Sample decomposition

The decomposition methods of rhenium-bearing ore samples include traditional magnesia sintering method, melting method, acid melting method and microwave digestion method.

62.5. 1. 1 MgO sintering decomposition

Magnesium oxide sintering is a traditional method to decompose rhenium samples. Put the sample into a porcelain crucible filled with magnesium oxide, stir it evenly, cover it with a layer of magnesium oxide, put it into a high-temperature furnace, gradually raise the temperature from low temperature to 600 ~ 700℃ (exceeding this temperature will cause rhenium loss), keep it for 2 hours, take it out after cooling, extract it with water, and the filtered filtrate can be used for rhenium determination. If magnesium oxide-zinc oxide sintering method is adopted, the sintering effect and efficiency will be better, and the recovery rate of secondary sintering will be higher, reaching 95%. This method is suitable for the determination of rhenium in molybdenite and other high rhenium ores.

62.5. 1.2 melting decomposition

Melting method is to melt strong oxidizing alkali such as sodium peroxide and sodium hydroxide or sodium hydroxide and sodium nitrate, and rhenium is oxidized into heptavalent soluble perrhenate, thus decomposing the sample. The biggest advantage of alkali melting method is its strong decomposition ability, which is suitable for all kinds of samples. This method needs to control the temperature to prevent the volatilization of rhenium.

62.5. 1.3 acid dissolution

Acid dissolution is the use of strong acid and strong oxidant to transform rhenium into acid-soluble substances. Because the sample can not be completely decomposed by acid solution, the recovery rate is slightly lower. But the recovery rate can be greatly improved by dissolving it with nitric acid-perchloric acid-hydrofluoric acid and finally with aqua regia.

When decomposing the ore with more sulfur, nitric acid is added to oxidize the sulfur in the sample into high-valent sulfur, and then hydrochloric acid is added to turn the solution into aqua regia, which can completely decompose the sample.

Generally, high boiling point acids such as sulfuric acid or perchloric acid are not used to dissolve the sample, because when the solution evaporates into smoke, rhenium is often partially lost by volatilization. It can also cause serious volatilization of rhenium in hot hydrochloric acid or hydrobromic acid solution. For example, adding equal mass of alkali metal salt to acidic solution can prevent rhenium from volatilizing in the presence of sulfuric acid.

62.5. 1.4 microwave digestion

See 62. 1. 1.3 microwave digestion.