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Other Leaching Processes
Published in C. K. Gupta, T. K. Mukherjee, Hydrometallurgy in Extraction Processes, 2017
Other investigators4,5 thought that intermediate agents like cyanogen gas [(CN)2] and potassium cyanate (KCNO) were responsible for the dissolution of Au and Ag. Such assumptions were, however, later proved6–8 to be wrong. Deitz and Halpem9 suggested that all these reactions could basically be considered as oxidation and reduction steps. The oxidation step can be represented as () Ag+2CN−→Ag(CN)2−+e
Cyanidation of Gold-Bearing Ores
Published in Sadia Ilyas, Jae-chun Lee, Gold Metallurgy and the Environment, 2018
Cyanate formation: MacArthur (1905) argued for the effectiveness of potassium cyanate in gold dissolution that is formed by the oxidation of cyanide with supplied oxygen. Nevertheless, the assumption was refuted by Green (1913) by showing that cyanate had no action on gold. Thermodynamic evidence given by Barsky et al. (1934) determined the free energies for the complexes of auro- and argento-cyanide ions, based on which the calculated free energy changes were in favour of Eisner and Bodländer’s equations; whereas Janin’s equation was thermodynamically not feasible.
Elastic Adhesives
Published in A. Pizzi, K. L. Mittal, Handbook of Adhesive Technology, 2017
Johann Klein, Christina Despotopoulou
The next leap in the advancement of SMPs happened with the development of isocyanatomethyldimethoxymethylsilane. This isocyanatosilane is synthesized through photochlorination of dimethyldichlorosilane [37] (one of the most important silicone raw materials) to dichloro(chloromethyl)methylsilane. Esterification of this precursor with methanol to chloromethylsilane, followed by reaction with potassium cyanate in the presence of methanol to carbamatosilane, and after pyrolysis with one of the processes mentioned, leads to the desired silane (Figure 7.16).
Copper(I) azide and copper(I) cyanate π-complexes
Published in Journal of Coordination Chemistry, 2021
Sodium azide (Acros organics, 99+%), potassium cyanate (Fluka, purum), copper sulfate pentahydrate (Zorka Šabac, p.a.), copper tetrafluoroborate hexahydrate (Alfa Aesar, 98%), allylamine (Alfa Aesar, 98+%), and ethanol (Carlo Erba, p.a) were used as supplied. High-quality single crystals of Cu[C3H5NH2]N3 (1) were obtained by alternating current electrochemical synthesis [35] in ethanol. A solution containing CuSO4 · 5H2O (0.71 g, 2.0 mmol) and allylamine (0.8 mL, 11 mmol) was placed in a small test-tube and solid sodium azide (0.15 g, 2.0 mmol) was added. A copper wire was wrapped into a spiral of ∼1 cm diameter. A straight copper wire was placed inside the spiral. These copper electrodes were inserted in cork, immersed in the above-mentioned solution and alternating current of 50 Hz voltage 0.4 V was applied. Next day, colorless prismatic crystals of Cu[C3H5NH2]N3 appeared on the electrodes. In a similar way crystals of Cu[C3H5NH2]NCO (2) were synthesized. Solid potassium cyanate (0.10 g, 1.25 mmol) was placed in a small test-tube and a drop of water was added. Cu(BF4)2 · 6H2O (0.35 g, 1.0 mmol) and allylamine (0.8 mL, 11 mmol) were dissolved in ethanol, and the deep-blue solution was decanted into a test-tube. Copper electrodes were inserted in cork, immersed in the solution and alternating current of 50 Hz voltage 0.4 V was applied. Next day solution was discolored, and the test-tube was placed in a refrigerator and stored at −18 °C. Very air sensitive crystals appeared at electrodes after one week.
A novel low temperature and green salt bath nitriding of titanium alloy
Published in Surface Engineering, 2021
Yan Song Zhu, Xing Nong Wei, Yu Xuan Yin
TC4 titanium samples (25 mm × 10 mm × 5 mm) were polished to 1200 grit surface finish, the main composition of which is listed in Table 1 [20]. Before nitriding, samples were cleaned with acetone for 10 min. The salt bath nitriding experiments were conducted using three groups of nitriding agents, the detailed composition of the nitriding agent mixture is listed in Table 2. Here, the potassium cyanate (KCNO, 99.5% purity) and sodium cyanate (NaCNO, 99.5% purity) salts serve as the main source of nitrogen (N); rare earth (RE) oxide (CeO2, 99.5% purity) is to serve as the catalyst; potassium sulphate (K2SO4) is to inhibit the production of cyanide; potassium chloride (KCl) is to promote the fluidity of molten salt, and Lithium carbonate (Li2CO3) is to reduce the melting point of the salt bath. In addition, owing to the sulphur ion (S2ˉ) having strong electronegativity, once the content of S2ˉ decomposed from K2SO4 (Reaction 6) reaches a certain degree, the electronegativity effect of S2ˉ could cause the corrosion damage on the nitrided sample surface [21]. Thus, to ensure the inhibition effect of K2SO4 on the production of cyanide and reduce the electronegativity effect of S2ˉ, in this study, the content of K2SO4 in the nitriding agent was controlled within the range of 2 wt-%. After that, the nitriding agent was packed in a crucible, ensuring a sufficiently thick pack around the treated sample. Furthermore, to reduce the effect of nitriding temperature on the microstructural characteristics of the titanium matrix and ensure the growth of the nitride layer, after deeply analysing the current research about the salt bath nitriding of titanium alloy [14,15], the nitriding temperature and time are determined to be 550°C and 7 h (shown in Table 2), respectively. Then, the nitriding experiments were performed in a box-type resistance furnace; after the treatments, samples were taken out and cooled by air.
Biosorption of cyanate by two strains of Chlamydomonas reinhardtii: evaluation of the removal efficiency and antioxidants activity
Published in International Journal of Phytoremediation, 2021
Mostafa M. S. Ismaiel, Yassin M. El-Ayouty, Asmaa H. Al-Badwy
All chemicals used in this study were of analytical grade and obtained from Sigma-Aldrich (Munich, Germany). The stock solution of potassium cyanate was freshly-prepared daily with deionized water throughout the tests.