Method for efficiently recovering gold from gold-containing waste

Abstract

The invention discloses a method for efficiently recovering gold from gold-bearing waste. According to the method, the gold-bearing material is treated through the technological process of raw material pretreatment, light wave precise heating, controlled potential separation and chaotic enhanced leaching. According to the light wave heating technology, heating can be accurately controlled, metal reaction activity is excited, and high efficiency and energy saving are achieved. According to the chaos strengthening technology, the chaos function of a frequency converter is set, the motor power and the stirring rotating speed are aperiodically adjusted, the chaos state of the solution is maintained, the solid-liquid mixing efficiency and the heat and mass transfer rate are improved, and energy conservation and emission reduction in the leaching process are achieved. According to the method, a multi-field cooperation mode is adopted, selective removal and efficient leaching of precious metal and base metal are enhanced, consumption of a leaching agent and an oxidizing agent is reduced, the environmental pollution risk is reduced, energy conservation and emission reduction in the whole leaching process are achieved, and obvious economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to a method for efficiently recovering gold from gold-containing waste materials, belonging to the technical field of hydrometallurgy. Background Art

[0002] Gold is a strategic precious metal with excellent physical and chemical properties. It is widely used in electronic technology, aerospace, medical chemicals, gold jewelry and other fields. Gold is mainly distributed in gold mines and gold-containing secondary resources. The extraction process mainly includes pyrometallurgical process and hydrometallurgical process. With the large-scale mining and utilization of gold mines, gold-containing secondary resources are increasingly becoming the main raw materials for gold extraction. At present, gold extraction from secondary resources is mostly hydrometallurgical extraction. The process mainly includes physical crushing-wet leaching-extraction-electrolytic refining, among which leaching is a crucial link in hydrometallurgy. However, the leaching process usually has problems such as liquid-solid isolation zone, long leaching time, and low metal leaching rate.

[0003] The metals in gold-containing waste are diverse and complex in composition, mainly copper, iron, tin, lead, zinc, gold, silver, etc., among which the content of precious metals ranges from 0.01% to 90.0%. For gold-containing waste after pyrometallurgical treatment of waste circuit boards, precious metals will be captured by metals such as copper, lead, and iron to form solid solutions and alloys, resulting in a low leaching rate of precious metals in the leaching process. In addition, too much impurity metal will also affect the consumption of acid and oxidant in the leaching process and the judgment of the leaching end point, increase production costs and uncontrollability of operations, and ultimately result in a low leaching rate of precious metals mainly gold and a large loss.

[0004] Chinese patent CN 107841630 B authorizes a method for separating precious and base metals from circuit boards. This invention mainly uses a potential-controlled + sulfuric acid oxidation system to leach copper, tin, iron and other metals, but has not studied the efficient leaching of gold. Summary of the invention

[0005] The purpose of the present invention is to provide a method for efficiently recovering gold from gold-containing waste materials to solve the problems existing in the above-mentioned prior art. By heating with infrared light, the solution temperature can be precisely controlled, and the reaction activity of the metal can be stimulated. Then, the base metals can be separated by the potential control technology, and the excessive consumption of acid and oxidant can be reduced to achieve efficient separation of precious and base metals. Finally, the chaotic stirring technology is combined to enhance the solid-liquid chaotic mixing effect, strengthen the heat and mass transfer process of the material, improve production efficiency, reduce the energy consumption of the leaching process, and achieve efficient leaching of precious metals such as gold, which helps the entire leaching process save energy and reduce emissions. To achieve the above purpose, the present invention provides the following scheme:

[0006] (1) Dry and crush the gold-containing waste, then sieve and classify it to obtain gold-containing waste particles.

[0007] (2) Place gold-containing waste particles in a reaction kettle, add hydrochloric acid solution, turn on the light wave heating equipment, add an oxidant to form a leaching system, control the amount of oxidant added to maintain the solution potential at a certain value for leaching, and terminate the leaching when the potential of the leaching system does not change, and separate the leaching residue and the leaching solution.

[0008] (3) placing the leached residue obtained in step (2) into a reactor equipped with a chaotic stirring device, adding a hydrochloric acid solution containing an oxidant, and maintaining the chaotic state of the solution by adjusting the chaotic stirring device to obtain silver-containing leaching residue and gold leaching solution.

[0009] Preferably, the gold-containing waste materials are waste circuit boards, waste gold-plated parts, and anode mud, wherein the gold content is 28.18% to 33.22%.

[0010] Preferably, the mass of hydrochloric acid in the hydrochloric acid solution in step (2) is 1.0 to 1.2 times the theoretical mass required for complete oxidation of copper and iron, and the liquid-to-solid ratio of the hydrochloric acid solution to the gold-containing waste particles is 3:1 to 4:1.

[0011] Preferably, in step (2), the potential is maintained at 300 mV to 350 mV.

[0012] Preferably, the concentration of the oxidant in step (2) is 0.1 mol / L to 2.0 mol / L, and the oxidant is sodium chlorate.

[0013] Preferably, the light wave heating temperature in step (2) and step (3) is 20°C to 100°C.

[0014] Preferably, the liquid-to-solid ratio of the hydrochloric acid solution containing the oxidant to the leached residue in step (3) is 10:1 to 50:1, in units of mL:g, the molar concentration of the oxidant in the hydrochloric acid solution is 2.0 mol / L to 3.0 mol / L, and the oxidant is sodium chlorate.

[0015] Beneficial Effects of the Invention

[0016] (1) The present invention uses hydrochloric acid and sodium chlorate, which can avoid the introduction of impurity ions and can be applied to the leaching of multiple metals, ultimately achieving simultaneous and efficient leaching of multiple metals and reducing the reaction time.

[0017] (2) By controlling the potential to separate metals, the separation efficiency of noble metals and base metals is as high as over 99%. The leaching solution can be recycled to avoid excessive consumption of leaching agents and oxidants, reduce the amount of acid used by 5% to 10%, and reduce the amount of oxidants used by 10% to 30%.

[0018] (3) The leaching rate of gold in the traditional uniform stirring system can reach up to 98%. The present invention designs and builds a chaotic stirring device, nonlinearly strengthens the chlorination leaching process, improves the mixing efficiency and heat and mass transfer rate, shortens the reaction time, and realizes efficient leaching of precious metals. The leaching rate can reach 99.99% in a shorter time, the production efficiency is increased by 25% to 50%, and the energy consumption in the leaching process is reduced by 40% to 60%. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below by specific implementation methods. However, the following embodiments are only simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0020] Example 1

[0021] The gold-containing waste in Example 1 is waste gold-plated parts, and the metal contents thereof are shown in Table 1. The method for efficiently recovering gold from waste gold-plated parts specifically comprises the following steps:

[0022] (1) Dry and crush the waste gold-plated parts, and then sieve them through a 200-mesh sieve to obtain waste gold-plated part particles.

[0023] (2) 10g of waste gold-plated particles are placed in a reactor, and a hydrochloric acid solution is added. The mass of the hydrochloric acid in the hydrochloric acid solution is 1.0 times the theoretical mass required for complete oxidation of metals such as copper and iron. The liquid-solid ratio of the hydrochloric acid solution to the waste gold-plated particles is 4:1. The leaching temperature is controlled to be 25°C by a light wave heating device. Sodium chlorate with a molar concentration of 0.1 mol / L is gradually added to control the solution potential to be maintained at 300mV for leaching. The leaching is terminated when the potential of the leaching system no longer changes. The solid and liquid are separated to obtain leaching residue and leaching solution. The leaching residue composition and the leaching rate of each metal are shown in Tables 2 and 3. It can be seen that most of the iron and copper in the waste gold-plated parts have been removed through this step.

[0024] (3) After washing the leached residue, place it in a reactor with a chaotic stirring device, add a hydrochloric acid solution containing sodium chlorate, the molar concentration of the hydrochloric acid solution is 3.0 mol / L, and the molar concentration of sodium chlorate in the hydrochloric acid solution is 0.5 mol / L. Select the inverse descending logarithmic function as the control function, set the chaotic stirring speed at 300-360 rpm, and control the leaching temperature to 25 ° C through the light wave heating device to obtain a gold-containing leaching solution. The leaching rate of precious metals at different leaching times is shown in Table 4, and the energy consumption of the leaching process is shown in Table 5. Compared with the energy consumption of uniform stirring, the relative energy saving is about 43.6%.

[0025] Example 2

[0026] The gold-containing waste in Example 2 is anode mud, and the metal contents thereof are shown in Table 1. The method for efficiently recovering gold from anode mud specifically comprises the following steps:

[0027] (1) The anode mud is dried and crushed, and then sieved through a 200-mesh sieve to obtain anode mud particles.

[0028] (2) 20g of anode mud particles are placed in a reactor, and hydrochloric acid solution is added. The mass of hydrochloric acid in the hydrochloric acid solution is 1.2 times the theoretical mass required for complete oxidation of copper and iron. The liquid-solid ratio of the hydrochloric acid solution to the secondary gold-containing material particles is 3:1. The leaching temperature is controlled to be 25°C by light wave heating equipment. Sodium chlorate with a molar concentration of 2.0 mol / L is gradually added, and the solution potential is controlled to be maintained at 350mV for leaching. The leaching is terminated when the potential of the leaching system no longer changes. The leaching residue and the leaching solution are obtained after solid-liquid separation. The leaching residue composition and the leaching rate of each metal are shown in Tables 2 and 3. It can be seen that most of the iron and copper in the anode mud have been removed through this step.

[0029] (3) After washing the leached residue, place it in a reactor with a chaotic stirring device, add a hydrochloric acid solution containing sodium chlorate, the liquid-solid ratio of the hydrochloric acid solution to the leached residue is 30:1, the molar concentration of the hydrochloric acid solution is 2.0 mol / L, and the molar concentration of sodium chlorate in the hydrochloric acid solution is 1.0 mol / L. Select positive exponential and sine functions as chaotic stirring control functions, set the stirring speed at 400-460 rpm, and control the leaching temperature to 50 ° C through the light wave heating device to obtain a gold-containing leaching solution. The leaching rate of precious metals at different leaching times is shown in Table 4, and the energy consumption of the leaching process is shown in Table 5. Compared with the energy consumption of uniform stirring, the relative energy saving is about 59.7%.

[0030] Comparative Example 1

[0031] Comparative Example 1 is substantially the same as Example 1, except that the leaching process of step (2) of Comparative Example 1 maintains the solution potential at 250 mV, and the leaching slag composition and the leaching rates of each metal are shown in Tables 2 and 3. Comparison between Example 1 and Comparative Example 1 shows that increasing and maintaining the solution potential at 300 mV can significantly increase the leaching rate of copper. This is because when the potential is lower than 300 mV, copper cannot be fully oxidized into ions, resulting in a reduced copper leaching rate of only 52.15%. In addition, the copper involved will also affect the amount of acid and oxidant used in the subsequent gold leaching process, the gold leaching efficiency and leaching time, etc.

[0032] Comparative Example 2

[0033] Comparative Example 2 is substantially the same as Example 1, except that the leaching process temperature of step (2) of Comparative Example 2 is heated by water bath, and the leaching residue composition and the leaching rate of each metal are shown in Table 2 and Table 3. Comparison between Example 1 and Comparative Example 2 shows that the metal leaching effect of water bath heating is not as good as that of light wave heating, because light wave heating can better control the temperature, activate the reaction activity of copper metal by light, increase the leaching rate of copper and iron, and reduce the impact on the subsequent gold leaching process.

[0034] Comparative Example 3

[0035] Comparative Example 3 is basically the same as Example 1, except that the leaching process of step (3) of Comparative Example 3 adopts uniform stirring, and the stirring speed is set at 400rpm. The leaching rates of precious metals at different times are shown in Table 4, and the energy consumption of the leaching process is shown in Table 5. By comparing Example 1 with Comparative Example 3, it can be seen that the speed of constant-speed stirring is higher than that of chaotic stirring, but the gold leaching rate per unit time is not as good as that of chaotic stirring. This is because the speed change of chaotic stirring can drive the nonlinear movement of the solution, reduce solid accumulation and solid-liquid isolation area, increase the solid-liquid reaction contact area, and achieve efficient leaching of gold.

[0036] Table 1 Chemical composition of gold-containing waste (wt.%)

[0037] Group Au Ag Cu Fe Example 1 28.18 1.64 68.86 1.32 Example 2 33.22 3.74 62.16 0.88 Comparative Example 1 28.18 1.64 68.86 1.32 Comparative Example 2 28.18 1.64 68.86 1.32 Comparative Example 3 28.18 1.64 68.86 1.32

[0038] Table 2 Chemical composition of leached residue (wt.%)

[0039] Group Au Ag Cu Fe Example 1 92.32 4.87 2.12 0.20 Example 2 89.04 9.73 1.04 0.19 Comparative Example 1 65.95 3.51 30.28 0.26 Comparative Example 2 91.78 3.63 3.65 0.24 Comparative Example 3 92.41 4.76 2.08 0.27

[0040] Table 3 Leaching rate of each metal (%)

[0041] Group Au Ag Cu Fe Example 1 0.02 0.26 98.02 99.89 Example 2 0.03 0.32 99.85 99.92 Comparative Example 1 0.01 0.28 52.15 99.68 Comparative Example 2 0.01 0.22 95.45 99.72 Comparative Example 3 0.02 0.25 96.25 99.62

[0042] Table 4 Leaching rate of precious metal (Au) at different leaching times (%)

[0043] Group 30min 60min 120min 180min Example 1 23.75 52.12 99.85 99.99 Example 2 79.80 99.90 99.99 99.99 Comparative Example 1 5.35 21.16 58.45 83.85 Comparative Example 2 17.30 41.85 85.90 97.24 Comparative Example 3 20.75 48.85 90.75 98.82

[0044] Table 5 Energy consumption required to achieve the same leaching rate at different times (kWh)

[0045] Group 30min 60min 120min 180min Example 1 <![CDATA[6.55×10 -2 ]]> <![CDATA[1.31×10 -1 ]]> <![CDATA[2.62×10 -1 ]]> <![CDATA[3.93×10 -1 ]]> Example 2 <![CDATA[2.50×10 -2 ]]> <![CDATA[5.00×10 -2 ]]> <![CDATA[5.00×10 -2 ]]> <![CDATA[5.00×10 -2 ]]> Comparative Example 1 <![CDATA[6.85×10 -2 ]]> <![CDATA[1.37×10 -1 ]]> <![CDATA[2.74×10 -1 ]]> <![CDATA[4.11×10 -1 ]]> Comparative Example 2 <![CDATA[7.50×10 -2 ]]> <![CDATA[1.50×10 -1 ]]> <![CDATA[3.00×10 -1 ]]> <![CDATA[4.50×10 -1 ]]> Comparative Example 3 <![CDATA[8.15×10 -2 ]]> <![CDATA[1.63×10 -1 ]]> <![CDATA[3.26×10 -1 ]]> <![CDATA[4.89×10 -1 ]]>

[0046] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for efficiently recovering gold from gold-containing waste, characterized in that: The following steps are involved: (1) drying and crushing the gold-containing waste, and then sieving and screening to obtain gold-containing waste particles; (2) placing gold-containing waste particles in a reaction kettle, adding hydrochloric acid solution, turning on the light wave heating device, adding an oxidant to form a leaching system, controlling the amount of the oxidant added to maintain the solution potential at a certain value for leaching, and terminating the leaching when the potential of the leaching system does not change, and separating to obtain leaching residue and leaching solution; (3) placing the leached residue obtained in step (2) into a reactor equipped with a chaotic stirring device, adding a hydrochloric acid solution containing an oxidant, and maintaining the chaotic state of the solution by adjusting the chaotic stirring device to obtain silver-containing leaching residue and gold leaching solution.

2. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: The gold-containing waste materials are waste circuit boards, waste gold-plated parts and anode mud, wherein the gold content is 28.18% to 33.22%.

3. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: The mass of the hydrochloric acid in the hydrochloric acid solution of step (2) is 1.0 to 1.2 times the theoretical mass required for complete oxidation of copper and iron, and the liquid-to-solid ratio of the hydrochloric acid solution to the gold-containing waste particles is 3:1 to 4:

1.

4. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: In step (2), the potential is maintained at 300 mV to 350 mV.

5. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: The molar concentration of the oxidant in step (2) is 0.1 mol / L to 2.0 mol / L, and the oxidant is sodium chlorate.

6. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: The light wave heating temperature in step (2) and step (3) is 20°C to 100°C.

7. The method for efficiently recovering gold from gold-containing waste according to claim 1, characterized in that: The liquid-to-solid ratio of the hydrochloric acid solution containing the oxidant to the leached residue in step (3) is 10:1 to 50:1, in units of mL:g, the molar concentration of the oxidant in the hydrochloric acid solution is 2.0 mol / L to 3.0 mol / L, and the oxidant is sodium chlorate.