Abstract: A process for purifying and refining platinum group metals such as platinum, iridium, palladium, rhodium and the like by an electrochemical process using ammonium chloride as the electrolyte to form ammonium chloride platinum group salts as a "slime" followed by the use of ammonia hydroxide to dissolve and separate said salts from other materials in the slime. A further step to precipitate the platinum metals from the ammonia hydroxide may be employed.

Abstract: A recovery system for precious metal particles in wash solutions includes a pair of filter elements and a pump mounted within a closed tank. The first filter is of relatively large pore size, and traps layer particles. The prefiltered liquid is collected within the tank. A pump is mounted within the tank, and drives the collected liquid and remaining particles through the second filter, which is of a small pore size chosen to trap the remaining particles. After passage through the second filter the wash water may be discarded.

Abstract: A process for purifying and refining gold from wastes and ores is disclosed. The gold to be refined is made the anode in an electroytic cell against an inert cathode. The electrolyte, essentially consists of an impregnated ammonium chloride solution. The impregnant is a nascent-oxygen source for leveling the gold overvoltage at the anode. The cathode is isolated from the gold-containing liquidus by a semi-permeable membrane. The ammonium chloride electrolyte serves as a solvent for the dissolved gold and also complexes with any silver and/or copper commonly found in the impure anode gold. The precipitation of the pure gold at 99.5'% purity is described. The anode is enclosed in an ion permeable bag for collecting any impurities which are insoluble in the gold-containing electrolyte. The pregnant electrolyte, the method and an apparatus for practicing the invention are described.

Abstract: A process for purifying and refining gold to 98+% purity is dislosed. The gold to be refined is made the anode in an electrolytic cell with a solution of ammonium chloride as the electrolyte. The purified gold is collected in anode bags and the non-gold impurities including silver are dissolved in the electrolyte. The silver is complexed with the ammonium ion in the electrolyte.

Abstract: A novel gold purification method is provided which comprises electrolyzing gold into a novel pregnant electrolyte, segregating the dissolved gold ions from the cathode by a semipermeable barrier, separating insoluble impurities from the gold-containing liquidus, and then selectively reducing the gold to metallic form from the liquidus by a selective chemical reducing agent. The electrolyte is impregnated with a catalyst for leveling the overvoltage of gold and preferably contains a peroxide or a nascent oxygen source. A unitary apparatus for the method is provided.