behavior on the Surface of the Microfiltration Membrane Based on a Quartz Crystal Microbalance (QCM)

How to fast and efficiently determinate the fouling behavior of the microfiltration membrane has great significance for the industrial membrane application. In this paper, the MF membrane was put on the surface of a gold-coated quartz crystal of QCM to study the adsorption behavior of protein at different conditions. The adsorbed mass increased with the increasing of concentration, ionic strength and temperature while decreased with the increasing of pH. Then the BSA adsorption results were compared with the corresponding membrane flux in dead-end cell at the identical conditions. Furthermore, the BSA adsorption process can be described by Langmuir and Freundlich isotherms very well. These results suggested that directly putting the membrane on the surface of a gold-coated quartz crystal of QCM can be used as a rapid and efficient approach to study protein fouling on the membrane surface. This approach using QCM and a small piece of the membrane could yield quantitative information for adsorption kinetics investigation and reduce the workload in large-scale industrial project.

Simultaneous removal of arsenate and nitrate from aqueous solutions using micellar-enhanced ultrafiltration process

Arsenate (As(V)) and nitrate (NO3– removal from aqueous solutions was investigated via micellar-enhanced ultrafiltration (MEUF) using a prepared polyacrylonitrile (PAN) membrane and cetylpyridinium chloride (CPC) as the cationic surfactant. The PAN ultrafiltration (UF) membrane was produced using the phase inversion method and used in a dead-end cell system. The morphology and physiochemical properties of the prepared membrane were characterized using SEM, EDX, XRD, FTIR, and AFM. Parameters, including surfactant concentration, solution pH, and transmembrane pressure (TMP) were examined to determine their effects on the permeate flux and removal efficiency of As(V) and NO3–, besides CPC rejection. Increasing CPC concentration from 0.1 to 5 mM, removal of As(V) and NO3– increased from 49.3% to 96.9% and from 0.3% to 90.5%, and the permeate flux reduced from 36.6 to 10.2 L/m2/h and from 54.2 to 33.3 L/m2/h, respectively. In addition, simultaneous removal of As(V) and NO3– via MEUF was studied, which showed that removal of NO3– was majorly prevented by As(V) because of competitive binding of CPC micelles between NO3– and As(V); however, As(V) removal was only slightly inhibited by NO3–. It was shown that the prepared PAN membrane could remove more than 90% of As(V) and NO3– under optimal conditions (CPC concentration = 5 mM, pH = 7–8, and TMP = 1 bar), using the MEUF process.

Influence of nanofiltration membrane features on enrichment of jussara ethanolic extract (Euterpe edulis) in anthocyanins

Anthocyanins were concentrated from ethanolic jussara (Euterpe edulis) extract by nanofiltration. Six commercial flat-sheet membranes with nominal molecular weight cut-off ranging from 150 to 1000 g mol−1 (NF270 and NF90 from Filmtec Dow, NP010 and NP030 from Microdyn Nadir and Desal 5-DK and Desal 5-DL from GE Osmonics) were characterized in terms of their textural properties, surface morphology and further evaluated for jussara extract nanofiltration performance. Nanofiltration trials were conducted on a stainless steel stirred dead-end cell, in which permeate fluxes were recorded by keeping operational conditions constant at 25 bar and 25 °C. N2 adsorption isotherms and atomic force microscopy images revealed a nanoporous bulk for all membranes. Changes in roughness and contact angle of membranes were observed to occur after nanofiltration trials. The Desal 5-DK membrane showed the highest efficiency for jussara extract nanofiltration due to its highest flux and smallest flux decline, in addition to the highest anthocyanins retention capacity in relation to the other commercial nanofiltration membranes.

Poly(vinylidene fluoride-hexafluoropropylene)/bayerite composite membranes for efficient arsenic removal from water

Polymer composite membranes based on poly(vinylidene fluoride-hexafluoropropylene), PVDF-HFP, with different aluminum hydroxide filler content, bayerite polymorph, were prepared by solvent casting for arsenic removal from water by filtration and adsorption. Morphological, structural and mechanical characterization of the membranes were performed. The arsenic removal efficiency of the membranes was also evaluated. Composite membranes presented homogeneous porous structures with a degree of porosity between 65 and 75%. They were hydrophobic e (contact angle >90°), showed a compressive strength >100 kPa and water flux ranging from 65 to 215 L/h m2. Further, arsenic rejections around 60% were found after 1 h reaction in dead-end cell filtration tests of an arsenic standard solution of 100 μg/L. A bayerite arsenic adsorption mechanism was also proposed. Thus, the PVDF-HFP/bayerite composite membranes showed a suitable performance for arsenic removal in water purification systems.

Editorial: Platelets as Immune Cells in Physiology and Immunopathology.

Blood platelets are essential for the earliest stages of coagulation, namely, primary hemostasis. They adhere to damaged vessel endothelium, stick to each other (aggregate), and form clots; this prevents bleeding. For most physicians, those attributes of platelets are exactly what they learned in medical school years ago, and this basic knowledge seems quite enough to allow a valid therapeutic strategy when numbers or hemostatic functions of platelets are aberrant. In some cases, this consists in prescribing anti-platelet drugs (aspirin or more sophisticated drugs) to prevent overly active clotting in cardiovascular and metabolic dysfunctions. In other instances, this consists in prescribing platelet transfusions when the platelet count is dangerously low (or – in exceptional occasions – when platelets are dysfunctional). It could be as simple as that, but in fact, it is often not, because platelets are more versatile than initially thought (or expected) and some modification is needed in many cases (1). To cite only one example, anti-viral treatment of HIV infection causes atheroma and platelet deposition, emphasizing the recently recognized inflammatory function of platelets (2, 3); anti-platelet therapy seems a likely approach, but this is not current practice yet.

The effect of UV irradiation on PSf/TiO2 mixed matrix membrane for chromium rejection

The study investigated a novel approach for surface modification of membranes and sustainable water recovery from chromium contaminated water by employing a lab scale dead-end cell filtration unit. Various PSf/TiO2 composite membranes prepared with different concentrations of TiO2 nanoparticles were exposed to UV radiations for surface modification. On exposure to UV light, TiO2 nanoparticles emit electrons and create a surface roughness with a charge on the membranes which resulted in enhanced chromium rejection as well as flux. The surface modification has been analyzed by AFM and SEM (surface and cross sectional) images. The structural modification was investigated by ATR-IR and UV–Visible spectroscopy. The expected enhancement in hydrophilicity was studied by water uptake and contact angle measurements. The analysis of water flux and chromium rejection performed in a dead end filtration unit revealed a high water flux and 100% chromium rejection with 2wt.% of TiO2 composite membrane in acidic pH. The pH of feed plays an important role in chromium rejection. The rejection of chromium decreases with an increase in feed concentration due to the variation in ion distribution. The effect of interference of other metals in chromium rejection is investigated. The overall work not only demonstrates the positive effects of surface modification, but also effective removal of hazardous chromium.

Experimental study of the effect of high pressure on the efficiency of whey nanofiltration process using an OPMN-P membrane

The results of experimental investigation of the separation of milk whey with the use of OPMN-P nanofiltration membranes (Vladipor, Russia) at pressures of 1.6–6 MPa are presented. A dead-end membrane cell has been used for the experiments. Both the whole whey (without pretreatment) and the whey after microfiltration alone or micro- and ultrafiltration have been subjected to separation. It has been shown that the working pressure range of OPMN-P membranes can be extended from 1.6 to 5 MPa. The highest specific productivity and selectivity for lactose have been observed during the separation of whey ultrafiltration permeates. The presence of residual fats and proteins in the whey reduces the specific productivity. On the basis of calculation of the specific energy consumption, it has been concluded that a high pressure (5 MPa) is useful only for separation of whey ultrafiltration permeates.

The preparation of porous polyamide-imide nanofiber membrane by using electrospinning for MF application

ABSTRACT A membrane material based on polyamide-imide (PAI) has received a great attention lately due to its thermal resistance, outstanding mechanical property, and low thermal expansion coefficient. In this study, we have focused on the preparation of porous PAI nanofiber membranes (PNMs) for water treatments. The preparation of PNMs was completed via the electrospinning method using PAI in a mixed solvent of dimethylacetamide and tetrahydrofuran. The resulting PNMs were then thermally treated to improve mechanical properties. These PAI-based membranes were characterized by scanning electron microscope, tensometer (tensile strength and elongation), pore characteristic, contact angle analyzer (contact angle), and dead-end cell device (water flux). We noticed that the pore diameter (1.0–0.3 μm) of PNMs was systematically controlled by simply increasing the number of PNMs layers. As these nanofiber membranes were found to be highly hydrophobic, we also attempted to prepare hydrophilic PNMs with a PAI solut...

Comparative Assessment of Membrane Fouling Propensity Using Colloidal Silica as Foulant

Other than silt density index (SDI), modified fouling index (MFI) is claimed as one of most useful fouling predictive tools in the practice of reverse osmosis. In this study, the effect of colloidal silica particles on the MFI value with the presence of crossflow sampler (CFS) cell at the upstream of MFI setup was systematically investigated. Colloidal silica with the particle size ranging from 70-100 nm was used as the model foulant in this experiment. The feed silica suspension was 0, 50, and 200 mg/L. The effect of membrane pore size as the test membrane in the dead-end cell on the fouling indices was also studied. Polyvinylidene fluoride (PVDF) membranes with molecular weight cut-offs of 150 and 100 kDa were employed. As predicted, the experiment results demonstrated that the fouling indices increased significantly as the feed silica concentration increased. The CFS-MFI values were always lower than the MFI in all the fouling index tests due to the shear force effect generated under the crossflow filtration mode. The fouling index generated from PVDF100 was higher than that of PVDF150 due to the retention of smaller particles. For this reason, PVDF100 membrane was preferred to be used as the test membrane for fouling index tests using colloidal silica over the PVDF150.

On the electrostatic interactions in the transfer mechanisms of iron during nanofiltration in high concentrated phosphoric acid

Concentrated phosphoric acid issued from the “wet process” contains at least 19 different contaminants, among which are metal elements, that must be removed to obtain purified acid valuable in many applications. Nanofiltration of concentrated inorganic acids is an emerging application for NF that could be used for purification of raw phosphoric acid. Nevertheless, an in-depth study of transfer mechanisms is required in order to properly understand the observed retentions of metal species during NF of raw phosphoric acid and to be able to propose a better management of the process for further purification. NF mechanisms concerning metal ions in diluted aqueous solutions are extensively studied, but up to now limited literature data deal with concentrated acids. This paper is a contribution to a better understanding of transfer of low amount of metal species in concentrated phosphoric acid, the concentration of which can be as high as 5.9molL−1. The study focuses on the transfer of iron that is the main metal contaminant of the raw acid.To achieve this goal, model solutions without and with iron chloride (18.6×10−3molL−1 FeCl3) in H3PO4 (0.12−1.2–5.9molL−1) are filtered in a stirred dead-end cell using a MPF34 membrane. Retentions of phosphoric acid, that can be in neutral (H3PO4) and charged (H2PO4−) form, is discussed. Dealing with iron-phosphate chelates, Fe(H2PO4)4− is the predominant one whereas two cations can sometimes exist: Fe(HPO4)+ and Fe(H2PO4)2+. The divalent cation is in significant amount only in 0.12molL−1 acid concentration medium. Retentions of iron chelates by the NF membrane are determined from both the mass balance of iron and their dissociation constants. For 5.9 and 1.2molL−1 media, retentions decrease in the following order: Fe(H2PO4)4−>H3PO4>H2PO4−>H+.Cl−. At high acid concentration, chloride retention is negative suggesting that electrostatic interactions can be involved in transfer mechanism at both 5.9 and 1.2molL−1.

The influence of operating conditions on the filtration behavior of actual extracellular polymeric substances (EPS) using dead-end membrane filtration cell

Abstract The EPS solution extracted from the activated sludge of sequencing batch reactors (SBRs) by the formaldehyde–NaOH extraction method was filtered in dead-end cell with 0.1 μm PVDF micro filtration membrane under various operating conditions, and the filtration behaviors of actual EPS solution were investigated. The experimental results show that: firstly, the membrane filtration mechanism is governed by cake filtration, and the cake is compressible; secondly, the cake specific resistance increased with the increase of transmembrane pressure (TMP) and decreased as the concentration increased; thirdly, all operating conditions had a significant influence on the cumulative filtrate volume (CFV) of actual EPS solution; finally, the CFV increased with the rise of temperature and TMP, but decreased as EPS concentration increased. The sequence of influence degree of operating conditions is the temperature (38.1%) > the TMP (34.8%) > the EPS concentration (27.1%). A quantitative regression relationship be...

Zinc removal from wastewater by complexation-microfiltration process

As a result of its wide industrial applications, zinc has become an important contaminant in aquatic environment since it is a toxic heavy metal and some of its compounds such as zinc arsenate and zinc cyanide, may be extremely hazardous. Therefore, there is a growing need for developing simple methods capable of separating and recovering trace zinc from environmental waters. Nowadays, the ultra and microfiltration method for trace metals removal from waters by the addition of water-soluble polymers into the aqueous solutions has become a significant research area. The choice of watersoluble macroligands remains important for developing this technology. Sodium carboxymethyl cellulose (Na-CMC) was selected as complexing agent. The microfiltration experiments were carried out in stirred dead-end cell. To separate formed polymer-metal complex Versapor membranes were used. The concentration of heavy metal ions after microfiltration in aqueous solution was determined using atomic absorption spectroscopy (AAS). Effects of amount of complexing agent, pH value, type of anion, ionic strength and operating pressure on the flux (J) and rejection coefficient (R) were investigated. Experimental results indicate a considerable influence of the pH, ionic strength and type of anion on the rejection coefficient, while effect of amount of complexing agent is relatively insignificant. The Na-CMC used in the research proved to be very effective, which may be supported by the high rejection coefficients obtained (99%).

Effects of operating parameters on efficiency of lead removal by complexation-microfiltration process

Majority of lead content found in the environment is the result of human activities. Heavy metals can be hazardous because they tend to bioaccumulate. Complexation-microfiltration process for the removal of Pb(II) ions was studied. The aim of microfiltration of the model wastewater containing heavy metal ions was finding an optimum ratio between the concentrations of the complexing agent and metal, and determining the most favorable pH value. The microfiltration experiments were carried out in a stirred dead-end cell. Diethylaminoethyl cellulose (DEAE 23) was selected as the complexing agent. Versapor membranes were used to separate formed polymer-metal complex. The concentration of heavy metal ions after microfiltration in aqueous solution was determined using the atomic absorption spectroscopy (AAS). Effects on the amount of complexing agent, concentration of metal ion, pH value and operating pressure on the flux, J, and rejection coefficient, R, were investigated. Experimental results indicate that the pH of the solution has considerable influence on the rejection coefficient. An increase in pH and the amount of complexing agents enabled us to obtain very high retention coefficient (99%).

New express dynamic technique for liquid permeation measurements in a wide range of trans-membrane pressures

In this work a new dynamic pressure decay (DPD) self-calibration technique was proposed for the express determination of liquid flux through flat-sheet membranes and films in a wide pressure range. The main principle is based on precise registration of elastic deformations of tested liquid as a function of pressure. When the volume of the pressurized liquid above the membrane keeps constant the developed method enables measuring of liquid permeability. By using this technique, the ethanol and propanol permeability coefficients were determined by DPD technique for dense PTMSP membranes (2 cm of diameter and 30 μm of thickness) in the pressure range of 30–150 bar. These results are in good agreement with traditional dead-end cell measurements. The reversible character of membrane compaction is of great importance. In addition, possible collapsing of porous support of commercial membranes currently available on the market could significantly limit the range of operated pressures in DPD technique.

New polypropylene supported chitosan NF-membrane for desalination application

In the present study, a new NF membrane was prepared by coating chitosan on polypropylene fiber support, by the dissolution of chitosan in 2% acetic acid solution. The resulting membrane was characterized by thermo gravimetric analysis, water absorption, contact angle measurement and scanning electron microscopy. Prepared membrane showed two Tg peaks, one at ~ 90 °C that was due to chitosan and the other peak at ~ 170 °C that was corresponding to the supporting polypropylene membrane. The membrane showed a low swelling ratio at pH 7, 9, and 11 as compared with pH 5. The performance of the membrane was assessed out using dead end cell. Water flux was studied at different pressures. The salt rejection study was done using NaCl solution and the effect of pH on performance of the membrane was also examined. Newly prepared membrane showed improved water flux, and % of rejection is highest in acidic pH and lowest in basic pH. Hydrulic permeability coefficient and the dielectric constant confirms that the prepared membrane is nanofiltration membrane.

Assessment of water treatment processes: detailed organic matter characterisation and membrane fouling indices at the Loddon Water Treatment Plant, Victoria, Australia

Recent advances in membrane technology have led to its broad application, and reverse osmosis (RO) systems now represent the fastest growing segment of the desalination market. Its performance is hindered by membrane fouling. In this study pre-treatment methods to reduce RO fouling were investigated including flocculation, adsorption and ion exchange. Detailed organic characterisations were made in terms of florescence spectroscopy excitation emission matrix (EEM), UV254 absorbance and liquid chromatography-organic carbon detection (LCOCD). The different pre-treatment methods were assessed in terms of the fouling potential. This was quantified in terms of the modified fouling index measured using a dead-end cell micro-filtration (MF) unit. The existing pre-treatment of granular activated carbon (GAC) filter led to a good organic removal. Among the pre-treatment methods tested in the laboratory, purolite ion exchange/adsorption was found to be better than FeCl3 flocculation in terms of the amount as well as the wide range of organics removal. A pre-treatment of flocculation with Poly-ferric-silicate (PFSi) as flocculent gave a higher removal of organic matter compared to other pre-treatments tested. DOC was reduced from 11.5 to 4.25 mg/L, and it removed mostly the humic type substances.

Ultrafiltration optimization for the recovery of β-glucan from oat mill waste

The scope of the current study is to investigate the ultrafiltration process of high molecular weight β-glucan molecules with a final purpose to optimize their recovery from oat mill waste. Therefore, standard β-glucan solutions were processed in a dead-end cell using three types of membranes (regenerated cellulose, polyethersulfone and polysulfone) under several transmembrane pressures. Optimization was conducted by monitoring performance parameters and retention coefficients for each experimental combination. In terms of membrane type, polysulfone was selected as the most appropriate membrane material since it obtained satisfactory retention coefficient and performance parameter values when the β-glucan concentration was less than 600 mg/L. Thereafter, the polysulfone membrane was applied in a pilot cross-flow module instead of a dead-end cell. The retention of β-glucan as well as the flux recovery was markedly improved with no important reduction of the permeate flux. Finally, polysulfone membrane was applied in the pilot cross-flow module for the ultrafiltration of β-glucan containing feeds (<600 mg/L) recovered from the industrial oat mill waste. Results indicated that the optimized ultrafiltration process (polysulfone in cross-flow module, with transmembrane pressure ≤2 bar and β-glucan concentrations < 600 mg/L) could be utilized in order to recover β-glucan from the oat mill waste feeds and clarify them from smaller organic and inorganic compounds. A disadvantage of the latter application was the small degree of separation between β-glucan and proteins.

Selection of membranes for purification of fructooligosaccharides

The aim of this study was to purify fructooligosaccharides (FOS) present in a mixture of sugars, containing also glucose, fructose and sucrose through, nanofiltration membranes. Four membranes were used: NP010 and NP030 (Microdyn Nadir, Germany), Desal−5 DL and Desal−5 HL (GE Water & Process Technologies). Experimental assays were performed in a dead-end cell and tangential cell filtration to select the most appropriate membrane. Then, with the membrane selected performed diafi ltration in tangential cell fi ltration up to a concentration about 80% FOS. In the dead-end filtration cell experiments the NP010, NP030, HL and DL membranes were selected, since they performed the highest retentions of FOS, and lowest retention of glucose. The results showed that NP030 membrane performed the highest differences between the retention of FOS and sucrose, where the retentions of the different saccharides were: fructooligosaccharides (Robs = 0.66), glucose (R obs = 0.18), fructose (R obs = 0.15) and sucrose (R obs = 0.24). The results clearly demonstrate the potential of diafiltration using the NP030 membrane in the purification of FOS from mixtures containing mono and disaccharides.

Quantitative estimation of protein fouling of ultra-filtration membranes by photoacoustic spectroscopy

This study focused on quantitative chemical analysis of organic fouling of ultrafiltration membranes by protein (bovine serum albumin-BSA) in the presence of a polysaccharide (alginic acid-AA). Filtration experiments were performed in a dead-end cell with two microporous membranes. Prior to the filtration experiments, the ultraviolet-visible absorbance spectra of 140 solutions with various BSA and AA concentrations were used to calibrate a partial least square (PLS) model for estimating BSA concentration. This model, which had a validation error of less than 0.7mg BSA/l, was used in the filtration experiments to estimate the concentration of BSA in the feed and permeate solutions, as well as in a solution containing the BSA fouling removed by simple water rinsing. These measurements, together with a mass balance of the different fractions of the filtration process, were used to estimate the reversible and irreversible fouling. Direct analysis of the fouled membrane was done by photoacoustic spectroscopy (FTIR-PAS), and a PLS model was used to estimate the amount of BSA present on the membrane. The fouling estimated from the FTIR-PAS spectra by PLS correlated well with the estimates from the mass balance approach, with typical errors of less than 10% of the range investigated.

Comparison of MFI-UF constant pressure, MFI-UF constant flux and Crossflow Sampler-Modified Fouling Index Ultrafiltration (CFS-MFI UF)

Understanding the foulant deposition mechanism during crossflow filtration is critical in developing indices to predict fouling propensity of feed water for reverse osmosis (RO). Factors affecting the performance on different fouling indices such as MFI-UF constant pressure, MFI-UF constant flux and newly proposed fouling index, CFS-MFI UF were investigated. Crossflow Sampler-Modified Fouling Index Ultrafiltration (CFS-MFI UF) utilises a typical crossflow unit to simulate the hydrodynamic conditions in the actual RO units followed by a dead-end unit to measure the fouling propensity of foulants. CFS-MFI UF was found sensitive to crossflow velocity. The crossflow velocity in the crossflow sampler unit influences the particle concentration and the particle size distribution in its permeate. CFS-MFI UF was also found sensitive to the permeate flux of both CFS and the dead-end cell. To closely simulate the hydrodynamic conditions of a crossflow RO unit, the flux used for CFS-MFI UF measurement was critical. The best option is to operate both the CFS and dead-end permeate flux at flux which is normally operated at industry RO units (∼20 L/m 2 h), but this would prolong the test duration excessively. In this study, the dead-end flux was accelerated by reducing the dead-end membrane area while maintaining the CFS permeate flux at 20 L/m 2 h. By doing so, a flux correction factor was investigated and applied to correlate the CFS-MFI UF measured at dead-end flux of 120 L/m 2 h to CFS-MFI UF measured at dead-end flux of 20 L/m 2 h for RO fouling rate prediction. Using this flux correction factor, the test duration of CFS-MFI UF can be shortened from 15 h to 2 h.