Method for recovering trace elements from coal

Abstract

The present invention is directed to a method for the recovery of one or more trace elements including gold and one or more platinum group elements from coal. More particularly, the present invention may specify parameters for the selection of coal for combustion, the parameters for combustion of the pre-selected coal, the parameters for the preparation and mixing of a charge for a furnace including ash from the combustion of the coal with an inquart and a fluxing agent, the parameters for the heating of the charge and casting of a dore bar and the parameters for the production of an anode slime from the dore bar. The method of the present invention may also specify parameters for the recovery of silver, gold and one or more trace platinum group elements from the anode slimes.

1 . A method for recovering trace elements from coal including the steps of: 
 mixing a charge including an ash formed by the combustion of coal, the ash including gold and one or more platinum group elements, an inquart including one or more platinum group elements and a fluxing agent;    charging a furnace with the charge;    heating the charge in the furnace to a pre-selected temperature forming a molten charge including a molten inquart;    absorbing a portion of the gold and one or more platinum group elements of the ash into the molten inquart;    discharging a molten slag from the furnace;    casting a dore bar by discharging the molten charge ncluding the inquart including an absorbed portion of the gold and one or more platinum group elements of the ash to a mold;    digesting the dore bar in an electrowinning process wherein the dore bar is introduced into an acidic bath as an anode and an electrical potential is maintained between the anode and a metallic plate cathode;    reducing silver ions onto the metallic plate cathode; and    precipitating and dissolving trace elements in the electrolytic solution producing an anode slime.    
     
     
         2 . The method for recovering trace elements from coal of  claim 1  including the additional steps of: 
 digesting the anode slimes in an acid;    filtering the digested anode slimes precipitating a compound including silver from the digested anode slimes and producing a residue containing gold platinum and palladium;    dissolving the residue in an aqua regia solution;    mixing the aqua regia solution with a solvent;    recovering a gold-loaded solvent from a mixture of the aqua regia solution and the solvent;    reducing the gold-loaded solvent with a reducing agent; and    filtering a reduced gold-loaded solvent producing a residue including gold.    
     
     
         3 . The method for recovering trace elements from coal of  claim 2  including the additional steps of: 
 precipitating palladium out of the aqua regia solution;    filtering a precipitated palladium solution producing a residue including palladium and a liquid including platinum;    reducing the residue including palladium with a reducing agent; and    ashing a reduced residue including palladium to yield palladium.    
     
     
         4 . The method for recovering trace elements from coal of  claim 3  including the additional steps of: 
 treating a liquid extracted from the precipitated palladium solution filtration with ethanol, hydrogen peroxide and ammonium chloride;    filtering a treated precipitated palladium solution producing a residue including platinum;    reducing the residue including palladium with a reducing agent; and    ashing a reduced residue including platinum to yield platinum.