Diffusion Of Salt Ions Research Articles

Microscopic Mechanism for Gradient Diffusion of Salt-Containing Droplets Induced by Electromagnetic Synergy: A Molecular Dynamics Study.

The electromagnetic synergy has been proven to be highly effective in separating oil-water emulsions. However, the dynamic impact mechanism of electromagnetic fields on the internal structure of salt droplets remains unclear. In this study, the molecular dynamics (MD) simulation was used to investigate the molecular diffusion of salt ions and water molecules, as well as the dynamic behavior of droplets under the combined influence of electromagnetic fields. The results indicate that ions accumulate in the electromagnetic synergistic field, causing the deformation amplitude of droplets to be smaller than that in a single electric field. The magnetic field affects the energy of the system, when the magnetic field strength is between 1 and 5T, the nonbonded energy significantly increases nonlinearly; when the magnetic field strength is greater than 5T, the total energy of the system significantly changes. In addition, the viscosity of the medium is significantly lower when the intensity of the magnetic and electric fields is controlled within a specific range, providing a new way to regulate the fluidity of fluids.

Advanced bionic inverted coral solar evaporator: Enhancing sustainable water utilization with efficient and salt-resistant evaporation

Interfacial solar-driven steam generation technology shows great potential in addressing desalination and wastewater purification. However, there is a lack of advanced evaporators with high evaporation efficiency and salt tolerance, which is an obstacle to its widespread application. Drawing inspiration from marine coral structures, we develop a bionic inverted coral-type 3D solar evaporator with an array structure using structural engineering design. The microscopically porous vertical channel structure within the overall skeleton enhances the longitudinal reflux of salt ions and water evaporation, while macroscopic gaps in the bionic coral branching facilitate lateral advection–diffusion of salt ions. Numerical simulations confirm that this bionic coral structure design improves the diffusion rate of concentrated brine. Due to the localized surface plasma resonance and the Marangoni effect, the evaporator achieves remarkable water evaporation performance (evaporation rate: 2.72 kg m−2h−1, energy efficiency: 95.8 %) and operates reliably even under 20 % brine concentration (evaporation rate: 2.65 kg m−2h−1) without significant salt crystallization. Furthermore, it exhibits good wettability and robust mechanical properties, capable of withstanding a wide range of temperatures. The efficient and salt-resistant evaporation makes it valuable for applications including desalination, various wastewater treatments, and agricultural irrigation, thereby promoting the sustainable utilization of water resources.

Spongy polyelectrolyte hydrogel with Janus porous for solar-driven interfacial evaporation and sustainable seawater desalination

Janus-structured hydrogels exhibit excellent advantages in interfacial solar desalination due to their hydrophilicity and low evaporative enthalpy of evaporation, as well as the better salt resistance and mechanical properties. In this research, a simple one-step self-stratification foaming technique is employed to transform hydrogels into Janus structured for seawater desalination. Polyvinyl alcohol (PVA), poly (diallyldimethylammonium chloride) (PDADMAC), and a photothermal material (carbon black, CB) are mechanically stirred with a foaming agent (sodium dodecyl sulfate, SDS), allowing for full mixing and air incorporation, ultimately forming a sponge-like polymeric electrolyte hydrogel with abundant Janus pore structures (PANS-J). The formation of Janus pores in the hydrogel is attributed to the flocculation and high density of hydrophilic PDADMAC, causing it to sink during gelation while hydrophobic PVA floats to the surface. The Janus structure produced by this method reduces heat loss and enhances evaporation performance, achieving a pure water evaporation rate of 3.35 kg m−2 h−1 under sunlight (1 kW m−2). Moreover, quaternary ammonium ions on PDADMAC effectively separate anions and cations in saltwater, reducing salt ion diffusion into the evaporator, preventing premature pore structure blockage, and thus improving long-term evaporator performance which can improve the salt resistance and mechanical properties. By combining these advantages, Janus evaporators hold significant promise for solar-driven water purification and other applications.

Biomimetic Design of 3D Fe3O4/V-EVOH Fiber-Based Self-Floating Composite Aerogel to Enhance Solar Steam Generation Performance.

An interfacial solar steam generation evaporator for seawater desalination has attracted extensive interest in recent years. Nevertheless, challenges still remain in relatively low evaporation rate, unsatisfactory energy conversion efficiency, and salt accumulation. Herein, we have demonstrated a biomimetic bilayer composite aerogel consisting of bottom hydrophilic and vertically aligned EVOH channels and an upper hydrophobic conical Fe3O4 array. Thanks to the design merits, the 3D Fe3O4/V-EVOH evaporator exhibits a high evaporation rate of ∼2.446 kg m-2 h-1 and an impressive solar energy conversion efficiency of ∼165.5% under 1 sun illumination, which is superior to those of state-of-the-art evaporators reported so far. Moreover, the asymmetrical wettability not only allows the evaporator to self-float on the water but also facilitates the salt ion diffusion in the channels; thus, the evaporator shows no salt crystals on its surface and only a 6% decrease in evaporation performance even after the salt concentration increases from 0 to 10.0 wt %.

Superhydrophilic Interconnected Biomass-Based Absorbers Toward High-Speed Evaporation for Solar Steam Generation.

Taking abundant and sustainable solar energy as the only energy source, solar-powered interface evaporation has been regarded as a promising method to alleviate the pressure of freshwater shortage. However, the uptake of clean water from brine is constantly accompanied by evaporation of water and condensation of vapor, which inevitably generates salt solid, preventing further continuous and stable evaporation. The most direct method is to fabricate a photothermal material with salt self-resistance by using the reflux of salt ions. Here, a superhydrophilic interconnected biomass carbon absorber (SBCA) is prepared by freeze-drying and carbonization, realizing strong liquid pumping, and self-blocking salt. In combination with superior broadband light absorption (94.91%), high porosity (95.9%), superhydrophilicity, and excellent thermal localization, an evaporation device with excellent evaporation rate (2.45kg m-2 h-1 under 1kW m-2) is successfully proposed. In the meantime, the porous skeleton and rapid water transport can enhance the diffusion of salt ions and slow down the rate of salt deposition. As a result, no salt deposition is found on the SBCA surface after continuous irradiation at 1kW m-2 for 15 h. The design can provide a convenient and low-cost efficient strategy for solar steam generators to address clean water acquisition.

Insights into Salt Ion Diffusion Behavior in Imbibed Fluids and the Source of Salt Ions in Clay-Rich Shale from Upper Cretaceous Qingshankou Formation, Songliao Basin

Insights into Salt Ion Diffusion Behavior in Imbibed Fluids and the Source of Salt Ions in Clay-Rich Shale from Upper Cretaceous Qingshankou Formation, Songliao Basin

Salt Ion Diffusion Behavior and Adsorption Characteristics of Fracturing Fluid in Tight Sandstone Gas Reservoir

The degree of salinity in the hydraulic fracturing rejection fluid of the Shaximiao reservoir in the central Sichuan Basin is high, and the underlying mechanism causing this salinity is not clearly understood. We evaluated the rock structure of tight sandstone, including rock composition, pore structure, ion diffusion, and adsorption behavior, to determine how the rock structure influences the mechanism of the sandstone’s interaction with the fracturing fluid. X-ray diffraction revealed that the rock mineral fraction has a significant clay mineral concentration. The results of linear swelling experiments revealed that the water sensitivity of tight sandstone reservoirs exhibits moderately robust characteristics. The time required for salt ion diffusion stabilization is much longer than that required for self-imbibition stabilization, and the diffusion of salt ions is almost log-linear with time after imbibition stabilization. The diffusion rates of salt ions were determined for different single minerals and particle sizes, with clay minerals and particle sizes controlling the diffusion rates. The samples were treated with different concentrations of KCl and acrylamide polymer solutions, and both the pore size distribution and pore throat properties were characterized by low-temperature nitrogen adsorption. Although the adsorption isotherms of both KCl and polymers are consistent with the Langmuir model, their adsorption mechanisms acting on tight sandstone and the effect of adsorption on the pore throat structure are inconsistent. The adsorption of potassium chloride enhances the rock’s pore throat diameter and permeability by increasing the uniformity of the pore throat by electrostatic adsorption with clay particles. However, polymer adsorption reduces the pore diameter of the rock and forms a thin film that obstructs the pore throat, complicating the pore throat and weakening its permeability. This research has led to a greater comprehension of the ion diffusion characteristics of the tight sandstone in the Shaximiao reservoir and the adsorption mechanism on the pore structure of the rock.

A polyelectrolyte hydrogel coated loofah sponge evaporator based on Donnan effect for highly efficient solar-driven desalination

Solar desalination is considered an efficient way to alleviate the global shortage of freshwater resources. However, the salt accumulation on the surface of solar absorbers drastically reduces light absorption and steam evaporation efficiency, especially in highly concentrated brines. Herein, inspired by the salt rejection mechanisms of the mangrove trees, a sodium polyacrylate carbonized loofah (PAAS-CLF) was designed using the biomass porous loofah sponge as the matrix, modified with sodium polyacrylate (PAAS) hydrogel coating for solar-driven desalination. The loofah sponge coated PAAS hydrogel as a substrate could obtain a naturally high porosity. Moreover, relying on the negatively charged PAAS hydrogel rich in –COO– groups, it could confine Na+ to induce the Donnan effect, thus reducing the diffusion of salt ions into the water supply layer and avoiding salt accumulation fundamentally. The PAAS-CLF had high water evaporation rates of 1.83 kg m−2h−1 with an efficiency of 94.54% attained under 1 sun. More notably, the evaporator maintained stable water evaporation rates over 1.45 kg m−2h−1 in salt water with a broad range of salinity (35–200 g kg−1), and no salt accumulation was observed during the long-time evaporation. Therefore, this work provides an approach of the flexible application using environmentally friendly biomass sponge composite polyelectrolyte hydrogel for salt-resistant evaporator in solar desalination and concentrated brine treatment.

Computational simulation-driven discovery of novel zeolite-like carbon materials as seawater desalination membranes.

Freshwater is a scarce and vulnerable resource that has never encountered such an extensive focus on a nearly worldwide scale as it does today. Recently, it has been found that desalination powered by two-dimensional (2D) carbon materials as separation membranes has significantly reduced the operational costs and complexity but presents heavy requirements for the structural stability and separation properties of the membrane materials. Here, we combined carbon materials with promising adsorption properties and zeolites characterized by a regular pore structure to obtain a zeolite-like structured carbon membrane Zeo-C and investigated the suitability of the Zeo-C membrane for seawater desalination based on the computational-simulation-driven approach. The results of molecular dynamics (MD) simulations and density functional theory (DFT) calculations revealed that the periodic pore distribution conferred favorable structural stability and mechanical strength to the Zeo-C desalination membrane. The rejection rate of Na+ and Cl- is ensured at 100% under a pressure of 40-70 MPa, and that of Na+ could reach 97.85% even though the pressure increases to 80 MPa, exhibiting superior desalination properties. The porous nature of the zeolite-like structure and the low free energy potential barrier are conducive for reliable adsorption and homogeneous diffusion of salt ions, which facilitates the acquisition of desirable water molecule permeability and salt ion selectivity. In particular, the interlinked delocalized π-network imparts inherent metallicity to Zeo-C for self-cleaning in response to electrical stimulation, thereby extending the lifetime of the desalination membrane. These studies have greatly encouraged theoretical innovations and serve as a guiding reference for desalination materials.

A Janus and superhydrophilic design for stable and efficient high-salinity brine solar interfacial desalination

Solar interfacial desalination is a potential pathway for freshwater using solar energy and brine. Many recent advances have been extensively studied to high-efficiency solar steam yield, however, the decrease of evaporation performance resulted from salt accumulation at absorbers inevitably hinder their development, especially in high-salinity brine (>10 wt%). Here, we propose a Janus and superhydrophilic designed evaporator for efficient and stable solar interfacial desalination in high-salinity brine. The Janus structure of the absorber, which has an upper layer of very light-absorbing (>95 %) carbon fiber powder and a bottom layer of insulated aramid fiber powder, allows for efficient light absorption and thermal management to promote efficient water evaporation. Furthermore, the impact of carboxylate cellulose ensures that the absorber with an ultra-high-water content and salt ion diffusion rate. Therefore, the Janus and superhydrophilic design can realize an evaporation rate as high as 1.25 kg m−2h−1 with a salinity of 15 wt% brine under 1-sun illumination and achieve salt resistance in outdoor conditions for a long time. Therefore, this technique simply integrates outdated fiber powder with the current solar interfacial evaporators and establishes a new paradigm for very effective and reliable high-salinity brine treatment.

Bio-inspired salt-fouling resistant graphene evaporators for solar desalination of hypersaline brines

Solar seawater desalination may provide an economical and environmentally friendly means to address the global freshwater crisis. However, salt crystals can precipitate and accumulate on evaporator surfaces during solar seawater desalination, leading to significant deterioration of the performance. Current anti-salt fouling strategies generally suffer from low evaporation rates particularly during the desalination of hypersaline brines. In this paper, we propose bio-inspired graphene evaporators with well-aligned tubular channels to achieve effective solar desalination of hypersaline brines with simultaneously enhanced evaporation rate and long-term anti-salt fouling performance. The unique hierarchical large and small channels inside the evaporators not only increase evaporating surface area, but also provide low-tortuosity pathways for fast salt ion diffusion from the evaporation surfaces to bulk brine. Consequently, the proposed device achieves a high evaporation rate of 2.60 kg m−2 h−1 during a 24-h continuous evaporation test in a hypersaline brine (20 wt% NaCl solution) under one-sun irradiation, among the best values reported in previous studies. Meanwhile, salt precipitation is observed to preferentially occur at the edges of the top surface, leaving the main evaporation area clean during the desalination process. The bio-inspired graphene evaporators with well-aligned tubular channels exhibit great potential for practical solar seawater desalination applications.

Hierarchical N-Doped porous 3D network electrode with enhanced capacitive deionization performance

Capacitive deionization (CDI) has emerged as a promising method of desalination owing to its outstanding regeneration efficiency, low energy consumption, and without secondary contamination. The electrosorption capacity is largely determined by the electrode material. Nevertheless, the bottlenecks of present carbon-based CDI electrode materials are their limited desalination capability and single pore channel, which are unfavorable for salt ion diffusion and access to the internal space. Herein, we synthesized nitrogen-doped porous carbon (NPC) and performed a facile activation to obtain hierarchical porous carbon (KNPC) for CDI desalination. The optimized KNPC showed a remarkable desalination performance of 28.40 mg/g in 500 mg/L NaCl solution, with an exceptional regeneration performance of 94.44% after 15 consecutive cycles. The enhanced CDI performance could be attributed to the following aspects: (1) KNPC was introduced plenty of microporous and mesoporous structures, which provides convenient transport channels and accelerated salt ion transport. (2) The enlarged specific surface area and pore volume provide sufficient adsorption sites for salt ions. (3) The modified KNPC exhibited excellent electrochemical properties and wettability, consisting of higher specific capacitance, decreased internal resistance, and ultra-high hydrophilicity. (4) KOH activation promoted the capacitive contribution of the KNPC electrode, thus improving its CDI performance.

Experimental Investigation into Three-Dimensional Spatial Distribution of the Fracture-Filling Hydrate by Electrical Property of Hydrate-Bearing Sediments

As a future clean energy resource, the exploration and exploitation of natural gas hydrate are favorable for solving the energy crisis and improving environmental pollution. Detecting the spatial distribution of natural gas hydrate in the reservoir is of great importance in natural gas hydrate exploration and exploitation. Fracture-filling hydrate, one of the most common types of gas hydrate, usually appears as a massive or layered accumulation below the seafloor. This paper aims to detect the spatial distribution variation of fracture-filling hydrate in sediments using the electrical property in the laboratory. Massive hydrate and layered hydrate are formed in the electrical resistivity tomography device with a cylindrical array. Based on the electrical resistivity tomography data during the hydrate formation process, the three-dimensional resistivity images of the massive hydrate and layered hydrate are established by using finite element forward, Gauss–Newton inversion, and inverse distance weighted interpolation. Massive hydrate is easier to identify than layered hydrate because of the big difference between the massive hydrate area and surrounding sediments. The diffusion of salt ions in sediments makes the boundary of massive hydrate and layered hydrate change with hydrate formation. The average resistivity values of massive hydrate (50 Ω⋅m) and layered hydrate (1.4 Ω⋅m) differ by an order of magnitude due to the difference in the morphology of the fracture. Compared with the theoretical resistivity, it is found that the resistivity change of layered hydrate is in accordance with the change tendency of the theoretical value. The formation characteristic of massive hydrate is mainly affected by the pore water distribution and pore microstructure of hydrate. The hydrate formation does not necessarily cause the increase in resistivity, but the increase of resistivity must be due to the formation of hydrate. The decrease of resistivity in fine-grains is not obvious due to the cation adsorption of clay particles. These results provide a feasible approach to characterizing the resistivity and growth characteristics of fracture-filling hydrate reservoirs and provide support for the in-situ visual detection of fracture-filling hydrate.

Engineering a superhydrophilic TiC/C absorber with multiscale pore network for stable and efficient solar evaporation of high-salinity brine

Achieving stable and efficient solar-driven evaporation of high-salinity brine is highly desirable while challenging because of salt inevitably blocking the evaporator surface during vapor generation. One of the effective resolvents is to construct macropores to ensure sufficient diffusion and convection of concentrated salt back into the bulk water. Herein, inspired by the interconnected pores of the balsa wood, superhydrophilic porous TiC/C absorber (SPTCA) with macro-/micro-/nano-pores network is successfully built by carbothermic reduction. The macropores channel plays the role of water transport, steam overflow, and salt ion diffusion backflow. The micro-/nano-pores channel enables broadband light absorption and keeps the moisture in a small range to achieve high-efficiency evaporation. With this rational design, the evaporator alloys for a stabilized evaporation of 1.78 kg/m2 h from simulated seawater for over 100 days and 1.75 kg/m2 h from high-salinity brine (15 wt.% NaCl) for over 50 days under 1 sun irradiation. The SPTCA provides a promising avenue for architecting the multiscale-pores network for solar desalination of high-salinity brine.

Influence of rock fabric on salt ion diffusion behavior in upper cretaceous lacustrine shale from Songliao Basin

Some shale reservoirs have high salt ion concentration in flow-back fluid, about which the mechanism is still unclear. To learn the rock fabric of lacustrine shale and its influence on the salt ion diffusion behavior, the investigation of rock component, pore structure, spontaneous imbibition and salt ion diffusion were conducted. Rock component includes inorganic minerals and organic matter. Pore structure includes overburden porosity-permeability, scanning electron microscope (SEM), nitrogen adsorption (NA), mercury intrusion porosimetry (MIP). Comparing the pore size distribution between NA and MIP, lots of pores are connected by small throat, and the pore volume controlled by throat can be 18 times of throat volume. Based on fractal dimensions analysis, which was defined by using the fractal Frenkel-Halsey-Hill (FHH) method based on NA, lacustrine shale has a smoother pore surface and a complex pore structure. The fractal dimensions are mainly controlled by specific surface area. Imbibition liquid is a medium for salt ion diffusing out of matrix and the salt ion diffuse nearly linearly with time in log scale after imbibition becomes stable. The slope of fitting line by using late diffusion data is defined as salt ion diffusion rate. The salt ion diffusion rate is mainly controlled by clay content, TOC, pore volume and specific surface area. The interaction between clay and liquid has the potential to release lots of salt ion, and a higher specific surface area provide more area for liquid interaction with minerals, and a higher pore volume provide more channel for salt ion diffusing out of sample. Our research is conducive to understanding the rock fabric of lacustrine shale in Qingshankou Formation and its influence on salt ion diffusion behavior.

Breaking through permeability–selectivity trade‐off of thin‐film composite membranes assisted with crown ethers

AbstractIn this study, we deployed a modified interfacial polymerization process to incorporate multifunctional crown ethers (CEs) into thin‐film composite (TFC) polyamide membranes. CE additives acted as both the phase‐transfer catalyst and co‐solvent to facilitate the diffusion of amine monomers into the organic phase via interacting with amine monomers (form the host‐guest inclusion complex), and enhanced the free volume content of the selective layer, therefore facilitating water transport and inhibiting the diffusion of salt ions. Various characterization techniques were employed to elucidate the modification mechanism as a function of CE chemical and physical properties on the microstructure of resultant TFC membranes and consequently separation performances. Compared to TFC membranes produced from traditional interfacial polymerization method, CE‐modified membranes exhibited a 146% water flux enhancement and 59% lower reverse salt fluxes with a suitable draw solution. CE‐modified membranes also showed the improved antifouling behavior and chemical stability in various harsh conditions.

Fractal characterization of pore structure and its influence on salt ion diffusion behavior in marine shale reservoirs

Hydraulic fracturing becomes a significant way to develop fossil hydrogen energy from marine shale. Some marine shale formations have a higher salt ion concentration in flowback fluid, about which the mechanism is still unclear. In this study, both the fractal characterization of pore structure and its influence on salt ion diffusion was researched. The fractal dimension D1 can reflect the roughness of pore surface, and the fractal dimension D2 can reflect the complexity of pore structure. The fractal dimension D1 of Sichuan Niutitang Formation is only 2.0069 and the ones of other shale samples are between 2.5291 and 2.6341, which means that the pore surface of Sichuan Niutitang Formation is far smoother than the ones of other samples. The fractal dimension D2 ranges from 2.7396 to 2.9546, which indicates that all samples have complex pore structure. The salt ion diffusion rate is mainly controlled by specific surface area, median pore-throat radius and clay content. A higher specific surface area provides more surface for the interaction between liquid and matrix, and lots of salt ion was released into imbibed liquid. A larger median pore-throat radius benefits to salt ion diffusing out of sample, thus a higher salt ion diffusion rate appears. The liquid can cause the clay-swelling which has the potential to reduce the salt ion diffusion channel, thus the higher the clay content, the lower the salt ion diffusion rate. Our research is conducive to understanding the fractal characterization of marine shale and its impact on high salt ion concentration in flowback fluid.

A comparative study of ion diffusion during water imbibition in shale, sandstone and volcanic rock

The recovered fracturing fluid is generally high in salinity (close to 200 kppm), which is related to the diffusion of salt ions from shale reservoir to the fracturing fluid. However, it is not clear about the diffusion capacity of salt ions in different types. In this paper, the shale, tight volcanic and sandstone are selected as comparative study and a series of tests are carried out for the porosity, permeability and mineral composition. The results show that the shale immersing in fracturing fluid will cause ions dissolution and diffusion, which will increase the salinity of the fracturing fluid. The solution salinity increases rapidly in the early stage and gradually slows down in the later stage. The salinity of the fracturing fluid has a linear relationship with the square root of time, so the slope of the curve can be used as a characteristic parameter to evaluate the ion diffusion rate. The process of dissolution and diffusion of salt ions will induce the expansion of micro-cracks, increasing the contact area between the fracturing fluid and shale and enhancing the solution salinity. The ion diffusion rate is positively related with the content of clay minerals and carbonate. The soluble ions include mainly SO 4 2− , Ca 2+ , Na + and K + . The Na + /Cl − ratio is closely related to the content of clay minerals and carbonate minerals. It has a positive correlation with content of illite and chlorite, and a negative correlation with carbonate minerals, suggesting NaCl source from illite and chlorite. This study is significant for understanding the salinity characteristics of recovered fracturing fluid and evaluating the fracture network shape. Cited as : Yang, L., Chen, C., Liu, Y., Zheng, Y. A comparative study of ion diffusion during water imbibition in shale, sandstone and volcanic rock. Capillarity, 2020, 3(2): 16-27, doi: 10.46690/capi.2020.02.01

Impact of cross-linking of polymers on transport of salt and water in polyelectrolyte membranes: A mesoscopic simulation study.

Our recent atomistic simulation studies demonstrated that the transport properties of salt ions and water in non-crosslinked polymer electrolyte membrane exhibit an intriguing dependence on salt concentration that is opposite to that seen in electrolyte solutions. Here, we extend our study to probe the influence of the degree of cross-linking of the polymer on the transport properties of salt and water in polymer electrolyte membranes. Towards this objective, we use a coarse-grained model embedded within dissipative particle dynamics (DPD) mesoscale simulations, which allows us to access time scales necessary for studying crosslinked polymer systems. Our DPD simulations on non-crosslinked membranes reproduce results that are in qualitative agreement with our atomistic simulations. For the case of crosslinked membranes, our results demonstrate that the diffusion of salt ions and water is reduced significantly relative to crosslinked systems. However, the trends exhibited by the salt concentration dependence of diffusivities and the coordination of the cations with anions and with the polymer backbone remain qualitatively similar to those observed in non-crosslinked membranes.

Diffusivity of Mono- and Divalent Salts and Water in Polyelectrolyte Desalination Membranes.

The dynamics of ions and solvent molecules in polyelectrolyte desalination membranes is key to water purification technologies in which selective transport of the different components is desired. Recent experimental and our computational results have shown that nontrivial mechanisms underlie the transport properties of salt ions and water in charged polymer membranes. Explicitly, in polymer electrolytes, we found a reversal in the salt concentration dependence of the mobilities of Na+, Cl- salt ions and water molecules when compared with aqueous solutions. Motivated by such results, in this study, we have used atomistic molecular dynamics simulations to probe whether the mechanisms deduced in our earlier work apply to other salt systems and to mixtures of salts. Specifically, we report results for the ion diffusivities in aqueous KCl, MgCl2, and a 1:1 mixture of NaCl and MgCl2 salt solutions at different concentrations (ranging from 0.06 to 1 M) and investigate, at the molecular level, the mechanisms underlying the behaviors of salt and water transport properties. Our results show that diffusion of salt ions and water in charged polymer membranes are in general influenced by their association with polymer charge groups and ion pairing effects. Divalent ions are more strongly coupled with the polymeric ionic groups than monovalent salt ions and exhibit diffusivity trends that are distinct relative to monovalent salts. Further, we demonstrate that the mobilities of water molecules are influenced by coordination of water with polymer charge groups and their ion pairing tendencies and also exhibit distinct trends in monovalent and divalent salt solutions.