CN111041207A - Electrochemical gold leaching agent and method for recovering gold from waste gold-plated circuit board - Google Patents
Electrochemical gold leaching agent and method for recovering gold from waste gold-plated circuit board Download PDFInfo
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- CN111041207A CN111041207A CN201911187006.3A CN201911187006A CN111041207A CN 111041207 A CN111041207 A CN 111041207A CN 201911187006 A CN201911187006 A CN 201911187006A CN 111041207 A CN111041207 A CN 111041207A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/006—Wet processes
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22B11/00—Obtaining noble metals
- C22B11/04—Obtaining noble metals by wet processes
- C22B11/042—Recovery of noble metals from waste materials
- C22B11/046—Recovery of noble metals from waste materials from manufactured products, e.g. from printed circuit boards, from photographic films, paper or baths
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Abstract
The invention discloses an electrochemical gold leaching agent, which comprises the following components in percentage by mass: 15-25% of a metal complexing agent; 0.1-0.3% of an oxidant; 2-10% of a conductive agent; 0.1-0.2% of a pH regulator; 1-3% of a reducing agent; the pH value of the electrochemical gold leaching agent is 6-8, the electrochemical gold leaching agent can effectively leach the precious metal gold on the waste circuit board under the power-on condition, and the electrochemical gold leaching agent is neutral in pH value, safe to use and small in environmental pollution. The invention also discloses a method for recovering gold from the waste gold-plated circuit board by using the electrochemical gold leaching agent, which comprises the steps of soaking the waste circuit board in the electrochemical gold leaching agent, electrifying the electrochemical gold leaching agent for leaching reaction, taking out the waste circuit board after a period of time, and carrying out solid-liquid separation to obtain filter residue, namely gold powder.
Description
Technical Field
The invention belongs to the technical field of electronic waste recovery, and particularly relates to an electrochemical gold leaching agent and a method for recovering gold from a waste gold-plated circuit board.
Background
Printed wiring boards are basic components in electronic and electrical products, are present in almost all electronic products, and are the foundation of the electronics industry. China is a big country for producing and consuming electric and electronic products, and along with the great increase of electronic wastes, the number of waste printed circuit boards is also increased sharply.
According to statistics, the amount of waste circuit boards to be treated in China is up to more than 50 million tons every year. The basic composition of the printed wiring board comprises 40% of metal, 30% of resin and plastic w, and 30% of glass fiber. Among them, the communication circuit board requires high reliability, and the surface thereof generally adopts a nickel-gold immersion process, so that the waste circuit board contains a lot of precious metals such as gold, and has a high recovery value, wherein the waste mobile phone circuit board is one of the most representative ones.
For a circuit board of a mobile phone, precious metals and nonferrous metals account for about 30% of the total mass of the mobile phone, and mainly comprise metal elements such as gold, palladium, silver, copper, tin, nickel and the like. Taking gold as an example only, the gold content of the gold-plated circuit board and the mobile phone circuit board is about 200 g/ton and 300 g/ton respectively, and the average grade of the gold ore is only 5 g/ton, i.e. the "gold content" of the waste circuit board is 40 to 60 times of that of the gold ore, so that great economic benefits are obtained.
But at the same time, the waste mobile phone circuit board also contains toxic and harmful substances. Therefore, in the process of recycling and processing the waste mobile phones, if the waste mobile phones are properly disposed, the waste mobile phones can become valuable urban mines; otherwise, serious environmental hazards are brought.
At present, the precious metals such as gold, silver, palladium and the like are mainly extracted from waste circuit boards by simple incineration or means such as aqua regia, cyanide, nitric acid and the like at home. However, when the incineration method is adopted, the flame retardant containing halogen elements in the waste circuit board generates carcinogenic substances in the combustion process, pollutes the atmosphere and poses great threat to human health; chemical reagents such as aqua regia, cyanide, nitric acid and the like are toxic or corrosive, on one hand, in the treatment process, operators need to be careful and careless, and accidents which harm human bodies can be caused, on the other hand, the treatment difficulty of waste water, waste gas and residues generated in the treatment process is high, and the environment can be seriously polluted after the waste water, the waste gas and the residues are discharged.
For example: (1) the Chinese patent application CN104372176A discloses a method for extracting gold, silver and palladium from waste mobile phones, which comprises the steps of 1) crushing waste circuit boards and then sorting the crushed waste circuit boards to obtain metal concentrates; 2) roasting and washing the metal concentrate to obtain a precious metal concentrate; 3) dissolving the noble metal enrichment with nitric acid to obtain chloride precipitate silver, dissolving with ammonia, and reducing to obtain silver powder; 4) dissolving with nitric acid to obtain a solution containing gold and palladium, replacing the obtained solution with zinc powder to obtain slag, performing secondary chlorination leaching, and reducing the leachate with sodium nitrite to obtain gold powder; 5) and adding hydrazine hydrate into the solution after gold reduction for reduction to obtain palladium powder.
(2) The Chinese patent application CN105154678A discloses a high-efficiency environment-friendly gold extraction method for waste mobile phone electronic elements, which comprises the steps of 1) crushing; 2) physical separation is carried out, so that the separation of non-metal materials mainly containing epoxy resin and metal materials mainly containing copper is realized; 3) reacting metal powder with nitric acid to obtain gold-rich residue; 4) reacting the gold-rich residue with a DMSO-CuBr-KBr gold leaching system to obtain a gold-containing solution; 5) adding water into the gold-containing solution and precipitating to obtain a gold-containing precipitate; 6) and purifying to obtain gold powder.
(3) The Chinese patent application CN106734058A discloses a comprehensive environment-friendly separation process for valuable metals of a waste mobile phone circuit board, which comprises the steps of 1) shearing and crushing a circuit board substrate; 2) carrying out magnetic separation on the broken circuit board; 3) further fine grinding by using a hammer crusher, and screening out materials with the diameter of less than 1 mm; 4) sorting with a pneumatic sorting system; 5) further sorting using static electricity; 6) adding dilute sulfuric acid and introducing oxygen, carrying out solid-liquid separation after leaching reaction; 7) heating the acidic leaching solution and adjusting the pH value, separating out iron in a precipitate form, and performing solid-liquid separation to obtain a copper sulfate filtrate; 8) adding a nitric acid solution into the sulfuric acid leaching residue slurry for leaching reaction, performing solid-liquid separation to obtain a filtrate, namely a silver nitrate solution, and adding a reducing agent to obtain silver powder; 9) adding aqua regia into the residue slurry to carry out leaching reaction, adding sodium sulfite to reduce to obtain gold powder, and adding zinc powder to obtain platinum-palladium powder after solid-liquid separation.
(4) The method for extracting precious metals from waste mobile phones disclosed in the Chinese patent application CN109576502A comprises the steps of 1) calcining the waste mobile phones and then leaching the calcined mobile phones with nitric acid; 2) adding sodium chloride into the leachate, heating, removing nitrate, and filtering to obtain silver chloride; 3) adding silver chloride into a sodium chloride solution for filtering treatment; 4) and (4) carrying out hydrazine hydrate reduction drying treatment on the filtered solution to obtain pure silver.
The process method of the patent application does not have the step of leaching precious metals in the waste circuit board by calcining or acidic strong corrosive chemical reagents such as nitric acid, dilute sulfuric acid, aqua regia and the like, and then reducing the leached metals by a reducing agent so as to achieve the purpose of recycling. The common defects are that the process flow is long, and the use of acid chemical reagents in leaching can generate environmental pollutants such as waste water and gas.
In order to reduce pollution in the leaching process, the prior art develops a process for leaching gold by using thiourea instead of aqua regia and nitric acid. Although the pollution problem is improved to a certain extent and the safety of the process is also improved, the thiourea has poor stability, is easy to oxidize and lose efficacy and is difficult to control in actual production.
According to the current practical situation, waste products of waste electronic products and electromechanical products are classified into plastic-dominant types, glass-dominant types, metal-dominant types and rare and precious metal-dominant types according to different constituent materials. The most valuable to be recovered is the main type of rare and precious metals, especially the recovery and utilization of gold. According to the measurement and calculation research, the value of gold accounts for about 80% of all metal values of the waste circuit board. Therefore, how to develop a recycling process which is short in time consumption, simple in process and environment-friendly becomes a technical problem to be solved urgently.
Disclosure of Invention
The first purpose of the invention is to provide an electrochemical gold leaching agent which can effectively leach the precious metal gold on a waste circuit board under the condition of electrifying, has neutral pH, is safe to use and has little pollution to the environment.
The second purpose of the invention is to provide a method for recovering gold from waste gold-plated circuit boards by using the electrochemical gold leaching agent.
The first purpose of the invention is realized by the following technical scheme:
an electrochemical gold leaching agent comprises the following components in percentage by mass:
15-25% of a metal complexing agent; 0.1-0.3% of an oxidant; 2-10% of a conductive agent; 0.1-0.2% of a pH regulator; 1-3% of a reducing agent;
the pH value of the electrochemical gold leaching agent is 6-8.
Other components of the electrochemical gold leaching agent also comprise a solvent, such as deionized water and the like.
Preferably, the electrochemical gold leaching agent comprises the following components in percentage by mass: 15% of metal complexing agent; 0.3 percent of oxidant; 8% of a conductive agent; 0.1% of pH regulator; 2% of reducing agent.
The metal complexing agent is selected from one or more of sodium thiosulfate, ammonium thiosulfate, calcium polysulfide, ammonium polysulfide, sodium thiocyanate, ammonium thiocyanate, glycine, succinic acid, lactic acid, sodium citrate, potassium sodium tartrate, sodium Nitrilotriacetate (NTA), sodium Ethylene Diamine Tetracetate (EDTA), sodium gluconate and calcium sulfide.
The oxidant is selected from one or more of ferric sulfate, ferric chloride, hydrogen peroxide, manganese dioxide, sodium persulfate, sodium percarbonate, calcium peroxide, sodium perborate, potassium permanganate, thiourea dioxide, potassium hydrogen persulfate and sodium nitrobenzene sulfonate.
The conductive agent is selected from inorganic salts such as sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, ammonium sulfate and the like.
The pH regulator is selected from sodium hydroxide, calcium oxide, calcium hydroxide, sodium carbonate or sodium bicarbonate.
The reducing agent is selected from sodium sulfite or sodium bisulfite.
The second purpose of the invention is realized by the following technical scheme:
a method for recovering gold from waste gold-plated circuit boards by using the electrochemical gold leaching agent comprises the following steps:
soaking the waste circuit board in an electrochemical gold leaching agent, electrifying the electrochemical gold leaching agent for leaching reaction, taking out the waste circuit board after a period of time, and carrying out solid-liquid separation to obtain filter residue, namely gold powder.
Preferably, the specific process is as follows:
(1) mixing a conductive medium with the waste circuit board to ensure that the conductive medium is fully contacted with the gold-plated layer on the waste circuit board;
(2) putting a conductive medium and a waste circuit board into an electrochemical gold leaching solution, taking the conductive medium as a conductive anode, putting a conductive cathode into the electrochemical gold leaching solution, and introducing direct current into the electrochemical gold leaching solution;
(3) and (3) after the step (2) is electrified and soaked for a period of time, taking out the conductive medium and the waste circuit board, and filtering the electrochemical gold leaching solution to obtain filter residues, namely the gold powder.
In the electrifying process, under the dual actions of direct current and the electrochemical gold leaching solution, the gold plating layer on the waste circuit board is gradually dissolved to form gold complex ions, and the gold complex ions are reduced into gold powder by a reducing agent in the electrochemical gold leaching solution, so that the purpose of recovering gold from the waste circuit board is realized.
The invention is suitable for all waste circuit boards with gold plating layers, such as communication circuit boards requiring high reliability, including circuit boards of waste mobile phones.
Preferably, before the step (1), a process of washing the waste circuit board with water is further included to remove other dirt such as dust on the waste circuit board, so as to avoid the dirt from accumulating in a subsequent leaching process to affect a leaching effect.
And (3) taking the conductive medium and the waste circuit board out of the electrochemical gold leaching solution, screening, separating the conductive medium from the waste circuit board, and using the separated conductive medium in the next step (1). In the screening process, the waste circuit boards are preferably separated from the conductive medium using a stainless steel vibrating screen. The waste circuit board with the gold-plated layer removed can be subjected to subsequent physical separation to separate resin powder and copper metal powder, so that copper can be recovered.
The conductive medium is preferably stainless steel shot, metal titanium beads, graphite particles or polymer conductive particles, the conductive medium serving as a conductive anode in the step (2) cannot be dissolved, and the particle size of the conductive medium is preferably 0.1-0.6 mm.
In order to facilitate the electrochemical gold leaching in the step (2), in the invention, preferably, in the step (1), the conductive medium and the waste circuit board are placed in a porous conductive roller, and the aperture of the conductive roller is smaller than the particle size of the conductive medium so as to avoid the conductive medium from leaking out of the hole; and (3) immersing the conductive roller into the electrochemical gold leaching solution in the step (2) to serve as a conductive anode, and continuously rolling the conductive roller in the process so that the gold plating layer of the waste circuit board in the conductive roller is continuously contacted with the granular conductive medium to form a conductive path.
The material of the conductive roller and the conductive cathode is preferably 304 stainless steel.
And (3) filtering by adopting a stainless steel bag type centrifuge, drying the filtered substances, and adding a smelting agent to carry out pyrogenic smelting to obtain the crude gold. The obtained gold powder can be further mixed with a smelting agent for smelting to obtain a gold ingot.
Compared with the prior art, the invention has the following beneficial effects:
(1) the electrochemical gold leaching agent does not contain strongly corrosive and highly toxic substances such as nitric acid, cyanide and the like, has a pH value of 6-8, is safe to operate, generates fewer pollutants, and accords with the concept of environmental protection;
(2) after the leaching reaction of the electrochemical gold leaching agent is finished, filtrate obtained by filtering can be recycled, and the next round of leaching reaction is carried out, so that the utilization rate of the agent is improved, the discharge amount of waste water is reduced, and the electrochemical gold leaching agent belongs to an environment-friendly agent;
(3) according to the invention, the gold-plated layer on the waste circuit board is leached and dissolved by an electrochemical method, gold with the highest recovery value on the waste circuit board is recovered at first, and then the circuit board after gold removal is further treated, so that the process flow is greatly simplified, the recovery rate of gold is improved, and the method has remarkable economic and environmental benefits;
(4) the invention reduces gold complex ions into sponge gold during leaching, and obtains coarse gold ingots through filtering, washing and smelting, and the invention has the advantages of short flow, simple process and convenient operation.
Drawings
The invention is further illustrated by the following figures.
FIG. 1 is a flow chart of a recycling process of waste circuit boards.
Detailed Description
The present invention will be further described with reference to the following specific examples.
In the following examples, the initial concentration of the gold complex ions in the leachate and the final concentration of the remaining gold complex ions after precipitation were measured by inductively coupled plasma atomic emission spectroscopy ICP, the concentration being PPM (mg/L), and the recovery rate of gold was calculated by the following formula (1):
P＝(C2-C1)/C2×100％ (1)
in the formula: recovery of P-gold, percent
C2Initial concentration of gold complex ion, mg/L
C1Final concentration of gold complex ion, mg/L.
Example 1
(1) Removing dust and grease on 10kg of waste mobile phone circuit boards by using a cleaning agent, and then washing the circuit boards by using clear water;
(2) setting the temperature to be 20-45 ℃, putting the cleaned waste mobile phone circuit board into a stainless steel conductive roller, and then putting conductive medium stainless steel shots, wherein the grain size is 0.4mm, and the mass ratio of the waste mobile phone circuit board to the conductive medium is 1: 4;
(3) preparing an electrochemical gold leaching agent according to the following table-1, immersing a conductive roller into the electrochemical gold leaching agent according to a solid-to-liquid ratio (mass ratio of the waste circuit board to the electrochemical gold leaching agent) of 1:2, wherein the conductive roller is connected with the anode of a direct-current power supply, a stainless steel plate is connected with the cathode of the direct-current power supply, a conductive medium is fully contacted with the waste mobile phone circuit board for conduction through the rolling action of the conductive roller, and is electrified and immersed, in the process, a gold plating layer is dissolved through the electrochemical action, and gold complex ions are reduced to form precipitates;
(4) after reacting for a period of time, carrying out solid-liquid separation on the leaching solution to obtain filter residue and filtrate, washing the filter residue, and carrying out acid washing to remove metals to obtain gold powderThe obtained gold powder can be further added with a smelting agent to be smelted into a crude gold ingot, and P ═ C is calculated according to the formula (1)2-C1)/C2ⅹ100％＝(225.52-2.11)/225.52＝99.06％；
The filtrate can be recycled for more than 10 cycles after being mixed with the electrochemical gold leaching agent, the solution is invalid due to sodium ion accumulation after being used for many times, most of sodium salt is removed through heating, cooling and crystallization, the sodium salt can be recycled, and finally only a small amount of generated wastewater reaches the standard and is discharged;
(5) the taken out waste mobile phone circuit board can be washed clean and sent to the physical crushing and sorting process, and then the waste mobile phone circuit board is crushed and sorted into metal copper powder and resin powder.
TABLE-1
The leaching reaction process parameters are as follows
| Name (R) | Parameter(s) |
| pH value | 8.0 |
| Conductive medium | 0.4mm stainless steel shot |
| Groove pressure (V) | 6 |
| Current density(A/dm) | 10 |
| Area ratio of cathode to anode | 2:1 |
| Cathode electrode | 304 or 316 stainless steel plate |
| Temperature (. degree.C.) | 30 |
| Reaction time (min) | 10 |
| Filtration | Continuous filtration of bath solution |
Example 2
(1) Removing dust and grease on 10kg of waste mobile phone circuit boards by using a cleaning agent, and then washing the circuit boards by using clear water;
(2) setting the temperature to be 20-45 ℃, putting the cleaned waste mobile phone circuit board into a stainless steel conductive roller, and then putting a conductive medium, namely metal titanium beads, wherein the particle size of the metal titanium beads is 0.2mm, and the mass ratio of the waste mobile phone circuit board to the conductive medium is 1: 3;
(3) preparing an electrochemical gold leaching agent according to the following table-2, immersing a conductive roller into the electrochemical gold leaching agent according to a solid-to-liquid ratio (the mass ratio of the waste circuit board to the electrochemical gold leaching agent) of 1:2, wherein the conductive roller is connected with the anode of a direct-current power supply, a stainless steel plate is connected with the cathode of the direct-current power supply, a conductive medium is fully contacted with the waste mobile phone circuit board for conduction through the rolling action of the conductive roller, and is electrified and immersed, in the process, a gold plating layer is dissolved through the electrochemical action, and gold complex ions are reduced to form precipitates;
(4) after reacting for a period of time, carrying out solid-liquid separation on the leaching solution to obtain filter residue and filtrate, washing the filter residue, carrying out acid washing to remove metals, obtaining gold powder, further adding a smelting agent into the obtained gold powder, smelting the obtained gold powder into a crude gold ingot, and calculating according to a formula (1) to obtain P ═ C2-C1)/C2 x 100 ═ C226.32-2.20)/226.32 ═ 99.03%;
the filtrate can be recycled for more than 10 cycles after being mixed with the electrochemical gold leaching agent, the solution is invalid due to sodium ion accumulation after being used for many times, most of sodium salt is removed through heating, cooling and crystallization, the sodium salt can be recycled, and finally only a small amount of generated wastewater reaches the standard and is discharged;
(5) the taken out waste mobile phone circuit board can be washed clean and sent to the physical crushing and sorting process, and then the waste mobile phone circuit board is crushed and sorted into metal copper powder and resin powder.
TABLE-2
| Components | Mass percent/%) |
| Ammonium thiosulfate | 15 |
| Ammonium thiocyanate | 8 |
| Citric acid | 2 |
| Ferric sulfate | 0.1 |
| Sodium sulfate | 5 |
| Sodium bisulfite | 2 |
| Sodium hydroxide | 0.2 |
| Deionized water | Balance of |
The leaching reaction process parameters are as follows
| Name (R) | Parameter(s) |
| pH value | 8.0 |
| Conductive medium | 0.2mm metal titanium pill |
| Groove pressure (V) | 10 |
| Current Density (A/dm) | 8 |
| Area ratio of cathode to anode | 3:1 |
| Cathode electrode | 304 or 316 stainless steel plate |
| Temperature (. degree.C.) | 40 |
| Reaction time (min) | 8 |
| Filtration | Continuous filtration of bath solution |
Example 3
(1) Removing dust and grease on 10kg of waste mobile phone circuit boards by using a cleaning agent, and then washing the circuit boards by using clear water;
(2) setting the temperature to be 20-45 ℃, putting the cleaned waste mobile phone circuit board into a stainless steel conductive roller, and then putting conductive medium graphite with the particle size of 0.5mm, wherein the mass ratio of the waste mobile phone circuit board to the conductive medium is 1: 2;
(3) preparing an electrochemical gold leaching agent according to the following table-3, immersing a conductive roller into the electrochemical gold leaching agent according to a solid-to-liquid ratio (the mass ratio of the waste circuit board to the electrochemical gold leaching agent) of 1:2, wherein the conductive roller is connected with the anode of a direct-current power supply, a stainless steel plate is connected with the cathode of the direct-current power supply, a conductive medium is fully contacted with the waste mobile phone circuit board for conduction through the rolling action of the conductive roller, and is electrified and immersed, in the process, a gold plating layer is dissolved through the electrochemical action, and gold complex ions are reduced to form precipitates;
(4) after reacting for a period of time, carrying out solid-liquid separation on the leaching solution to obtain filter residue and filtrate, washing the filter residue, carrying out acid washing to remove metals, obtaining gold powder, further adding a smelting agent into the obtained gold powder, smelting the obtained gold powder into a crude gold ingot, and calculating according to a formula (1) to obtain P ═ C2-C1)/C2 x 100 ═ C221.78-2.1)/221.78 ═ 99.05%;
the filtrate can be recycled for more than 10 cycles after being mixed with the electrochemical gold leaching agent, the solution is invalid due to sodium ion accumulation after being used for many times, most of sodium salt is removed through heating, cooling and crystallization, the sodium salt can be recycled, and finally only a small amount of generated wastewater reaches the standard and is discharged;
(5) the taken out waste mobile phone circuit board can be washed clean and sent to the physical crushing and sorting process, and then the waste mobile phone circuit board is crushed and sorted into metal copper powder and resin powder.
TABLE-3
| Components | Mass percent/%) |
| Ammonium polysulfate | 6 |
| Ammonium thiocyanate | 9 |
| Glycine | 1 |
| Potassium hydrogen persulfate | 0.1 |
| Ammonium sulfate | 4 |
| Sodium carbonate | 0.1 |
| Sodium bisulfite | 2 |
| Deionized water | Balance of |
The leaching reaction process parameters are as follows
Example 4
(1) Removing dust and grease on 5kg of waste computer circuit boards by using a cleaning agent, and then washing the circuit boards clean by using clear water;
(2) setting the temperature to be 30 ℃, putting the cleaned waste mobile phone circuit board into a stainless steel conductive roller, and then putting conductive medium graphite with the particle size of 0.4mm, wherein the mass ratio of the waste mobile phone circuit board to the conductive medium is 1: 3;
(3) preparing an electrochemical gold leaching agent according to the following table-4, immersing a conductive roller into the electrochemical gold leaching agent according to a solid-to-liquid ratio (the mass ratio of the waste circuit board to the electrochemical gold leaching agent) of 1:3, wherein the conductive roller is connected with the anode of a direct-current power supply, a stainless steel plate is connected with the cathode of the direct-current power supply, a conductive medium is fully contacted with the waste mobile phone circuit board for conduction through the rolling action of the conductive roller, and is electrified and immersed, in the process, a gold plating layer is dissolved through the electrochemical action, and gold complex ions are reduced to form precipitates;
(4) after reacting for a period of time, carrying out solid-liquid separation on the leaching solution to obtain filter residue and filtrate, washing the filter residue, carrying out acid washing to remove metals, obtaining gold powder, further adding a smelting agent into the obtained gold powder, smelting the obtained gold powder into a crude gold ingot, and calculating according to a formula (1) to obtain P ═ C2-C1)/C2 x 100 ═ C216.54-2.08)/216.54 ═ 99.04%;
the filtrate can be recycled for more than 10 cycles after being mixed with the electrochemical gold leaching agent, the solution is invalid due to sodium ion accumulation after being used for many times, most of sodium salt is removed through heating, cooling and crystallization, the sodium salt can be recycled, and finally only a small amount of generated wastewater reaches the standard and is discharged;
(5) the taken out waste mobile phone circuit board can be washed clean and sent to the physical crushing and sorting process, and then the waste mobile phone circuit board is crushed and sorted into metal copper powder and resin powder.
TABLE-4
The leaching reaction process parameters are as follows
| Name (R) | Parameter(s) |
| pH value | 8.0 |
| Conductive medium | 0.4mm graphite particles |
| Groove pressure (V) | 10 |
| Current Density (A/dm) | 15 |
| Area ratio of cathode to anode | 3:1 |
| Cathode electrode | 304 or 316 stainless steel plate |
| Temperature (. degree.C.) | 30 |
| Reaction time (min) | 15 |
| Filtration | Continuous filtration of bath solution |
Example 5
(1) Removing dust and grease on 5kg of waste computer memory bars by using a cleaning agent, and then washing the waste computer memory bars by using clear water;
(2) setting the temperature to be 30 ℃, putting the cleaned waste mobile phone circuit board into a stainless steel conductive roller, and then putting conductive medium graphite with the particle size of 0.4mm, wherein the mass ratio of the waste mobile phone circuit board to the conductive medium is 1: 3;
(3) preparing an electrochemical gold leaching agent according to the following table-5, immersing a conductive roller into the electrochemical gold leaching agent according to a solid-to-liquid ratio (the mass ratio of the waste circuit board to the electrochemical gold leaching agent) of 1:2, wherein the conductive roller is connected with the anode of a direct-current power supply, a stainless steel plate is connected with the cathode of the direct-current power supply, a conductive medium is fully contacted with the waste mobile phone circuit board for conduction through the rolling action of the conductive roller, and is electrified and immersed, in the process, a gold plating layer is dissolved through the electrochemical action, and gold complex ions are reduced to form precipitates;
(4) after reacting for a period of time, carrying out solid-liquid separation on the leaching solution to obtain filter residue and filtrate, washing the filter residue, carrying out acid washing to remove metals, obtaining gold powder, further adding a smelting agent into the obtained gold powder, smelting the obtained gold powder into a crude gold ingot, and calculating according to a formula (1) to obtain P (C2-C1)/C2 x 100% ((356.54-2.58)/356.54) 99.27%;
the filtrate can be recycled for more than 10 cycles after being mixed with the electrochemical gold leaching agent, the solution is invalid due to sodium ion accumulation after being used for many times, most of sodium salt is removed through heating, cooling and crystallization, the sodium salt can be recycled, and finally only a small amount of generated wastewater reaches the standard and is discharged;
(5) the taken out waste mobile phone circuit board can be washed clean and sent to the physical crushing and sorting process, and then the waste mobile phone circuit board is crushed and sorted into metal copper powder and resin powder.
TABLE-5
| Components | Mass percent/%) |
| Calcium polysulfide | 6 |
| Calcium sulfide | 7 |
| Ammonium polysulfide | 2 |
| Manganese dioxide | 0.1 |
| Potassium sulfate | 3 |
| Sodium carbonate | 0.1 |
| Sodium bisulfite | 2 |
| Deionized water | Balance of |
The leaching reaction process parameters are as follows
| Name (R) | Parameter(s) |
| pH value | 7.0 |
| Conductive medium | 0.4mm stainless steel shot |
| Groove pressure (V) | 10 |
| Current Density (A/dm) | 20 |
| Area ratio of cathode to anode | 4:1 |
| Cathode electrode | 304 or 316 stainless steel plate |
| Temperature (. degree.C.) | 30 |
| Reaction time (min) | 10 |
| Filtration | Continuous filtration of bath solution |
The metal complexing agent of the electrochemical gold leaching agent can be selected from one or more of sodium thiosulfate, ammonium thiosulfate, calcium polysulfide, ammonium polysulfide, sodium thiocyanate, ammonium thiocyanate, glycine, succinic acid, lactic acid, sodium citrate, potassium sodium tartrate, sodium nitrilotriacetate, sodium ethylene diamine tetracetate, sodium gluconate and calcium sulfide; the oxidant is selected from one or more of ferric sulfate, ferric chloride, hydrogen peroxide, manganese dioxide, sodium persulfate, sodium percarbonate, calcium peroxide, sodium perborate, potassium permanganate, thiourea dioxide, potassium hydrogen persulfate and sodium nitrobenzene sulfonate; the conductive agent is selected from sodium sulfate, sodium chloride, potassium sulfate, potassium chloride and ammonium sulfate; the pH regulator is selected from sodium hydroxide, calcium oxide, calcium hydroxide, sodium carbonate or sodium bicarbonate; the reducing agent is selected from sodium sulfite and sodium bisulfite. The components can be combined at will, the mass percentage content of the components can be adjusted within the range of the invention, only the difference of the reaction time is caused, but the recovery rate of the electrochemical gold leaching agent to the gold-plated layer on the waste circuit board is not influenced.
It should be noted that the above-mentioned embodiments are only illustrative and not restrictive, and any modifications or changes within the meaning and range of equivalents to the technical solutions of the present invention by those skilled in the art should be considered to be included in the protection scope of the present invention.
Claims (10)
1. An electrochemical gold leaching agent is characterized by comprising the following components in percentage by mass:
15-25% of a metal complexing agent; 0.1-0.3% of an oxidant; 2-10% of a conductive agent; 0.1-0.2% of a pH regulator; 1-3% of a reducing agent;
the pH value of the electrochemical gold leaching agent is 6-8.
2. The electrochemical gold leaching agent according to claim 1, wherein the metal complexing agent is selected from one or more of sodium thiosulfate, ammonium thiosulfate, calcium polysulfide, ammonium polysulfide, sodium thiocyanate, ammonium thiocyanate, glycine, succinic acid, lactic acid, sodium citrate, potassium sodium tartrate, sodium nitrilotriacetate, sodium ethylenediaminetetraacetate, sodium gluconate, and calcium sulfide.
3. The electrochemical gold leaching agent of claim 1, wherein the oxidizing agent is selected from one or more of ferric sulfate, ferric chloride, hydrogen peroxide, manganese dioxide, sodium persulfate, sodium percarbonate, calcium peroxide, sodium perborate, potassium permanganate, thiourea dioxide, potassium hydrogen persulfate, and sodium nitrobenzene sulfonate.
4. The electrochemical gold leaching agent according to claim 1, wherein the conductive agent is selected from the group consisting of sodium sulfate, sodium chloride, potassium sulfate, potassium chloride, and ammonium sulfate.
5. The electrochemical gold leaching agent according to claim 1, wherein said pH adjusting agent is selected from the group consisting of sodium hydroxide, calcium oxide, calcium hydroxide, sodium carbonate and sodium bicarbonate.
6. The electrochemical gold leaching agent according to claim 1, wherein said reducing agent is selected from sodium sulfite and sodium bisulfite.
7. A method for recovering gold from waste gold-plated circuit boards by using the electrochemical gold leaching agent as claimed in any one of claims 1 to 6, which is characterized by comprising the steps of soaking the waste circuit boards in the electrochemical gold leaching agent, electrifying the electrochemical gold leaching agent for leaching reaction, taking out the waste circuit boards after a period of time, and carrying out solid-liquid separation to obtain filter residues, namely gold powder.
8. The method for recovering gold from waste gold-plated circuit boards according to claim 7 is characterized by comprising the following steps:
(1) mixing a conductive medium with the waste circuit board to ensure that the conductive medium is fully contacted with the gold-plated layer on the waste circuit board;
(2) putting a conductive medium and a waste circuit board into an electrochemical gold leaching solution, taking the conductive medium as a conductive anode, putting a conductive cathode into the electrochemical gold leaching solution, and introducing direct current into the electrochemical gold leaching solution;
(3) and (3) after the step (2) is electrified and soaked for a period of time, taking out the conductive medium and the waste circuit board, and filtering the electrochemical gold leaching solution to obtain filter residues, namely the gold powder.
9. The method for recovering gold from waste gold-plated circuit boards according to claim 8, wherein the conductive medium and the waste circuit boards are placed in the porous conductive roller in the step (1), and the pore diameter of the conductive roller is smaller than the particle diameter of the conductive medium to prevent the conductive medium from leaking out of the pores; and (3) immersing the conductive roller into the electrochemical gold leaching solution in the step (2) to serve as a conductive anode, and continuously rolling the conductive roller in the process so that the gold plating layer of the waste circuit board in the conductive roller is continuously contacted with the granular conductive medium to form a conductive path.
10. The method of claim 8, wherein the conductive medium is stainless steel shot, metallic titanium beads, graphite particles or polymer conductive particles.
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| CN112522522A (en) * | 2020-11-29 | 2021-03-19 | 湖南金裕环保科技有限公司 | Environment-friendly cyanide-free gold extraction liquid, preparation method and application |
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| CN118028904A (en) * | 2024-01-12 | 2024-05-14 | 武汉理工大学 | Method for leaching noble metal by thiosulfate electrochemical oxidation |
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Application publication date: 20200421 |