Single Salt Solutions Research Articles

Qualitative discrimination and quantitative prediction of salt in aqueous solution based on near-infrared spectroscopy

Freshwater resources have been gradually salinized in recent years, dramatically impacting the ecosystem and human health. Therefore, it is necessary to detect the salinity of freshwater resources. However, traditional detection methods make it difficult to check the type and concentration of salt quickly and accurately in solution. This paper uses a portable near-infrared spectrometer to qualitatively discriminate and quantitatively predict the salt in the solution. The study was carried out by adding ten salts of NaCl, KCl, MgCl2, CaCl2, Na2CO3, K2CO3, CaCO3, Na2SO4, K2SO4, MgSO4 to 2 mL of deionized water to prepare a single salt solution (0.02 %–1.00 %) totaling 100 sets. It was found that the Support vector machine (SVM) model was only effective in discriminating the class of salt anions in the solution. The Partial least squares-discriminant analysis (PLS-DA) model, on the other hand, can effectively discriminate the classes of salt in solution, and the accuracies of the optimal model prediction set and the interactive validation set are 98.86 % and 99.66 %, respectively. Furthermore, the Partial least squares regression (PLSR) models can accurately predict the concentration of NaCl, KCl, MgCl2, CaCl2, Na2CO3, K2CO3, CaCO3, Na2SO4, K2SO4, MgSO4 salt solutions. The coefficients of determination R2 of their model interactive validation sets were 0.99, 0.99, 0.99, 0.97, 0.99, 0.99, 0.98, 0.99, 0.98, and 0.98, respectively. This study shows that NIRS can achieve rapid and accurate qualitative and quantitative detection of salts in solution, which provides technical support for the utilization of safe water resources.

Density and speed of sound measurements of aqueous solutions of potassium formate, potassium bicarbonate and their mixtures

Potassium formate and potassium bicarbonate are currently subject of research in a variety of new potential technical applications. One example of this is the use of the mixture of both salts in solution as a reversible hydrogen storage system and thus as a potential renewable energy carrier. In order to develop these new technologies, knowledge of the thermophysical properties of the individual salt solutions and mixtures is essential. Due to the limited data available in literature, which are only available for the single salt solutions, measurements of density and speed of sound as well as mathematical correlations based on the data were carried out in order to predict the behaviour of the salt solutions as a function of concentration and temperature. Good approximation equations were found for both properties, which agree with the existing data in the literature and result in deviations well below 1 % over wide concentration and temperature ranges. The large number of measurements, the clear trends in the results and the good agreement with existing data from the literature allow to assume that reliable predictions of concentration, and thus degree of hydrogen charging, can be realized utilizing density measurements. With the help of this fundamental research, it will not only be possible to investigate the newly discussed applications in more detail in the future, but also enable more precise design calculations, models and simulations. In addition, material properties that result from the measured variables or are related to them, such as thermal expansion or isentropic compressibility, can be analysed.

Modulating ion coordination environment for improved Li+/Mg2+ selectivity in mixed solutions

AbstractThe outstanding ionic sieving capabilities of the nanoporous membranes have been evident; however, the selectivity in mixed solutions is often lower than that in single salt solutions. Given that the inherent properties of nanochannels remain the same, the ionic coordination structure in mixed solution becomes a remarkable factor for the inferior selectivity, and may change due to the interaction between anions and multivalent cations, a phenomenon rarely explored. Herein, molecular simulations demonstrated some free hydrated ions transfer to ionic clusters consisting of multi‐ions in representative LiCl/MgCl2 mixed solutions, and the ionic permeability discrepancy is exponentially associated with ionic cluster change. Ionic clusters are engaged by the enhanced coordination of chloride ions under the interference of divalent cations. Hence, by introducing anions with weak coordination ability, this detrimental effect is mitigated and ion selectivity is improved. This work provides essential theoretical foundations for further ion sieving applications in complex system.

Modelling of selective ion partitioning between ion-exchange membranes and highly concentrated multi-ionic brines

In recent years, the growing interest in the use of Ion-Exchange Membranes, in the treatment of highly concentrated multi-ionic brines for the selective recovery of critical elements, has prompted the research of fundamental models capable of predicting the IEMs selectivity towards like-charged species. Prior studies have proposed ion partitioning models limited to single-salt solutions that were validated only up to moderate salt concentrations. In this work, we developed a novel multi-ionic extension of the Manning counter-ion condensation model, aiming to predict the sorption selectivity of like-charged counter-ions. Furthermore, the peNRTL model was coupled with the extended Manning model to broaden its applicability range, encompassing membrane equilibrated with very highly concentrated solutions. Novel experimental ion sorption tests with single-salt and binary solutions including NaCl, KCl, MgCl2, and CaCl2 at high concentrations were performed with the commercial cation-exchange membrane Fumasep FKE-50. To the best of Authors’ knowledge, the proposed model for the first time successfully provided quantitative predictions of multi-ionic ion partitioning for all the systems investigated up to extremely high external salt concentrations. The outcomes of this work suggest a strong influence of the local non-electrostatic interactions on the activity coefficients in the membrane phase at high external concentration and highlight the key role of counter-ions hydration state in the condensation phenomenon.

The Microstructural Investigation and the Temperature-Changing Separation of Brine with a High Mg/Li Ratio

The difficult separation of magnesium–lithium has always been a problem that impedes the comprehensive utilization of salt lake brine resources. In this paper, a method for the separation of magnesium and lithium based on the crystallization of magnesium sulfate at high-temperature supersaturation and a low viscosity was investigated. The microstructure of soluble solutions was analyzed, and the results showed that, in a single-salt solution, controlling the temperature can change the contact ion pair structure of MgSO4 solution, and the arrangement of SO42− and H2O in the second hydration layer changes. In the Li2SO4 solution, the hydrogen bonds between SO42− and H2O break, and the surrounding water structure changes, breaking the similarity of the microstructure of magnesium–lithium and enhancing the separation effect. In a multi-ion system, the change in water structure in the solution decreases with the increase in Cl− concentration. Controlling the temperature of salt lake brine with different magnesium–lithium mass ratios, it was found that the magnesium–lithium mass ratio in the brine could be reduced by one-third; when the magnesium–lithium mass ratio was 10:1~160:1, the loss of lithium could be controlled within 5%, but when the magnesium–lithium mass ratio was 5:1, the loss of lithium was 25.06%. The main reason for lithium loss is that Li2SO4 in the liquid phase enters the solid phase as a cluster and is entrapped during the MgSO4 crystallization process. The entire experiment shows that controlling the temperature process is more suitable for salt lake brine with a high magnesium–lithium ratio.

Isotope effects accompanying δ2 H, δ18 O and δ17 O analyses of aqueous saline solutions using cavity ring-down laser spectroscopy.

The presence of substantial amounts of dissolved salts creates serious difficulties in isotope analyses of water samples using conventional isotope ratio mass spectrometry. Although nowadays laser-based instruments are increasingly used for this purpose, a comprehensive assessment of isotope effects associated with direct analyses of aqueous saline solutions using this technology is lacking. Here we report the results of laboratory experiments aimed at quantifying isotope effects associated with direct, δ2 H, δ18 O and δ17 O analyses of single-salt solutions and double-salt mixtures prepared with a water of known isotopic composition. Three single-salt solutions (NaCl, CaCl2 and MgSO4 ) and two double-salt mixtures (NaCl + CaCl2 and NaCl + MgSO4 ) were prepared and investigated for a wide range of molalities. The triple-isotope composition of the prepared solutions was analysed with the aid of a Picarro L2140-i Cavity Ring-Down Spectroscopy analyser. The NaCl and CaCl2 solutions revealed small negative salt effects, independent of molality and comparable with measurement uncertainty. The MgCl2 solution showed the highest salt effects, reaching saturated solution ca. +2.7‰ (2 H), -3.5‰ (18 O) and -1.7‰ (17 O). Salt effects for the double-salt mixtures generally mirrored the effects observed for the single-salt solutions. The observed salt effects are discussed in the context of processes occurring during the injection of the salt solutions into the vaporizer unit of the CRDS analyser. The presented study has demonstrated feasibility of direct, triple-isotope analyses of aqueous salt solutions using a Picarro L2140-i CRDS analyser for a broad range of salinities up to saturated conditions. Large uncertainties of 17 O-excess determinations for solutions forming hydrated salts preclude the use of this parameter for interpretation purposes.

Separation Performance of Lithium and Calcium from Synthetic Geothermal Brine Using Electric Field-assisted Membrane

Green low-carbon technology development has spurred an increased demand for lithium. Brine, including geothermal brine, is the world’s largest source of lithium. However, the low lithium content and the presence of other ions pose challenges in concentrating lithium. An electric field-assisted membrane is a separation approach combining nanofiltration membranes with an electric field as an additional driving force, effectively separating lithium from magnesium and strontium. This study was conducted to separate lithium and calcium from synthetic geothermal brine using an electric field-assisted membrane. The separation process is conducted for lithium (50 ppm) and calcium (300, 800, and 2,000 ppm) with variations in electrical voltage (0V, 2V, and 3V). The decrease in lithium rejection reaches up to 50% at an electrical voltage of 2V. Conversely, the increase in electrical voltage does not significantly impact calcium rejection (calcium rejection remains at 89% with an electrical voltage of 3V) and the permeate flux for lithium and calcium. The increasing calcium concentration affects permeate flux significantly but does not notably affect calcium rejection, with the rejection remaining above 85%. The findings suggest the feasibility of concentrating lithium through electric field application without compromising calcium rejection within a single salt solution system.

Analyzing ion uptake in ion-exchange membranes using ion association model

Predicting ion uptake and selectivity in ion-exchange membranes is desired for many applications, yet a suitable physical description defining the most appropriate ion-specific parameters is still challenging. Here, we systematically develop an ion-association-based approach to modeling ion uptake in ion-exchange membranes from solutions of symmetric and non-symmetric salts. The model treats association in an ion-specific manner, self-consistently accounting for equilibria between free ions in solution and within the membrane phase (salt injection) and between free and associated species within the membrane (association equilibria), subjects to overall membrane electroneutrality. The resulting models, including different possible association equilibria, were employed to fit the reported data for Nafion 117 and CR61 cation-exchange membranes in equilibrium with NaCl, MgCl2, CaCl2, and Na2SO4 single-salt solutions. The results are compared with the previously reported fits to the Manning condensation model, which shows that both models produce similarly good fits for NaCl, MgCl2, and CaCl2 solutions in the 0.01 to 1 M range. However, the greater flexibility and specificity of the association model allow addressing deviations observed for Na2SO4 solutions and for CaCl2 above 1 M as free-ion paring and possible formation of charged NaSO4- and CaCl+ pairs, respectively. The results demonstrate the present model may be a sound non-mean-field alternative to the Manning condensation model, capable of addressing ion-specificity and multiple modes of association.

Graphene Oxide/Polyethyleneimine-Modified Cation Exchange Membrane for Efficient Selective Recovery of Ammonia Nitrogen from Wastewater.

Competition for the migration of interfering cations limits the scale-up and implementation of the Donnan dialysis process for the recovery of ammonia nitrogen (NH4+-N) from wastewater in practice. Highly efficient selective permeation of NH4+ through a cation exchange membrane (CEM) is expected to be modulated via tuning the surface charge and structure of CEM. In this work, a novel CEM was designed to form a graphene oxide (GO)-polyethyleneimine (PEI) cross-linked layer by introducing self-assembling layers of GO and PEI on the surface of a commercial CEM, which rationally regulates the surface charge and structure of the membrane. The resulting positively charged membrane surface exhibits stronger repulsion for divalent cations compared to monovalent cations according to Coulomb's law, while, simultaneously, GO forms π-metal cation conjugates between metal cations (e.g., Mg2+ and Ca2+), thus limiting metal cation transport across the membrane. During the DD process, higher NH4+ concentrations resulted in a longer time to reach Donnan equilibrium and higher NH4+ flux, while increased Mg2+ concentrations resulted in lower NH4+ flux (from 0.414 to 0.213 mol·m-2·h-1). Using the synergistic effect of electrostatic interaction and non-covalent cross-linking, the designed membrane, referred to as GO-PEI (20) and prepared by a 20 min impregnation in the GO-PEI mixture, exhibited an NH4+ transport rate of 0.429 mol·m-2·h-1 and a Mg2+ transport rate of 0.003 mol·m-2·h-1 in single-salt solution tests and an NH4+/Mg2+ selectivity of 15.46, outperforming those of the unmodified and PEI membranes (1.30 and 5.74, respectively). In mixed salt solution tests, the GO-PEI (20) membrane showed a selectivity of 15.46 (~1.36, the unmodified membrane) for NH4+/Mg2+ and a good structural stability after 72 h of continuous operation. Therefore, this facile surface charge modulation approach provides a promising avenue for achieving efficient NH4+-selective separation by modified CEMs.

Evaluating the role of salts on wettability alteration in dolomite rocks: Possibility of water based oil mobilization application

While many low salinity studies have been conducted on chalks, calcite minerals and sandstone rocks, few research articles have explored the same for applications in dolomite rocks. To explore the effect of mineralogy, a comparative study on the wettability alteration in the presence of low salinity brines for 2 carbonate rocks of varying composition was studied. The contact-angle experiments were performed for two carbonate samples. One carbonate sample was composed of ∼100 % dolomite mineral whereas the other carbonate rock sample was composed of both dolomite and calcite mineral (5 % calcite and 95 % dolomite). The ionic solutions were composed of NaCl, MgCl2, CaCl2 and CaSO4 single salt solutions of concentration (500 ppm to 5000 ppm). The contact angle reduction was observed in the following order CaSO4 > MgCl2 > CaCl2 > NaCl for the carbonate sample containing calcite and dolomite minerals and the maximum reduction in contact angle for the carbonate sample containing dolomite and calcite minerals was observed for CaSO4 brines was 26.13 % for 1000 ppm concentration. The contact angle reduction observed for the carbonate sample containing dolomite mineral was found to be in the following order MgCl2 > CaCl2 > CaSO4 > NaCl and the maximum reduction in contact angle was observed for MgCl2 brines was 24.58 % for 3000 ppm concentration. The wettability alteration observed in the carbonate sample containing dolomite mineral was less as compared to the carbonate sample containing calcite and dolomite mineral. In the presence of MgCl2 brines, the pH of the brines dominates the mineral dissolution, thereby improving or reducing the extent of wettability alteration. However, the complete wettability reversal has not been observed in this study. An increase in temperature (from 70 to 90 °C) was found to be favourable for wettability alteration while the presence of calcites, along with dolomites has the potential to further improve oil recovery.

Study on the Permeability of GCL Materials in Coupled Environment

As a new-type anti-seepage material, Geosynthetic Clay Liner (hereinafter referred to as GCL) has been applied in various anti-seepage projects and achieved good benefits. Based on different salt solution types, concentrations, dry-wet, and freeze-thaw cycles, this paper designs a permeability test of GCL after aging, and the result shows that: (1) under the influencing factors of single salt solution, there is a threshold concentration of 0.15 mol/L, which means that the increase rate of GCL permeability coefficient suffers a significant decrease above this concentration. (2) With fewer numbers (<4 ) of dry-wet cycles the GCL permeability coefficient shows faster growth and then returns gradually to stability. (3) Compared with dry-wet and freeze-thaw environments, cation concentration and valence have a more prominent inhibition effect on the anti-seepage property of GCL. The research results can provide data reference and reasonable advice for the deterioration of various indicators of GCL material and its service life in corresponding projects in saline soil areas.

Metal-Organic-Framework-based nanofiltration membranes for selective multi-cationic recovery from seawater and brines

Nanofiltration (NF) is gaining a role of increasing importance in Zero Liquid Discharge (ZLD)/Minimal Liquid Discharge (MLD) systems, enhancing the efficiency of downstream technologies to recover valuable minerals from seawater and brines. However, often the purity of the recovered minerals does not meet market specifications, making ZLD/MLD currently economically unfeasible. To such end, in this study, a novel positively charged NF membrane was developed to enhance magnesium and calcium selectivity. The membrane comprised: (i) an ultrafiltration substrate and (ii) an active layer that incorporated NH2-MIL-101(Al) and ZnO nanoparticles in a chitosan matrix. The influence of different loadings of NH2-MIL-101(Al) and ZnO on membrane structure, selectivity and water permeability was investigated. Initial filtration tests with single-salt solutions at 1000 ppm (NaCl, Na2SO4, MgCl2, CaCl2) showed that the membrane with 35%wt of ZnO presented the highest rejections of MgCl2 (90.10%) and CaCl2 (86.49%). Selectivity towards MgCl2 and CaCl2 was higher than those of commercial membranes (NF90 and NF270) and the positively charged membranes introduced in recent literature. The novel synthesized membrane in this work was also tested with synthetic seawater and brine at a trans-membrane pressure of 30 bar. Results highlighted the intriguing competitiveness of the novel membrane in terms of magnesium and calcium selectivity with NF90 and NF270 within the field of both seawater and brine valorization.

Sensing System for Mixed Inorganic Salt Solution Based on Improved Double Label Coupling RFID

As a crucial part in sewage, high-salt wastewater contains abundant corrosive components and heavy metal elements, which makes it difficult for invasive monitoring. Therefore, based on coupling Radio Frequency Identification(RFID) tags, this paper proposes a non-invasive monitoring method for concentration of inorganic salt in sewage. In this method, Cole-Cole model and Slit Cylindrical Capacitance(SCC) model are combined to explore the relationship between capacitance of RFID and concentration of inorganic salt in sewage pipeline. A New Efficient Levenberg-Marquardt(NELM) algorithm is used for regression between relative permittivity and concentration of inorganic salt categorically. Then, measurement data is processed under modified relative permittivity mixing rule of electrolyte and solvent. Finally the concentration of each component in the multi-component inorganic salt wastewater are obtained. Experimental results show that the maximal relative error (MRE) and average relative error(ARE) of single inorganic salt solution are 1.1% and 0.5%, while mixed solution are 2.6% and 1.89%. Such results indicate significant improvement comparing with previous works. Great potential of RFID in working sewage monitoring is sufficiently confirmed.

Effect of different soluble salt ions on deformation of desulfurization gypsum in high humidity environment: a statistically designed experimental analysis method

In response to the green energy-saving goal of carbon neutralization and carbon peak, the research and development of green building materials have become a key research direction. Desulfurization gypsum is widely used in building materials because of its good energy saving, but it cannot be used in high humidity areas because of its highly soluble salt. Based on this reason, this paper uses statistically designed experiments (SDE) to design the experiments on the influence of four common soluble salt ions and on the sagging deformation of desulfurization gypsum, and studies the significance of their influence by SDE experimental analysis method. The results show that: (1) in the environment of a single salt solution, ion, ion, ion, and ion will cause sagging deformation of desulfurization gypsum, and their values are 0.432 mm, 1.933 mm, 0.942 mm, and 0.940 mm respectively. It can be seen that the effect of the ion is the most significant. (2) In the environment of composite salt solution, ions will inhibit the sagging deformation of desulfurization gypsum. Specifically, in the compound salt solution environment of and the deformation values are 0.605 mm and 0.596 mm respectively.

Ultra-selective chelating membranes for recycling of cobalt from lithium-ion spent battery effluents by electrodialysis

The recovery of valuable resources from spent effluents is critical to ensure sustainable growth and reduce commodity shortages at global levels. Spent batteries are largely untapped resources containing multiple high-value metal ions that may be harnest and resued indefinitely to develop a circular battery economy. Challenges however lay with the cost of purification and recovery strategies and the limited selectivity of existing processes. This work presents the development of selective cation exchange membranes suitable for the selective recovery of cobalt from mixtures of lithium, cobalt, and nickel from spent battery effluents. Efficient cation exchange membranes were generated by modifying poly(vinyl chloride) films with ethylene diamine followed by grafting of 5-chloro-8-hydroxyquinoline (5C8Q) chelating agents and two synthesis routes were compared including surface and bulk grafting and the membrane separation properties were benchmarked against CIMS Neosepta. Besides being stable across a pH range between 2 and 8, relevant to spent battery lixiviat, the surface grafted membranes exhibited the lowest energy of sorption in comparison to bulk membranes, which was ten times lower than that of the commercial CIMS Neosepta reference membranes. The transfer of ions from model single salt solutions across the surface grafted membranes allowed for over 60 % of cobalt recovery within 1 h, while nickel and lithium were transferred only up to 18 % and 0.2 %, respectively. In addition, the electrodialysis-based separation of multi-component solutions remained very cost-effective with cobalt ion removal amounts up to 58 %, leading to Co/Li separation factors as high as 247. This novel chelating agent strategy opens avenues for the development of highly efficient and selective membrane materials, which are able to operate in extreme pH environments and supporting ultra-selective ionic transfer.

Lithium-ion extraction using electro-driven freestanding graphene oxide composite membranes

Lithium-ion extraction and recovery from unconventional aqueous sources by utilizing membranes as a separation barrier are potential technologies to address the challenge of increased lithium demand. Separating lithium from other competing metal ions is challenging due to their low selectivity when using conventional membranes as selective barriers. Graphene oxide (GO) nanofluidic membranes possess a higher monovalent ion permeation rate than multivalent ions, however, the selectivity of lithium over other monovalent ions is low. In this study, we created freestanding GO-based membranes with enhanced Li+/monovalent ions selectivity to concentrate and recover lithium from aqueous solutions containing competing monovalent ions (e.g., K+ and Na+). Specifically, sulfonate groups are introduced into the membrane matrices by intercalating the spacing agent, polystyrene sulfonate (PSS), into the adjacent GO nanosheets. Additionally, neutral and positively charged spacing agents are also used for comparison, and to further investigate the transport mechanisms. The Li+ permeation rate of GOM-S (PSS-incorporated GO membrane) is higher than the other GO-based membranes in a single salt solution. In a mixed salt solution, the Li+/K+ selectivity of GOM-S depends on concentration and we observed the highest value, 3.43, when using 0.5 M LiCl and 0.5 M KCl as the feed (high) concentrations and 0.001 M LiCl and 0.001 M KCl as permeate (low) concentrations. We observed that as permeate concentration decreased the selectivity increased and the pH values from 3 to 10 did not change the selectivity. DFT calculations show that the Li–SO3H pair has smaller binding energy, facilitating lithium-ion transport along the membrane nanochannel. Also, the solution concentration is crucial to the competitive mixed ionic transport, which results from the preferential surface transport induced by the electrical double layer (EDL) extension within the confined membrane nanochannels.

The Water Activity of Mars-relevant Multicomponent Brines: The Changing Influence of Perchlorate on Habitability over Time

Low water activity limits the habitability of aqueous environments, and salts present on Mars are known to reduce water activity. As environmental brines are not pure solutions of a single salt, predicting their water activity is difficult without direct measurement. Martian brines are likely complex and dominated by ions including sulfates and perchlorates, unlike typical terrestrial aqueous environments dominated by sodium chloride. We used the Pitzer model to predict the water activity of multicomponent brines and tested against laboratory-produced brines, including for the first time perchlorate salts that are known to exist on Mars. Our calculations match measurements of single-salt solutions and predict the water activity of multicomponent brines with an accuracy dependent on the quality of thermodynamic data available for a given ion combination. We tested the hypothesis that some salts will dominate the water activity, and therefore habitability, of multicomponent brines. Some salts, such as sodium and magnesium sulfates, did not strongly modulate the water activity of the solution, whereas others such as magnesium chloride and some perchlorates did. Applied to the history of Mars, the data suggest that sulfates and sodium chloride present in Noachian and early Hesperian environments would not have limited habitability. Perchlorates produced photochemically later in the Amazonian could impose a water activity limit at high concentrations that is not significantly changed by other salts. Overall we found that magnesium and calcium chlorides mixed with perchlorates can reach the lowest water activity values and therefore the lowest habitability of the brines tested.

Separation Mechanisms and Anti-Fouling Properties of a Microporous Polyvinylidene Fluoride-Polyacrylic Acid-Graphene Oxide (PVDF-PAA-GO) Composite Membrane with Salt and Protein Solutions.

This research demonstrates the preparation of composite membranes containing graphene oxide (GO) and investigates the separation mechanisms of various salts and bovine serum albumin (BSA) solutions. A microporous polyvinylidene fluoride-polyacrylic acid-GO (PVDF-PAA-GO) separation layer was fabricated on non-woven support. The GO-incorporating composite resulted in enlarged pore size (0.16 μm) compared with the control membrane (0.12 μm). The zeta potential of the GO composite was reduced to -31 from -19 mV. The resulting membranes with and without GO were examined for water permeability and rejection efficiency with single salt and BSA solutions. Using the non-woven/PVDF-PAA composite, the permeance values were 88-190 kg/m2hMPa, and the salt rejection coefficients were 9-28% for Na2SO4, MgCl2, MgSO4, and NaCl solutions. These salt removals were based on the Donnan exclusion mechanism considering the ion radii and membrane pore size. Incorporating GO into the separation layer exhibited limited impacts on the filtration of salt solutions, but significantly reduced BSA membrane adhesion and increased permeance. The negatively charged protein reached almost complete removal (98.4%) from the highly negatively charged GO-containing membrane. The GO additive improved the anti-fouling property of the composite membrane and enhanced BSA separation from the salt solution.

A Physicochemical Study of Cost-Effective Liquid Desiccants for Use in an air conditioning systems

Liquid desiccant systems (LDS) have attracted attention as promising low-energy alternative cooling solutions relative to conventional systems. An integral part of the LDS dehumidification capability depends on the composition of the hygroscopic desiccants utilized. The vapour pressure of different hygroscopic salt solutions and mixtures thereof have been measured at a temperature of 298.15K using a Yamamoto configuration. The initial validation of the measurement configuration using a single salt solution has exhibited a satisfactory correlation with vapour pressures reported by previous authors at various concentrations. The performance of MgCl2 solution was found to be comparable to that of LiCl. The results have shown that MgCl2 solution with 30% w/v concentration is sufficient to maintain the equilibrium relative humidity (ERH) at 50%, the recommended value for the human comfort zone, a value close to that obtained from LiCl solution (ERH = 55%) with the same concentration. Moreover, the best performing salt solution mixtures were found to be magnesium and lithium chlorides. Considering that the cost of LiCl is 23 times higher than that of MgCl2, the potential replacement of LiCl with MgCl2 in LDS is very promising from both a performance and cost point of view. The concentrated seawater brines have also shown a very promising performance comparable with that of 50% CaCl2– 50% MgCl2 artificial mixture.

Phase equilibria in the ternary systems LiCl–LiBr–H2O and LiCl–LiBr–CH3OH at 298 K

Oil gas field brine is a dominant liquid mineral resource in Sichuan Basin, and its rational development and utilization is of great significance to the national economy. In order to explore the physicochemical properties of brine and provide theoretical guidance for the comprehensive utilization of brine, the isothermal solubilities of the ternary systems LiCl − LiBr − H2O and LiCl − LiBr − CH3OH at 298 K were determined by employing the isothermal dissolution equilibrium method. Based on the measured composition of the liquid phase, wet solid phase and equilibrium solid phase, isothermal phase diagrams of the two systems at 298 K were drawn. The results show that according to the phase diagram of the ternary system LiCl − LiBr − H2O at 298 K, there is no single salt and double salt formation, but the crystalline region precipitated by the solid solution occupies all the crystalline space. The phase region is divided by a solubility boundary line into two parts, namely the liquid phase unsaturated region located below the isotherm and the completely mutually soluble solid solution crystallization region above it. Therefore, the two single salts LiCl and LiBr could not be successfully separated with the guidance of this phase diagram. The ternary system LiCl − LiBr − CH3OH at 298 K has single salt and solid solution formed, but no double salt determined. The phase diagram of the ternary system LiCl − LiBr − CH3OH consists of an invariant point, two isothermal solubility lines, and two crystallization regions precipitated with Li(Cl, Br) and LiCl, respectively. Using the phase diagram as a guiding tool for phase separation, LiCl can be acquired by crystallization and filtration operations, but it cannot be achieved for LiBr. In this work, a combination of wet residue method and XRD is used to identify the equilibrium solid phase. Selecting the particle swarm optimization algorithm, the solubility predictions of the ternary systems LiCl − LiBr − H2O and LiCl − LiBr − CH3OH at 298 K were achieved through the well-established Pitzer model. The solubility simulation results satisfactorily matched with the experimental values, indicating that the parameters selected for the simulation have strong applicability.