Initial Salt Concentration Research Articles

Получение проводящих пленок SnO2 с использованием гидрохимического осаждения

Thanks to such unique properties as transparency and conductivity tin dioxide often utilize as transparent contact layer to produce displays, solar cells, and sensor devices. Hydrochemical method of deposition SnO2 films is a perspective due to its simplicity, and economical efficiency. The ionic equilibria analysis was carried out and the boundary conditions of Sn(OH)2 solid phase formation in the «Sn2+ – H2O – OH‾» system calculated. It was established, that tin(II) hydroxide may be obtain in the range 2 < pH < 12. Preliminary results allow to determinate an optimal mixture sourness interval 1 < pH < 5. Revealed, that the thickness of the Sn(OH)2 films strongly depends on the solution pH. Maximum value of 488 nm reached at pH = 8. Conductive SnO2 layers were obtained on a glass and sitall substrates with simultaneously presence of antimony chloride and ammonium fluoride followed by annealing in air. The thickness vs temperature and thickness vs tin initial salt concentration dependences were installed. The uniform tin hydroxide layers with a thickness of ~74 nm may be synthesized under pH = 2 conditions. By the electron microscopy method the average particle size was established changing from 200 to 400 nm for as-synthesized films, to ~20 nm for annealed which indicates the nanostructure nature of the films. The morphology, elemental composition and conductive properties of deposited films were investigated before and after heating stage. Studying the annealing temperature influence at the film resistance were identified a three temperature ranges within which the films sharply differ in their conductive properties, which is associated with phase and structural transformations in them. Shown, that the most conductive SnO2 films with the omic resistance 3-5 kOm/sm were obtained at the temperature range 620-870 K.

Comparison of crystallization behavior in a drop and in a thin layer of an aqueous salt solution of LiBr during non-isothermal desorption

An experimental study of the motion of the crystal front and the crystallization rate for a drop and a layer of an aqueous salt solution of LiBr was carried out. The nature of the crystal front motion depends on the initial salt concentration. For most of the crystallization time, the crystallization rate Jcr is many times higher for a drop than for a thin layer. For the final crystallization stage, Jcr is higher for the drop. Different crystallization kinetics is associated with a change in the place of origin of the first crystalline center, as well as with features of the temperature distribution on the free surface of the salt solution.

The effect of the initial salt concentration on the rate of crystallization in a thin layer of solution

When simulating crystallization, it is necessary to take into account the temperature distribution on the solution interface, the place of emergence of the first crystalline center, as well as the rate of evaporation and crystallization. Depending on the specified parameters, three crystallization scenarios are implemented: 1) a sharp decrease in the crystallization rate Jcr with time, 2) an increase in Jcr with time, 3) an increase in Jcr and reaching the maximum, and then a decrease in the crystallization rate.

Modeling and interpretation of membrane capacitive deionization responses to different salt load

AbstractMembrane capacitive deionization (MCDI) has been found to offer beneficial aspects compared with regular capacitive deionization as a promising process for water desalination. This research varied the salt load in a bench‐scale MCDI system and presented a kinetic model for describing its dynamic response of electrosorption and desorption. A pseudofirst‐order kinetic model was found to describe the MCDI process well according to graphical analyses of fitting results. Both regression and verification R2 values were greater than 0.97. Utilization of the model for the prediction of MCDI performance under the influences of initial salt concentration and flow rate led to proper calibration strategies. The impacts of the two parameters on both electrosorption and desorption can be interpreted by a layer resistance theory. Results of this research are beneficial for water professionals for improving desalination efficiency of an MCDI system as consideration of parameter settings is necessary for proper calibration and operation.

Гидрохимический синтез пленок халькогенидов металлов. Часть 42. Экспериментальная проверка областей осаждения PbSe селеносульфатом натрия и селеномочевиной в присутствии различных лигандов

Calculation of ionic equilibria in the reaction system for synthesis of PbSe thin films was carried out. Three reaction systems containing the following combinations of reagents were considered: sodium citrate with liquid ammonia and sodium selenosulfate (system 1) or selenourea (system 2) used as chalcogenizer, ethilendiamine, sodium acetate and selenourea (system 3).The main lead complex compoundsprevented the fast PbSe formation in system 1 and 2 in region of pH of intensive selenosulfate and selenourea decomposition were hydroxo-citrate complexes. In the system 3 complexes with ethilendiamine and acetate-ions played the most significant role. For evaluating the deposition conditions of the main and impurity phases (metal hydroxides and cyanamides) by thermodynamic calculations taking into account the sizes of critical nucleis, the boundary conditions and regions of formation of PbSe, Pb(OH)2, PbCN2 in the studied reaction systems were found. The calculation results are presented in the form of three-dimensional dependencies in the coordinates “indicator of the initial concentration of the metal salt – pH of the solution – ligand concentration” and “indicator of the initial concentration of the metal salt – pH of the solution – concentration of the chalcogenizer”. Based on the calculations and preliminary experiments, the compositions of the discussed reaction mixtures were formed for the chemical bath deposition of PbSe films, which, in addition to the main components, included a dopant in the form of ammonium iodide. In the synthesis process at a temperature of 353 K (system 1 and 2) for 60 minutes and 308 K for 90 minutes (system 3), using all the studied reaction systems on glass substrates, homogeneous PbSe layers with a thickness of ~500 to ~700 nm were obtained. The ratio between the main elements of Pb and Se in the film varies between 0.98-1.32, and the iodine content is 7-11 at.% depending on the composition of the reaction bath.

Experimental study on the hydraulic conductivity of unsaturated dispersive soil with different salinities subjected to freeze-thaw

The hydraulic conductivity of soil is a fundamental parameter that should be obtained both in hydrological and geotechnical studies since it relates to a series of hazards in earthen engineering projects, whereas investigations on dispersive soils, especially those distributed in cold regions, have rarely been reported. This study aims to explore the characteristics of permeability by using a dispersive soil from northeastern China, as well as the effects of soil salinity and freeze-thaw on the variation in hydraulic conductivity. Indoor constant-head permeation tests were conducted on artificially prepared specimens, and initial soil suctions were measured by the filter paper method to assist the analyses. The results demonstrated that the hydraulic conductivity decayed with permeation time until reaching relative stability, and both maximum and relatively-stable values (kmax and krs, respectively) should be adopted for comprehensively characterizing the permeability of dispersive soils. Increasing salt content increased the kmax exponentially, and the inflection salt content was approximately 1.5%, from which a sharp increase in kmax appeared; the krs showed a slight increase with initial salt contents as well. Freeze-thaw yielded nonmonotonic changes in the permeability as kmax peaked at 5 freeze-thaw cycles; the variation in krs was similar. The osmotic suction positively correlated with kmax but did not fully contribute to the sharp increase in kmax since it increased linearly with the salt content without mutation points. The number of freeze-thaw cycles influenced the relationship between the osmotic suction and kmax. The matric and osmotic suctions posed opposite impacts on the permeability. More importantly, detailed discussions for the underlying mechanisms of the abovementioned novel observations were illustrated. These results may serve as good references for understanding the features of the permeability of dispersive soils in seasonally frozen regions domestically or worldwide.

Adsorption mechanism of ReO4− on Ni–Zn layered hydroxide salt and its application to removal of ReO4− as a surrogate of TcO4−

The long-lived anionic radionuclide of 99Tc (pertechnetate ion TcO4−) is highly mobile under oxic conditions, and therefore long-term removal and immobilization of TcO4− from radioactively contaminated water have been major challenges. Mg–Al layered double-hydroxides (LDH) have been often investigated to remove anions from waste water. In this study, we propose Ni–Zn layered hydroxide salt (LHS) as an alternative adsorbent for anionic radionuclides. We prepared and characterized Ni–Zn LHS with the nominal composition of Ni0.77Zn0.46(OH)2(OCOCH3)0.46·0.96H2O, using X-ray diffraction (XRD) pattern, scanning electron microbe (SEM) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The formation of a layered structure was confirmed by XRD, and plate-like crystals of the Ni–Zn LHS were observed in SEM images. Analysis of Ni K-edge and Zn K-edge EXAFS spectra supported the structure proposed by previous works, where Ni ions form brucite-type layers with vacancies, and Zn ions were located at tetrahedral sites above and below the vacancy sites of the Ni hydroxide layers. The prepared Ni–Zn LHS was used for adsorption experiments of ReO4−, as a surrogate of TcO4−, in aqueous solutions with various initial Re and sodium salt concentrations. The maximum adsorption amount of Re was estimated at 127.7 mg/g (6.86 × 10−4 eq/g) by fitting adsorption isotherm of ReO4− to Langmuir plot. The adsorption of ReO4− at neutral pH was a reversible process by anion exchange, and decreased with increasing Cl−, NO3− and SO42− in solution. EXAFS analysis indicated that ReO4− was adsorbed as an outer-sphere complex on Ni–Zn LHS. The Ni–Zn LHS is a more robust adsorbent for ReO4− than the Mg–Al LDH in terms of solution pH and tolerance to competing anions, and may be an effective alternative to the traditional and more limited method of removing aqueous TcO4− by reductive precipitation.

Desalination using gas hydrates: The role of crystal nucleation, growth and separation

Seawater desalination using gas hydrates is a potential technique for water treatment. However, limited understanding and control in prior studies on nucleation, growth, and separation have prevented adequate commercialization of hydrate desalination processes. Hydrate formation and ‘memory’ experiments of C1 + C2 (74.7/25.3 mol%) gaseous mixtures were carried out using a Jerguson high pressure visual cell. The C1-C2 hydrate formation results indicate that formation onset times were three times longer in salt water compared to fresh water. Furthermore, it was observed that induction times decrease with increasing subcooling, and hydrate memory effects are reduced with increasing replenish time, i.e. the time lapse between dissociation and subsequent gas depressurization. A high-pressure desalination apparatus was also designed and constructed to produce the overflow of hydrates in the inner annulus of a gas bubble column placed inside a dissociation reactor. The working principle for this system is that the overflowing hydrates enter the outer annulus and are then dissociated. The salt removal efficiency was determined by measuring the conductivity of the recovered water. Experiments to assess the efficiency of the process were performed to determine how the salinity in the recovered water depends on different initial salt contents and subcooling for hydrate formation.

Crystallization of Salt Solutions on Surface of Droplet and Layer

The evaporation and crystallization of a droplet and a thin layer of aqueous solutions of LiBr and LiCl salts on a heated wall with a temperature Tw = 86°C were studied experimentally. Crystallization curves were obtained for a wide range of initial salt concentrations. For the first time it was shown that for different C01 values the crystallization rates Jcr were different; the Jcr curve was nonlinear. With C01 decreasing, the supersaturation at the onset of crystallization increased, because of different induction times with respect to the generation of the first active crystallization center. It is known for relatively large crystals that heat transfer influences the rate of crystallization. Processing of the experimental data with due account of the basic thermophysical parameters shows that supersaturation also affects the crystal growth. The crystallization rate in a thin layer is significantly higher than in a droplet. It was found that description of crystallization in a droplet should take into account strong anisotropy of the crystallization.

Hybrid optimization of preparative chromatography for a ternary monoclonal antibody mixture.

In the purification of monoclonal antibodies, ion-exchange chromatography is typically used among the polishing steps to reduce the amount of product-related impurities such as aggregates and fragments, whilst simultaneously reducing HCP, residual Protein A and potential toxins and viruses. When the product-related impurities are difficult to separate from the products, the optimization of these chromatographic steps can be complex and laborious. In this paper, we optimize the polishing chromatography of a monoclonal antibody from a challenging ternary feed mixture by introducing a hybrid approach of the simplex method and a form of local optimization. To maximize the productivity of this preparative bind-and-elute cation-exchange chromatography, wide ranges of the three critical operational parameters-column loading, the initial salt concentration, and gradient slope-had to be considered. The hybrid optimization approach is shown to be extremely effective in dealing with this complex separation that was subject to multiple constraints based on yield, purity, and product breakthrough. Furthermore, it enabled the generation of a large knowledge space that was subsequently used to study the sensitivity of the objective function. Increased design space understanding was gained through the application of Monte Carlo simulations. Hence, this work proposes a powerful hybrid optimization method, applied to an industrially relevant process development challenge. The properties of this approach and the results and insights gained, make it perfectly suited for the rapid development of biotechnological unit operations during early-stage bioprocess development.

Boron-nitride-carbon nanosheets with different pore structure and surface properties for capacitive deionization

Capacitive deionization (CDI) has long been identified as a hopeful solution for adsorption of ions from saline water. Developing stable electrode materials is of great significance to the improvement of CDI performance. In this work, two kinds of boron-nitride-carbon (BCN and MBCN) materials were synthesized for capacitive deionization (CDI) application. The BCN featured with high specific surface area (1097.5 m2 g−1) and positive surface charges (Epzc of −0.445 V vs. Ag/AgCl) is a good anodic candidate in the CDI device. After configuring with activated carbon, the asymmetric CDI cell exhibits excellent salt adsorption capacity of 17.46 mg g−1 at supplied voltage of 1.4 V when the feeding NaCl concentration is 300 mg L−1 and robust cycle performance with 81.4% capacity retention after 50 cycles at supplied voltage of 1.0 V with initial salt concentration of 500 mg L−1. Overall, in contrast to that of MBCN and carbon materials, the BCN nanosheets demonstrate a high removal capacity and superior cycling stability even at low salt concentration. The stable and positively charged BCN should be a good choice for next generation of high performance CDI electrode materials.

Removal of Fe (II) ions from drinking water using Electrocoagulation (EC) process: Parametric optimization and kinetic study

Presence of Fe (II) ions in drinking water across different parts of India is a serious health concern in recent years. To reduce the Fe (II) ions in drinking water, researches are now being carried out using efficient and economical methods like adsorption, electrocoagulation etc. In the present work, experimental studies were carried out to optimize various operating parameters of electrocoagulation (EC) for efficient removal of iron (Fe (II) ions) from drinking water. Further, total dissolved solids, turbidity, conductivity, salinity, pH was accessed to verify the quality of treated water. From experimental results it was observed that, initial pH of 6.34, current density of 2 mA cm−2 with inter-electrode distance of 1 cm, electrocoagulation time of 45 min, initial salt (NaCl) concentration of 0.33 g L-1, stirring speed of 400 RPM are the optimum operating parameters to produce drinkable water (Fe (II) ions <0.30 mg L-1) from tap water having initial Fe (II) ions of 20 mg L-1. Kinetic analysis of EC process infers that Fe (II) ion removal follows the first-order kinetic model with respect to different operating parameters. The rate constant (k) increased from 0.0352 min-1 to 0.1087 min-1 when the current density was increased from 1 mA cm-2 to 2.5 mA cm-2, due to availability of higher amounts of aluminium ion flocs during EC. Experimental studies confirm that suspended flocs generated during electrocoagulation can be separated by centrifugal methods as well as microfiltration membrane to replace laboratory scale filter paper-based methods.

Freezing-Driven DNA Adsorption on Gold Nanoparticles: Tolerating Extremely Low Salt Concentration but Requiring High DNA Concentration.

Attaching thiolated DNA to gold nanoparticles (AuNPs) is a highly important and useful reaction for many applications. Various methods such as adding salts, acids, polymers, and surfactants have been developed to facilitate the reaction. Recently, it was reported that a very high DNA density can be achieved simply by freezing AuNPs with the DNA without any other reagents. DNA oligonucleotides are also known to stretch and align upon freezing. In this work, a set of experiments were performed with a fluorophore and thiol dual-labeled DNA, and the DNA loading density and colloidal stability of AuNPs were measured. The initial salt concentration was unimportant, and even 0.1 mM Na+ allowed around 100 DNA attached to each 13 nm AuNPs. On the other hand, a high DNA concentration of 3 μM was needed to achieve the high DNA density and good colloidal stability of AuNPs. When the thiolated DNA was forced in stable secondary structures, the attachment was low, and preadsorbed DNA also inhibited the DNA attachment by the freezing method. Overall, nonstructured thiolated DNA strands need to align by freezing and quickly attached through the ends of the DNA. This work illustrates practical experiment design conditions and offers fundamental surface science insights for the DNA attachment by freezing.

Desalination and power generation of caspian sea by applying new designed microbial desalination cells in batch operation mode

The Caspian Sea is one of the largest water sources located in the north of Iran; so this research was carried out to investigate the new design of microbial desalination cell (MDC) (double layer) efficiency in water desalination and power generation of the enormous saline water source in the north of Iran. Actual (i.e., Caspian Sea) and artificial seawater with different initial salt concentrations (5, 25, and 35 g/L NaCl) and, different hydraulic retention times (24, 48, and 72 h) in batch and open circuit voltage (OCV) mode were examined. In addition, the oxidation and reduction processes during desalination of each stage were monitored at 10 min intervals for 60 min. According to the obtained experimental data, both the desalination efficiency and the power generation decreased from 65 ± 1% to 41 ± 1% and 80 ± 4.5 mW/cm2 to 51.20 ± 2.5 mW/cm2 by increasing the retention time from 24 to 72 h for Caspian Sea water and 5 g/L NaCl, respectively. Maximum and minimum desalination efficiencies were 48 ± 1% and 65 ± 1% for Caspian Sea water and 5 g/L NaCl, respectively. Moreover, the maximum power densities were 72.83 ± 3.36 mW/cm2 and 80.00 ± 4.00 mW/cm2 for 35 g/L NaCl and seawater, respectively. As far as the authors know, this is the first study on the application of the new designed stacked MDC for power generation and desalination of water from the Caspian Sea. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

Removal of Methylene blue from saline solutions by adsorption and electrodialysis

In this study, the removal of MB from saline solutions was evaluated by two methods by adsorption and electrodialysis; the adsorption of the mixture dye/salt on dried orange peel waste (OPW) was studied in batch method. In this study the biosorption of cationic dye by OPW was investigated as a function of initial solution pH, and initial salt (sodium chloride) concentration. The maximal dye uptake at pH >= 3.6 in the absence and in the presence of salt and the dye uptake diminished considerably in the presence of increasing concentrations of salt up to 8 g/L. The Redlich Peterson and Langmuir were the most suitable adsorption models for describing the biosorption equilibrium data of the dye both individually and in salt containing medium. As well, this work deals with the electrodialysis application to remove the dye. Synthetic solutions were used for the investigation of the main operational factors affecting the treatment performance; such as applied voltage, pH, initial dye concentration and ionic strength. The experimental results for adsorption and electrodialysis confirmed the importance of electrostatic interactions on the dye. The electrodialysis process with standard ion exchange membranes enabled efficient desalination of cationic dye solutions; there are two main factors in fouling: electrostatic interaction between cations of dyes and the fixed charged groups of the CEM, and affinity interactions.

Origin and Dynamics of Saltwater Intrusion in a Regional Aquifer: Combining 3‐D Saltwater Modeling With Geophysical and Geochemical Data

AbstractWorldwide, aquifers in low‐lying coastal areas are threatened by saltwater occurrence, as a result of small head gradients, high groundwater abstraction rates, and drain management of the landscape, which is likely to intensify with climate change. Numerical models can serve as tools to identify the sources of the salt and thus to increase understanding of the driving mechanisms and important parameters controlling the extent of saltwater intrusions. This way, areas vulnerable to sea level rise can be identified and managed. Challenges include unknown initial salt concentrations, heterogeneous geology, and anthropogenic alterations. In this study, hydrogeological, geophysical, and geochemical data are used to develop a numerical density‐dependent groundwater flow and transport model with the objective to understand the history of a saltwater‐affected groundwater system and its likely response to historic and future changes. The extent of the simulated saltwater intrusion compares well with Airborne Electromagnetic data that show salt water up to 20 km inland. The results reveal that the salt water originates from a combination of laterally intruding seawater and vertically infiltrating transgression water. Main features controlling the progression of the modern seawater into the coastal aquifers are high permeable, deep Miocene sand aquifers, buried valleys that provide preferential flow paths in combination with extensive Miocene clay layers that delay saltwater intrusion. Anthropogenic activity enhances the saltwater inflow from the ocean and induces transient conditions. Future scenarios show that saltwater progression due to nonstationarity leads to enhanced contamination of the deeper aquifers. Climate change affects primarily the shallow aquifer systems.

Microstructure Ceramic Changes Resulting from Sodium Sulphate Subflorescence

In this article, the influence of sodium sulphate crystallization on microstructure changes in traditional ceramic was discussed. The tested elements in form of brick halves underwent capillary moistening in sodium sulphate solution with concentration of 5, 10, 15, 20, and 25%, and then their bottom walls were protected with polyethylene covers in order to ensure drying only through side walls. After drying, samples were taken from face walls (5mm) and 2 subsequent lower layers (each 10mm thick). Prepared samples were used for comparative analysis of ceramic microstructure changes caused by salt crystallization and material damage visible after salt extraction. In the tests, mercury porosimetry and confocal microscopy were used. Because of necessity to dry the samples to solid mass, the temperature of 80°±5°C was defined which enabled removing free water without damaging of crystallized salt structure. Based on the ceramic analysis, the initial salt concentration when macroscopic damage starts as a result of subflorescence (face layer delamination) was found. The analysis of pictures from a confocal microscope enabled to define the mechanism for ceramic material damage. A characteristic granular diffusion was observed which is the effect of pushing out ceramic by building out the sulphate crystals.

FFD Analysis for the Effect of Fouling on the Permeate Flux in High-Pressure Membranes

Porous high-pressure membranes have been widely used for both brackish water and seawater desalination. However, fouling (concentration polarization) extensively reduces permeate flux in high-pressure membranes such that reverse osmosis (RO) and/or nanofiltration (NF). In this study, we have attempted to understand the effect of membrane fouling on the permeate water flux by modeling the salt concentration profile within a membrane of interest. A parabolic (or diffusion) partial differential equation was used to describe the change in salt concentration inside the membrane. Subsequently, the PDE equation was solved numerically, under certain assumptions, by using forward finite difference (FFD) explicit method. It was found that salt accumulation occurs at the membrane feed-side surface and there was a noticeable decrease in water flux as fouling increased. For waters with an initial salt concentration of 10000 ppm (NaCl) and with an average diffusivity of , results showed that both RO/NF would have flux rates of 74.9, 67.4, 22.5, 0, –37.4, –74.9 LMH for the feed-side surface concentrations 0, 1000, 7000, 10000, 15000 and 20000 ppm, respectively, where negative flux indicates a back-flow scenario.

Using ANFIS and BPNN Methods to Predict the Unfrozen Water Content of Saline Soil in Western Jilin, China

Saline soil in seasonally frozen soil areas has caused tremendous damage to engineering and the ecological environment. The unfrozen water is the main factor affecting the properties of saline soil in seasonally frozen soil area and therefore needs to be studied. However, due to the high cost of laboratory measurement of the unfrozen water content, this study focuses on using an adaptive network fuzzy inference system (ANFIS) and a back propagation neural network (BPNN) to predict the unfrozen water content of saline soil in the Zhenlai area, Western Jilin. The data for the constructed model is obtained by nuclear magnetic resonance (NMR) testing. The initial water content (W0), salt content (S), and temperature (T) are used as input parameters for predicting the unfrozen water content (Wu). The results of the ANFIS and BPNN models are compared. The results show that although both methods are suitable for predicting the unfrozen water content of saline soil in the Zhenlai area, western Jilin, the prediction accuracy of the ANFIS model is higher.

Microcryogels as plastic antibodies for transferrin purification

Abstract Molecular imprinting technology (MIT) presents self-organization of functional monomers around a template, leading formation of specific recognition sites for the template with high selectivity. In this study, cryogels in microscale were fabricated as novel plastic antibodies via MIT for transferrin purification. After chemical and physical characterization studies, optimal hsTf adsorption conditions for the plastic antibodies were then determined by investigating parameters including medium pH and temperature, initial analyte concentration and salt concentration. Selectivity studies were performed by considering both size and isoelectric points of the proteins. Compared with the non-imprinted P(HEMATrp) microcryogels, the relative selectivity coefficients of the plastic antibodies for hsTf/MYB and hsTf/HSA were found to be 2.24 and 2.10 times higher, respectively. The findings indicated that the molecularly imprinted microcryogels could be selective, reusable and cost-friendly potential plastic antibodies for purification of transferrin.