Recuperation of Arsenic as Trioxide

Another important aspect of the Selective Toasting is the recuperation of the As, Sb, Bi, S and others, of the gasses which come out, from which, after a proper treatment, one can obtain as sulphurs (AsxSy, SbxSy, BixSy, S”, etc.) or as oxydes As2O3, Sb2O3, Bi2O3, SO2 after the combustion.

In this manner, the nocive element of the arsenopyrrites will be converted in useful substance and of value such as trioxyde of arsenic. One brief description to follow for the production of this oxide, are:

The gasses proceeding from the oven of selective toasting are submitted to combustion to the temperature of 750°C according to the following exothermical reactions:

S2 (g) + 2O2 (g) – 2SO2 (g)

As4S4 (g) + 7 O2 (g) – 2As2 O3 (g) + 4 SO2 (g)

In the mining company El Indio (chile) where they treat energytes the resulting gasses from the post-combustion are cooled to 400°C and passed through an electrostatic separator, in this stage the oxydes of antimonious are separated such as bismute and other residual dusts. The gas which comes out of the precipitator is cooled directly by the air of the environment, precipitating the trioxyde of arsenic and collected in the chambers of filters. Finally, the gas which is resultant is eliminated to the atmosphere. (3)

The trioxide of raw arsenic produced, with a purity of 97% to 97.5% is packed and commerced.