ABSTRACT
The addition of either 3,6-dihydrazino-s-tetrazine (DHT) or 5-aminotetrazolium nitrate (HAT-NO3) to nitrocellulose-based propellants were investigated. At 25% (m/m) concentration, DHT and HAT-NO3 had significant impact on the burning rate of the propellant, up to 80% higher than that of the reference propellant. DHT was found to have very poor compatibility with nitrocellulose and the nitrated esters used in the formulation despite the presence of stabilizer. This lead to a rapid autocatalytic decomposition reaction resulting in a deflagration. HAT-NO3 also had poor compatibility with the same materials. On the contrary, non-ionic tetrazoles were found to be fully compatible with nitrocellulose and nitrated esters based propellants. Most nitrogen-rich energetic molecules have been studied for their explosive characteristics. This study shed light on the potential use of these materials as burning rate modifiers for gun propellant applications, for which very little is known. Moreover, it investigates the stability of the formulations incorporating nitrogen-rich molecules, as a means of assessing the safe use of these novel propellants.
ABSTRACT
A capillary electrophoretic (CE) protocol was developed for the separation and quantification of free cyanide and zinc cyanide complex, two key species in gold cyanidation of zinc-bearing sulfidic ores. Several common carrier electrolytes were implemented in an indirect UV detection method. The effect of electric field strength, injection volume, concentration of electro-osmotic flow (EOF) modifier and UV-absorbing agent in background electrolyte (BGE) was examined while peak height, peak area and noise were considered for optimization. The best results were obtained using a BGE that contained 35 mM sodium chromate, 12 mM free cyanide and 0.45 mM hexamethonium bromide at pH 10.5. Free cyanide concentration was compared to that measured with the conventional silver nitrate titration method in solutions containing free cyanides and weak cyano-complexes. The developed CE protocol proved very robust in capturing the concentration of free cyanides (4% error) unlike the titration method which exhibited substantial sensitivity to the interfering weak cyano-complexes (38% error).
ABSTRACT
A capillary electrophoretic protocol for the separation and quantification of the most important species potentially liberated during the cyanidation of gold sulfide-rich ores was accomplished in this study. The separation of 11 ions: S2O3(2-), Cu(CN)3(2-), Fe(CN)6(4-), Fe(CN)6(3-), SCN(-), Au(CN)2(-), Ag(CN)2(-), SO4(2-), OCN(-), SO3(2-), and HS(-) was achieved using an indirect UV detection method. The robustness of the analytical protocol was tested by analyzing ions speciation during the cyanidation of two gold sulfide-rich ores. The 1-h cyanidation of the two ores released up to six complexes into solution: S2O3(2-), Cu(CN)3(2-), SCN(-), Fe(CN)6(4-), OCN(-), and SO4(2-). The mineralogy of the ore was found to influence directly the nature and the amount of the dissolved species. Conserving the cyanidation solution for 72 h after sampling resulted in 96% total sulfur recovery. These results allow us to conclude that the analytical protocol developed in this study can become very useful for the optimization of precious-metals cyanidation plants.
Subject(s)
Cyanides/analysis , Electrophoresis, Capillary/methods , Gold/chemistry , Sulfur/analysis , Spectrophotometry, UltravioletABSTRACT
A CE protocol was developed for the identification and separation of inorganic polysulfides simultaneously with other inorganic sulfur-bearing species coexisting in aqueous hydrosulfide/sulfur solutions. The electrophoretic separation of thiosulfate, sulfate, hydrosulfide, sulfite, tetrathionate, and polysulfides was achieved at pH values between 8.2 and 12.2. The peaks attributed to the polysulfide species were strongly sensitive to pH. CE analysis of hydrosulfide/sulfur solutions at different pH values permitted possible identification of two forms of polysulfides: S4(2-) and S3(2-). Upon exposure to air at ambient temperature, thiosulfate was the main oxidation product of hydrosulfide/sulfur solutions mainly in the first 60 min, when hydrosulfide was rapidly consumed. Analysis of the oxidation reaction products provided retrospectively tentative evidence that the peaks separated and identified as tri- and tetrasulfide may be ascribed to polysulfides.
