Ionic Strength Conditions Research Articles

Pourbiax Diagrams as an Aid to Understanding the Impact of Acid/Base Disturbance on Blood Glucose Point-of-Care Testing.

Assays based on redox reactions that involve proton transfer are vulnerable to artifactual findings in metabolic acidosis/alkalosis. We evaluated the impact of pH on the measurement of blood glucose by the glucose dehydrogenase/pyrroloquinoline quinone system used in point-of-care-testing. We applied a series of thermodynamic equations to adjust the Gibbs energy for the pyrroloquinoline quinone couple. This adjusts values taken under standard conditions to those more closely resembling the physiological state. Under standard conditions, the pyrroloquinoline quinone couple has Eo = -0.125 V whereas adjustment to the physiological state (pH 7.40, ionic strength 0.15 mol/L, and temperature 310.15°K) yields Eo' = -0.166 V. This corresponds to an uncertainty in blood glucose determination of approximately 0.13 mmol/L. We have demonstrated that the impact of pH on blood glucose determination by the glucose dehydrogenase/pyrroloquinoline quinone system (under physiologically relevant conditions of ionic strength and temperature) is not clinically significant.

Adsorption Study of Rhodamine –B Dye on Plant (Citrus Leaves)

The current research includes the adsorption of Rhodmine-B Dye on the surface of Citrus Leaves using the technique of UV. Vis spectrophotometer to determine data of quantitative adsorption at various contact time, ionic strength, PH and temperature conditions. As a function of temperatures 25,35,45,55 0C, the dsorption phenomenon was examined, and the results showed that Rhodamine-B adsorption Citrus leaves rose with increasing temperatures on the surface (endothermic process). Using various NaCl solution concentrations, the effect of ionic strength on adsorption has also been studied. Increasing the importance of ionic strength has been shown to improve the amount of adsorption of Rhodamine-B on citrus leaves at constant temperatures.The quantity of Rh-B dye that was adsorbed on the citrus leaves was increased with increasing the PH of the solution in rang 3-7. Then the results were subjected to the practical results obtained with the use isotherms of the Langmuir, Frendelsh, and Temkin. The results can be shown that the isotherm suitable for adsorption applies to Ferndelsh and Temkin. The thermodynamic functions (the amount of change in enthalpy, the amount of change in entropy and the amount of change in the free energy of Gibbs) were also studied, and it was found that the thermodynamic results of the adsorption process of the Rhodamine-B dye on the powder of citrus leaves are endothermic and an automatic adsorption process.

Detection of DNA Hybridization Beyond the Debye Screening Length by CMOS Capacitive Sensors

Capacitive sensors are very promising to provide label-free and real-time biological detection for point-of-care diagnostic applications. However, the Debye charge screening effect severely hinders the detection under high ionic strength condition, such as in human serum. Therefore, most measurements are made indirectly in diluted solutions. To solve this problem, electric field modulation between the interdigitated sensing electrodes is applied in this study to increase the Debye length. For DNA (deoxyribonucleic acid) measurements, the two designs operating around 90 and 40 MHz exhibited sensitivities of 2.6 fF/log[DNA] and 10.8 fF/log[DNA] up to 100 fM and a response time of 12 minutes.

Preconcentration of Four Benzodiazepines Using a Magnetic Adsorbent Based on Fe3O4/Octanoic Acid Nanocomposite, and Their Quantification by HPLC‐UV

AbstractThe aim of this study is to apply the magnetic solid phase extraction and high performance liquid chromatography equipped with an ultraviolet detector for the simultaneous extraction of four mostly utilized kinds of drugs, Benzodiazepines, as acidic and basic drugs. Fe3O4/octanoic acid nanocomposite as adsorbent was synthesized during the facile one‐pot co‐precipitation method. The morphological, structural and magnetic characterization of the synthesized nanomaterial was carried out by different techniques. Main parameters, influencing the magnetic solid‐phase extraction efficiency, such as pH, the amount of Hexadecyltrimethylammonium bromide (HTAB), adsorbent amount, ionic strength, extraction time, and desorption conditions were optimized. To quantify the trace amounts of drugs, least amount of methanol was used for the proper elution and better preconcentration, while batch technique of extraction was used too. Under the optimized extraction conditions, the method proved to be effective due to the good linearity (10–5000 ng mL−1), low limits of detection (1.5–12.0 ng mL−1), and relatively high enrichment factors (118–132). The method was applied for monitoring of the benzodiazepines in urine, hair and water samples. In addition, the relative standard deviation was determined around 1.7–6.5, and the intra‐ and inter‐day precisions for five replications found lower 5 and 7 %, respectively. All attained results bring the suggested method in comparison with other before utilized methods.

Impact of Degree of Ionization and PEGylation on the Stability of Nanoparticles of Chitosan Derivatives at Physiological Conditions.

Nowadays, the therapeutic efficiency of small interfering RNAs (siRNA) is still limited by the efficiency of gene therapy vectors capable of carrying them inside the target cells. In this study, siRNA nanocarriers based on low molecular weight chitosan grafted with increasing proportions (5 to 55%) of diisopropylethylamine (DIPEA) groups were developed, which allowed precise control of the degree of ionization of the polycations at pH 7.4. This approach made obtaining siRNA nanocarriers with small sizes (100–200 nm), positive surface charge and enhanced colloidal stability (up to 24 h) at physiological conditions of pH (7.4) and ionic strength (150 mmol L−1) possible. Moreover, the PEGylation improved the stability of the nanoparticles, which maintained their colloidal stability and nanometric sizes even in an albumin-containing medium. The chitosan-derivatives displayed non-cytotoxic effects in both fibroblasts (NIH/3T3) and macrophages (RAW 264.7) at high N/P ratios and polymer concentrations (up to 0.5 g L−1). Confocal microscopy showed a successful uptake of nanocarriers by RAW 264.7 macrophages and a promising ability to silence green fluorescent protein (GFP) in HeLa cells. These results were confirmed by a high level of tumor necrosis factor-α (TNFα) knockdown (higher than 60%) in LPS-stimulated macrophages treated with the siRNA-loaded nanoparticles even in the FBS-containing medium, findings that reveal a good correlation between the degree of ionization of the polycations and the physicochemical properties of nanocarriers. Overall, this study provides an approach to enhance siRNA condensation by chitosan-based carriers and highlights the potential of these nanocarriers for in vivo studies.

Folding and Binding Mechanisms of the SH2 Domain from Crkl.

SH2 domains are structural modules specialized in the recognition and binding of target sequences containing a phosphorylated tyrosine residue. They are mostly incorporated in the 3D structure of scaffolding proteins that represent fundamental regulators of several signaling pathways. Among those, Crkl plays key roles in cell physiology by mediating signals from a wide range of stimuli, and its overexpression is associated with several types of cancers. In myeloid cells expressing the oncogene BCR/ABL, one interactor of Crkl-SH2 is the focal adhesion protein Paxillin, and this interaction is crucial in leukemic transformation. In this work, we analyze both the folding pathway of Crkl-SH2 and its binding reaction with a peptide mimicking Paxillin, under different ionic strength and pH conditions, by using means of fluorescence spectroscopy. From a folding perspective, we demonstrate the presence of an intermediate along the reaction. Moreover, we underline the importance of the electrostatic interactions in the early event of recognition, occurring between the phosphorylated tyrosine of the Paxillin peptide and the charge residues of Crkl-SH2. Finally, we highlight a pivotal role of a highly conserved histidine residue in the stabilization of the binding complex. The experimental results are discussed in light of previous works on other SH2 domains.

Chemical thermodynamics of ternary M-An(VI)-CO3 system (M = Mg, Ca, Sr, and Ba)

Abstract This review provides an overview of the chemical thermodynamics on ternary earth-alkaline metal-actinyl-tricarbonate systems (i.e., M-AnO2-CO3, M = Mg, Ca, Sr, and Ba) and discusses the aqueous complexation and dissolution/precipitation equilibrium for these ternary aqueous systems. The aqueous ternary U(VI) carbonate species are remarkably predominant in the U(VI) speciation under natural environmental conditions at ambient temperature and moderate ionic strength condition, while the omnipresence, according to recent studies, would be hindered by an increase in temperature and ionic strength. With respect to the ternary solid U(VI) carbonate phases, most of the previously reported data have been focused on physical properties and thus a notable lack of available data on chemical thermodynamic properties, i.e., solubility product constant, has been identified. Nevertheless, substantial influences of these ternary M-AnO2-CO3 systems on the aqueous speciation and the solubility limiting phase under the natural environmental condition are taken into account according to the thermodynamic calculation. The authors point out that the completeness of the chemical thermodynamic model for predicting the chemical behavior of actinides in nature can be further improved on the basis of a sufficient understanding of ternary M-AnO2-CO3 systems.

Heterogeneous adsorbent based on CeZrO2 nanoparticles doped magnetic graphene oxide used for vortex assisted magnetic dispersive solid phase extraction of erythromycin in chicken

A simple, fast, and efficient method of vortex assisted magnetic dispersive solid phase extraction for separation and pre-concentration of erythromycin in chicken samples prior to high LC-UV determination has been developed. The novel heterogeneous CeZrO2 nanoparticles doped magnetic graphene oxide, for use as an efficient nanosorbent, was synthetised and applied for the adsorption of erythromycin. The synthetised nanosorbent was characterised using both Fourier-transform infra-red (FT-IR) and energy dispersive X-Ray (EDX) spectroscopy together with field emission scanning electron microscopy-EDX. To obtain the best extraction condition and maximum extraction efficiency of erythromycin, the effect of important parameters including pH, amount of sorbent, vortexing time, ionic strength, sample volume, and desorption conditions were investigated. At optimum conditions, a linear range of 0.25–300 µg kg−1, LOD (S/N = 3) of 0.079 µg kg−1, and LOQ (S/N = 10) of 0.270 µg kg−1 were obtained. The precision of the method was established as having an RSD (%) at 100 µg kg−1 of erythromycin for seven replicates of 2.6% and 3.2% for the intra-day and the inter-day, respectively. Recoveries over 94.0% confirmed a high capability of the proposed method for separation and determination of erythromycin residues in chicken being one of the most important animal products.

Targeting Atmospheric Oxidants Can Better Reduce Sulfate Aerosol in China: H2O2 Aqueous Oxidation Pathway Dominates Sulfate Formation in Haze.

Particulate sulfate is one of the most important components in the atmosphere. The observation of rapid sulfate aerosol production during haze events provoked scientific interest in the multiphase oxidation of SO2 in aqueous aerosol particles. Diverse oxidation pathways can be enhanced or suppressed under different aerosol acidity levels and high ionic strength conditions of atmospheric aerosol. The importance of ionic strength to sulfate multiphase chemistry has been verified under laboratory conditions, though studies in the actual atmosphere are still limited. By utilizing online observations and developing an improved solute strength-dependent chemical thermodynamics and kinetics model (EF-T&K model, EF is the enhancement factor that represents the effect of ionic strength on an aerosol aqueous-phase reaction), we provided quantitative evidence that the H2O2 pathway was enhanced nearly 100 times and dominated sulfate formation for entire years (66%) in Tianjin (a northern city in China). TMI (oxygen catalyzed by transition-metal ions) (14%) and NO2 (14%) pathways got the second-highest contributions. Machine learning supported the result that aerosol sulfate production was more affected by the H2O2 pathway. The collaborative effects of atmospheric oxidants and SO2 on sulfate aerosol production were further investigated using the improved EF-T&K model. Our findings highlight the effectiveness of adopting target oxidant control as a new direction for sustainable mitigation of sulfate, given the already low SO2 concentrations in China.

Boron and lithium behaviour in river waters under semiarid climatic conditions

Boron (B) and Lithium (Li) concentrations were studied in the Platani river, one of the most important catchments of South-Central Sicily which is under semiarid climatic conditions for roughly eight months to a year. In this area, evaporites result in potential B and Li sources for surface waters. Results from river waters have measured ionic strength values between 0.1 and 4.54 M. B and Li distributions in these waters were studied in colloidal (CF, extracted by ultrafiltration from the 0.45 μm filtrate) and total dissolved (TDF) fractions and in fractions extracted from corresponding riverbed sediments, according to changes of the B/Li ratio.In river waters, CF and TDF showed very similar B/Li values, suggesting that only negligible fractionation occurs between Li and B in the aqueous phase. Similar evidence was observed between B/Li values in TDF and the labile sediment fraction, whereas an inverse relationship arose between B/Li values in TDF and in the easily reducible sediment fraction. This relationship indicates that Mn oxy-hydroxides preferentially react with aqueous B species relative to Li at the riverbed sediment interface.The extent of the B–Mn oxy-hydroxide reactions is influenced by the ionic strength, so that only B/Li values below 4 are measured in river waters with ionic strength values above 0.5 M. Comparing B/Li and ionic strength values measured in the Platani river with those from oxic brines worldwide, the same preferential B removal relative to Li is observed. This evidence suggests that B is removed as positively-charged borate ion-pairs, formed in the aqueous phase under higher ionic strength conditions, reacting with negatively charged surfaces of Mn oxy-hydroxides. The observed B reactivity relative to Li could be exploited to bring down the B excess from natural or waste waters, allowing the natural reactions with Mn oxy-hydroxides to take place under natural conditions.

Biocompatible magnetite nanoparticles coated with ionic liquid-based surfactant as a hydrophilic sorbent for dispersive solid phase microextraction of cephalosporins prior to their quantitation by HPTLC

Extraction of highly hydrophilic compounds from biological fluids including urine or plasma samples is a dilemma due to high hydrophilicity of the matrix itself. The main aim of the current work is to explore the competence of ionic liquid (IL)-based surfactant-coated mineral oxide nanoparticles (NPs) in dispersive solid-phase microextraction (d-SPME) of highly hydrophilic analytes taking cefoperazone (CPZ) as a model analyte for the study. The IL-based surfactant coated Fe3O4 NPs is utilized as an innovative adsorbent for the separation and pre-concentration of CPZ after intramuscular injection (I.M) in rabbits. The utilized magnetite NPs were synthesized via simple and reliable co-precipitation procedure, which doesn’t require any air-free environment and depends on a single iron (III) salt. Characterization of the as-synthesized NPs was achieved by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX). Surface area measurements show that Fe3O4 NPs have large surface area of 75 m2 g−1. The developed approach utilizes the unique properties of the IL-based surfactant including multiple polar interaction types provided by the polar head in addition to merits of Fe3O4 nanoparticles, which include large adsorptive capacity and magnetic properties, to improve separation, save time, and achieve satisfactory recovery. Comprehensive study was developed for the factors, that affect the adsorption capacity such as pH, NPs amount, IL-based surfactant concentration, ionic strength, adsorption time, and desorption conditions. Moreover, the adsorption data was fitted to Langmuir and second-order kinetic models as reflected by the reasonable determination coefficients of 0.9319 and 0.9726, respectively. Under the optimized conditions, the developed approach achieves good correlation coefficient of 0.9975, and 0.9981 over linearity range of 0.7–12.0 and 4.0–50.0 µg mL−1 for both CPZ standard solutions and spiked rabbit plasma, respectively. It also provides good sensitivity expressed by the low values of limit of detection (LOD) of 0.2 and 1.2 µg mL−1 and limit of quantitation (LOQ) of 0.7 and 4.0 µg mL−1 for both the standard solutions and spiked plasma, respectively. The developed approach was also applied successfully for monitoring CPZ in rabbit plasma samples with satisfactory recovery % (83–110). In addition, a detailed pharmacokinetic study is performed where pharmacokinetic parameters of CPZ in rabbit plasma samples were calculated.

High Level Expression and Purification of Cecropin-like Antimicrobial Peptides in Escherichia coli.

Cecropins are a family of antimicrobial peptides (AMPs) that are widely found in the innate immune system of Cecropia moths. Cecropins exhibit a broad spectrum of antimicrobial and anticancer activities. The structures of Cecropins are composed of 34–39 amino acids with an N-terminal amphipathic α-helix, an AGP hinge and a hydrophobic C-terminal α-helix. KR12AGPWR6 was designed based on the Cecropin-like structural feature. In addition to its antimicrobial activities, KR12AGPWR6 also possesses enhanced salt resistance, antiendotoxin and anticancer properties. Herein, we have developed a strategy to produce recombinant KR12AGPWR6 through a salt-sensitive, pH and temperature dependent intein self-cleavage system. The His6-Intein-KR12AGPWR6 was expressed by E. coli and KR12AGPWR6 was released by the self-cleavage of intein under optimized ionic strength, pH and temperature conditions. The molecular weight and structural feature of the recombinant KR12AGPWR6 was determined by MALDI-TOF mass, CD, and NMR spectroscopy. The recombinant KR12AGPWR6 exhibited similar antimicrobial activities compared to the chemically synthesized KR12AGPWR6. Our results provide a potential strategy to obtain large quantities of AMPs and this method is feasible and easy to scale up for commercial production.

Interactions of common scale inhibitors and formation mineral (calcium carbonate): Sorption and transportability investigations under equilibrium and dynamic conditions

Formation and deposition of mineral scales pose a serious threat to the safety and integrity of oilfield operations. Scale inhibitor chemicals have been widely employed to control scale threat and enhance production efficiency. The inhibitor-formation mineral interaction together with inhibitor transport behavior play significant roles in the design and optimization of oilfield inhibitor treatment. However, limited studies have been reported to investigate the principles dictating the inhibitor-mineral interaction under both equilibrium and dynamic conditions. Moreover, there are few studies focusing on the inhibitor transport at a lower inhibitor concentration. In this study, a systematic evaluation of the physicochemical nature of inhibitor-formation mineral interactions was conducted with a focus on lower inhibitor concentrations (below 50 mg L−1) by adopting two common oilfield inhibitors of diethylenetriamine pentamethylene phosphoric acid (DTPMP) and phosphino-polycarboxylic acid (PPCA). The formation mineral employed in this study is calcium carbonate (calcite). Both equilibrium and the kinetics aspects of inhibitor sorption behavior have been studied experimentally via static batch and dynamic column apparatus. It was found that the adsorption capacity of calcite for DTPMP is higher than that of PPCA. Laboratory fixed-bed column transport experiments were carried out at different physicochemical conditions of initial inhibitor concentration, ionic strength, temperature, flow rate and calcite particle size. Results indicate that an increase in both DTPMP and PPCA concentration can expedite inhibitor transport and a high initial DTPMP concentration could significantly affect the retention of DTPMP in the calcite porous medium. Ionic strength can result in a higher transportability in calcite medium for both inhibitors. Change in temperature has no significant impact on inhibitor transport. The flow rate has a considerable influence on the dispersion coefficient due to elevated mechanical dispersion at a higher flow rate for DTPMP. The calcite particle size can also impact inhibitor adsorption due to the change in surface area. Furthermore, adsorption of PPCA can subject the calcite surfaces more hydrophilic than DTPMP, which can affect the mobility of inhibitor in calcite medium. Atomic force microscopy characterization results confirmed that the wettability of calcite was increased through adsorption of DTPMP and PPCA inhibitor. This study provides deep insights into the sorptive behavior and transportability of DTPMP and PPCA inhibitors in calcite porous medium.

Adsorption Kinetics and Adsorption Thermodynamic Properties of Dibutyl Phthalate (DBP) Building Materials in Black Soil

The adsorption of organic pollutants by soil has an important impact on their migration, transformation and bioavailability. Black soil is rich in organic matter that plays an essential role in adsorption, which indicates that black soil may have a high adsorption capacity for DBP. The significant DBP adsorption capacity of black soil was discovered through research into the adsorption kinetics and thermodynamic properties of DBP in black soil. This finding was consistent with pseudo-second-order kinetics. The adsorption was chemical adsorption, and intramolecular diffusion was a critical control step in the adsorption process. The adsorption equilibrium time was 24 h. Analyzing the effects of temperature, pH, ionic strength and other conditions, it was found that reducing the temperature promoted the adsorption of DBP. When the pH was 7, the adsorption capacity was the greatest. The capacity of DBP to adsorb was boosted by the rise in ionic strength, which also hindered DBP adsorption once it reached a certain threshold.

Rapid Sulfate Formation via Uncatalyzed Autoxidation of Sulfur Dioxide in Aerosol Microdroplets.

Severe winter haze events in Beijing and North China Plain are characterized by rapid production of sulfate aerosols with unresolved mechanisms. Oxidation of SO2 by O2 in the absence of metal catalysts (uncatalyzed autoxidation) represents the most ubiquitous SO2 conversion pathway in the atmosphere. However, this reaction has long been regarded as too slow to be atmospherically meaningful. This traditional view was based on the kinetic studies conducted in bulk dilute solutions that mimic cloudwater but deviate from urban aerosols. Here, we directly measure the sulfate formation rate via uncatalyzed SO2 autoxidation in single (NH4)2SO4 microdroplets, by using an aerosol optical tweezer coupled with a cavity-enhanced Raman spectroscopy technique. We find that the aqueous reaction of uncatalyzed SO2 autoxidation is accelerated by two orders of magnitude at the high ionic strength (∼36 molal) conditions in the supersaturated aerosol water. Furthermore, at acidic conditions (pH 3.5-4.5), uncatalyzed autoxidation predominately occurs on droplet surface, with a reaction rate unconstrained by SO2 solubility. With these rate enhancements, we estimate that the uncatalyzed SO2 autoxidation in aerosols can produce sulfate at a rate up to 0.20 μg m-3 hr-1, under the winter air pollution condition in Beijing.

Experimental Data and Modeling the Adsorption-Desorption and Mobility Behavior of Ciprofloxacin in Sandy Silt Soil

The improved understanding of the behavior of antibiotics in soil is of great importance due to their environmental hazard and frequent detection. In this work, the adsorption-desorption and mobility behaviors of ciprofloxacin in sandy silt soil, affecting the fate of ciprofloxacin in the environment, were studied by a series of batch tests and column tests. In batch tests, the effects of contact time, initial ciprofloxacin concentration, sandy silt soil dosage, solution pH, and ionic strength on ciprofloxacin adsorption and desorption in sandy silt soil were considered. Adsorption results were satisfactorily modeled, with good fittings to the pseudo-second-order model (R2 > 0.999) and Langmuir model (R2 > 0.991), with the value for Langmuir’s maximum adsorption capacity (qm) 5.50 mg g−1. Ciprofloxacin adsorption decreased sharply by increasing the pH from 7.0 to 10.0 and the ionic strength from 0.01 to 0.2 mol L−1 CaCl2. Comparatively, ciprofloxacin was more readily desorbed from sandy silt soil at alkaline and high ionic strength conditions. Breakthrough curves of ciprofloxacin obtained from the column experiments were described by the two-site model, Thomas model, and Yan mode. Of these models, the two-site model was the most suitable to describe the mobility of ciprofloxacin. The retardation factor (R) obtained in the two-site model was 345, suggesting strong adsorption affinity with ciprofloxacin on the sandy silt soil surface. The results from the Thomas model suggested the extremely small external and internal diffusion resistances. The Yan model was not suitable. Cation exchange interaction, electrostatic interaction, mechanical resistance, entrapment between porous media, and gravity sedimentation were proposed to be the important adsorption mechanisms.

How do chlorite coatings form on quartz surface?

Chlorite-coats on quartz surfaces are ubiquitous in various sedimentary environments. Chlorite-coats shield the surface of quartz from quartz cement overgrowths, thus preserving anomalously high porosity in deeply buried sandstone reservoirs. The inhibition of the quartz cement implies that the chlorite-coats on the surface of quartz grains can significantly influence the physicochemical behavior of the quartz grains. Therefore, failure to notice the initial thin microscale coatings forming during deposition can have serious consequences for modeling several geochemical reactions occurring at liquid-solid interfaces. Despite this huge implication, the fundamental mechanisms involved in chlorite-coat formation is not well understood. Here we present an experimental study to determine the parameters that control chlorite-coat formation on the surface of quartz grains. The batch experiments were conducted in a concoction of quartz and chlorite under different conditions of ionic strength, pH, and presence of humic acid (HA), iron- (Fe) and aluminum (Al) oxides). HA, Fe- and Al oxides are suggested to aid the emplacement of chlorite-coat precursors. At pH 7, the quartz–chlorite and quartz–chlorite–Fe/Al-oxides mixing experiments performed in saline and non-saline solution result in equal chlorite-coat coverages, suggesting neither salinity nor Fe and Al-oxides explain the mechanisms of chlorite-coat formation. At pH 5 and 9, however the chlorite-coat coverage was superior only in saline solution, indicating differences in coat coverage may be caused by variable electrokinetic charge distribution due to the distribution and transport of dissolved salt. The chlorite-coat barely formed in experiments that contain HA in quartz–chlorite mixtures regardless of ionic strength and pH. Against a long-standing notion, the presence of organic matter cannot necessarily be prerequisites for binding chlorite on the surface of quartz grains. The dynamic interactions between solution chemistry and surface chemistry of solid phases (quartz, chlorite, HA, Fe and Al oxides) can result in changing the electrokinetic properties in a region near the solid phases and at mineral-solution interfaces. We therefore propose that the electrokinetic response that arises in heterogeneous systems may explain the mechanisms of chlorite-coat formation.

High-efficiency graphene oxide membranes intercalated by hollow TiO2 nanospheres and CNS@LDH composite spheres for enhancing dye separation from wastewater

Textile wastewater pollution with dyes has become a major source of water pollution. In the study, GO and composite nanospheres (CNS@LDH and HOTiO2) were used to form the composite materials by electrostatic self-assembly method, and the composite materials vacuum filtration on the surface of CA membrane to prepare the composite membranes for dyes separation. Among them, GO was used as a vertical separation layer in dyes separation, while the hollow structure of HOTiO2 nanosphere with a large specific surface area provided more adsorption sites, and the CNS@LDH nanosphere with core–shell structure played the role of expanding GO sheets and preventing HOTiO2 from collapsing. Compared with the GO membrane, the water flux of three dyes produced by GO/HOTiO2/CNS@LDH composite membrane increased by 18 times with a rejection rate of 99%. In addition, after 10 cycles of experiments, GO/HOTiO2/CNS@LDH composite membrane retained a rejection rate of over 98% with the flux of 79 L∙m−2∙h−1∙bar−1 for MB. GO/HOTiO2/CNS@LDH composite membrane retained a stable rejection rate on three dyes under extreme pH and ionic strength conditions. The composite membrane combined the adsorption and isolation effects of GO, HOTiO2, and CNS@LDH, which significantly enhanced the separation performance of dye wastewater. Accordingly, the GO/HOTiO2/CNS@LDH composite membrane has great potential in practical wastewater treatment.

Rheological characterization of β-lactoglobulin/lactoferrin complex coacervates

Heteroprotein complex coacervation between lactoferrin (LF) and β-lactoglobulin (β-LG), two oppositely charged proteins from whey, occurred under specific conditions of pH, ionic strength and protein molar ratio. The present work aims at characterizing the rheological properties of the concentrated phase called coacervate obtained after phase separation. Unlike some polysaccharide/protein coacervates, β-LG/LF heteroprotein coacervates exhibit a liquid-like behavior; the loss modulus G” being 100 times higher than the storage modulus G’ at low frequencies. This behavior was confirmed under creep-recovery tests. The heteroprotein coacervates exhibited a Newtonian viscous flow under low shear rate and a shear thinning behavior above 10 s−1. The coacervates are exceptionally viscous, reaching a viscosity value of 55 ± 10 Pa.s which is ∼2500 times higher than that measured on individual protein solutions of equivalent total concentration. Also, a structural change occurred in the coacervates, probably due to the weaknesses of electrostatic interactions inside the protein network at high shear rates. The observed time-dependent structural rearrangement was proved to be reversible. These findings open new ways for the use of coacervates as texturizing agents in food matrices.

Effect of background electrolytes on the adsorption of phosphorus (P) onto southern Tunisia natural clays

The purpose of the present research is to investigate the effect of background electrolytes on the phosphorus (P) sorption by four different natural clay samples (NCS): Jebel Tejera-Esghira (JTE) in Medenine area, Douiret (DR) in Tataouine area, Jebel Aidoudi (JA) and Zemlet El Beida (ZB) in Gabes area. The mineralogical and chemical characterization of the NCS showed that they are essentially composed of illite, kaolinite, smectite, with small fractions of quartz and calcite. The P sorption was investigated in batch mode in the presence of three different background electrolytes (CaCl2, NaCl and KCl with 99% of purity) under different experimental conditions of contact times (3 h), initial concentrations (25–150 mg.L−1), ionic strength (0–1 M), temperature (295–325 K) and pH (3–11). Experimental results indicated that P sorption in the presence of electrolytes is a rapid process since about 95% of P was observed within a contact time of 180mn. The highest P adsorption capacity was determined to 7.39 ± 0.65, 7.96 ± 0.82, 8.07 ± 0.55 and 8.83 ± 1.05 mg g1 for JTE, JA, ZB and DR. At equilibrium, the P adsorbed amount by the raw NCS was assessed to 7.75 ± 0.55, 8.34 ± 0.75, 8.8 ± 0.3 and 8.85 ± 0.75 mg g−1 for JTE, JA, ZB and DR. This amount increased by about 0.11, 0.08, 0.05%; 0.14, 0.06, 0.04%; 0.17, 0.1, 0.09 and 0.13, 0.11, 0.01% when adding the CaCl2, NaCl and KCl respectively. Moreover, the NCS capacity in removing increased with the increase of the initial P concentrations and the decrease of the liquid medium pH values. Also, P adsorption decreases with the increase of temperature. The P kinetic and isothermal removal experimental data were well fitted with the Pseudo-second order and Langmuir models respectively indicating that P adsorption onto NCS particles is mainly governed by chemical processes and occurs heterogeneously on multi-layers surfaces.