Hydrometallurgical Treatment of a Zinc Concentrate by Atmospheric Direct Leach Process
Advancing the chemical engineering fundamentals
Distillation, Absorption & Extraction (T2-10P)
Keywords: Leaching, zinc sulphide
A hydrometallurgical method to recover zinc and other precious metals from a zinc sulphide concentrate has been studied. Atmospheric direct leach processes employ less harsh conditions than pressure leaching processes and also avoid the roasting step, which is responsible for sulphur dioxide emissions. As the policy on discharge of sulphur dioxide becomes stricter, direct leaching processes, when possible, becomes more attractive.
The concentrate is supplied by Somincor, Portugal, and apart from a significant amount of Zn (40%) also contains Fe (12%), and Cu (4%), as major constituents, and Pb (0.84%), As (7000 ppm), Hg (400-1000 ppm), Sb (500 ppm), In (60-250 ppm), Tl (200 ppm), and Bi (50 ppm) as minor constituents.
Leaching studies of the concentrate in sulphide and chloride media are presented. Parameters such as the effect of reaction time, the solid-liquid ratio, temperature, and the concentrations of acid and oxidant (ferric salt), were investigated. The results indicated that 95 % zinc extraction was obtained after two hours in one stage of leaching at 80ºC, when 10 g of zinc concentrate were leached in a 200 ml solution containing 0,5 mol/L H2SO4 and 0,5 mol/L Fe2(SO4)3. The behavior of indium was similar.
In order to allow, in the subsequent stages, an effective separation between zinc and iron by liquid-liquid extraction, and to promote a decrease in the reagent consumption, the oxidation of Fe(II) produced during the leaching is required. The most favorable conditions to achieve this purpose are presented.
The optimization of the operational conditions to perform the selective recover of the interesting metals by solvent extraction is under research (type of extractant and modifier, pH, etc.).
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 13:30 to 15:00, in session Distillation, Absorption & Extraction (T2-10P).
