Chloride Sulfate Solutions Research Articles

Adsolubilisation of thiacloprid pesticide into the layered zinc hydroxide salt intercalated with dodecyl sulphate, for controlled release formulation

ABSTRACT Sodium dodecyl sulphate surfactant was intercalated into the layered zinc hydroxide salt for the successful adsolubilisation of poor water-soluble pesticide, thiacloprid. The intercalation of the dodecyl sulphate ion was confirmed by PXRD analysis with basal spacing 30.1 Å. The presence of thiacloprid into the interlayer gallery of zinc layered hydroxide also supported with Fourier transform infrared spectra and elemental analysis. Based on the thermal study, thiacloprid was thermally stable after the adsolubilisation compared to its solid form. The release of thiacloprid anions from the nanocomposite into an aqueous solution of sodium phosphate was governed by first-order kinetics. Whereas the release of thiacloprid into sodium sulphate and sodium chloride solution governed by parabolic diffusion kinetics model. In consideration of the obvious breakthrough made in the nanocomposite characterisation and release study, this nanocomposite could be a promising candidate for the profitable improvement of an environment-friendly pesticide formulation.

Solvent Extraction of Copper from Sulfate–Chloride Solutions Using LIX 84-IC and LIX 860-IC

ABSTRACT The effect of chloride ions on the copper extraction equilibria, the rate of extraction, copper/iron selectivity, and chloride extraction was studied for organic phases containing pure ketoxime (LIX 84-IC) and pure nonylaldoxime (LIX 860N-IC). In these systems, the used aqueous phase contained total chloride concentrations from 0 to 110 g/l. It was determined that the chloride ions in the aqueous solution had a large negative effect on the extraction equilibria for LIX 84-IC and a small effect for LIX 860N-IC. This deleterious effect is attributed to an increase in the hydrogen ion activity coefficient in the presence of chloride ions. The chloride accelerated the rate of copper extraction even though the reaction was fast in all the tested conditions. An increase in the temperature from 25°C to 35°C affected positively the extraction equilibria for LIX 84-IC.

Dismantling and electrochemical copper recovery from Waste Printed Circuit Boards in H2SO4–CuSO4–NaCl solutions

The worldwide growing of electrical and electronic equipment makes increasingly urgent to find environmentally friendly treatments for e-waste. In this paper, the attention has been focused on i) the eco-friendly dismantling of the electronic components from Waste Printed Circuit Boards and ii) recovering of pure metallic copper, which is the most abundant metal and one of the most valuable in Printed Circuit Boards. After an experimental optimization study, we found that a solution containing 0.5 M H2SO4, 0.4 M CuSO4, and 4 M NaCl can be successfully used to disassemble the electronic components from the boards by leaching of all exposed metals. Air was blown into the leaching solution in order to regenerate Cu2+ ions, which acts as the predominant oxidant specie. The key role in dismantling/leaching process is played by Cl− ion that stabilizes Cu+ through the chloro-complexes formation. The results show that, in this manner, the electronic components can be easier disassembled in undamaged state, allowing the efficient recycling and valorization of the base materials. The feasibility to recover electrochemically the copper from the solution resulting from dismantling/leaching tests was verified through a preliminary cyclic voltammetry study aimed to investigate the copper electrodeposition in sulphate-chloride solutions in the presence of other metal ions such as Ni2+, Fe2+, Zn2+, Pb2+, Sn2+. A two-compartment electrochemical cell operating in either galvanostatic or potentiostatic mode was employed to investigate simultaneous copper recovery and leaching solution regeneration. The results indicate that, in both modes, pure copper can be obtained after the removal of all surface impurities by dipping in acidic concentrated sodium chloride solution. The galvanostatic mode leads to deposit of higher quality, meanwhile the potentiostatic one determines a faster deposition and leaching solution regeneration.

Electrochemical analysis of SiC composite additions at 7.5% weight content on the corrosion resistance of monolithic aluminium alloy in sulphate–chloride solution

Effect of specific SiC particle sizes on the corrosion resistance and metastable pitting behaviour of AA1060 aluminium at 7.5% SiC weight content in 0.05M H2SO4, 0.3M NaCl and 0.05M H2SO4/0.3M NaCl solution was studied with potentiodynamic polarization, open circuit potential measurement and optical microscopy. SiC slightly increased the susceptibility of aluminium matrix composite (AA1060/SiC) at 9μm and 29μm in H2SO4 and NaCl solutions. The lowest corrosion rate values were observed at 3μm and 45μm SiC particle size. Two metastable pitting portions were visible on the polarization plots at these particles sizes due to passivation and re-initiation of transient corrosion pits. The metastable pitting portion of the polarization plots for AA1060/SiC in H2SO4 varied over wider corrosion potential and higher corrosion current compared to the plots from NaCl solution. The relatively smooth transition of the polarization plots in NaCl from anodic polarization to metastable pitting activity of the matrix composite resulted in more concentrated localized corrosion. The effect of SiC particle sizes in the admixed H2SO4–NaCl solution significantly contrasts the earlier observations. The OCP plots in H2SO4 and NaCl solution shows AA1060/SiC at 45μm was most electropositive due to the combined action of the protective oxide from aluminium and insulating properties of SiC. The plots at 0μm for both solutions were comparatively electronegative. Morphological damage of AA1060/SiC at 0μm was significantly more than the deterioration at 3μm and 45μm.

Durability of ettringite-based composite reinforced with polypropylene fibers under combined chemical and physical attack

High-performance fiber reinforced cementitious composites from ettringite-based binders require much understanding of durability before its real-life applications in construction industry. A strain-hardening fiber reinforced ettringite-based composite from the hydration between ladle slag and gypsum with polypropylene (PP) fibers was the object in this study. To investigate the durability of the developed composite under aggressive conditions in cold regions (e.g., the Northern Europe), the material was subjected to a combined sodium sulfate-chloride solution along with freeze-thaw cycling process, which represented the marine environment of cold regions. The experimental study reports the vital role of PP fibers in control crack propagation and, hence, greatly enhanced the durability of the composite. In addition, the developed composite attained good mechanical performance with deflection-hardening behavior and multiple crack even after aging processes. Materials, aged in water, was mainly destructed by volume expansion from water uptake in structural pores, while those, cured in Na2SO4NaCl solution, was mainly spoiled by volume increase from both physical and chemical attacks.

Corrosion resistance of low SiC particle variation at low weight content on 1060 aluminum matrix composite in sulfate-contaminated seawater

Abstract The effect SiC particle sizes (3 µm, 9 µm 29 µm and 45 µm) at 2.5% weight content on the corrosion resistance of 1060 aluminum in sulfate and sulfate-chloride solution was studied by potentiodynamic polarization, open circuit potential measurement and optical microscopy. Results showed the presence of SiC increases the susceptibility of monolithic aluminum (0 µm SiC particle size) to corrosion. In the sulfate solution, the corrosion rate values increased from 0.074 mm/y to 0.556 mm/y at 3 µm SiC particle size after which a progressive decrease in corrosion rate was observed to 0.240 mm/y at 45 µm SiC particle size. The corrosion rate value in sulfate-chloride solution increased significantly with increase in SiC particle size from 0.580 mm/y (0 µm) to 1.181 mm/y at 45 µm. Open circuit potential plots show monolithic aluminum in both solutions is the most electronegative, though potential transients were quite visible on the plot from sulfate-chloride solution. The surface of the corroded 1060AlSiC specimens agree with the results from electrochemical test with extensive morphological damage.

Conversion of chloride salts with the use of sodium sulfate when crystallizing salts from chloride-sulfate solutions

Conversion of chloride salts with the use of sodium sulfate when crystallizing salts from chloride-sulfate solutions

Possibility of Electromembrane Softening Treatment of Network Water at a Thermal Power Station

The possibility of electromembrane softening treatment of network water at a thermal power station is shown. Technology for the manufacturing of an inert anode free from noble metals or their compounds is proposed. Performed resource tests have demonstrated that such an anode can be in operation in chloride–sulfate solutions for several years almost without wear. A mathematical model describing the electrical current utilization efficiency as a function of process parameters and electrolysis regimes in the electromembrane softening of water has been developed. The results of calculating the current utilization efficiency coefficient by this model are in satisfactory agreement with experimental results. The current utilization coefficient in the formation of NaOH does not depend on the anolyte composition but appreciably decreases with increasing catholyte concentration and slightly grows with increasing current density at a constant catholyte concentration. Experiments have not disclosed any essential dependence between the specific water and CO 3 2- ion transports and the process parameters. Experiments on estimating the depth of the electromembrane softening of initial water for the heat supply networks of Kharkiv have demonstrated that the electromembrane method provides the residual hardness of 0.3–0.4 mg-equiv/dm3, which is almost four times lower than for water subjected to soda–lime treatment. The experiments performed on a test bench setup have confirmed that the application of heterogeneous cation-exchange membranes (both MK-40 (OAO Shchekinoazot) and CMI 9000 (Membrane International)) provides the possibility to attain a high current utilization ratio above 88%. The carbonate index of water after electromembrane softening corresponds to the normative requirements to water for heat supply networks with a heat transfer agent temperature below 150°C (no higher than 0.4 (mg-equiv/dm3)2]. This provides the possibility to use the treated water immediately in heat supply networks without further ion-exchange softening. Some technical and economic parameters of the softening process and the technical parameters of an industrial electromembrane softener are given, and the possibilities of the utilization of wastes and byproducts are considered.

Slag hydration and chloride binding in slag cements exposed to a combined chloride-sulphate solution

The effects of curing temperature (20 °C or 38 °C), slag composition and slag content on the hydration and chloride binding characteristics of ground granulated blast-furnace slag (ggbs) – blended cements have been studied. Two slags (CaO/SiO2 = 1.05 or 0.94) were each blended with CEM I 52.5R at 30% and 70% replacement. Paste samples of constant 0.5 w/b ratio were hydrated for 56 days, dried and exposed to either sodium chloride or combined sodium chloride – sodium sulphate solutions. Sodium sulphate concentration was 3 g/L, while chloride concentrations varied from 0.1 to 3.0 M. Post-exposure reaction products were characterised by XRD and thermal analysis. Chloride binding was followed via Friedel’s salt formation, with thermal analysis showing a decrease in Friedel’s salt formation in the presence of sulphate ions. Increasing slag content changed the nature of the chloride binding mechanism significantly. Hydration of slag studied by SEM-BSE image analysis showed that the higher basicity slag was more reactive, with the degree of slag hydration increasing with temperature. An increase in the slag load reduced the degree of slag hydration. Apart from the increase in slag load, the other changes in hydration corresponded well with the chloride binding characteristics of the blends.

Performance of limestone cement concretes in chloride–sulfate environments at low temperature

Portland–limestone cement concretes were stored in two chloride–sulfate solutions, corresponding to exposure classes XS2, XA2 and XA3 specified by the standard BS EN 206:2013, at 5 ± 1°C. Their performance was evaluated in terms of the limestone content (15% or 35% w/w) of the cements used and the partial replacement of limestone cement with natural pozzolana, fly ash, blast-furnace slag or metakaolin. Sulfate attack was monitored through visual inspection of the specimens, mass measurements, compressive strength tests and X-ray diffraction analysis. The penetration of chloride ions was evaluated by determining total (acid-soluble) and free (water-soluble) chloride contents, as well as apparent chloride diffusion coefficients. Limestone cements favoured thaumasite sulfate attack and chloride accumulation in concrete compared to ordinary Portland cement. Mineral admixtures improved the concrete's durability against sulfate attack, inhibited chloride penetration and enhanced chloride binding. Fly ash, metakaolin and blast-furnace slag were more effective than natural pozzolana. Higher sulfate content of storage solutions promoted deterioration, and decreased chloride diffusion coefficients. The results obtained for concretes with mineral admixtures were competitive with those achieved when ordinary Portland cement was used.

Performance of plain and slag-blended cements and mortars exposed to combined chloride–sulfate solution

The durability of reinforced concrete structures exposed to aggressive environments remains a challenge to both researchers and the construction industry. This study investigates the hydration, mechanical properties and durability characteristics of ground granulated blast-furnace slag (GGBS) – blended cements and mortars exposed to a combined sodium chloride–sulfate environment, at temperatures of 20°C and 38°C. The conditions were chosen so as to assess the performance of slag blends under typical temperate and warm tropical marine climatic conditions. Slags with calcium oxide-to-silicon dioxide ratios of 1·05 and 0·94, were blended with CEM I 52.5R at 30% replacement level to study the influence of slag composition and temperature. Parallel control tests were carried out with CEM I 42.5R. Pastes and mortar samples were cast using 0·5 water-to-binder ratio, pre-cured for 7 d in water before exposure. Flexural strengths were determined when the samples were 7, 28 or 90 d old. Hydration was followed using X-ray diffraction (XRD), thermal analysis and calorimetry. Also, sorptivity, gas permeability and chloride diffusion tests were carried out on mortar samples to measure transport and durability characteristics. The results show improved mechanical and transport properties for slag blended cements exposed to environments rich in sodium chloride and sulfate.

Factors affecting hematite precipitation and characterization of the product from simulated sulphate-chloride solutions at 150 °C

Precipitation of iron as hematite from acidic sulphate-chloride solutions was studied in a batch reactor at 150 °C. Several factors that either increase or decrease the extent of hematite precipitation (such as: sulphuric acid, chloride, seed, ferric iron, pre-neutralization, arsenic(V) and copper(II)) were studied. The presence of chloride in the solution increased the extent of hematite precipitation. The presence of low levels of arsenic(V) (<0.5 g/L) severely decreased the extent of precipitation. The presence of CuSO4 increased the extent of hematite precipitation. The nature of the product and uptake of elements from solution was affected by the acid levels and the nucleation and growth mechanism. Sulphate adsorption on hematite crystallites and incorporation of the hydroxyl ion into the hematite structure were found to be responsible for the broad and low intensity peaks of the hematite produced from a Fe(III)-Cu(II)-Cl-SO42− system.

Comparative Studies on the Codeposition of Antimony and Tin from Acidic Chloride and Sulfate-Chloride Solutions

Comparative Studies on the Codeposition of Antimony and Tin from Acidic Chloride and Sulfate-Chloride Solutions

CATHODIC DEPOSITION OF Mg(OH)2 COATINGS ON PURE Mg IN THREE Mg SALTS AQUEOUS SOLUTIONS

Film-forming effects of cathodic deposition on pure Mg substrate at constant DC in aqueous solutions of magnesium nitrate (Mg(NO3)[Formula: see text]6H2O), magnesium chloride (MgCl[Formula: see text]6H2O) and magnesium sulfate (MgSO[Formula: see text]7H2O) respectively were investigated systematically. Typical processes were studied by potentiodynamic cathodic polarization and galvanostatic polarization and typical samples were analyzed by SEM and XRD. The results indicate that the depositing efficiency is not only the highest but stablest, and deposited coatings show the best uniformity with Mg(NO3)[Formula: see text]6H2O solution employed as depositing medium and applied current density [Formula: see text][Formula: see text]mA cm[Formula: see text]. Cathodic deposition leads to regular mass loss of Mg substrate. The cathodic polarization curve of pure Mg in magnesium nitrate solution shows more obvious pseudo-passivation, several Tafel regions with different slopes appearing before diffusion-limited current density region, and oxygen consumption is the major cathodic reduction reaction under specified current density. However, hydrogen evolution reaction is dominant in both Mg chloride and Mg sulfate solutions. The deposition coatings are all composed of continuous and uniform mesh-like “basic layer” adjacent to substrate and discrete distributed snowball-like particles on the microscopic scale. The phase compositions are all crystal Mg(OH)2, and the coatings deposited in Mg chloride solution have (011) preferred orientation.

Self-healing of microcracks in Engineered Cementitious Composites under sulfate and chloride environment

Hydraulic structures are subject to high risk of deterioration associated with cracking and sulfate-chloride attack. Application of Engineered Cementitious Composites (ECC) with self-controlled tight microcracks and self-healing capacities could potentially lead to enhanced durability performance of hydraulic structures even after the formation of cracks under combined environmental and mechanical loadings. This research experimentally investigated the self-healing behavior of ECC under aggressive sulfate and chloride conditions. Resonant frequency (RF) and mechanical properties including stiffness, first cracking strength, ultimate tensile strength and tensile strain capacity were experimentally determined for ECC specimens that were preloaded to 1% strain and exposed to sulfate and sulfate-chloride solutions to simulate the service environment of hydraulic structures. The performance of ECC was found not to be adversely affected by the aggressive solutions. Instead, self-healing of the microcracks was observed leading to partial recovery of the mechanical properties. It was also found that ECC tends to heal faster and more completely in sulfate solutions than in water. These results demonstrate that ECC material remains durable under sulfate-chloride environment, which is beneficial for improving the long-term performance of hydraulic structures in such aggressive environments.

Effect of gelatine and 5-methyl-1H-benzotriazole on corrosion behaviour of copper in sulphuric acid containing Cl− ions

Copper corrosion behaviour in the presence of binary system containing 5-methyl-1H-benzotriazole and gelatine as well as 1H-benzotriazole and gelatine in 0.01 mol dm−3 H2SO4 with the addition of different concentration of Cl− ions was investigated in this study. The corrosion inhibition effect of these compounds was examined by electrochemical techniques (open circuit potential, potentiodynamic polarization and cyclic voltammetry measurements) and weight loss measurements. The surface analysis by scanning electron microscopy with energy X-ray spectroscopy was also performed to assess the morphology of untreated and treated surface of copper coupons. According to the potentiodynamic polarization results, these inhibitors showed good performance in the presence of Cl− ions and they act as mixed-type inhibitors. The inhibition efficiency of binary system is over 90% indicating that these compounds provide good copper protection in sulphate-chloride solutions. The results obtained from weight loss measurements are in good agreement with the results obtained by electrochemical measurements.

Durability study on engineered cementitious composites (ECC) under sulfate and chloride environment

The lack of durability of concrete hydraulic structures, especially under sulfate and chloride environment, has become a worldwide problem. The present paper investigated the feasibility of applying ductile engineered cementitious composites (ECC) as an alternative to conventional concrete in hydraulic structures to improve their durability performance. Specifically, the durability of ECC under sulfate and combined sulfate-chloride conditions were studied. Compressive and tensile behavior of ECC after long-term exposure to Na2SO4 and Na2SO4+NaCl solutions was experimentally characterized. Subsequently, micromechanical study was adopted to investigate the microscopic mechanisms underlying the composite level behavior of ECC under those aggressive environments. The research findings demonstrated that ECC remains durable and maintains its high mechanical performance even after 200days of exposure to concentrated sulfate and combined sulfate-chloride environments. In addition, the micromechanics-based study quantitatively characterized the influence of sulfate and sulfate-chloride solutions on the micromechanical parameters including matrix fracture toughness and fiber/matrix interfacial bond, providing insights into the underlying mechanisms of the composite level behavior of ECC under those environments.

Spontaneous Reduction of Cupric Complex on Titanium Oxides in Acidic Sulfate–Chloride Media

It is discovered in this work that Cu(II) can be spontaneously reduced on titanium oxides in a mixed sulfate-chloride solution at 85°C. X-ray photoelectron spectroscopy (XPS) suggests that after reaction, copper species exist in an oxidation state lower than 2+. Analysis using X-ray powder diffraction (XRD) shows that the reduced copper species could exist in the form of a CuTi alloy. Time of flight secondary ion mass spectrometry (ToF-SIMS) revealed the depth profile of copper signals in the oxide films. ToF-SIMS results demonstrated that copper signals co-existed with titanium oxide signals in the anodized oxide films, and copper species can diffuse deeply into the porous films within 60 minutes of immersion. Further electrochemical and surface characterizations have confirmed that the presence of chloride ions is a crucial factor for the spontaneous reduction of Cu(II). This phenomenon reveals the role of Cu(II) in a mixed sulfate-chloride solution and its effect on titanium oxide films. It also provides an approach to incorporate a CuTi alloy into titanium oxide films.

Treatment of the Heating System Water Using the Electro-Membrane Method

A method was developed to make a combined inert anode of plumbum dioxide on the titanium dioxide-manganese substrate that contains no precious metals and operates reliably during the electrolysis of chloride-sulfate solutions. On this basis the test unit for the electro-membrane water softening was developed and it was subjected to the bench tests. The technology consists in that the water passes through the cathode chambers of two-chamber membrane electrolyzer, including the separation of settled hardness salts, additional water softening in the sodium cation-exchange unit and its neutralization when it passes through the anode chambers of the electrolyzer. A number of required reagents is sharply decreased, and the amount of discharged mineralized drainages is also decreased, and the energy expenditures made up only 1,3 kW∙h/m 3 of wastewater. The produced water has a carbonate index of 0,09 (mg-ekV/dm 3 ) 2 and after the pH adjustment by ammonia it can be used to feed the heating system.

Characterization of Vanadium Species in Mixed Chloride–Sulfate Solutions: An Ab Initio Metadynamics Study

All-vanadium redox flow batteries have attracted considerable interest as promising electrical energy storage devices, because of their ability to store large amounts of energy and to resist fluctuating power supplies. A crucial parameter for battery efficiency is the solubility of vanadium in the electrolyte solutions. Recently, it has been shown that sulfate–chloride mixed electrolytes increase vanadium solubility. In this work, we identify the most stable complexation structures in this improved electrolyte, by means of ab initio molecular dynamics together with the well-tempered metadynamics algorithm. We characterize the first solvation shell of vanadium cations in solution and estimate the free energy difference of all of the configurations. Our results suggest that chloride ions play an important role in stabilizing V(II), V(III), and V(V) species. In the specific case of V(V), we find that the most stable configuration exhibits a simultaneous complexation operated by chloride and sulfate ions, sug...