|Barite concentrate (80-95% BaSO4), is the main feedstock material for barium extraction. It is obtained by barite flotation with using liquid glass as dead rock depressor. BaSO4 extraction ratio equals 55-60%. After BaSO4 reduction with lack coal, coke or natural gas BaS is obtained:|
BaSO4 + 4C => BaS + 4CO;
BaSO4 + 2CH4 => BaS + 2C + 4H2O
which then is converted into other barium compounds. After roasting at 800, 1400 and 700°C BaO is produced which then is reduced with aluminium powder at 1100-1200°C:
4BaO + 2Al => 3Ba + BaO*Al2O3.
This reaction is processed in the reactor; it is the main commercial method of barrium extraction. The extraction is processed in argon atmosphere or in vacuum, which is more preferable. Mole ratio BaO:Al =(1.5-2):1. The reactor is placed into the furnace in the way which puts its "cold part" into the zone with temperature around 520°C. On the next step barium is refined via vacuum distillation achieving impurities concentration less than 10-4 mass % or 10-6% via zone melting.
Small barium quantities may be extracted reducing BaBeO2, the product of synthesis Ba(OH)2 and Be(OH)2 with titanium at 1300°C or Ba(N3)2 decomposing at 120°C after exchange reactions between barium and NaN3.
Original Barrium Preparation
|As in the case of calcium and strontium, most of the earlier attempts to produce metallic barium only resulted in the formation of an amalgam with mercury, whether by electrolytic reduction of the oxide or chloride, using a mercury cathode, or by reduction of the chloride by sodium amalgam, or by reduction of the oxide with potassium, or of the chloride or iodide with sodium at red heat and subsequent extraction with mercury. Attempts to isolate it by the reduction of a mixture of oxide and chloride, or of the peroxide, by aluminium, resulted only in the formation of alloys. The reduction of barium oxide by magnesium gave a product of doubtful composition. Unsuccessful efforts have been made to separate barium directly by the electrolysis of fused barium chloride, with or without the addition of sodium chloride. Apparently only the subchloride is formed. |
Guntz made the first successful attempt to separate barium from mercury. By slow distillation at gradually increasing temperatures, he obtained a succession of amalgams richer and richer in barium. Finally, at a temperature of 950° C., a residue containing 98.3 per cent, of barium was left. Later the method of separation of barium from mercury through the formation and subsequent decomposition of the hydride, as carried out in the case of strontium, was successfully applied. Hydrogen was absorbed at 900° C., the mercury removed at 1200° C., just below the fusion point of the hydride, and, finally, the hydride decomposed in vacuo by further heating.
It was also found possible to apply the method, utilised later for strontium, of reduction of barium oxide at 1200° C., by aluminium powder.
A product of 98.8 per cent, purity was obtained. After redistillation in vacuo the metal was quite pure.
Matignon obtained metallic barium by heating the oxide with silicon, or with ferrosilicon containing 95 per cent, of silicon, in vacuo at 1200° C.
3BaO + Si = BaSiO3 + 2Ba - 37 Cal.
In spite of the large difference in the heats of formation of the oxides of barium and silicon, the barium, owing to its volatility, was separated, and a metal of 98.5 per cent, purity condensed.
An attempt has also been made to separate metallic barium by electrolysing a pyridine solution of barium iodide, but the barium combined with pyridine, forming a reddish-brown spongy mass. By using a mercury cathode a 30 per cent, amalgam was obtained.