Salts MgCl2 Research Articles

Corrosion behavior of pressureless-sintered SiC in molten NaCl–KCl–MgCl2 salt at 700 °C

The corrosion behavior of pressureless-sintered SiC in a molten NaCl–KCl–MgCl2 salt at 700 °C was investigated. Results indicate that it is prior for SiC and sintering aid B around grain boundaries to be corroded. MgCl2⋅xH2O(x=4,6) in the salt plays an important role in the corrosion of SiC. MgCl2⋅xH2O is hydrolyzed to HCl, H2O, and MgO, which react with SiC and B to form C, SiO2, SiCl4, B2O3, and Mg2SiO4. The corrosion depth of SiC and the concentrations of elements Si and B in the salt increase with the corrosion time, which are fitted well with Fick's law of diffusion.

Contrasting Effect of Salts on the Binding of Antimalarial Drug Hydroxychloroquine with Different Sequences of Duplex DNA.

Hydroxychloroquine (HCQ) is an important antimalarial drug which functions plausibly by targeting the DNA of parasites. Salts play a crucial role in the functionality of various biological processes. Hence, the effect of salts (NaCl and MgCl2) on the binding of HCQ with AT- and CG-DNAs as well as the binding-induced stability of both sequences of DNAs have been investigated using the spectroscopic and molecular dynamics (MD) simulation methods. It has been found that the effect of salts on the binding of HCQ is highly sensitive to the nature of ions as well as DNA sequences. The effect of ions is opposite for the binding of AT- and CG-DNAs as the presence of Mg2+ ions enhances the binding of HCQ with AT-DNA, whereas the binding of HCQ with CG-DNA gets decreased on the addition of both ions. Similarly, the presence of Mg2+ enhances the stabilization of HCQ-bound AT-DNA, whereas the effect is opposite for the CG-DNA in the presence of both the ions. The MD simulation study suggests that the hydration states of both ions are different and they interact differently in the minor and major grooves of both the sequences of DNA which may be one of the reasons for the different binding of HCQ with these two sequences of DNA in the presence of salts. The information about the effect of salts on the binding of HCQ with DNAs in a sequence-specific manner may be useful in understanding the mechanism of the action and toxicity effect of HCQ against malaria.

Iron Sulfide Scale Inhibition in Carbonate Reservoirs.

Hydrocarbon production operations include water injection, varying stimulation approaches, and enhanced oil recovery techniques. These treatments often affect reservoir formation, production, and injection facilities. Such sorts of well operations cause the formation of organic and inorganic scales in the near-wellbore region and various production and injection structures. Downhole squeeze treatment is commonly used as a control measure to prevent scale precipitation. A scale inhibitor solution is introduced into a formation by applying a squeeze treatment. The method allows scale inhibitors to adsorb on the internal rock surface to avoid settling down the scale precipitates. Thus, the study of adsorption of different types of inhibitors to prevent scale formation on the reservoir rock through the execution of downhole squeeze treatment is becoming necessary. This study incorporated different experimental techniques, including dynamic adsorption experiments of chelating agents employing a coreflooding setup, inductively coupled plasma-optical emission spectrometry (ICP-OES) to inhibit the formation of iron-containing scales in limestone rocks, and ζ-potential measurements targeting determination of iron precipitation in varying pH environments on calcite minerals. The influence of the inhibitor soaking time and salt existence in the system on chelating agent adsorption was also evaluated in the coreflooding experiments. The findings based on the coreflooding tests reveal that the concentration of chelating agents plays a significant role in their adsorption on carbonate rocks. The treatments with 20 wt % ethylenediaminetetraacetic acid (EDTA) and 20 wt % diethylenetriaminepentaacetic acid produced the highest adsorption capacity in limestone rock samples by inhibiting 84 and 85% of iron(III) ions, respectively. Moreover, the presence of the salts (CaCl2 and MgCl2) considerably decreased the adsorption of 10 wt % EDTA to 56% (CaCl2) and 52% (MgCl2) and caused nearly 20% more permeability reduction, while more inhibitor soaking time resulted in comparably higher adsorption and lesser permeability diminution. The results of ζ-potential measurements showed that the pH environment controls iron(II) and (III) precipitation, and iron(III) starts to deposit from a low pH region, whereas iron(II) precipitates in increased pH environments in calcite minerals.

Evaluating Corrosion Behaviour of Copper Under Deliquescent Drying/Wetting Cycles in Humid Air Condition

Most nuclear safety agencies around the world agree that deep geological repositories (DGRs) constructed hundreds of meters below ground in stable host rock formations are viable solutions to safely isolate used nuclear fuel. In Canada, the DGR design involves storing used nuclear fuel in sealed copper coated used fuel containers (UFC) surrounded by highly compacted bentonite blocks (HCB) ~500 m underground. Shortly after emplacement, heat generated by radioactive decay of the used fuel will warm the UFC and its surroundings, desiccating the HCB and decreasing moisture on the container surface. As water vapour is driven from the UFC surface, the presence of minor amounts of dissolved salts may cause droplet formation prior to complete evaporation, during which deposits of salts may be left behind on the UFC. Later, as conditions evolve and the relative humidity increases and the temperature decreases, condensation of liquid water on the UFC surfaces will produce droplets again, due to the deliquescence of minor salt deposits. In either the wetting or the drying scenario, secondary spreading and spatial separation of anodic and cathodic reactions and consequent non-uniform corrosion could be possible, due to the droplet geometry.To investigate this scenario, the quartz crystal microbalance (QCM) technique is being used. The QCM initially consists of a quartz plate, covered by gold electrodes on both sides where a layer of copper is deposited on the crystal by using magnetron sputtering. In this technique, the change in the resonance frequency of a vibrating quartz crystal is correlated to its mass change due to the corrosion process. To investigate the effect of salts and their deliquescence behaviours, different salts (NaCl, CaCl2, and MgCl2) and CR10-E simulated groundwater were loaded on the copper surface using an inkjet printer, and then corrosion tests were performed at different temperatures and relative humidity (RH) values. In parallel, a set of long-term vapour-phase corrosion tests was performed on wrought and cold-sprayed copper coupons at 75 °C and different RH values. As part of the post-experiment analysis, the corrosion products were analyzed using a suite of surface analysis techniques, including optical microscopy, Raman spectroscopy, and scanning electron microscopy (SEM).The results from QCM experiments at RH values below salts deliquescence point showed a low mass change that could correlate with less corrosion in comparison to the experiments at RH values above salts deliquescence point. It’s worth noting that even at RH values below the deliquescence point of the salts, a trace of corrosion was observed which could be indicative of the presence of monolayers of water on the surface. The results obtained from NaCl and CR10-E exposure conditions showed higher mass change and therefore higher corrosion in comparison to CaCl2 and MgCl2 salts. As for the long-term vapour-phase corrosion tests, Raman spectroscopy confirmed the presence of CuO and Cu2O on the surface as corrosion products. Further surface characterizations and mass loss measurements are underway to determine the extent of corrosion on the copper coupons.

Enhancing the flux and salt rejection of thin-film composite nanofiltration membranes prepared on plasma-treated polyethylene using PVA/TS-1 composite

The high hydrophobicity of polyethylene (PE) film restricts its application as a thin-film composite (TFC) support layer. Therefore, in this study, oxygen plasma treatment was used to generate hydrophilic groups on PE and facilitate the formation of the TFC membrane. The difference in the performance of the plasma treated-PE (P-PE) membrane compared to untreated-PE indicated the significant effect of plasma pretreatment. In the following, to enhance the hydrophilicity of the P-PE membrane, titanium silicate-1 (TS-1) was synthesized as a zeotype through the hydrothermal method and added to the aqueous solution of the interfacial polymerization process. Due to the decrease in the agglomeration of TS-1 in the membrane matrix, PVA/TS-1 composites with distinct concentrations of polymer were prepared and applied for modifying membrane properties. Membranes were characterized by FESEM, ATR-FTIR, AFM, zeta potential, and water contact angle analyses. Permeability, rejection of monovalent and divalent salts, and antifouling ability of the fabricated nanofiltration membranes were studied and the optimal polymer concentration was determined. Comparison of P-PE-TFC 0.1 membrane with P-PE showed an increase of ~42% in pure water flux. Also, the rejection of Na2SO4, MgSO4, MgCl2, and NaCl salts were 90.28%, 81.77%, 74.79%, and 70.94% for P-PE-TFC 0.1 membrane, respectively, which showed a notable improvement compared to the P-PE membrane. Evaluation of antifouling ability showed that P-PE-TFC 0.1 membrane had a higher resistance to fouling compared to other membranes. Flux recovery ratio of this membrane after three cycles of bovine serum albumin (BSA) filtration was higher than other membranes resulting from the reduced roughness due to the combined effect of PVA and TS-1.

Effect of Different Salts on Nutrients Uptake, Gene Expression, Antioxidant, and Growth Pattern of Selected Rice Genotypes.

Climate change leads to soil salinization, and the dynamic scarcity of freshwater has negatively affected crop production worldwide, especially Oryza sativa. The association among ion uptake, gene expression, antioxidant, biomass, and root and shoot development under different salt stress are not fully understood. Many studies are related to the effect of NaCl only. This study used two salts (CaCl2 and MgCl2) along with NaCl and analyzed their effects on mineral uptake (macronutrients and micronutrients), gene expression, seed germination, antioxidants, plant growth, and biomass in different rice genotypes. CaCl2 (up to 200 mM) slightly increased the germination percentage and seedling growth, whereas, 150 mM MgCl2 in the soil increased the root, shoot length, and fresh and dry weight in cultivars IR 28 and Cheongcheong. All agronomic traits among rice genotypes were drastically reduced by NaCl stress compared to other salts. Different salt stress differentially regulated ion uptake in the roots and shoots among different rice genotypes. Under different salt stress, a consistent decrease in Ca2+, Mn2+, and Fe2+ ions was observed in the roots of Cheongcheong, Nagdong, and IR 28. Similarly, under different salts, the stress in the shoots of Cheongcheong (Ca2+, Na+, and Zn2+) and Nagdong (Ca2+, Mg2+, Na+, and Zn2+) and the shoots of IR 28 (Ca2+ and Mg2+) consistently increased. Under different salts, a salt stress-related gene was expressed differentially in the roots of rice genotypes. However, after 6 and 12 h, there was consistent OsHKT1, OsNHX1, and OsSOS1 gene upregulation in the shoots of Nagdong and roots and shoots of the salt-tolerant cultivar Pokkali. Under different salt stress, glutathione (GSH) content increased in the shoot of IR 28 and Nagdong by NaCl, and MgCl2 salt, whereas, POD activity increased significantly by CaCl2 and MgCl2 in cultivar Cheongcheong and IR 28 shoot. Therefore, this study suggested that Pokkali responded well to NaCl stress only, whereas, the plant molecular breeding lab cultivar Nagdong showed more salt tolerance to different salts (NaCl, CaCl2, and MgCl2). This can potentially be used by agriculturists to develop the new salt-tolerant cultivar “Nagdong”-like Pokkali.

Ionic Strength of Methylcellulose-Based Films: An Alternative for Modulating Mechanical Performance and Hydrophobicity for Potential Food Packaging Application

The growing environmental concern with the inappropriate disposal of conventional plastics has driven the development of eco-friendly food packaging. However, the intrinsic characteristics of polymers of a renewable origin, e.g., poor mechanical properties, continue to render their practical application difficult. For this, the present work studied the influence of ionic strength (IS) from 0 to 500 mM to modulate the physicochemical properties of methylcellulose (MC). Moreover, for protection against biological risks, Nisin-Z was incorporated into MC’s polymeric matrices, providing an active function. The incorporation of salts (LiCl and MgCl2) promoted an increase in the equilibrium moisture content in the polymer matrix, which in turn acted as a plasticizing agent. In this way, films with a hydrophobic surface (98°), high true strain (85%), and low stiffness (1.6 mPa) can be manufactured by addition of salts, modulating the IS to 500 mM. Furthermore, films with an IS of 500 mM, established with LiCl, catalyzed antibacterial activity against E. coli, conferring synergism and extending protection against biological hazards. Therefore, we demonstrated that the IS control of MC dispersion presents a new alternative to achieve films with the synergism of antibacterial activity against Gram-negative bacteria in addition to flexibility, elasticity, and hydrophobicity required in various applications in food packaging.

MgO/MgAl2O4 nanocomposites synthesis by plasma torch from aqueous solution of MgCl2 and AlCl3 salts and studying the effect of raw material concentration on the products

MgO/MgAl2O4 nanocomposites synthesis by plasma torch from aqueous solution of MgCl2 and AlCl3 salts and studying the effect of raw material concentration on the products

Ionic liquids as completion fluids to mitigate formation damage

Formation damage can occur in any phase of oil and gas operation from drilling, completion, or stimulation. Fluids used to drill, complete, and fracture the formation may invade and damage the formation. These fluids may interact with clays present in the formation and adversely affect the flow performance. The change in flow performance could occur due to flow restriction or decrease in permeability, change in relative permeability, or unintended flow restriction during the specific operation. In this work, ionic liquids are proposed as clay swelling additives in completion fluid to overcome the formation damage problem. Imidazolium-based ionic liquids and three different salts are tested with 0.5 wt % and 3 wt % concentration, respectively, on tight sandstone formation containing high clay contents. Completion fluids prepared using ionic liquids resulted in complete stabilization of clays and therefore nearly maintain the in-situ permeability of tight sandstone. The completion fluids are prepared in deionized water for experimental consistency. Coreflooding experiments were performed on Scioto sandstone core samples containing an average porosity and permeability of 16.9% and 0.72 mD., respectively. Cores were saturated with completion fluids based on salts such as calcium chloride (CaCl2), magnesium chloride (MgCl2), and ammonium chloride (NH4Cl) and with Imidazolium-based ionic liquids before the coreflooding experiments. These coreflood experiments involve a preflush with the prepared completion fluid and post-flood with deionized water. Moreover, Nuclear Magnetic Resonance (NMR) tests were performed on all samples before and after coreflood to estimate the change in porosity and pore size distributions of the rock samples. Results showed that the porosity and permeability loss were significantly large in cores flooded with CaCl2 and NH4Cl salts solution when flooded with water. MgCl2 salt solution showed exceptionally stable porosity and permeability compared to other completion fluids. Furthermore, the results of ionic liquid-based completion fluids showed no significant loss in porosity and permeability when flooded with water. Therefore, the proposed ionic liquid-based completion fluids can be used for well-completion operation without any formation damage.

NMR Characterization of unfrozen brine vein distribution and structure in model packed beds

When a brine mixed with particles is frozen, some liquid water persists due to the freezing point depression caused by the solute impurity, surface energy, and disjoining pressure (wetting forces). This unfrozen water forms a complex “liquid vein network” (LVN). However, details of the freezing process are still not fully understood, including the permeability/tortuosity of the LVN, and the unfrozen water content at a given temperature. Here, we have applied nuclear magnetic resonance (NMR) relaxation, self-diffusion measurements and magnetic resonance imaging (MRI) to investigate the distribution and structure of LVNs. Magnesium chloride (MgCl2) salt concentrations of 15, 30, and 60 mM were investigated with and without poly-methyl methacrylate (PMMA) particles of diameter 0.4, 9.9, and 102.2 μm, allowing us to quantify unfrozen water content and the structure of the LVN as a function of temperature, MgCl2 concentration, and PMMA particle size. The results of magnetic resonance imaging (MRI) and self-diffusion confirm that the inhibition of ice recrystallization is a function of particle size. To gain information on LVN structure, we compared NMR results to Monte Carlo simulations of freezing in brine-particle systems. Comparisons between laboratory and simulation data suggest that, for our experimental range of temperature (−17.4 °C to −0.9 °C ± 0.5 °C), solutes make the dominant contribution to the unfrozen liquid fraction for particle sizes larger than a few microns, whereas in the finest grained porous media we tested, the unfrozen liquid fraction is controlled primarily by the films that wet particle-ice interfaces.

Experimental insight into the silica nanoparticle transport in dolomite rocks: Spotlight on DLVO theory and permeability impairment

Nanoparticles (NPs) have been proposed as a promising agent for groundwater aquifer remediation, greenhouse geological storage, and enhanced oil recovery (EOR) applications. Nevertheless, in many of these cases, NPs applications require long transport distances, which may be limited by NPs retention in porous media, especially at high saline conditions as is the case with some oil reservoirs, causing a reduction in rock permeability and subsequent formation damage. Therefore, understanding of NPs transport through porous media and their stability behavior are significant challenges before their large-scale applications, which has been less explored in previous works. This paper investigates silica NPs transport through dolomite rocks, which are the host rocks of many sub-surface reservoirs. To this end, the stability of silica nanofluids with different concentrations in the presence of different ionic strength and ion types was explored by zeta potential measurement and particle size analysis. NPs adsorption on rock surface was examined by SEM images. The DLVO analysis was conducted to determine the interaction energies between NPs and the rock, and investigate the reversibility of NPs adsorption on the rock. Single-phase coreflooding experiments aided by NPs effluent analysis were performed to obtain breakthrough curves. Results indicated that increasing silica NPs concentration from 0.1 to 0.5 wt% leads to a reduction in nanofluid stability in which the average size of silica NPs increased from 110 to 220 nm. Higher ionic strength (50,000 ppm) decreased nanofluids stability and this negative effect was more pronounced for nanofluids containing MgCl2 salt. It was found that less stable nanofluids showed higher NPs retention through porous media. Highly stable nanofluids exhibited a higher probability of NPs to be detached during the brine post-flushing stage. As to the results of silica nanofluid injection in dolomite rock, increase of the silica NPs concentration and decrease of their stability in suspension were two causes of the rock permeability impairment; a 10% reduction in rock permeability was observed by 0.1 wt% salt-free silica nanofluid, whereas it decreased by 87% using 0.5 wt% of saline nanofluids prepared by 50,000 ppm MgCl2. According to the interpretations based on the deep bed filtration model, the higher salinity of nanofluid is, the higher filtration coefficient would be, meaning that the higher rate of particle capture at higher salinities. Also, no internal/external filter cake was formed and instead, the pore filling process was found to be the major mechanism of the permeability impairment by silica NPs.

Aggregation of DNA-Grafted Nanoparticles in Water: The Critical Role of Sequence-Dependent Conformation of DNA Coating.

Aggregation behavior of nanoparticles in water, particularly in the presence of surface coating, is a fundamental behavior to understand as it closely relates to the material function, reactivity, and toxicity. Engineered DNA, an important type of surface coating, is essentially different from conventional polymeric coatings with homogeneous repeating units. The heterogeneous nature of DNA with numerous combinations of the four nucleotides poses a challenge to understand the aggregation of nanoparticles coated with them. In this study, we use both experimental and computational approaches to study how DNA properties influence the aggregation of DNA-conjugated gold nanoparticles (DNA-AuNPs). Aggregation kinetics under different pH values and in three salts (NaCl, CaCl2, and MgCl2) were investigated. Overall, DNA-AuNPs demonstrated similar aggregation behavior of electrosterically stabilized nanoparticles, where the surface coating layer thickness played a determining role. The underlying interactions between DNA-AuNPs were analyzed by an extended DLVO model, and the excluded volume repulsion, which varied as a function of layer thickness, was the dominant stabilizing repulsion. Interestingly, the DNA sequence was found to cause different layer thicknesses and thus profoundly different aggregation behaviors in the presence of cations. The interactions between DNA strands with different sequences and surrounding counterions were investigated via molecular dynamics simulations. The simulation results were consistent with experimental observations and supported the sequence-dependent conformational change of DNA coating. Our study provides new molecular-level insights into aggregation of nanoparticles with heterogeneous surface coating such as DNA.

Effect of bacteria on oil/water interfacial tension in asphaltenic oil reservoirs

Microbial enhanced oil recovery (MEOR), due to the formation of biofilm and the presence of biosurfactants generated by microorganisms in the reservoir, can play a role in reducing interfacial tension (IFT) and wettability alteration. In this work, the fluid-fluid interaction by measuring the IFT has been evaluated for combining two EOR methods, including low salinity water and MEOR, due to the high importance of fluid-fluid interaction in EOR. GeoBacillus stearothermophilus has been used as a bacterium to study changes in IFT. The effect of different salts, including monovalent and divalent cations and anions at different salinities, on biosurfactant performance, is investigated using IFT measurements. Also, the type of oil is evaluated in terms of its acidic and basic properties on the performance of biosurfactants. According to the results of this study, injection of GeoBacillus stearothermophilus bacteria reduces interfacial tension in acidic oil by 10.26% and in basic oil by 5.26%. According to the results, increasing salinity in the presence of oil-containing asphaltene with basic properties increases the IFT of the solution containing GeoBacillus stearothermophilus bacteria, but in the presence of acidic oil, a decrease in IFT is observed. The most significant effect of reducing the IFT of acidic oil and solution containing GeoBacillus stearothermophilus is obtained in the presence of the following salts, respectively: CaCl2 > MgCl2 > NaCl. The results show that with increasing CaCl2 concentration, the IFT between basic oil and GeoBacillus stearothermophilus solution gradually increases. This ascending trend is in the presence of NaCl salt with a lower slope. However, in the presence of MgCl2 salt, dual behavior is observed before and after the concentration of 1000 ppm, so that before this concentration, the IFT increases and then decreases. The findings of this study can help for a better understanding of the interaction of bacteria with asphaltenic oils in the presence of effective salts for low salinity water injection. The results of this study showed that by combining low salinity water with bacteria, less IFT could be obtained than low salinity water or bacteria alone.

Influence of foreign salts on the CaCO3 pre-nucleation stage: application of the conductometric method

Electrical conductivity modeling applied to the fast controlled precipitation method data is used to underline the existence of different ion pairs during the prenucleation stage as a function of the foreign salts NaCl, MgCl2, Na2SO4 and MgSO4.

Investigation of Influential Parameters on Oil/Water Interfacial Tension During Low-Salinity Water Injection

Abstract Injecting low-salinity water has proved to be an efficient displacement process in oil reservoirs, owing to its ability to modify the properties at the fluid-rock and fluid-fluid interfaces in favor of mobilizing more oil. In this regard, reduction of interfacial tension (IFT) between oil and water is one of the key controlling parameters. It is suspected that the asphaltene constituents of the oil and type of water ions are responsible for such a reduction in IFT. In this study, systematic experimental investigations were carried out to scrutinize the influence of brine salinity, asphaltene concentration, and temperature on IFT. Single and multi-component brines, which in particular compose of NaCl, CaCl2, and MgCl2 salts, and two synthetic oils with 1 and 10 wt% asphaltene content were used at temperatures ranging from 25 to 80 °C. The results showed that the presence of salt in the solution can alter the distribution of polar components at the oil-brine interface due to the electrostatic effects, which in turn would change IFT of the system. IFT also decreased when temperature increased from 25 to 80 °C; however, the level of changes was strongly depended on the brine type, salinity level, and asphaltene content. The results also demonstrated that the crude oil with the higher asphaltene concentration experiences higher IFT reduction when is contacted with the low-salinity water. The new findings from this study will improve the understanding of the underlying mechanisms for low salinity water flooding in oil reservoirs.

Molecular dynamics approach to study the effects of MgCl2 salt atomic ratio on the phase transition phenomenon in the phase change materials

In general, phase change materials reduce energy consumption in different structures by increasing the thermal conductivity or decreasing the phase change time. On the other hand, hydrated salts are the most important group of phase change materials with high phase change temperatures and are extensively studied in latent thermal energy storage systems. Today, these atomic structures are used in different usages such as thermal transfer compounds, commercial and industrial applications, for cooling and heating on a small scale, etc. In the current computational study, we utilized Molecular Dynamics procedure to explain the thermal and phase transition (from liquid to solid-state) behavior of water liquid in the presence of MgCl2 salt as salts hydrate compound. Computationally, physical parameters like temperature, potential/total energy, phase transition time, thermal conductivity, and velocity/density profile of H2O-MgCl2 nanofluid were reported for time=15 ns. Molecular Dynamics outputs indicated that the phenomenon of phase transition in simulated nanofluid happens in a shorter time using a 4% atomic ratio salt structure. This atomic behavior of simulated structure causes thermal behavior improvement is defined nanofluid. Numerically, by MgCl2 salt ratio optimizing, H2O-MgCl2 nanofluid thermal conductivity converged to 0.67 W/m.k. Technically, thermal conductivity calculation in current research is done by using the Green-Kubo method.

Effect of chloride salt on the phase evolution in alkali-activated slag cements through thermodynamic modelling

In this study thermodynamic modelling was used to investigate the effect of chloride salt on the phase evolution in alkali-activated slag paste. The effects of different sources of chloride salts (NaCl, CaCl2, and MgCl2) and slag chemistry were studied. In thermodynamic modelling, a new solid solution model, i.e. MgAl–Cl-LDH_ss, was proposed to consider the uptake of chloride ions by hydroxylated hydrotalcite. The modelling results show that the valence of cation in chloride salt and slag chemistry both significantly affect the phase assemblage, pore solution composition and chemical chloride binding capacity of alkali-activated slag paste. The hydroxylated hydrotalcite decomposes upon NaCl attack, while upon the attack by CaCl2 and MgCl2 it transforms to chloride intercalated hydrotalcite. Decalcification, dealumination and altering mean chain length of C-(N-)A-S-H gel are predicted upon chloride salt attack. Increasing Al2O3 content in slag thermodynamically favors the formation of Friedel's salt, leading to a higher chemical chloride binding capacity.

Evaluation of the relationship between freezing point and suction in chloride loess

In this study, the relationship between freezing point and suction of four types of chloride loess samples (CaCl2, MgCl2, NaCl and KCl) was investigated by freezing point tests and filter paper method-based suction tests. Break points were observed from the freezing point versus water content curves near the plastic limit, which decline at higher salt contents. The freezing point declines roughly linearly with salt content for samples with 2–1 type chloride salts (CaCl2 and MgCl2), while decreases attenuatedly for those with 1–1 type chloride salts (NaCl and KCl). The higher the cation content, the more significant the freezing point depression, and the ranking of Mg2+ > Ca2+ > Na+ > K+ was roughly noted, which is linked with the cation hydration capacity. In addition, the relationship between the osmotic suction of samples h0soil and that of chloride solution h00solution was suggested to be described by a linear relationship. The freezing point of samples depends on both matric suction and osmotic suction. The limitations of the Mizoguchi's model were noticed through data analysis and by retaining its basic construct, a suction-based model for freezing point of chloride loess was established and verified.

Effects of calcium, magnesium, and strontium chlorides in determining the total acid number using potentiometric titration

The most widely used method for determining the total acid number (TAN) in crude oils is American Society for Testing and Materials (ASTM) D664, which is subject to interference from hydrolyzable salts. This study investigated and determined at which salt concentration NaCl, CaCl2, MgCl2, and SrCl2 significantly interfere with the determination of the TAN in crude oil using the ASTM D664 method. To evaluate the influence of salts on the titration solvent of ASTM D664 and crude oil, pure chloride salts, and two mixtures of these salts, were added to the titration solvents (at 1500–8000 mg kg−1) and water-in-oil emulsions (alpha and gamma). Precipitation was observed during the titrations of these solvents. Analysis of the precipitates via gravimetric analysis, X-ray diffraction, and attenuated total reflection Fourier transform infrared spectroscopy demonstrated that they were composed of Ca(OH)2, Mg(OH)2, and Sr(OH)2. The alpha oil exhibited an increase in acidity from 0.28 up to 2.47 mg KOH g−1 with the chloride salt mixtures, whereas gamma oil exhibited an increase in acidity from 2.26 up to 4.17 mg KOH g−1 with the chloride salt mixtures. One hundred milligrams of CaCl2, MgCl2, or SrCl2 remaining in the oil was sufficient to interfere with the in TAN determination using the ASTM D664 method.

PH-dependent chloride desorption isotherms of Portland cement paste

Carbonation, sulfate, and acid attack can lead to the release of bound chlorides, increasing the concentration of free chlorides in concrete pore solutions. The objective of this study was to develop pH-dependent chloride desorption isotherms for OPC paste exposed to MgCl2, CaCl2, and NaCl solutions. This study showed that the Langmuir isotherm suits the chloride binding of ground OPC paste the best, and the amount of bound chloride is predominantly influenced by the cation-type of chloride in the decreasing order CaCl2 > MgCl2 > NaCl. The results of the thermogravimetric analysis also confirmed this. The mass loss of Friedel's salt apparent in DTG curves indicated that more chlorides from CaCl2 salt may bind with cement hydrates. The phase assemblages predicted by thermodynamic modeling were found to be in good agreement with the experimental results. The drop in the pH of the exposure solution, achieved by adding nitric acid to the exposure solution, initially resulted in the total dissociation of the bound chlorides from the MgCl2 and NaCl salts. However, only 58% of the bound chlorides from the CaCl2 solution could be dissociated as a result of the reduced pH of the exposure solution. Moreover, the dissociation of bound chlorides resulted in the removal of Friedel's salt and the formation of calcium nitrate. The further addition of nitric acid resulted in the formation of a calcium-rich hydrogel capable of absorbing free chlorides.