Method and apparatus for preparing silver compound from metallic silver

Abstract

Provided is a method and apparatus for preparing a silver compound from metallic silver. The method includes the following steps: (1) arranging at least one electrolytic cell with the metallic silver as an anode and an insoluble electrical conductor as a cathode; (2) feeding an alkaline electrolyte into the at least one electrolytic cell to be in contact with the anode; and (3) starting the electrolytic power supply to conduct electrolysis, such that the metallic silver undergoes a dissolution reaction at the anode and a silver ion resulting from the dissolution reaction reacts with the alkaline electrolyte to produce a solid silver compound and/or a soluble silver complex. This application addresses the major issues of safety, pollution, and cost in the existing production technologies for silver compounds.

What is claimed is: 
     
         1 . A method for preparing a silver compound from metallic silver, comprising following steps:
 (1) arranging at least one electrolytic cell with the metallic silver as an anode and an insoluble electrical conductor as a cathode; and connecting the anode to a positive terminal of an electrolytic power supply, and connecting the cathode to a negative terminal of the electrolytic power supply;   (2) feeding an alkaline electrolyte into the at least one electrolytic cell to be in contact with the anode; and   (3) starting the electrolytic power supply to conduct electrolysis, such that the metallic silver undergoes a dissolution reaction at the anode and a silver ion resulting from the dissolution reaction reacts with the alkaline electrolyte to produce a solid silver compound and/or a soluble silver complex.   
     
     
         2 . The method for preparing a silver compound from metallic silver according to  claim 1 , wherein a material of the cathode is at least one selected from the group consisting of gold, platinum, silver, copper, titanium, iron, an alloy comprising at least one of the gold, the platinum, the silver, the copper, the titanium, and the iron, stainless steel, and conductive graphite; and
 the alkaline electrolyte comprises an alkaline substance, and the alkaline substance is specifically at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium carbonate, sodium carbonate, potassium carbonate, ammonium bicarbonate, sodium bicarbonate, potassium bicarbonate, ammonia water, and a silver-ammine complex.   
     
     
         3 . The method for preparing a silver compound from metallic silver according to  claim 2 , wherein an electrolytic cell provided with an electrolytic cell separator to divide the electrolytic cell into an anode compartment and a cathode compartment is provided; the alkaline electrolyte is adopted as an anode electrolyte, and an electrolyte-containing aqueous solution is adopted as a cathode electrolyte; and
 the electrolytic cell separator is at least one selected from the group consisting of a filter cloth, a filter plate, an anion exchange membrane, a cation exchange membrane, a bipolar membrane, a reverse osmosis membrane, and a non-ion-selective diaphragm.   
     
     
         4 . The method for preparing a silver compound from metallic silver according to  claim 3 , wherein when the anode electrolyte comprises ammonia and/or an ammonium ion, the electrolytic cell separator is at least one selected from the group consisting of the anion exchange membrane, the bipolar membrane, and the reverse osmosis membrane; and when the anode electrolyte does not comprise ammonia and/or an ammonium ion, the electrolytic cell separator is the filter cloth and/or the filter plate. 
     
     
         5 . The method for preparing a silver compound from metallic silver according to  claim 4 , wherein the material of the cathode is the metallic silver. 
     
     
         6 . The method for preparing a silver compound from metallic silver according to  claim 5 , wherein a total concentration of the alkaline substance in the alkaline electrolyte is 0.05 mol/L to 21 mol/L. 
     
     
         7 . The method for preparing a silver compound from metallic silver according to  claim 6 , wherein to primarily generate silver oxide from the metallic silver during the electrolysis, a sodium hydroxide and/or potassium hydroxide solution is adopted as the alkaline electrolyte and the filter cloth or the filter plate is adopted as the electrolytic cell separator; and to produce diaminesilver hydroxide from the metallic silver during the electrolysis, the ammonia water or a mixture of the ammonia water and the diaminesilver hydroxide is adopted as the alkaline electrolyte and at least one selected from the group consisting of the anion exchange membrane, the bipolar membrane, and the reverse osmosis membrane is adopted as the electrolytic cell separator. 
     
     
         8 . The method for preparing a silver compound from metallic silver according to  claim 7 , wherein after the solid silver compound is generated from the metallic silver of the anode through the electrolysis, a silver compound filter residue produced after solid-liquid separation is allowed to undergo a chemical reaction to produce other desired silver compounds, and the chemical reaction is at least one selected from the group consisting of following:
 (1) when the silver compound filter residue comprises silver carbonate, heating is conducted to make the silver carbonate decompose into silver oxide and carbon dioxide;   (2) the silver compound filter residue and/or a silver compound filter residue left after the reaction (1) is allowed to react with an acid and/or a salt to produce other silver salts; and   (3) the silver compound filter residue or the silver compound filter residue left after the reaction (1) is allowed to react with ammonia water and/or sodium hydroxide and/or potassium hydroxide to produce at least one selected from the group consisting of a diaminesilver hydroxide complex Ag[NH 3 ] 2 OH, a silver ammine carbonate complex [Ag(NH 3 ) 2 ] 2 CO 3 , silver fulminate Ag 2 C 2 N 2 O 2 , and a silver ion-hydroxide ion complex.   
     
     
         9 . The method for preparing a silver compound from metallic silver according to  claim 8 , wherein when the silver compound filter residue is treated to produce the silver ion-hydroxide ion complex, a concentration of the sodium hydroxide and/or the potassium hydroxide in a reaction solution is not less than 7%. 
     
     
         10 . An apparatus for preparing a silver compound from metallic silver to implement the method according to  claim 1 , comprising: at least one electrolytic cell, at least one soluble metallic silver anode, at least one electrolytic cathode, and at least one electrolytic power supply,
 wherein when a solid silver compound product needs to be prepared, at least one solid-liquid separator is further provided, and the at least one electrolytic cell is connected to the at least one solid-liquid separator through a pump and a pipeline; and   when a liquid silver compound product needs to be prepared, a storage tank configured to store the liquid silver compound product is further provided or the storage tank and a solid-liquid separator that are connected through a pipeline are further provided, and the at least one electrolytic cell is connected to the storage tank either through a pipeline or through the solid-liquid separator and the pipeline.   
     
     
         11 . The apparatus for preparing a silver compound from metallic silver according to  claim 10 , wherein in the at least one electrolytic cell, an anode is metallic silver connected to a positive terminal of the at least one electrolytic power supply, and a cathode is an insoluble electrical conductor connected to a negative terminal of the at least one electrolytic power supply; and
 the insoluble electrical conductor is at least one selected from the group consisting of gold, platinum, silver, copper, titanium, iron, an alloy comprising at least one of the aforementioned metals, stainless steel, and conductive graphite.   
     
     
         12 . The apparatus for preparing a silver compound from metallic silver according to  claim 11 , wherein the at least one electrolytic cell is provided with an electrolytic cell separator to divide the at least one electrolytic cell into an anode compartment and a cathode compartment; and the electrolytic cell separator is at least one selected from the group consisting of an anion exchange membrane, a cation exchange membrane, a bipolar membrane, a reverse osmosis membrane, a non-ion-selective diaphragm, a filter cloth, a microporous membrane, and a filter plate. 
     
     
         13 . The apparatus for preparing a silver compound from metallic silver according to  claim 12 , wherein a liquid jet pipe with a liquid outlet facing toward the anode is provided in the at least one electrolytic cell, and the liquid jet pipe is configured to enable a solution from the at least one electrolytic cell to flush the anode. 
     
     
         14 . The apparatus for preparing a silver compound from metallic silver according to  claim 13 , wherein the at least one electrolytic cell is further provided with a pump-tube liquid-flow circulating stirrer; and a liquid outlet pipe of the pump-tube liquid-flow circulating stirrer is the liquid jet pipe with the liquid outlet facing toward the anode to enable flushing of the anode. 
     
     
         15 . The apparatus for preparing a silver compound from metallic silver according to  claim 14 , wherein the anode is wrapped with an anode filter cloth bag to collect and intercept silver compound particles generated from the anode. 
     
     
         16 . The apparatus for preparing a silver compound from metallic silver according to  claim 14 , wherein a titanium basket is provided to hold the metallic silver as the anode for an electrochemical reaction; the titanium basket is a titanium basket-shaped structure electrically connected to the positive terminal of the at least one electrolytic power supply and is arranged in the at least one electrolytic cell;
 a suction and discharge pipe is provided in the titanium basket, and during or after electrolysis, the solid silver compound in the titanium basket is taken out of the at least one electrolytic cell and collected; and a solid feeder is further provided to feed the metallic silver into the titanium basket to enable an electrolytic reaction.   
     
     
         17 . The apparatus for preparing a silver compound from metallic silver according to  claim 12 , wherein the at least one electrolytic cell is further provided with a heat exchanger; the at least one electrolytic cell is further provided with a gas drainage collector, and the gas drainage collector is connected to a hydrogen eliminator for a safe treatment of hydrogen evolved; and the gas drainage collector is a spray tower or a vacuum ejector. 
     
     
         18 . The apparatus for preparing a silver compound from metallic silver according to  claim 17 , wherein a temporary storage tank is further provided to temporarily store a chemical or hold a prepared silver compound solution product or to serve as a chemical reaction tank; and the temporary storage tank is connected to the at least one electrolytic cell and/or the solid-liquid separator through a liquid pipeline and/or a gas pipeline, or is arranged below a liquid outlet of the at least one electrolytic cell and/or the solid-liquid separator to receive an overflowing liquid. 
     
     
         19 . The apparatus for preparing a silver compound from metallic silver according to  claim 18 , wherein a water-washing tank is further provided for washing to remove soluble impurities from the solid silver compound; and an electrothermal furnace is further provided to heat silver carbonate produced after electrolysis to produce silver oxide. 
     
     
         20 . The apparatus for preparing a silver compound from metallic silver according to  claim 19 , wherein a sensor and an automatic program controller are further provided, such that the apparatus undergoes automated production according to a preset program; and the sensor is at least one selected from the group consisting of a pH meter, a liquid level meter, a gravimeter, a thermometer, a weightometer, and a hydrogen concentration detector.