Salts ZnCl2 Research Articles

Hydrogen production from ZnCl2 salt: Application of chlor-alkali method

This experimental study investigates the efficiency of hydrogen production from an aqueous ZnCl2 solution using an electrochemical method within a chlor-alkali reactor. A laboratory-scale reactor with separate anode and cathode compartments was constructed for this purpose. The compartments are separated by a Nafion 212 membrane, which prevents the mixing of the anolyte and catholyte solutions while allowing the passage of positive ions (Zn+). Each compartment is equipped with five carbon rod electrodes. The anode chamber is fed with an aqueous ZnCl2 solution, while the cathode chamber is supplied with pure water. The experiments were conducted with a constant electrolyte transfer rate of 0.3g/s into the reactor, at three different cell voltages (5.0, 7.5, and 10.0V) and two different cell temperatures (20 °C and 45 °C). Due to the small reactor dimensions and the dilution effect caused by adding pure water to the cathode compartment which decreases electrolyte density and adversely affects the current a noticeable reduction in hydrogen gas production was observed. Furthermore, the ZnCl2 electrolyte mass flow rate did not significantly impact the current or the generation of hydrogen and chlorine gases. Consequently, no changes were made to the mass flow rate of pure water or the electrolyte. The presence of active chlorine gas was found to cause the erosion of the carbon rod electrodes in the anode chamber. As a result, the amount of chlorine gas produced in the anode chamber is significantly lower than the hydrogen gas produced in the cathode chamber. At a cell temperature of 20 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 5 V with ZnCl2 aqueous solution, the minimum hydrogen production rate is 0.625 mL/min. In contrast, at a cell temperature of 45 °C, a mass flow rate of 0.3 g/s, and a cell voltage of 10 V, the maximum hydrogen production rate is 4.97 mL/min.

Molten salt-confined construction of biocarbon 2D based on Megathyrsus Maximus biomass for high-performance symmetric supercapacitor

Exploring infinite resources, green strategy, and inexpensive for producing 2D biocarbon nanosheets is an essential method in renewable energy. This study aims to develop a eutectic salt-induced activation process for the production of porous carbon nanosheets with well-controlled microstructure using varying ZnCl2 molarity levels. The results showed that biocarbon featuring thin nanosheets with 2D structure and a high specific surface area of 1294 m2g−1 could be obtained in eutectic salt ZnCl2 at 0.5 molarity with a specific capacitance reaching 495 Fg−1. In addition, the capacitive properties of the cells decreased when the molarity was increased to 0.7 M, leading to a decline in specific capacitance to 171 Fg−1. Based on these results, the new and low-cost strategy of eutectic salt media provided an effective method of converting guinea grass into highly valuable biocarbon in the field of electrochemical energy storage.

Characterization and Adsorption Capacity Evaluation of ZnCl2 Impregnated Cassava Peel Carbon for Removal of Fe, Ca, Mg and Zn ions in Wastewater from Cassava processing Industry

The objective of this paper was to prepare, characterize and evaluate the adsorption capacity of cassava peel carbon (CPC) impregnation with ZnCl2 salt for the removal of Fe, Ca, Mg and Zn ions in wastewater derived from cassava processing which has been noted to be problematic in terms of management. CPC and cassava peel activated carbon (CPAC) at 1:3, 2:3, and 1:1 impregnation levels were placed in fixed bed adsorption columns to determine metal ion adsorption capacities of the carbon materials after 120, 240, 360 and 480-minute contact times. Langmuir and Freundlich isotherm models were used in assessment of adsorption of the carbon materials, while pseudo-first and second order models were used to validate the adsorption kinetics of Fe, Ca, Mg and Zn. Pore space development was also monitored using scanning electron microscope (SEM) imagery. Results SEM images revealed hexagonal honeycomb surface structure at 2:3 impregnation level and spongy configuration at 1:1 ZnCl2 impregnation level. The correlation coefficient of Langmuir isotherm was observed to be between 0.86 to 1, indicating that the adsorbent is very good in adsorption of the metals, however, Freundlich isotherm is found to be unfavorable in describing CPAC’s capacity in adsorbing zinc ion contaminant. The pH of the carbon materials was observed to have increased while the bulk density reduced with increasing level of impregnation. Conclusively, CPC and CPAC materials are well suited to Langmuir isotherm as well as pseudo-second order model, implying that adsorption occurs well in a monolayer form on the surface material surface.

Reaction Between Hot-Dip Aluminized Coating on Fe–Cr–B Cast Steel and Molten ZnCl2 Salt

Reaction Between Hot-Dip Aluminized Coating on Fe–Cr–B Cast Steel and Molten ZnCl2 Salt

Impact of molten salts composition on the corrosion behavior of NiMoCr and CoNiCrAl coatings on L-PBF 316L stainless steel for CSP plants

The high-temperature corrosion performance of NiMoCr and CoNiCrAl coatings produced by high velocity oxy-fuel (HVOF) on laser powder bed fusion (L-PBF) 316L stainless steel substate has been evaluated in presence of three different molten salts used as thermal energy storage (TES) materials for concentrated solar power (CSP) plants. The coatings have an excellent oxidation resistance at 700 °C, showing a percentage of affected thickness lower than 2 %, due to the formation of a protective layer of Cr2O3 and Al2O3 in both NiMoCr and CoNiCrAl coatings, respectively. The carbonates-based molten salt accelerates the corrosion of the NiMoCr coating, affecting around 43 % of the coating thickness, due to the formation of chromates and the high depletion of Mo in the coating. In contrast, the effective protection shown by the CoNiCrAl coating is explained because the grown LiAlO2 after the lithiation process has a high capacity to act as a strong diffusion barrier for metal ions and inhibited the formation of chromates. In the presence of two different ZnCl2 and MgCl2-rich molten salts, the CoNiCrAl coating behaved worse than NiMoCr coating due to the breakage of the (Al,Cr)-rich oxide layer as a consequence of an active oxidation mechanism and due to the formation of voids along the entire thickness, which were identified in 100 % of the coating thickness. The superior corrosion resistance of the NiMoCr coating in presence of the chloride rich molten salts was attributed to the presence of Mo, which fixed the Cr and inhibited the diffusion of oxygen.

Hydroxybenzoic acid derived porous carbons for low pressure CO2 capture

There is an urgent need to mitigate CO2 emissions released into the atmosphere from coal-fired power plants. 4-Hydroxybenzoic acid (HBA) is a cost-effective small organic molecule (SOM) that has been used in this study as a molecular precursor for CO2-philic and affordable solid sorbent production. Many pore development strategies and comprehensive characterization techniques were employed. It is found that pyrolysis of HBA (H-800) without any additives allows reaching a capacity of 1.09 mmol g−1 at 0.15 bar, 298 K or 0.86 mmol g−1 at 0.15 bar, 313 K, which shows that simple carbonization of appropriate SOM may yield competitive results over well-known carbonization methods. Several carbonization techniques were employed on the SOM, including CO2, ZnCl2, KOH activations, or potassium salt thermolysis, and zinc salt thermolysis. Starting from zinc salt ends up with very low carbon yield (3 wt%) and high meso-macro pore volume, which is in the range of 2.78 cm3 g−1. KOH activation or potassium salt thermolysis results are comparable to the CO2 capture performance of H-800, though higher micropore volumes up to 0.55 cm3 g−1 were achieved. Additionally, CO2 activation resulted in similar CO2 capture capability and micropore volume as in the case of H-800. Finally, it was found that ultramicropores are the effective pore range for low pressure CO2 adsorption (0.15 bar) at 298 K or 313 K.

Facile One-Step Pyrolysis of ZnO/Biochar Nanocomposite for Highly Efficient Removal of Methylene Blue Dye from Aqueous Solution.

In this work, we developed a facile one-step pyrolysis method for preparing porous ZnO/biochar nanocomposites (ZBCs) with a large surface area to enhance the removal efficiency of dye from aqueous solution. Peanut shells were pyrolyzed under oxygen-limited conditions with a molten salt ZnCl2, which played the roles of the activating agent and precursor for the formation of nanoparticles. The effects of the mass ratio between the molten salt ZnCl2 and peanut shells as well as pyrolysis temperature on the formation of ZBCs were investigated. Characterization results revealed that the as-synthesized ZBCs exhibited a highly porous structure with a specific surface area of 832.12 m2/g, suggesting a good adsorbent for efficient removal of methylene blue (MB). The maximum adsorption capacity of ZBCs on MB was 826.44 mg/g, which surpassed recently reported adsorbents. The formation mechanism of ZnO nanoparticles on the biochar surface was due to ZnCl2 vaporization and reaction with water molecules extracted from the lignocellulosic structures. This study provides a basis for developing a simple and large-scale synthesis method for wastewater with a high adsorption capacity.

Hot corrosion behaviors of 921A alloy and HVAF-sprayed Fe-based amorphous coating covered with KCl–ZnCl2 salts

Hot corrosion behaviors of 921A alloy and HVAF-sprayed Fe-based amorphous coating covered with KCl–ZnCl2 salts

Bifunctional Zinc-Molybdate or Zinc molybdenum Oxide/Metal-Nitrogen-Carbon catalytic layers with improved four-electron selectivity for oxygen reduction in acidic medium

Platinum-group-metal-free metal-nitrogen-carbon catalysts for the oxygen reduction reaction have demonstrated high initial activity and power performance in proton exchange membrane fuel cells. The main challenge facing this class of catalysts is their poor durability in operating acidic fuel cells. Their key operando degradation mechanisms involve oxidative attacks triggered by the catalysis of the oxygen reduction on atomically-dispersed 3d transition metals. Reactive oxygen species such as H2O2 or radical species are particularly aggressive to the carbon matrix. Minimizing H2O2 by-product formation during oxygen reduction or actively scavenging any formed H2O2 are therefore promising routes to improve their durability.Here, we report that Zn-molybdate and Zn molybdenum oxide have low activity towards H2O2 decomposition and electro-reduction in acid, but result in a strong synergistic effect with various M-N-C catalysts. The addition of α-ZnMoO4 or Zn3(OH)2(MoO4)2 in cathode layers resulted in improved four-electron ORR selectivity of M-N-C catalysts (M = Fe, Co, Cr) as well as moderately improved durability in accelerated stress tests in O2-saturated pH 1 electrolyte. The improvement in selectivity could be rationalized by hydrogen peroxide electro-reduction measurements and catalase enzyme-like activity tests. Both types of measurements revealed higher reactivity towards H2O2 scavenging when Metal-N-C catalysts are physically mixed (in a catalytic layer) or together in a suspension in solution with Zn-molybdate or Zn molybdenum oxide, revealing a synergy effect. Control experiments with ZnCl2 and Na2MoO4 salts however suggest that leached ions from ZnMoO4 in acidic solution are likely at the root of the synergy effect.

A Nonflammable Organic Electrolyte with a Weak Association State for Zinc Batteries Operated at −78.5 °C

AbstractTraditional rechargeable Zn batteries fail to work in cold regions due to the high freezing point (Tf) and severe corrosivity of the aqueous electrolytes with excessive association (solvent‐solvent and solute‐solvent interactions). In this study, a nonflammable weak‐associated electrolyte (WASE) consisting of ZnCl2 salt and methanol/dichloromethane mixture as a solvent is developed to achieve high reversible Zn plating/stripping at low temperatures. The low self‐association interaction of the mixed solvent not only endures WASE with a low Tf of −119.2 °C but also facilitates the desolvation of interfacial Zn2+ and induces smooth Zn plating at low temperatures. Moreover, the water‐free WASE inhibits the hydrolysis of ZnCl2 and thus restrains the corrosion of Zn electrodes. Thanks to the above merits, the Zn||Zn, Zn||Cu, and Zn||polyaniline cells with WASE exhibit superb electrochemical performance at temperatures as low as −78.5 °C.

Effect of enamel coating on the hot corrosion of 304 stainless steel beneath KCl–ZnCl2 deposits at 450 °C

The hot corrosion behavior of 304 stainless steel (304SS) and the enamel coating in KCl–ZnCl2 salts is studied. The corrosion kinetics of the samples shows that the mass loss of enamel coating is far lower than that of 304SS, indicating that the enamel coating can effectively block the diffusion of Cl element to the enamel coating/alloy interface due to its high chemical stability in chloride salts and low grain boundary density. Fe2O3 and (Fe,Cr)2O3 are mainly formed on the surface of 304SS covered by KCl–10%ZnCl2, whereas no corrosion products are found on the surface of the enamel coating. When the content of ZnCl2 is increased to 55%, Fe2O3 and Cr2O3 are mainly formed on the surface of 304SS, and Zn2SiO4 is formed on the surface of the enamel coating. In the two salts, the corrosion layer of 304SS is composed of Fe-rich oxides (external) and Cr rich oxides (internal). The enrichment of high amounts of Cl element near the interface between the corrosion products and alloy matrix indicate that metal chlorides are formed at the interface. These results are in line with the characteristics of “active oxidation” mechanism.

Impact of the additive manufacturing process on the high-temperature corrosion of 316L steel in the presence of NaCl–KCl–ZnCl2 molten solar salt

A comparative study of the high-temperature oxidation and corrosion resistance of wrought and additive manufacturing selective laser melting (SLM) 316L stainless steel was performed in presence of molten NaCl–KCl–ZnCl2 salt used for thermal energy storage in the new generation of concentrated solar plants. Isothermal tests at 650 and 700 °C in a dry air atmosphere were conducted to evaluate (i) the effect of the manufacturing process and (ii) the effect of molten salts on the corrosion behavior of the steel by dimensional metrology analysis, scanning electron microscopy and X-ray diffraction characterization. The manufacturing process had a significant influence on the oxidation resistance. The wrought samples had a mass gain after 48 h that was four times greater than that of SLM samples at 650 °C, and 50% greater at 700 °C. The presence of the salt primarily increased the corrosion rate of all the samples and, again, the wrought pieces suffered 13% and 6% more corrosion in terms of metal loss than the SLM ones at 650 and 700 °C, respectively. The presence of more pathways for Cr diffusion associated with a higher number of defects in the microstructure of the SLM sample, as dislocations and grain boundaries, facilitated the formation of Cr2O3 scales in the SLM sample, avoiding the intergranular attack shown in the wrought one.

Ionothermal Synthesis of Covalent Triazine Frameworks in a NaCl-KCl-ZnCl2 Eutectic Salt for the Hydrogen Evolution Reaction.

Covalent triazine-based frameworks (CTFs) are typically produced by the salt-melt polycondensation of aromatic nitriles in the presence of ZnCl2 . In this reaction, molten ZnCl2 salt acts as both a solvent and Lewis acid catalyst. However, when cyclotrimerization takes place at temperatures above 300 °C, undesired carbonization occurs. In this study, an ionothermal synthesis method for CTF-based photocatalysts was developed using a ternary NaCl-KCl-ZnCl2 eutectic salt (ES) mixture with a melting point of approximately 200 °C. This temperature is lower than the melting point of pure ZnCl2 (318 °C), thus providing milder salt-melt conditions. These conditions facilitated the polycondensation process, while avoiding carbonization of the polymeric backbone. The resulting CTF-ES200 exhibited enhanced optical and electronic properties, and displayed remarkable photocatalytic performance in the hydrogen evolution reaction.

Ionothermal Synthesis of Covalent Triazine Frameworks in a NaCl‐KCl‐ZnCl2Eutectic Salt for the Hydrogen Evolution Reaction

AbstractCovalent triazine‐based frameworks (CTFs) are typically produced by the salt‐melt polycondensation of aromatic nitriles in the presence of ZnCl2. In this reaction, molten ZnCl2salt acts as both a solvent and Lewis acid catalyst. However, when cyclotrimerization takes place at temperatures above 300 °C, undesired carbonization occurs. In this study, an ionothermal synthesis method for CTF‐based photocatalysts was developed using a ternary NaCl‐KCl‐ZnCl2eutectic salt (ES) mixture with a melting point of approximately 200 °C. This temperature is lower than the melting point of pure ZnCl2(318 °C), thus providing milder salt‐melt conditions. These conditions facilitated the polycondensation process, while avoiding carbonization of the polymeric backbone. The resulting CTF‐ES200exhibited enhanced optical and electronic properties, and displayed remarkable photocatalytic performance in the hydrogen evolution reaction.

Ternary SLE Measurements for the Systems H2O+ZnCl2+Zn(H2PO2)2 at T= (298, 313 and 333) K

The solid-liquid equilibrium (SLE) of H2O+ZnCl2+Zn(H2PO2)2 ternary system at 298, 313 and 333 K have been studied with the use of isothermal method. Solid phase compositions have been determined with Schreinemaker’s method. H2O+ZnCl2+Zn(H2PO2)2 ternary systems have simple eutectic type in 298, 333K. One invariant point, two invariant curves and two crystallization region have been observed in the phase diagrams at 298, 333K. Otherwise, One invariant point, three invariant curves and two crystallization region have been observed in the phase diagrams in 313K. In the crystallization regions; (i) Zn(H2PO2).H2O and ZnCl2, (ii) Zn(H2PO2)2, Zn(H2PO2).H2O and ZnCl2, (iii) Zn(H2PO2)2 and ZnCl2 salts have been observed at 298 K, 313K, and 333 K, respectively. In H2O+ZnCl2+Zn(H2PO2)2 ternary system, the increasing salting-out effect of Zn(H2PO2)2 on ZnCl2 with temperature.

Solid-liquid phase equilibria in the ternary systems H2O+ZnCl2+NaCl at temperatures of 298, 313 and 333 K

In this study, an economic separation method is suggested with the use of phase equilibria in order to ensure the recycling of ZnCl2, the industrial waste amount of which is very high, and to prevent it from an environmental pollutant. Sodium chloride?zinc chloride?water systems were examined by the isothermal method at temperatures of 298, 313 and 333 K. The analyses of the liquid and solid phases were used to determine the composition of the solid phase using the Schreinemaker?s graphic method. The solid?liquid phase equilibrium and viscosity data belonging to all the ternary systems were identified and the solubility and viscosity changes with temperature were compared. The viscosity values were inversely proportional to the temperature as the amount of ZnCl2 in the solution increased. NaCl, 2NaCl ZnCl2 nH2O (n: 2, 0), ZnCl2 salts were observed at 298, 313 and 333 K in the solid phases that are in equilibrium with the liquid phase at the invariant point.

Template-activated bifunctional soluble salt ZnCl2 assisted synthesis of coal-based hierarchical porous carbon for high-performance supercapacitors

A series of coal-based hierarchical porous carbons with adjustable pores were successfully prepared with the assistance of the soluble salt Zinc chloride (ZnCl2). During the carbonization process, ZnCl2, with a low melting point (238 °C), “in situ occupied” and “occupied” within the coal solids to generate interconnected pores, which acted as a template. Simultaneously, the activation of ZnCl2 reduced the oxygen content of products and further improves their electrical conductivity. Optimization of the mass of the salt and the carbonization temperature resulted in targeted product with a suitable specific surface area (1581 m2 g−1) and unique pores (Vmeso/Vtotal = 45%), which exhibited a high specific capacitance (470.7 F g−1 at 0.5 A g−1) in 6 M KOH electrolyte. The symmetrical supercapacitor of targeted product has favorable rate performance (256.7 F g−1 at 0.5 A g−1, 84.8% capacity retention at 30 A g−1) and excellent cycling performance (after 10000 cycles, the specific capacitance increases to 115% of the initial capacity at 10 A g−1). In the EMIMBF4 electrolyte system, the energy density is 95.31 Wh kg−1 at 213.13 W kg−1. Therefore, this work provides an effective method to improve the green and efficient use of coal.

Effect of CaCl2 and ZnCl2 salts on isobaric vapor-liquid equilibrium in separation of the azeotropic mixture of ethanol + water

Present work analyzes potential of calcium chloride (CaCl2) and zinc chloride (ZaCl2) salts as entrainer for breaking the minimum boiling azeotrope of ethanol and water. Isobaric vapor-liquid equilibrium (VLE) data for the binary systems of water + ethanol and ternary system of water + ethanol + calcium chloride, and water + ethanol + zinc chloride were measured at a constant pressure of 94.5 kPa. The effect of salts on the relative volatility of ethanol to water as well as on the vapor phase mole fractions of ethanol were also studied experimentally. From the experimental results, it is observed that with addition of salts, the azeotropic point of the ethanol and water system can be eliminated. Salting out effects in case of calcium chloride was more than that zinc chloride salt. The results obtained in this work showed that calcium chloride could be a better choice for separation of the water + ethanol azeotrope. Electrolyte nonrandom two-liquid (eNRTL) model was used to correlate the experimental VLE data. The model prediction with the regressed parameters was found in well agreement with the experimental data. The experimental data obtained in this work was found thermodynamically consistent using van Ness test.

Gamma radiation-induced defects in KCl, MgCl2, and ZnCl2 salts at room temperature.

Room temperature post-irradiation measurements of diffuse reflectance and electron paramagnetic resonance spectroscopies were made to characterize the long-lived radiation-induced species formed from the gamma irradiation of solid KCl, MgCl2, and ZnCl2 salts up to 100 kGy. The method used showed results consistent with those reported for electron and gamma irradiation of KCl in single crystals. Thermal bleaching of irradiated KCl demonstrated accelerated disaggregation of defect clusters above 400 K, due to decomposition of Cl3-. The defects formed in irradiated MgCl2 comprised a mixture of Cl3-, F-centers, and Mg+ associated as M-centers. Further, Mg metal cluster formation was also observed at 100 kGy, in addition to accelerated destruction of F-centers above 20 kGy. Irradiated ZnCl2 afforded the formation of Cl2- due to its high ionization potential and crystalline structure, which decreases recombination. The presence of aggregates in all cases indicates the high diffusion of radicals and the predominance of secondary processes at 295 K. Thermal bleaching studies showed that chloride aggregates' stability increases with the ionization potential of the cation present. The characterization of long-lived radiolytic transients of pure salts provides important information for the understanding of complex salt mixtures under the action of gamma radiation.

Synthesis, crystal structures and theoretical studies of Zinc(II) coordination compounds with 4-trifluoromethylphenyl)imino-methyl]pyridine bidentate Schiff base ligand

[Zn(dip)(Br)2] (1) and [Zn2(dip)2Cl4] (2) zinc(II) coordination compounds were synthesized using 4-trifluoromethylphenyl)imino-methyl]pyridine (dip) bidentate Schiff base ligand and ZnBr2 and ZnCl2 salts. In structure 1, zinc(II) ion exhibits a tetrahedral arrangement while adopting a ZnN2Cl3 trigonal bipyramidal geometry in structure 2. Moreover, in structures 1 and 2, the neutral molecules form a 1D chain structure through the C-H•••F hydrogen bonds. Complex 1 is a monomeric structure while complex 2 has a dimeric structure. Coordination compounds 1 and 2 have been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction. Density Functional Theory (DFT) calculations at the B3LYP level of theory have been carried out to investigate three types of reactions between ZnCl2 and ZnBr2 metal salts and ligand L in both gas and solution phases. The optimized geometrical parameters of the complexes were evaluated using SDD, CEP-121G, and LANL2DZ basis sets. The gas phase calculations show that the binuclear Zn2L2X4 (Zn2L2Cl4 and Zn2L2Br4) complexes are more stable than mononuclear ZnLX2 (ZnLCl2 and ZnLBr2) and ZnL22+ complexes. However, the solution studies indicate that the formation of Zn2L2Cl4 and ZnLBr2 complexes is energetically more favorable compared with the other complexes.