Method for the production of a collector alloy comprising precious metal or of pure silver

A method for producing a collector alloy comprising 25 to 100 wt % precious metal in total, comprising 0 to <97 wt % of the precious metal silver, 0 to 75 wt % of at least one precious metal selected from the group consisting of gold, platinum, rhodium and palladium, and 0 to 75 wt % of at least one non-precious metal selected from the group consisting of copper, iron, tin and nickel, comprising the steps of:

• (1) providing precious metal sweeps comprising 4 to 30 wt % precious metal in total, comprising 0 to 30 wt % of the precious metal silver, 0 to 10 wt % of at least one precious metal selected from the group consisting of gold, platinum, rhodium and palladium, 0 to 10 wt % of at least one non-precious metal selected from the group consisting of copper, iron, tin and nickel, and 70 to 96 wt % of at least one refractory inorganic material,
• (2) providing a flux which, during collective melting with the refractory inorganic material from the precious metal sweeps provided in step (1), is capable of forming a molten slag consisting of >35 to 45 wt % calcium oxide, 35 to 45 wt % silicon dioxide, 15 to <20 wt % aluminum oxide, and 0 to <15 wt % of one or more refractory inorganic compounds other than calcium oxide, silicon dioxide and aluminum oxide,
• (3) collective melting of the materials provided in steps (1) and (2) at a temperature in the range from 1300 to 1600° C., forming a melt comprising at least two phases of different densities arranged one above the other, and
• (4) separating the low-density upper phase and the high-density lower phase,
• wherein the upper phase comprises a slag phase consisting of >35 to 45 wt % calcium oxide, 35 to 45 wt % silicon dioxide, 15 to <20 wt % aluminum oxide, and 0 to <15 wt % of one or more refractory inorganic compounds other than calcium oxide, silicon dioxide and aluminum oxide, and the lower phase comprises the collector alloy,
• wherein none of the materials used in the method comprises copper oxide, except for copper oxide optionally present as an outer copper oxide layer on metallic copper.