3. Metallurgical treatments

3.1 Pretreatments

In order to be processed by the traditional reductive smelting process, intermediate-grade concentrates (30 to 50% Sn) containing sulfur and arsenic (e.g. in contents of a few percent and a few tenths of a percent respectively) must first undergo an oxidizing roasting operation to remove these elements by volatilization in the form of SO ₂ and As ₂ O ₃ . Failing this pre-treatment, there is a risk, during smelting, of losing tin by volatilization in the form of sulfide and of dissolving arsenic in tin.

This is the classic process used to treat gold-bearing arsenopyrites. Above all, arsenic oxidation must not...