Mixture Of Na2SO4 Research Articles

The effects of electrolyte on the capacitive behavior of nanostructured molybdenum oxides

AbstractBACKGROUNDNanostructured metal oxides have shown capabilities in the application of energy conversion and storage. Among a variety of metal oxide semiconducting materials, molybdenum oxide recently became a promising candidate as an electrochemical supercapacitor for storing electrical energy. Supercapacitors, which are storage devices for electrical energy, benefit from the separation of opposite charges in electrochemical double‐layer capacitors and charge transfer as a function of electrochemical potential in pseudocapacitors.RESULTSA thin film of nanostructured molybdenum oxide was prepared using potentiodynamic electrodeposition on the surface of a stainless‐steel electrode. Its electrochemical capacitive behavior was investigated using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). To investigate the effects of the electrolyte ion type, two solutions were investigated in a comparative way: 0.005 mol L–1 H2SO4 and 0.005 mol L–1 H2SO4 + 0.095 mol L–1 Na2SO4 mixture where each solution has the same initial concentrations of hydronium ions but with different ionic strengths. The EIS studies gave rise to the specific capacitances of 340 and 160 F g–1 for H2SO4 and mixed solutions, respectively. An appropriated electrical circuit was used to interpret these EIS results.CONCLUSIONSThe present studies show that the electrolyte cations contribute to the capacitive behavior of the nanostructured molybdenum oxide in different ways. Sodium ions only participate in the process of charging the double layer from the outer Helmholtz and diffusion layers, whereas hydronium ions contribute to the Faradaic process of electrosorption by penetrating into the inner Helmholtz layer. © 2019 Society of Chemical Industry

Hot corrosion behaviour of Mo-62Si-5B (at. %) alloy in different molten salts at 900°C

Hot corrosion behaviour of SPS-processed Mo-62Si-5B (at. %) alloy in pure Na2SO4 and mixture of Na2SO4 + NaCl melts at 900 °C was studied. The results show that the damage process of Mo-62Si-5B alloy is deteriorated in presence of Na2SO4 and Na2SO4 + NaCl. After hot corrosion at 900 °C for 100 h, the mass changes of the alloy in Na2SO4 and mixture of Na2SO4 + NaCl are −0.24 mg/cm2 and −0.50 mg/cm2, respectively. Oxides mainly contained SiO2 and amorphous borosilicate. Hot corrosion mechanisms of the alloy in presence of Na2SO4 and mixture of Na2SO4 + NaCl deposits are discussed.

High‐temperature corrosion behavior of some post‐plasma‐spraying‐gas‐nitrided metallic coatings on a Fe‐based superalloy

AbstractThe objective of the present study is to propose a cost‐effective process for modifying commercially available coatings by gas nitriding using commonly available equipment and starting materials. Al–Cr and Ti–Al metallic coatings were deposited on Superfer 800H (Fe‐based superalloy) using a plasma spray process. Then the gas nitriding of the coatings was done in the lab and the parameters were optimized after conducting several trials on plasma‐sprayed‐coated specimens. Characterization and high‐temperature corrosion behavior of coatings after exposure to air and molten salt at 900°C were studied under cyclic conditions. Techniques like XRD, SEM/EDX, and X‐ray mapping analysis were used for the characterization of the coatings and analysis of the oxide scale. Both the coatings successfully protected the substrate and were effective in decreasing the corrosion rate when subjected to cyclic oxidation (Type‐I hot corrosion) at 900°C for 50 cycles in air and molten salt (a salt mixture of Na2SO4–60%V2O5 dissolved in distilled water). Based on the findings of the present study, the coatings under study are recommended for tapplications to super‐heater and reheater tubes of boilers and all those surfaces that face fireside corrosion, such as fluidized beds, industrial waste incinerators, internal combustion engines, gas turbines or steam turbines, to provide protection against degradation in these environments. The cost of the product/process is approximately Rs. 0.62 per mm2 in case of Al–Cr coating and Rs. 1.86 per mm2 in case of Ti–Al coating.

Hot corrosion Type II of FeCr‐based model alloys for boiler and heat exchanger applications

The hot corrosion Type II of the alloys FeCr20, FeCr20Ni10, FeCr20Ni20, and FeCr20Co10 is investigated at 700°C in air + 0.5% SO2 with deposits consisting of Na2SO4 and a eutectic mixture of Na2SO4 and MgSO4 for 24, 100, and 300 h. The alloying elements nickel and cobalt have a positive influence when tests are conducted using a MgSO4‐Na2SO4 deposit. In this case, they reduce the metal loss and increase the time to the propagation stage. In contrast, when the alloys are exposed with a Na2SO4 deposit, these alloying elements increase the metal loss and allow for the transition to the propagation stage because they can form molten phases with the Na2SO4. During the incubation stage an oxide scale forms on the FeCr20 alloy, which is thicker than the one formed during exposure without a deposit, and iron oxides are observed, which precipitate in the deposit. The propagation stage occurs by a dissolution and precipitation mechanism forming localized pitting attack. Iron is the main species that dissolves and precipitates, while chromium remains mainly as an oxide beneath the initial surface. The additional elements are found in the pit and in the salt deposit.

Hot Corrosion Resistance of Laser-Sealed Thermal-Sprayed Cermet Coatings

Hot corrosion affects the components of diesel engines and gas turbines working at high temperatures, in the presence of low-melting salts and oxides, such as sodium sulfate and vanadium oxide. Thermal-sprayed coatings of nickel–chromium-based alloys reinforced with ceramic phases, can improve the hot corrosion and erosion resistance of exposed metals, and a sealing thermal, post-treatment can prove effective in reducing the permeability of aggressive species. In this study, the effect of purposely-optimized high-power diode laser reprocessing on the microstructure and type II hot corrosion resistance of cermet coatings of various compositions was investigated. Three different coatings were produced by high velocity oxy-fuel and was tested in the presence of a mixture of Na2SO4 and V2O5 at 700 °C, for up to 200 h: (i) Cr3C2–25% NiCr, (ii) Cr3C2–25% CoNiCrAlY, and (iii) mullite nano–silica–60% NiCr. Results evidenced that laser sealing was not effective in modifying the mechanism, on the basis of the hot corrosion degradation but could provide a substantial increase of the surface hardness and a significant decrease of the overall coating material consumption rate (coating recession), induced by the high temperature corrosive attack.

Influence of composition on molten sulfate-vanadate salt corrosion resistance of lanthanum zirconate coatings

Three lanthanum zirconate (LZO) thermal barrier coatings with designed La/Zr ratios, i.e., 0.7:1 (LZO-7), 1:1 (LZO-10), and 2:1 (LZO-20), are fabricated by laser enhanced chemical vapor deposition and their corrosion resistance in 40 wt% V2O5 + 60 wt% Na2SO4 mixture is studied at 900 °C. The reaction between lanthanum zirconate coatings and NaVO3 produces LaVO4 and ZrO2, which form impediment layer and prevent deeper penetration of the corrosive sulfate-vanadate molten salt. Meanwhile, no severe transverse cracks are found in all the coatings due to the columnar crystalline microstructures. Furthermore, LZO-20 shows the better corrosion resistance than others as the result of the decreased concentration of corrosive molten salts at the contacting interface, which is attributed to the fact that the excess lanthanum consumes maximum NaVO3. Correspondingly, the LaVO4/ZrO2 ratios rise with the increase of lanthanum content. These results uncover the key role of the lanthanum content on the corrosion resistance of the sulfate-vanadate molten salt and are expected to guide the optimization of the future thermal battier coating design by tailoring the composition.

Proteomic analysis of the salt-adapted and directly salt-(NaCl and NaCl+Na2SO4 mixture) stressed cyanobacterium Anabaena fertilissima

Salinity is a serious threat to agriculture productivity. Beneficial microbes could be simple and low-cost biological methods to mitigate the salt toxicity. The present study describes proteome dynamics and salt stress tolerance of the salt-primed (pre-exposed to salt) and directly salt-stressed cyanobacterium Anabaena fertilissima. The difference in the proteome of differently salt-treated and the control cells was the abundance of proteins. Out of 130 proteins resolved in control, 51.8% remained constant, 25.5% were upregulated, and 22.7% protein spots were downregulated in salt-adapted cells (exposed to 500 mM NaCl). However, in cells exposed to 250 mM NaCl, percentage of constant, upregulated, and downregulated proteins was 56.8, 16, and 27.2, whereas in the cells exposed to equimolar NaCl+Na2SO4 mixture, these values were 41.8, 29.4, and 28.7, respectively. This indicated that an altered protein expression occurred in large number of protein species under different salt-stress regimes. Four proteins showing significant and reproducible changes under salt stress showed close homology with photosystem I reaction center subunit XII, epoxyqueuosine reductase, response regulator protein VraR, and molybdopterin biosynthesis protein. The kinetic analysis revealed that salt treatment increased the abundance of all the four identified proteins. Despite the exposure to higher NaCl concentration (500 mM), salt-adapted cells showed minimal hyper accumulation of these four proteins, followed by NaCl and NaCl+Na2SO4 mixture. Lesser accumulation of these identified proteins in salt mixture stressed cells than that of NaCl stressed cells revealed that the availability of sulfur during salt-stress relieved the salt-toxicity, while Cl− increased it.

Phenomenological prediction of desalination brines nanofiltration through the indirect determination of zeta potential

Abstract The prediction of nanofiltration (NF) performance at environmentally relevant conditions, e.g.: highly saline brine solutions, is becoming of increasing interest for the recovery of waste materials in the water desalination industry. In this work, the prediction of the separation of sulfate and chloride contained in the retentate of reverse osmosis brackish water desalination by means of the commercial NF270 membrane is studied. Prior to theoretical modelling, streaming potential measurements were performed for aqueous single and binary mixtures of NaCl and Na2SO4 within the range of ionic strengths 1–100 mol/m3. Zeta potential values were obtained applying an extrapolation method from recent literature to allow the calculation of surface charge density under higher ionic strengths found in reverse osmosis desalination brines (100–1200 mol/m3). Then, the obtained surface charge density was used to simulate sulfate, chloride and sodium rejections by means of the Donnan steric pore model (DSPM), in the pressure range 2–20 bar. The good agreement between experimental and simulated rejection values allows validating the approach that enables the prediction of NF performance for the separation of monovalent and divalent anions, of interest for the purification of desalination brines before their further exploitation as a source of sodium chloride concentrated solutions.

Quantitative proteomic analysis using iTRAQ to identify salt-responsive proteins during the germination stage of two Medicago species

Salt stress is one of the primary abiotic stresses responsible for decreasing crop yields worldwide. Germinating seeds can be greatly influenced by saline conditions. In this study, the physiological and phenotypic changes induced by salt treatments (10–50 mM NaCl and Na2SO4 mixtures) were analysed for Zhongmu-3 (Medicago sativa) and R108 (Medicago truncatula) seedlings. Our observations indicated that Zhongmu-3 was more salt-tolerant than R108. To characterize the protein expression profiles of these two Medicago species in response to salt stress, an iTRAQ-based quantitative proteomic analysis was applied to examine salt-responsive proteins. We identified 254 differentially changed salt-responsive proteins. Compared with control levels, the abundance of 121 proteins increased and 44 proteins decreased in salt-treated Zhongmu-3 seedlings, while 119 proteins increased and 18 proteins decreased in R108 seedlings. Moreover, 48 differentially changed proteins were common to Zhongmu-3 and R108 seedlings. A subsequent functional annotation indicated these proteins influenced diverse processes, such as catalytic activity, binding, and antioxidant activity. Furthermore, the corresponding transcript levels of 15 differentially changed proteins were quantified by qRT-PCR. The data presented herein provide new insights into salt-responsive proteins, with potential implications for enhancing the salt tolerance of Medicago species.

Sodium sulfate activation mechanism on co-sulfating roasting to nickel-copper sulfide concentrate in metal extractions, microtopography and kinetics

Due to the complexity of occurrence of valuable metals and high content of alkali gangue in nickel-copper sulfide concentrate, traditional pyrometallurgical processing is not suitable. In this work, a two-stage co-sulfating roasting process was used to selectively extract valuable metals from Chinese nickel-copper sulfide concentrate. A mixture of (NH4)2SO4 and Na2SO4 was selected as the co-sulfating agents. The effect of the dosage of (NH4)2SO4 and Na2SO4, first stage roasting temperature, roasting time and second roasting temperature on metal’s extractions were investigated. XRD, SEM, DTA-TG, and DSC-TG were used to reveal the mechanism of action of Na2SO4 and the mineral phase transformations in the two-stage sulfating roasting process. The results show that nearly all of Ni and Co, Cu, and 1.12% of Fe were extracted at the mass ratio of ammonium sulfate to ore of 3.5, first roasting at 500 °C for 2 h, dosage of sodium sulfate of 4 g (10 g ore), followed by second roasting at 680 °C for 2 h, then water leaching at 95 °C for 2 h. Na2S2O7 generated from Na2SO4 in the roasting process, shrinks the particle size of the ore, decrease the surface area of the roasted product, significantly promotes extent of the sulfating of metals, in particular for Ni. Thermal analysis kinetics indicates that Na2SO4 significantly reduces the apparent activation energy of the sulfating roasting process. The metal bearing mineral phases were transformed into sulfates or sodium double or ternary sulfates in the first roasting process, then the sodium double sulfates of Na3Fe(SO4)3 were decomposed.

Preparation of alumina ceramic template by the molten salt method

ABSTRACTSingle-crystal alpha alumina (α-Al2O3) platelets were synthesised with aluminium sulphate in the study. Moreover, the effects of the heating temperature, holding time, and different power mixtures of γ-Al2O3 and sodium sulphate (Na2SO4) on the morphology of as-prepared α-Al2O3 platelets were explored. The crystalline phase evolution and morphology of the samples were characterised by X-ray diffraction and scanning electron microscopy. According to the further analysis results, most of α-Al2O3 platelets were hexagonal particles. After the power mixture of γ-Al2O3 and Na2SO4 (1:2) was heated at 1200°C for 1 h, the platelet size became relatively uniform with an average diameter of 3–5 μm and a thickness of 50–100 nm. This method is an easily controllable, simple, and green method to produce high-quality α-Al2O3 platelets.

A clean technology to separate and recover vanadium and chromium from chromate solutions

In this work, a clean technology is introduced to separate and recover vanadium and chromium from vanadium-containing chromate solution. It was found that vanadium can be precipitated from vanadium-containing chromate solution by hydrolysis. The hydrolysate is the mixture of polyvanadic acid and sodium polyvanadate. The concentration of V in the solution can be decreased to 0.76 g/L under pH 2.0 at 95 °C. The Na in the mixture can be effectively removed by washing with (NH4)2SO4 solution as the bind of NH4-VO3 is stronger than that of Na-VO3. The V2O5 with purity 98.6% was acquired by calcining the washed mixture. The vanadium residue in precipitated solution can be completely removed by adding Fe2+ or Fe3+ to form iron vanadate under pH 3.8–4.5. The chromium in the V free solution was reduced from Cr(VI) to Cr(III) with Na2SO3, and then the precipitate of Cr2O3∙xH2O was formed under pH above 8.5 at 90 °C. At last, the Cr2O3 with purity 98.7% was obtained by the treatment of the chromic oxide hydrate. Using the process above, the generation of V-Cr-bearing reducing slag and the mixture of Na2SO4 and (NH4)2SO4 can be avoided in vanadium pentoxide production from vanadium-containing chromate solution.

Physiological responses to salt stress of salt-adapted and directly salt (NaCl and NaCl+Na2SO4 mixture)-stressed cyanobacterium Anabaena fertilissima.

Soil salinity in nature is generally mixed type; however, most of the studies on salt toxicity are performed with NaCl and little is known about sulfur type of salinity (Na2SO4). Present study discerns the physiologic mechanisms responsible for salt tolerance in salt-adapted Anabaena fertilissima, and responses of directly stressed parent cells to NaCl and NaCl+Na2SO4 mixture. NaCl at 500mM was lethal to the cyanobacterium, whereas salt-adapted cells grew luxuriantly. Salinity impaired gross photosynthesis, electron transport activities, and respiration in parent cells, but not in the salt-adapted cells, except a marginal increase in PSI activity. Despite higher Na+ concentration in the salt mixture, equimolar NaCl appeared more inhibitive to growth. Sucrose and trehalose content and antioxidant activities were maximal in 250mM NaCl-treated cells, followed by salt mixture and was almost identical in salt-adapted (exposed to 500mm NaCl) and control cells, except a marginal increase in ascorbate peroxidase activity and an additional fourth superoxide dismutase isoform. Catalase isoform of 63kDa was induced only in salt-stressed cells. Salinity increased the uptake of intracellular Na+ and Ca2+ and leakage of K+ in parent cells, while cation level in salt-adapted cells was comparable to control. Though there was differential increase in intracellular Ca2+ under different salt treatments, ratio of Ca2+/Na+ remained the same. It is inferred that stepwise increment in the salt concentration enabled the cyanobacterium to undergo priming effect and acquire robust and efficient defense system involving the least energy.

Hot Corrosion of Ti\u2013Re Alloys Fabricated by Selective Laser Melting

Selective laser melting (SLM) is an additive manufacturing process that enables novel alloy production by combining metals with significantly different physical properties. In this paper, the hot corrosion behavior of Ti–Re alloys fabricated by SLM was studied in a mixture of Na2SO4 and NaCl salts at 600 °C. The morphology and composition of the corrosion products were characterized by scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction to understand the degradation mechanisms. It has been shown that the hot corrosion resistance of Ti–Re alloys was influenced by the chemical inhomogeneity of the oxide scale resulting from the presence of rhenium particles undissolved during the SLM process.

The impact of monovalent and divalent ions on wettability alteration in oil/low salinity brine/limestone systems

Waterflooding is applied worldwide to improve oil recovery. Due to the complexity of the crude oil-brine-rock interactions, the mechanism behind the low saline enhanced oil recovery (EOR) process has been debated in the literature for the last decade. Both physical and chemical mechanisms have been proposed, but it appears that none of the suggested mechanisms have got a general acceptance in the scientific literature so far. The main objective of this paper is to investigate the affinity of ions toward the surface during low and high salinity injection by measuring the contact angle (CA) and interfacial tension (IFT) in a carbonate rock substrate/oil/brine system, in different salinity and pH levels. The brines were original sea and formation water, brine solutions containing single component salt such as; MgSO4, KCl, Na2SO4, CaCl2, MgCl2, NaCl, and multicomponent mixtures of them at different concentrations. Three different stock-tank crude oils are utilized in this study. Results showed that the asphaltenic-acidic crude oils have a positive impact to wettability alteration of carbonate rocks during low salinity water injection. Also we observed that the low salinity waterflooding possibly behaving similar to alkaline flooding due to increase in pH. The IFT results show that the lowest IFT value is obtained at 5000ppm smart water containing divalent ions, Mg2+ and SO42−.

Hot corrosion of the ceramic composite coating Ni3Al–Al2O3–Al2O3/MgO plasma sprayed on 316L stainless steel

Abstract Ni3Al–Al2O3–Al2O3/MgO three-layered coatings with thicknesses of 50, 100, and 150 μm for Al2O3/MgO and 100 μm for the other layers were deposited on 316L stainless steel using plasma spraying. X-ray diffraction, atomic force microscopy, furnace hot corrosion testing in the presence of a mixture of Na2SO4 and V2O5 corrosive salts and scanning electron microscopy were used to determine the structural, morphological and hot corrosion resistance of samples. Results revealed that the crystalline grains of MgO and Al2O3 coating were very small. Weight loss due to hot corrosion decreased from approximately 4.267 g for 316L stainless steel without coating to 2.058 g. The samples with 150 μm outer coating showed improved resistance with the increase in outer layer thickness. Scanning electron microscopy of the coated surface revealed that the coating's resistance to hot corrosion is related to the thickness and the grain size of Al2O3/MgO coatings.

Evaluation and correlation of solubility and solvation thermodynamics of glycine, dl-alanine and dl-valine in aqueous sodium sulphate solutions at two different temperatures

In the present study the saturated solubilities of glycine, dl-alanine, and dl-valine in aqueous mixtures of Na2SO4 were determined at 298.15K and 323.15K by using an analytical ‘gravimetric method’. The nature and extent of such solubilities of the experimental amino acids in aqueous Na2SO4 solutions are discussed in the light of salting-in and salting-out effect and compared with the values of the same amino acids reported earlier. The physicochemical and chemical factors affecting the solubility results were suggested and correlated with the thermodynamical aspects and parameters. Finally the transfer Gibbs free energies were calculated and employed to discuss the relative stability of the amino acids in aqueous and aqueous electrolyte solution.

Hot corrosion behaviour of 7YSZ + Gd2O3 nano-composites in molten salts prepared by spark plasma sintering

ABSTRACTThis study compares the hot corrosion performance of yttria-stabilised zirconia (7YSZ), and 7YSZ + Gd2O3 composite samples in the presence of molten mixture of Na2SO4 + V2O5 at 1150°C. For 7YSZ, the reaction between NaVO3 and Y2O3 produces YVO4 and leads the transformation of tetragonal ZrO2 to monoclinic ZrO2. A high-density in sintered 7YSZ + Gd2O3 samples, led minor amounts of monoclinic ZrO2 and tetragonal GdVO4 as the hot corrosion products with only traceable amounts of YVO4, and a stable corroded layer was formed. Due to the synergic effect of doping of zirconia with Gd2O3, the 7YSZ + Gd2O3 sample has a much better hot corrosion crack resistance than 7YSZ.

ChemInform Abstract: Hydrogen Bond‐Assisted Crystallization: Structure, Growth and Characterization of a New Mixed‐Anion Transition Metal Fluoride Na3NH4(TiF6) (SO4)·H2O.

AbstractSingle crystals of Na3NH4(TiF6) (SO4)·H2O are grown by hydrothermal reaction of a 3:1:1 molar mixture of Na2SO4, NaF, and (NH4)2TiF6 (autoclave, 210 °C, 4 d; cooling to 25 °C at a rate of 4 °C/h).

Design and statistical analysis of plasma coatings on superalloy for gas turbine applications

The Influence of plasma sprayed NiCr–Cr2O3 and Al2O3–40% TiO2 (A40T) coatings on Inconel 617 are investigated at 900 and 1000 °C under mixed salt environment for gas turbine applications. The results revealed that the plasma coated alloy exhibits lower mass change than bare alloy in the Na2SO4 and NaCl salt mixture with and without V2O5. The response to the experimental analysis is statistically evaluated using 23 factorial design. Further the exposed samples were analyzed by means of optical image, SEM, EDS and XRD results. The EDS and XRD analysis revealed that the oxides are rich in Ni and Mo on the surface of the samples. The coated samples exhibited better corrosion resistance in A40T when compared to NiCr–Cr2O3 coatings than bare alloy.