Process of recovering non-ferrous metal values, especially nickel, cobalt, copper and zinc, by using melt and melt coating sulphation, from raw materials containing said metals

A process of recovering non-ferrous metal values, especially nickel, cobalt, zinc, manganese and magnesium from raw materials containing said metals, by converting the non-ferrous metal values into sulphates by melt and melt coating sulphation and recovering non-ferrous metal compounds comprising:

• (a) when necessary, pretreating the raw material to convert the metals therein into oxidic and ferritic forms;
• (b) forming a reaction mixture containing the pretreated raw materials and sufficient amounts of iron(III)sulphate and alkali metal sulphates to permit complete sulphation;
• (c) melt sulphatizing and melt coating sulphatizing the reaction mixture to cause formation of metal sulphates;
• (d) dissolving the metal sulphates in water to form a solution and separating the undissolved solid material from the solution;
• (e) precipitating iron(III) from the solution as alkali metal jarosite and recycling the alkali metal jarosite to the formation step described in paragraph (b);
• (f) separating the non-ferrous metals from the solution by fractionation or combined hydroxide or sulphide precipitation, ion exchange or liquid-liquid extraction;
• (g) precipitating magnesium from the solution by the addition of lime thereby forming calcium hydroxide and gypsum, separating the gypsum from the solution, separating the magnesium hydroxide from the solution, recycling magnesium hydroxide to either of the steps described in paragraphs (e) and (f) and removing any excess magnesium hydroxide from the process;
• and
• (h) separating the alkali metal sulphates from the solution by evaporation crystallization, recycling the alkali metal sulphates to any of the steps described in paragraphs (a), (b) and (c), and removing any excess alkali metal sulphates from the process.