Residual Chloride Content Research Articles

Low-Temperature Steam Annealing of Metal Oxide Thin Films from Aqueous Precursors: Enhanced Counterion Removal, Resistance to Water Absorption, and Dielectric Constant

Aqueous solution deposition has emerged as a potentially scalable, high-throughput route to functional metal oxide thin films. Aqueous routes, however, generally require elevated processing temperatures to produce fully condensed films that are resistant to water absorption. Herein, we report a low-processing-temperature method for preparing more fully condensed, stable metal oxide films from aqueous precursors. We show that a steam anneal at ≤200 °C reduces residual nitrates in zinc oxide, yttrium aluminum oxide, and lanthanum zirconium oxide (LZO) films. An in-depth study on LZO dielectric films reveals steam annealing also reduces residual chloride content, increases resistance to post-anneal water absorption, eliminates void formation, and enhances the dielectric constant. This investigation demonstrates that steam annealing directly affects the decomposition temperatures and chemical evolution of aqueous precursors, suggesting a general means for producing high-quality films at low processing tempera...

Performance of Separation Processes for Precipitated Calcium Carbonate Produced with an Innovative Method from Steelmaking Slag and Carbon Dioxide

In this work, experiments were performed to determine the filterability of calcium carbonate produced with an alternative calcium carbonate production concept. The concept uses steelmaking slag as raw material and has potential to fix CO2 emissions and utilize steelmaking slag, simultaneously. As calcium carbonate is precipitated in a solution containing ammonium chloride, calcium chloride and ammonia, the product needs to be washed and hence filtered. In this work different separation processes, including washing, filtering and drying, were tested on two calcium carbonate slurries produced from steel converter slag and CO2 by a laboratory-scale pilot facility, with the aim of obtaining a solid product with a low chloride content using a minimum amount of washing water. The order of maximum filtration rates achievable of the calcium carbonate slurries was determined by experimental work. The tests included pressure filtration and vacuum filtration and the test series contained altogether 21 different filtration cycles with varying combinations of filtering, washing, and drying steps. The filtered cakes were analyzed by their residual moisture content, chloride content and conductivity, and the filtrates by their residual solids content, chloride content and conductivity. Pressure filtration gave a high capacity (400-460 kg/m2h) and a low cake residual moisture content (12-14 wt-%). Vacuum filtration gave slightly higher filtration rates (500-610 kg/m2h at the lowest residual chloride contents of the cakes), but the cake residual moisture also stayed higher (25-26 wt-%). As the vacuum filtration tests used a filter cloth with higher permeability than that of the pressure filtration tests, a slightly higher filtration rate was expected. However, both filtration technologies seem suitable for filtering and washing calcium carbonate prepared with the studied method as a residual chloride content as low as 10 ppm of the filtered solids can be achieved with quite a small amount of washing water and the filtration rate is fast.

Determination of residual chloride content in ionic liquids using LA-ICP-MS

Residual chloride in ionic liquids is analyzed using LA-ICP-MS in a sustainable and easy-to-handle approach.

The efficiency of chloride extraction from archaeological iron objects using deoxygenated alkaline solutions

Chloride-contaminated archaeological iron is unstable and problematic to store and display within museum collections. Reducing its chloride ion content using aqueous desalination followed by storage in controlled relative humidity offers one treatment option. This study reports a quantitative assessment of chloride extraction by aqueous deoxygenated alkaline desalination solutions from 120 individual archaeological iron nails. The three treatment methods comprised alkaline sulphite solution (0.1 M NaOH/0.05 M Na2SO3) at room temperature and at 60°C and sodium hydroxide solution (0.1 M) deoxygenated using a nitrogen gas positive pressure system at room temperature. Chloride extraction was monitored using a specific ion meter. The nails were digested after treatment to measure their residual chloride content. A wide range of extraction patterns emerged, with the majority of individual treatments extracting 60–99% of the chloride present. Residual chloride levels for 87% of the objects fell below 1000 ppm and 42% were below 200 ppm. Although no treatment extracted 100% of the chloride in the object, alkaline desalination produced very significant reductions in chloride content. The impact of this on future corrosion of the objects is discussed. This quantitative and statistically viable assessment of deoxygenated desalination treatments provides evidence to support their use in conservation practice, which will impact on procedures for the preservation and management of archaeological heritage.

A New Route for the Synthesis of Alkali Polyphosphate from Economical Starting Materials: Preparation and Characterization of Sodium Cyclotriphosphate

Thermal synthesis of sodium cyclotriphosphate (SCTP) – Na3P3O9 was investigated in the temperature range of 150 °C to 750 °C using sodium chloride (NaCl) and 85 wt% orthophosphoric acid (H3PO4) as economical starting materials. Reaction temperature had a crucial impact on the chloride elimination rate and the formation of SCTP. The best result was obtained at 600 °C with 96% of elimination of the initial chloride as hydrochloric acid and 84% of selectivity in SCTP. At lower temperatures, residual chloride contents were high. At higher temperatures (650 °C and 750 °C), SCTP was melted and transformed into glassy products.

Effect of the preparation of supported gold particles on the catalytic activity in CO oxidation reaction

Gold catalysts supported on hydrotalcite (HT) with a Mg:Al molar ratio 4:2 were prepared by direct anionic exchange (DAE) or by deposition–precipitation (DP) with NaOH or urea, in order to investigate the influence of the synthesis parameters on the catalytic conversion in CO oxidation. The highest activity was obtained for Au/Mg 4Al 2 prepared by DAE. The influence of various parameters on CO conversion such as the HAuCl 4 concentration in the initial solution, the washing procedure, the pre-treatment temperature, the precursor of HT and the gold loadings were investigated. This study confirms the poisoning effect of chloride. The average gold particle size is higher for the catalysts with higher residual chloride content. In order to remove the remaining chloride from the sample, different washing procedures were used, i.e. either with warm water or with ammonia. Changes in activity and particle size were observed according to the washing procedure. Higher calcination temperature increases the surface area of HT, contributing to better dispersion of gold. A smaller particle size, as measured by XRD and TEM, is obtained on HT prepared from sulfate precursor rather than nitrate.

Supported Au catalysts for low temperature CO oxidation

Supported Au catalysts are very active for low temperature CO oxidation. However, the reported activity from different laboratories for apparently similar catalysts can differ quite substantially. Recent progress in resolving this difficulty is summarized. Residual chloride in the sample is a very effective poison of the active site. The effect of water vapor on the catalytic activity differs depending on the support and the residual chloride content. A model of the active site, which consists of an ensemble of metallic Au atoms and Au cations with hydroxyl ligands, the reaction mechanism for CO oxidation, and the mechanism for deactivation during reaction as well as regeneration are discussed with respect to the available data.

Studies on microwave irradiated Pd/Nb2O5 catalysts: Effect of palladium chloride precursor on the chlorobenzene hydrodechlorination activitya

Catalysts containing 10 wt. % Pd supported on Nb2O5 were prepared by microwave irradiation and conventional electrical heating, using palladium chloride as the precursor for Pd. Whereas higher residual chloride content decreased the activity and stability of the microwave irradiated catalyst, formation of PdO during calcination in air improved the performance of the conventionally heated catalyst. Calcination after microwave irradiation offers the highest activity and stability.

X-ray Fluorescence Used to Characterize the Salt Content of Proteins

The quantitative measurement of the salt content in solid protein samples was performed using X-ray fluorescence. Linear calibration curves were obtained for chloride, calcium and sulfur using sulfur and chloride as internal standards in the range 1-10 protein molar equivalents. The detection limit was approximately 0.02 molar equivalents for chloride and less than 0.01 molar equivalents for calcium. X-ray fluorescence thus provides a non-destructive sensitive method of testing the efficiency of different purification methods. Commercial hen egg white lysozyme samples contain from 15 to 46 molar equivalents of chloride, whereas the calcium content remains less than 0.2 equivalents. Deionization on ion-exchange resins is a very efficient tool for removing ionic species since deionized lysozyme samples contain less than 0.34 molar equivalents of chloride. Extensive dialysis against water only partially removes chloride ions, the residual chloride content corresponding to the number of counter-ions necessary to ensure the electroneutrality of lysozyme when dissolved in water.

The Effects of Residual Chlorides on Gas Sensing Characteristics of Tin Oxide Gas Sensors

In an investigation on carbon monoxide sensors, the effect on electrical conductivity of residual chloride content of tin oxide materials have been studied to provide information relating to the sensitivity and selectivity in the detection of carbon monoxide. The starting material was α‐stannic acid, precipitated in the reaction between tin chloride and ammonia, which was calcined at 650°C for 2 h. The lower the chloride content of the original dried precipitate, the greater was the surface area and the greater was the sensitivity to carbon monoxide of the calcined material. Conversely, the higher the chloride content, the smaller was the surface area and lower the sensitivity to carbon monoxide and higher the sensitivity to propane and methane. The residual chloride content in the calcined material, whatever the amount of chloride in the original precipitate, was invariably about 0.2 weight percent.

Elution and analysis of residual chloride from anion exchangers

Strong anion exchangers can be transformed to the hydroxyl forms by elution with analytical grade sodium hydroxide. The residual chloride contents remain above the 0.1% level. Such chloride amounts can rapidly and easily be determined with a radiochemical method using 110mAg as tracer. This method was compared with neutron activation and potentiometric titration methods.