Recovery of gold from refractory arsenic concentrates (II)

At different temperatures, the processing capacity is 1 kg / hr of continuous operation of the blast furnace to pre-granulate and dry the concentrate after roasting. The yield of slag is 87~89% . During the roasting process, gold has no soot loss. Gold is all enriched in the slag, so the gold content is increased by 11 to 13% . After condensing and trapping the sulfide-type sublimate, the exhaust gas contains, by volume ( % by volume): SO ₂ 9.5 , CO ₂ (product of carbonate decomposition) 4.9 , N ₂ 85.7 .

The pellets are calcined and then ground to 0.3 mm And cyanide for 48 hours under the conditions of liquid: solid = 2 : 1 . Barium peroxide is used as the oxidant.

The baking temperature is 620~ 650 °C When the cinder is cyanated under the conditions, the highest recovery of gold is 95% , and the consumption of sodium cyanide is 6.6 kg / ton (see table).

If the calcination temperature is increased to 700 ° C or more, the gold will undergo thermal passivation, which has an adverse effect on the cyanidation effect.

Obviously, in order to reduce the consumption of cyanide , the calcined slag must be treated with a NaOH solution or a H ₂ S0 ₄ solution. With 7.5% NaOH ~ H ₂ SO ₄ leach solution slag 4 hours, leaching temperature is 20 °C Then, it was washed carefully with water and cyanized for another 48 hours. As a result, the cyanide consumption can be reduced to 1.12~2.2 kg / ton.

According to the research results, the process of processing gold - arsenic sulfide flotation concentrate was proposed (see figure). This procedure has the advantage that the heat from the exothermic reaction can be utilized during the oxidation - sulfation roasting process, and the arsenic can be discharged quite completely from the concentrate in a slightly toxic form. This can meet the requirements of environmental protection.

Arsenic sulfide can be used as a raw material for the production of elemental arsenic and arsenic trioxide. Even if the demand for arsenic sulfide is too small, its storage cost (calculated per ton of arsenic) is much lower than the storage cost of substandard calcium arsenate.

According to the recommended process, concentrate granulation should be calcined in a continuously operating blast furnace. Thus, when the slag is treated in the copper smelter, the amount of arsenic entering the process can be greatly reduced.

Whether the refractory gold - arsenic concentrate is treated in situ or the rationality of the copper smelter treatment must be determined according to the technical - economic accounting results.

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