PRODUCTION OF LEAD AND SILVER FROM THEIR SULFIDES

摘要

A process for producing metallic lead and silver from materials such as ores and concentrates containing the corresponding sulfides in which the materials are subjected to a first leaching with an aqueous ferric salt solution such as ferric chloride to convert the sulfides to the corresponding salts containing lead and silver and generating the corresponding ferrous salt solution which may be separated as a filtrate, subjecting the solid residue from this first leaching to a second leaching with aqueous sodium chloride brine to dissolve the lead and silver salts such as the chlorides so that their solutions can be separated as a filtrate and leaving a further solid residue, cooling this solution of the lead and silver salts to crystallize and thereby separate the lead salts leaving the silver sales dissolved in the filtrate, removing the lead salt crystals from the resulting silver salt solution, contacting this silver salt solution with metallic copper to produce cement silver, and producing lead metal and chlorine gas by electrolysis of the lead chloride. The disclosure also includes a further leaching with sodium sulfide after the brine leach followed by a further ferric leach and a further brine leach. The ?isclosure also includes a process in which ferric chloride solution is regenerated in situ in the portion of the apparatus where the first leaching takes place from the ferrous chloride solution that is produced during the leaching plus added chlorine gas which may be produced from molten salt electrolysis of lead chloride to produce lead metal and the chlorine. The disclosure also includes a process in which the metal sulfides include tetrahedrite minerals that are normally resistant to ferric salt solution leaching and in which this ore is pretreated prior to the ferric solution first leaching with an aqueous alkaline sodium hydroxide solution to decompose the tetrahedrite after which the solid residue remaining is subjected to the process outlined above.