Copper dross treatment

Table 4. Composition of Products from Copper Dross Treatment...

Copper dross treatment using sodium metal (the Glover process)... 

Precipitation can also occur upon chemical reaction between the impurity and a precipitating agent to form a compound insoluble in the molten metal. The refining of cmde lead is an example of this process. Most copper is removed as a copper dross upon cooling of the molten metal, but the removal of the residual copper is achieved by adding sulfur to precipitate copper sulfide. The precious metals are separated by adding zinc to Hquid lead to form soHd intermetaHic compounds of zinc with gold and silver (Parkes process). The precious metals can then be recovered by further treatment (see Lead). 

The various by-products are stockpiled to accumulate sufficient material to fill a silo. By far the lai est amount of material requiring treatment is the BRM floor copper dross. The material is allowed to cool for several days to less than 30°C. The molasses will degrade at... 

Any lead bullion recovered from matte treatment will be rich in copper and can form a significant circulating load through the lead bullion refining stage (see Chapter 12 - Copper Removal or Copper Drossing). 

Where high purity concentrates are processed and only minor amounts of copper have to be removed, one method used at the Naoshima smelter in Japan is to add aluminium to form the intermetallic compound CUAI2. Aluminium is added as a 40 per cent alloy with zinc because of its low melting point at 560°C compared with aluminium at 660°C. Zinc is removed from the lead later either in the dezincing process or by caustic soda treatment. This method produces a dry powdery dross, which is easily handled and can reduce copper levels to less than one gram per tonne (Moriya, 1989). 

---