Osmotic Pressure Of Solution Research Articles

Technical Feasibility of Extraction of Freshwater from Produced Water with Combined Forward Osmosis and Nanofiltration.

This study assesses the technical feasibility of a forward-osmosis-based system for concentrating produced water and extracting freshwater. Forward osmosis was combined with nanofiltration, the latter system used to restore the initial osmotic pressure of the diluted draw solutions while concurrently obtaining the final freshwater product. Three draw solutions, namely, MgCl2, NaCl, and C3H5NaO2, were initially tested against a synthetic water mimicking a pretreated produced water effluent having an osmotic pressure equal to 16.3 bar. MgCl2 was thus selected for high-recovery experiments. Different combinations of draw solution osmotic pressure (30, 40, 60, 80, and 120) and draw-to-feed initial volume ratios (1, 1.6, and 2.2) were tested at the laboratory scale, achieving recovery rates between roughly 35% and 70% and water fluxes between 4 and 8 L m-2h-1. One-dimensional, system-wide simulations deploying the analytical FO water flux equation were utilized to validate the experiments, investigate co-current and counter-current configurations, and understand the system potential. The diluted draw solutions were then transferred to nanofiltration to regenerate their original osmotic pressure. There, the highest observed rejection was 96.6% with an average flux of 21 L m-2h-1, when running the system to achieve 100% relative recovery.

Isopropanol concentration by osmotically assisted reverse osmosis

Isopropanol (IPA) is a versatile solvent used in a wide range of industrial and consumer applications, and its disposal may pose high costs and environmental concerns. In this work, the osmotically assisted reverse osmosis (OARO) technology was employed to demonstrate the effective treatment and concentration of IPA wastewater. The effect of various operating parameters, including feed solution concentration, number of membrane modules, flow rate, and applied pressure, was systematically investigated. Both permeance and IPA rejection decreased with an increase in IPA concentration, due to increase of feed solution osmotic pressure and occurrence of membrane swelling. By adjusting the feed flow rate and applied pressure, we can effectively control the final IPA concentration. Specifically, lowering the feed flow rate will result in higher IPA concentration, and increasing the applied pressure will also lead to higher IPA concentration. Long-term operational stability was also investigated, and results showed that the OARO process could maintain stable operation over an extended period of 180 days. Lastly, real IPA wastewater sourced from an electronics devices factory was treated using the OARO system and the wastewater sample was concentrated for more than four times. The results of this work exhibit the great practical application potential of the OARO process for the concentration of IPA wastewater.

Teaching Design of Basic Chemistry Based on PBL Methodology for Medical Undergraduates: A Case Study on “Osmotic Pressure of Solution”

Teaching Design of Basic Chemistry Based on PBL Methodology for Medical Undergraduates: A Case Study on “Osmotic Pressure of Solution”

EFFECT OF INORGANIC CHEMICALS ON RADIORESISTANCE OF SEEDS

Introduction. Exposure to inorganic substances can modify the sensitivity of plants to ionizing radiation when preparing seeds for sowing, as well as in the case of exposure directly in the soil due to radiation accidents and possible nuclear conflicts. Since many classic mineral fertilizers (nitrate, phosphate, and potash) are inorganic water-soluble substances and enter the soil annually, their action will directly affect the radioresistance of germinating plants. An initial assessment of the conducted studies will avoid repetitions and determine the limits of additional research on the problem. Aim. This study aimed to aggregate and systematize information on the effect of soluble inorganic substances of ionic structure on the radioresistance of plants. Methods. The information was collected, processed, and analyzed. A format similar to the salt solubility table was chosen to conceptualize the material. The main results. Using chemicals before and after irradiation can change the effect of ionizing radiation. However, other factors such as pH, solution osmotic pressure, and seed moisture may also affect radiosensitivity. All these factors can affect the total radioresistance of seeds. Halides, dihydrogen phosphates, and dithionite have a radioprotective effect. The protective effect of divalent metal sulfates depends on the concentration and their chemical interaction with cellular structures. Heavy metal nitrates negatively affect the radioresistance of seeds. Sodium and calcium ions have a protective effect due to cell dehydration. Pretreatment with potassium preparations increases its content, compensating for its loss due to radiation exposure. Heavy metal ions can act as effective radiosensitizers. Metal ions with a high proton number, such as platinum, gold, gadolinium, and hafnium, could have a potential radiosensitizing effect. They can form nanoparticles that can become a source of secondary electrons, increasing point damage. Conclusions. The action of the most active groups of chemical inorganic ionic compounds has been sufficiently studied to create a primary table structure and approaches to conceptualizing the result. The study of the effects of combinations of cations and anions and their subsequent effects requires additional attention. A more detailed study of these effects will help form strategies for the radiation protection of plants in the event of radiation accidents and nuclear incidents. As well as in understanding the role of soluble inorganic soil elements on the radioresistance of plants at the initial stages of development.

Dynamic, Spontaneous Blistering of Substrate-Supported Graphene in Acidic Solutions.

We report that for monolayer and few-layer graphene on common silicon and glass substrates, acidic solutions induce fast, spontaneous generation of solution-enclosing blisters/bubbles. Using interference reflection microscopy, we monitor the blister-generating process in situ and show that at pH < ∼2, nanoscale to micrometer-sized graphene blisters, up to ∼100 nm in height, are universally generated with high surface coverages on hydrophilic, but not hydrophobic, surfaces. The spontaneously generated blisters are highly dynamic, with growth, merging, and reconfiguration occurring at second-to-minute time scales. Moreover, we show that in this dynamic system, graphene behaves as a semipermeable membrane that allows the relatively free passing of water, impeded passing of the NaCl solute, and no passing of large dye molecules. Consequently, the blister volumes can be fast and reversibly modulated by the solution osmotic pressure.

Dysregulation of miR-638 in diabetic nephropathy and its role in inflammatory response

BackgroundMicroRNA (miRNA) can be used as a biomarker for the early diagnosis of diabetic nephropathy (DN). The purpose of this study was to evaluate the diagnostic value of miR-638 in DN and to analyse its regulatory effect on inflammation.MethodsThis retrospective study involved 98 subjects, including non-diabetic healthy controls (n = 30), patients with type 2 diabetes (T2DM, n = 36) without complications and patients with DN (n = 32). After the anthropometric and biochemical evaluation, serum miR-638 levels were assessed by real-time reverse transcription-polymerase chain reaction (qRT-PCR). The levels of inflammatory cytokines (interleukin [IL]-1β, IL-6, and tumor necrosis factor-alpha [TNF-α]) were detected using enzyme-linked immunosorbent assay. The Spearman correlations were used to analyze the correlation between miR-638 and urinary albumin excretion (UAE), estimated glomerular filtration rate (eGFR), and inflammatory factors. Furthermore, the receiver operating characteristic (ROC) curve was used to measure the diagnostic value of miR-638 in DN. Human mesangial cells (HMCs) were treated with normal glucose (NG, 5.5 mM glucose), high glucose (HG, 30 mM glucose), or high osmotic pressure solution (HO, 5.5 mM glucose + 24.5 mM mannitol) in vitro to simulate the hyperglycamic state in vivo. Subsequently, the HMCs were transfected with miR-638 mimics to regulate the level of miR-638 in the cells and detect its regulation on cell inflammation and proliferation.ResultsCompared with healthy controls and patients with T2DM, serum miR-638 in patients with DN was significantly lower. The reduced miR-638 expression has a significant diagnostic value, which can significantly distinguish patients with DN from healthy controls or patients with T2DM. Inflammatory factors were significantly upregulated in patients with DN and negatively correlated with miR-638 levels. In addition, miR-638 was negatively correlated with UAE and positively correlated with eGFR. HG decreased the level of miR-638 and promoted the expression of inflammatory factors and proliferation in HMCs. However, miR-638 mimic significantly decreased the levels of inflammatory factors and inhibited the proliferative ability induced by HG.ConclusionsSerum miR-638 expression was low in DN and can be a potentially valuable biomarker for DN. This miRNA seems to influence inflammatory responses and participate in the progression of DN by regulating proliferation.

Assessment of Therapeutic Ultrasound Effect on Cell Viability, Osmotic Integrity, and Dielectric Behavior

Ultrasound (US) is a sound wave with frequency beyond the human hearing limit (20 kHz). US is relatively available, simple and energy saving. As a result it became hence an emerging technology for many biomedical applications. Low energy (low power, low intensity (>100kHz, 1 W/cm2) ultrasound is used for monitoring the composition and physico-chemical properties. on the other hand, High energy(high power, high-intensity,≤ 500 kHz ) ultrasound may induce mechanical, physical and chemical / biochemical changes through cavitation that is potentially compromising cell viability. Here in the goal of this work to investigate the potential effect of using therapeutic ultrasound on biological cell viability and integrality. Red blood cells (R.B.Cs) were our choice to investigate cell viability under the therapeutic intensity range of 0.5 – 3 W/cm2). Trypan blue dye exclusion test was to determine the integrity of cellular membrane. Cell membrane osmotic fragility of (R.B.Cs) was measured under series of saline solution osmotic pressure. The electrical signature of (R.B.Cs) was correlated before and after ultrasound irradiation. The results showed no significant alteration in (R.B.Cs) integrity and electrical behavior under US irradiation intensity range. As results using of therapeutic ultrasound intensity range of 0.5 – 3 W/cm2), showed no significant harmful effect on R.B.CS integrity and viability under current experimental conditions.

The relevance of critical flux concept in the concentration of skim milk using forward osmosis and reverse osmosis

Skim milk was concentrated at 10 °C using forward osmosis (FO), reverse osmosis (RO) and pressure-assisted forward osmosis (PAFO). A pressure of 40 bar, in the form of draw solution osmotic pressure (FO and PAFO modes) or transmembrane hydraulic pressure (RO mode) was applied; an additional hydraulic pressure of 2 bar was applied in the PAFO mode. More severe protein fouling was observed in RO, followed by PAFO and then FO. This was credited to the difference in the initial permeate flux, induced by the different effective driving pressures, with RO having a greater deviation of the initial flux from the critical flux value. The critical flux was determined for the FO and RO modes using a step-wise increase of draw solution osmotic pressure or hydraulic pressure, at a constant milk solids content. The critical flux was between 5.4 L/m2h (1.5 × 10−6 m3/m2s) and 7.2 L/m2h (2 × 10−6 m3/m2s) for both the FO and RO modes at a cross flow velocity of 0.2 m/s. The similarities in the critical flux for FO and RO suggests that the critical flux does not depend on the nature of pressure applied on the system (hydraulic or osmotic). Therefore, when operated at the same flux and crossflow velocity, FO would not fundamentally provide a lower fouling environment compared to RO. An increase of the solids content from 8.7% to 17.3% caused a reduction in the critical flux from 5.4 L/m2h to 3.1 L/m2h (8.5 × 10−7 m3/m2s).

Assessing efficiency of synthetic peptide-containing spray in combination therapy of chronic generalized periodontitis

Antibacterial drugs are routinely used in therapy of periodontal diseases. However, increasing incidence of antibiotics resistance necessitates development of novel therapeutic approaches for oral diseases. Currently, newly designed antibacterial agents based on natural, semi-synthetic and synthetic peptides is the most promising approach in dentistry. Among them is a product containing synthetic peptide (ZP2) replicating active site of granulocyte-macrophage colonystimulating factor (GM-CSF) as the main active ingredient in Atsegram-spray (manufactured by Academic Innovation Research Center, Chelyabinsk). Our study was aimed at assessing efficacy of a combination therapy of inflammatory periodontal diseases by introducing Atsegram-spray as well as examining potential relationship between peptide ZP2-related biological properties, physicochemical properties of the spray and mechanism of antibacterial and immunotropic action for substantiating its application on oral mucosa. During the first stage experiments, it was found that the peptide ZP2 was able to trigger lymphocyte blast transformation in vitro indicating that it might influence cell proliferation and exhibit marked immunotropic activity. Next, we assessed potential effects of the peptide ZP2 on biofilm formation mediated by staphylococcal clinical isolates. It was shown that peptide ZP2 inhibited biofilm formation in 75.0±9.0% of S. aureus and 50.0±15.1% of S. epidermidis strains, with mean inhibition index of biofilm formation reaching 25.1±3.8 and 50.4±6.0%, respectively. However, peptide ZP2 in 8.3–25.0% of staphylococcal clinical isolates was found to stimulate/lack effect on biofilm formation by 14.9–48.5 and 16.7–25.0% cultures, respectively. Thus, the synthetic peptide ZP2 exerts divergent, but mainly inhibitory effects on biofilm formation with staphylococcal clinical strains, which are characterized by inter- and intraspecific (strain) variability. Use of a synthetic peptide-based spray in antibacterial therapy of mild chronic generalized periodontitis (main group) one month after the onset was found to improve oral hygiene by 28.5% as well as decrease PMA index and gum bleeding index by 82.8 and 100%, respectively. In contrast, such parameters in patients receiving basic therapy (comparison group) were lower on average by 2-fold. While analyzing physicochemical properties of the spray such as pH, buffer capacity and solution osmotic pressure, it was found that they were related to the antibacterial mechanism of drug activity and efficacy in treatment of inflammatory periodontal diseases. Thus, assessing peptide ZP2-related biological properties and physicochemical parameters of the spray allows to evaluate their role in mechanism of previously unknown antibacterial and immunotropic activity. These findings confirm feasibility and efficacy of using Atsegram-spray in dentistry as an alternative means to antimicrobial agents, such as antibacterial drugs.

Evaluation of second osmotic virial coefficients from molecular simulation following scaled-particle theory

ABSTRACTWe report a scaled particle theory-based method for evaluation of second osmotic virial coefficients from molecular simulations of dilute species in solution. In this method, we evaluate the work associated with growing a cavity in solution that is perfectly permeable to the solvent but is completely impermeable to the solutes, thereby establishing an osmotic stress between the cavity interior and exterior. Extrapolating our results to determine the solute concentration in contact with a cavity with an infinite radius, we are able to evaluate the solute osmotic pressure and second osmotic virial coefficient. A finite size correction is introduced to account for the impact of effectively concentrating the solutes in the periphery of the simulation box with increasing cavity size. We demonstrate the utility of the proposed method by evaluating second osmotic virial coefficients for methane in water as a function of temperature. The approach proposed here provides a physically transparent route for calculation of second osmotic virial coefficients by direct interrogation of simulation configurations without having to explicitly evaluate the long-range integral over solute-solute correlations required following McMillan-Mayer theory.

Mass Transfer Study in Brine Water Treatment by Forward Osmosis Process

Forward osmosis (FO) is an energy-saving separation process that can be used in desalination applications. This work investigated the effect of mass transfer phenomenon on the FO desalination process. For this purpose, the water flux was studied through a bench scale system using a flat sheet FO membrane and feeds with various salinity. Then, the mass transfer resistances, which appear in the form of concentration polarization (CP) for the FO process, were evaluated qualitatively and quantitatively, using the collected experimental data and by employing a mathematical model. The results indicated that the increase in feed salinity led to a decrease in water flux due to the counteracted part of the draw solution osmotic pressure, thus leading to a lower effective osmotic pressure and driving force. Also, according to the results, there was a significant difference between the theoretical and experimental fluxes, indicating the influence of the mass transfer effects on the osmotic pressure drop. The modeling results showed that the internal concentration polarization (ICP) still held more contribution to the osmotic pressure loss. Furthermore, it was observed that as the feed solution concentration increased, both the ICP and dilutive external concentration polarization (DECP) decreased, whereas the concentrative ECP (CECP) intensified. Therefore, increasing the CECP led to a significant reduction in the effective osmotic pressure. In addition, increasing the draw solution concentration was accompanied by a much more severe ICP that limited the enhancement of effective flux.

Nanofiltration fractionation of radioactive solution components as a method for reducing the volume of wastes intended for permanent disposal

Baromembrane purification methods as part of liquid radioactive media processing complexes are increasingly included in the practice of radioactive waste management. The paper presents the results of a comparative study of the performance of commercially available hyper- and nanofiltration elements when a simulated solution is continuously phosphatized. The study revealed the influence of changes in the feed solution salinity on the permeability, working pressure in the brine chamber of the hyper- and nanofiltration apparatus and the permeate salinity. It is shown that, in a closed loop of liquid radioactive waste, the introduction of polyphosphates to stabilize the truly dissolved forms of multivalent metals on the ULP reverse-osmotic membrane leads, as expected, to a systematic performance degradation, first of all, in the membrane permeability at a fixed pressure in the apparatus. The permeate of the system with a nanofiltration membrane, VNF (Vontron NanoFiltration), contains a sufficiently high salt concentration indicating that sodium salts formed during complexation are removed from the circuit, thereby reducing the solution osmotic pressure which critically affects the yield of the purified solution. Thus, nanofiltration in combination with chelating agents can be an effective tool for fractionating components of radioactive solutions, ensuring the achievement of standard indicators for wastewater and biologically hazardous substances that are subject to permanent disposal.

Hybrid Forward Osmosis⁻Nanofiltration for Wastewater Reuse: System Design.

The design of a hybrid forward osmosis–nanofiltration (FO–NF) system for the extraction of high-quality water from wastewater is presented here. Simulations were performed based on experimental results obtained in a previous study using real wastewater as the feed solution. A sensitivity analysis, conducted to evaluate the influence of different process parameters, showed that an optimum configuration can be designed with (i) an influent draw solution osmotic pressure equal to 15 bar and (ii) a ratio of influent draw solution to feed solution flow rate equal to 1.5:1. With this configuration, the simulations suggested that the overall FO–NF system can achieve up to 85% water recovery using Na2SO4 or MgCl2 as the draw solute. The modular configuration and the size of the NF stage, accommodating approximately 7000 m2 of active membrane area, was a function of the properties of the membranes selected to separate the draw solutes and water, while detailed simulations indicated that the size of the FO unit might be reduced by adopting a counter-current configuration. Experimental tests with samples of the relevant wastewater showed that Cl−- and Mg2+-based draw solutes would be associated with larger membrane fouling, possibly due to their interaction with the other substances present in the feed solution. However, the results suggest that fouling would not significantly decrease the performance of the designed system. This study contributes to the further evaluation and potential implementation of FO in water reuse systems.

A pilot scale study on the concentration of milk and whey by forward osmosis

The concentration of skim milk and whey was investigated at a pilot scale using forward osmosis membranes with an installed membrane area of 24 m2. The pilot plant was operated in batch mode using a draw solution (48–57 g/L of NaCl) that mimics the potential brine streams available in a dairy processing plant. This approach avoids or limits the need for the regeneration of a synthetic draw solution. A concentration factor of ∼2.5 was achieved for both the skim milk and fresh whey, resulting in a total solids concentration of ∼21 wt% and 15 wt%, respectively. Increasing the transmembrane pressure was found to be effective in improving the water flux, whereas a much greater increase in the draw solution osmotic pressure would be needed to achieve the same enhancement of flux. This study also showed that small organic molecules, such as lactose, were not fully rejected by the forward osmosis membranes. A cleaning protocol was established for recovering the membrane performance after milk and whey concentration. The specific energy required for milk and whey concentration using only the forward osmosis step (5–10 kWh/t water removed) is much lower than that required by reverse osmosis. Forward osmosis is an energy efficient and effective process for dairy applications if unlimited access to a brine stream can be made available within or in the proximity of dairy processing plants.

Измерение осмотического давления почвенного раствора криоскопическим методом и его метрологическая характеристика

Cryoscopic technique to measure soil solution osmotic pressure is based on the thermodynamic relationship between chemical potential (pressure) and decresasing of the soil solution freezing temperature. The pressure is determined on the basis of the freezing temperature difference beyween distilled water and soil solution. To characterize metrologically soil solution osmotic pressure (OP) measurements by cryoscopic method a laboratory experiment was carried out with several different soil samples, collected from the A horizon of the typicalheavy-clay chernozm (Kursk region, Russia, and light-cloured clay and sandy chestnut soils (Volgograd region, Russia). Sodium chloride solution was added to soil aliquots at 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 eq/L, while Na2SO4 solution was added at 0.50 0.85 eq/L. Distilled water was added to the control variants. Depending on the granulometric composition of soils, soil water content was adjusted to 28, 23 and15%. The samples prepared in such a way were placed in 40-ml Dewar vacuum flasks with 10-4-10-5 mm Hg of vaccuum. The cryoscope measured temperature according to the Beckman thermometer scale. The temperature of the cooling mixture of crushed ice and NaCl (1:5 v/v) in Dewar flasks was maintained in the range of -21º -17º C. The freezing of soil solutions and distilled water went with overcooling. The temperature jump was indicated by clear Hg meniscus stop at the beginning of crystallization. Statistical analysis of the data obtained produced correlations and corresponding scales of the relative standard deviation(V, %) and relative permissible deviation(Drel, %) of the measured OP values. The V was shown to range from 2 to 50%, while the Drel varied from 5 to 100% between 1 and 15 atm. The threshold between the quantitative and semiquantitative esimates when V=30% was found to lie between 1.3-1.7 atm. Based on the correlation between Drel values and the measured OP, a scale for estimating OP is suggested: when Drel is 100% the corresponding OP value is 0.9-1.2 atm, at 80% Drel 1.2-1.7, at 60% Drel 1.7-2.2, at 40% Drel 2.2-3.2, at 30% Drel 3.2-4.2, at 20% Drel 4.2-9.2, at 10% Drel 9.2-10.2 atm, whereas at 9% Drel the OP can be estimated as ranging 10.2-11.2 atm, while at 8% Drel as 11.2-12.5, at 7% Drel as 12.5-14.2 and at 5% Drel as 14.2-14.5 atm. The scale can be used to estimate the reproducibility of experimental measures of soil solution osmotic pressure.

MiR-374a Regulates Inflammatory Response in Diabetic Nephropathy by Targeting MCP-1 Expression.

The microRNA (mir)-374a has been implicated in several types of human cancer; however, its role in diabetic nephropathy (DN) remains unclear. Monocyte chemoattractant protein (MCP)-1 is a chemokine that recruits macrophages to inflammatory sites and is important for the development and progression of DN. However, the relationship between miR-374a and MCP-1 in DN is unknown. We addressed this in the present study by examining the expression of these factors in kidney tissue samples from DN patients and through loss- and gain-of-function experiments using HK2 human renal tubular epithelial cells. We found that miR-374a was downregulated whereas MCP-1 was upregulated in DN tissue. A bioinformatics analysis revealed that MCP-1 is a putative target of miR-374a. To confirm this relationship, HK2 cells treated with normal glucose (5.6 mmol/l D-glucose), high glucose (HG) (30 mmol/l D-glucose), or high osmotic pressure solution (5.6 mmol/l D-glucose + 24.4 mmol/l D-mannitol) were transfected with miR-374a mimic or inhibitor. miR-374a mimic reduced MCP-1 mRNA expression and migration of co-cultured U937 cells, whereas miR-374a inhibition had the opposite effects. Additionally, interleukin-6 and -18 and tumor necrosis factor-α levels were downregulated by transfection of miR-374a mimic. On the other hand, MCP-1 overexpression reversed the inhibitory effects of miR-374a in HK2 cells. Thus, miR-374a suppresses the inflammatory response in DN through negative regulation of MCP-1 expression. These findings suggest that therapeutic strategies that target the miR-374a/MCP-1 axis can be an effective treatment for DN.

The Dynamics of Chemical Reactions: Atomistic Visualizations of Organic Reactions, and Homage to van 't Hoff.

Jacobus Henricus van 't Hoff was the first Nobel Laureate in Chemistry. He pioneered in the study of chemical dynamics, which referred at that time to chemical kinetics and thermodynamics. The term has evolved in modern times to refer to the exploration of chemical transformations in a time-resolved fashion. Chemical dynamics has been driven by the development of molecular dynamics trajectory simulations, which provide atomic visualization of chemical processes and illuminate how dynamic effects influence chemical reactivity and selectivity. In homage to the legend of van 't Hoff, we review the development of the chemical dynamics of organic reactions, our area of research. We then discuss our trajectory simulations of pericyclic reactions, and our development of dynamic criteria for concerted and stepwise reaction mechanisms. We also describe a method that we call environment-perturbed transition state sampling, which enables trajectory simulations in condensed-media using quantum mechanics and molecular mechanics (QM/MM). We apply the method to reactions in solvent and in enzyme. Jacobus Henricus van 't Hoff (1852, Rotterdam-1911, Berlin) received the Nobel Prize for Chemistry in 1901 "in recognition of the extraordinary services he has rendered by the discovery of the laws of chemical dynamics and osmotic pressure in solutions". van 't Hoff was born the Netherlands, and earned his doctorate in Utrecht in 1874. In 1896 he moved to Berlin, where he was offered a position with more research and less teaching. van 't Hoff is considered one of the founders of physical chemistry. A key step in establishing this new field was the start of Zeitschrift für Physikalische Chemie in 1887.

Drought resistance of Astragalus cicer and A. sulcatus at the initial stages of plants development

The article considers laboratory evaluation methods of water stress influence on the initial stages of Astragalus cicer and A. sulcatus development by seeds ability to germinate in osmotic sucrose solutions, characteristics of radicles and depression of shoots growth processes induced by the solution osmotic pressure. Osmoregulatory characteristics of seeds are estimated. It was ascertained that the rise in solution osmotic pressure up to 2 atm leads to a twofold and fivefold decrease in seeds germinating capacity in A. cicer and A. sulcatus respectively. At the sucrose concentration level of 4 atm, seeds do not germinate at all. Strong concentrations of osmotic solutions cause the depression of shoots growth processes and the reduction of astragaluses dry biomass.

Unpacking compaction: Effect of hydraulic pressure on alginate fouling

High pressure is often considered to be the cause of the high fouling propensity of reverse osmosis (RO) relative to forward osmosis (FO). Several experimental studies have shown that alginate fouling is more susceptible to cleaning in FO than in RO, but the theory that foulant compaction causes this disparity seems to be contradicted by the incompressibility of alginate hydrogels. In addition, the effect of hydraulic pressure on fouling in osmotic membrane desalination has never been experimentally isolated, because fixed-flux comparisons at different hydraulic pressures require different draw solution osmotic pressures. In this study, a new approach to isolating the effect of hydraulic pressure on alginate fouling and cleaning is introduced: operating FO with elevated but equal feed and draw hydraulic pressures. The same concentration of sodium chloride is used as the draw solution in all trials to eliminate possible effects of draw solution osmotic pressure on membrane fouling or cleaning. Theoretical modeling of the effect of alginate foulant compaction on flux reveals that foulant compaction should accelerate flux decline with low salinity feeds but retard flux decline at high salinity. However, in low-salinity alginate fouling trials, for which foulant compaction should accelerate flux decline, the measured flux decline rate was not affected by hydraulic pressure. Furthermore, when fouled membranes were cleaned by increasing the feed velocity and reducing the draw osmotic pressure, there was no apparent relationship between hydraulic pressure and cleaning effectiveness. Finally, in situ visualization of foulant removal during the cleaning process revealed no difference in foulant removal mechanisms between different hydraulic pressures. These findings demonstrate that alginate gel compaction by high feed hydraulic pressure does not occur and suggest that other explanations should be sought for FO's high fouling resistance relative to RO.

Ultrafiltration behavior of an Fc-fusion protein: Filtrate flux data and modeling

Fc-fusion proteins are an important new class of biotherapeutics; however, there is currently little published data on the behavior of these proteins in downstream processing operations. The objective of this study was to evaluate the ultrafiltration behavior of a highly purified Fc-fusion protein in both citrate/phosphate and histidine buffers over a wide range of protein concentrations. Filtrate flux data were obtained using a Pellicon 3 tangential flow filtration cassette. Results were analyzed using a modified version of a recently developed ultrafiltration model that accounts for the effects of intermolecular interactions on protein mass transfer, suitably extended to include the flux in the pressure-dependent regime. The key parameters in this model were evaluated from independent measurements of the solution viscosity and osmotic pressure for protein concentrations up to 200g/L. The filtrate flux and maximum achievable protein concentration in the histidine buffer were both significantly lower than the corresponding values in the citrate/phosphate buffer due primarily to the greater viscosity in the histidine buffer. The modified concentration polarization model was in good agreement with filtrate flux data over the full range of protein concentrations in both the pressure-dependent and pressure-independent regime. These results provide important insights into the factors controlling the ultrafiltration behavior of the Fc-fusion protein.