Preparation method of copper modified aluminum composite material and application of copper modified aluminum composite material to cyanide gold-containing wastewater or precious liquid reduction method for breaking the complex and recovering gold

Abstract

The application discloses a preparation method of copper modified aluminum composite material and application of the copper modified aluminum composite material to reduction and breakage of a gold cyanide complex in alkaline cyanide gold-containing wastewater or a gold extraction liquid and recovery of gold from the gold cyanide complex. A certain amount of copper salt and micron zero-valent aluminum are mixed according to a certain proportion, and the copper modified aluminum composite material is prepared through mechanical ball milling with a certain rotating speed and time. The application of the material is also disclosed. The material is put into the gold cyanide complex wastewater or the gold extraction liquid, the material and the gold cyanide complex are fully contacted through continuous shaking, the copper on the surface of the material serves as an electron transmission bridge to transmit the electrons released by the aluminum in the material to Au, direct reduction and decomplexation occur, and the gold cyanide complex is removed; in the process, high-valence Au is reduced to Au 0 , and is attached to the surface of the material, and the material with the gold is recovered through negative pressure suction filtration. The material preparation method of the application has the advantages of wide and cheap material sources, simple preparation process, no need of pretreatment for gold recovery, performance at normal temperature and pressure, mild and convenient reaction conditions and easy engineering.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water pollution treatment and resource utilization, and particularly relates to a preparation method of copper-modified aluminum composite material and application of the copper-modified aluminum composite material to reduction and gold recovery from alkaline cyanide-containing gold-containing wastewater or gold-containing solution in a wet gold extraction method. BACKGROUND

[0002] Due to the irreplaceable advantages of cyanide in the gold industry, cyanide plating solution is usually used to improve the quality of the plating layer during gold plating, and a large amount of cyanide-containing gold-containing wastewater is generated in the electroplating, electronics, jewelry processing and other industries in China every year. In addition, as the largest gold producing country in the world, wet gold extraction is widely used, and the gold-containing solution is usually reduced by zinc method. At present, about 80% of gold in the world is still extracted by cyanide leaching. In cyanide-containing gold-containing wastewater and gold-containing solution, gold and cyanide ions form a stable complex Au(CN)2 - , which increases the difficulty of gold recovery. However, the reserves of gold are limited, and it is still of great practical significance to recover gold from cyanide-containing wastewater or improve the efficiency of gold-containing solution treatment.

[0003] There are two difficulties in recovering gold from gold-containing cyanide complex water: ① the complex formed by cyanide and gold is very stable (lg β Au(CN)2- = 36.6), which increases the difficulty of gold recovery; ② the water usually has strong alkalinity (pH = 9.5 ~11), and reducing the pH will dissociate the toxic cyanide ions or hydrogen cyanide gas (K p a = 9.21). Due to the difficulty of recovering gold from cyanide-containing gold-containing wastewater, there are few related researches at present, and the traditional adsorption method, solvent extraction method and electrodialysis method can only perform simple enrichment without breaking the complex, and further means are needed for extraction and reduction. In addition, the commonly used zero-valent metal (zinc powder) reduction displacement method for cyanide gold-containing solution gold extraction is simple and easy to implement, but has the disadvantages of low utilization rate and easy secondary pollution.

[0004] In order to meet the requirement of efficient and convenient gold recovery, it is urgent to develop a new technology to break the complex stability of gold cyanide under alkaline conditions and recover gold from low-concentration gold cyanide water. As a rising star in zero-valent metals, zero-valent aluminum (Al 0 ) has more excellent performance and is developing a new type of water treatment technology. Al 0 has a very negative redox potential (E0(Al 3+ / Al 0 ​) = - 2.33 V), is stronger and has amphoteric properties, and still has high activity under strong alkaline conditions, and is expected to achieve efficient direct reduction of gold cyanide complexes. However, the existence of the oxide film on the aluminum surface inhibits the release of its activity, and the in-situ generation of zero-valent copper on the surface of the copper-modified zero-valent aluminum forms an aluminum-copper primary cell to promote electron transport. Based on this, the present application uses a one-step method of adding copper-modified aluminum composites, and for the first time uses zero-valent aluminum materials to achieve the reduction and recovery of gold in gold cyanide complex water 0 . SUMMARY

[0005] The present application aims to overcome the application bottleneck of zero-valent aluminum to prepare copper-modified aluminum composites, and to achieve the direct reduction and destruction of gold cyanide complexes by simply adding them in a one-step method.

[0006] The copper-modified micron aluminum new material (copper-modified aluminum composite material) is obtained by mechanical ball milling with the aid of copper salt. The cutting action of the copper salt crystal causes the oxide film on the surface of the micron aluminum to be destroyed, and Cu 0 is locally generated and covers the aluminum surface to prevent secondary passivation of the material. In addition, the formation of aluminum-copper microcells improves the electron transport of the material. Based on this, the copper-modified aluminum composite material can achieve reduction and destruction in strong alkaline cyanide gold-containing wastewater or gold extraction liquid, and high-valence Au is directly reduced to Au 0 on the surface of the material. The present application has a wide source of materials, low price, and simple preparation process, and can maintain high activity and high electron utilization rate under strong alkaline conditions.

[0007] The present application provides a preparation method of copper-modified aluminum composite material and its application to reducing and destroying gold cyanide-containing wastewater or gold extraction liquid and simultaneously recovering gold from it under alkaline conditions, and the specific steps are as follows:

[0008] P1. Preparation method of copper-modified aluminum composite material: mix zero-valent aluminum powder and copper salt, use grinding balls as grinding medium, and ball mill in an inert gas protective atmosphere. Then the copper-modified aluminum composite material can be obtained;

[0009] P2. Add the copper-modified aluminum composite material to the cyanide gold-containing wastewater or gold extraction liquid, continuously stir / shock, ensure that the material and gold cyanide ions in the water are in full contact, and keep it in a suspended state to carry out the reduction and destruction reaction.

[0010] The molar ratio of the zero-valent aluminum powder and the copper salt in step P1 is 5-200:1. The grinding balls are one or more of zirconia grinding balls, chromium alloy cast iron grinding balls, martensitic spheroidal iron grinding balls, steel balls, and agate balls. The copper salt includes, but is not limited to, CuSO4 and its hydrates, CuCl2 and its hydrates, Cu(NO3)2 and its hydrates, and the like. The inert gas is nitrogen, helium, argon, or the like.

[0011] In step P2, the copper-modified aluminum composite material is added in an amount of 0.5-4 g / L (not limited thereto, and the amount depends on the content of the gold cyanide complex in the water, calculated as the gold element).

[0012] In step P2, the water needs to be deoxygenated (continuous inert gas is introduced, or after a certain time, the air is isolated and operated in a closed condition), and the dissolved oxygen concentration is maintained at <0.5 mg / L.

[0013] After the reaction in step P2 is completed, the stirring / vibration is stopped, and the solid powder containing Au 0 is recovered by negative pressure filtration and freeze-drying.

[0014] The copper-modified aluminum composite material can be prepared by a simple mechanical ball milling process. The cutting effect of the copper salt crystals can destroy the oxide film on the micron aluminum surface, and the solid-phase chemical reaction can generate Cu 0 in situ to locally cover the aluminum surface, thereby inhibiting the secondary formation of the passivation film. In addition, the formation of the aluminum-copper galvanic cell can improve the electron utilization rate of the material.

[0015] The advantages of the present application are as follows:

[0016] (1) The copper salt used in the present application is an industrial-grade raw material, which can be used on a large scale. Aluminum resources are abundant, and micron aluminum is low in price.

[0017] (2) The preparation method of the copper-modified aluminum composite material is carried out at room temperature and normal pressure, and the reaction conditions are mild and simple. The one-step method is suitable for industrial production.

[0018] (3) The removal method described in the present application is simple. The material can be directly added under the original alkaline conditions of the cyanide gold-containing wastewater or the gold extraction liquid, without other pretreatment or repeated pH adjustment, which is convenient and fast.

[0019] (4) The present application solves the problem of the surface passivation film hindering electron release in the actual application of zero-valent aluminum, and makes it have certain stability and sustained utilization capacity.

[0020] (5) The present application can effectively break the complex and recover gold in a strong alkaline pH range, various ion interferences, and various real water environments, realizing the resource utilization of wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Effect diagram of Au(CN)2- removal by copper modified aluminum composites prepared by ball milling micron aluminum with CuSO4·5H2O, CuCl2·2H2O, Cu(NO3)2·3H2O respectively. -

[0022] Figure 2 Effect diagram of Au(CN)2- removal by copper modified aluminum composites prepared by different ball milling time. -

[0023] Figure 3 Effect diagram of Au(CN)2- removal by copper modified aluminum composites prepared by different ball milling speed. -

[0024] Figure 4 Effect diagram of Au(CN)2- removal by copper modified aluminum composites, micron aluminum alone, CuSO4·5H2O alone, micron aluminum ball milled alone, CuSO4·5H2O ball milled alone, and micron aluminum physically mixed with CuSO4·5H2O. -

[0025] Figure 5 Effect diagram of Au(CN)2- removal by copper modified aluminum composites under different pH conditions. -

[0026] Figure 6 Effect diagram of Au(CN)2- removal by copper modified aluminum composites under different dissolved oxygen concentrations. -

[0027] Figure 7 Effect diagram of Au(CN)2- removal by copper modified aluminum composites with different dosages. -

[0028] Figure 8 Effect diagram of Au(CN)2- removal by copper modified aluminum composites in cyclic degradation. -

[0029] Figure 9 Effect diagram of Au(CN)2- removal by copper modified aluminum composites under different coexisting substance interference. -

[0030] Figure 10 XPS spectrum of the solid filtered out after the reaction of copper modified aluminum composites with Au(CN)2- was complete. - DETAILED DESCRIPTION

[0031] ​​​​​​​​​​The application is further described below in combination with specific implementation cases, and the specific implementation cases described are only used to explain the application and do not limit the application.

[0032] Example 1 Removal of Au(CN)2 in water by different copper salt ball-milled copper modified aluminum composites - Effect comparison

[0033] Micron-sized zero-valent aluminum powder was mixed with CuSO4·5H2O, CuCl2·2H2O and Cu(NO3)2·3H2O respectively according to a certain molar ratio. Ball-milling was performed in a nitrogen atmosphere to obtain different copper modified aluminum composites. Au(CN)2 - simulation water with a concentration of 20 mg / L (calculated based on gold elements) was prepared, and the initial pH of the Au(CN)2 - simulation water was adjusted to 10.5, nitrogen was used to remove dissolved oxygen in water and isolate air, then different materials were directly added and oscillated to mix uniformly and maintain a suspended state to maintain the reduction reaction, and Au(CN)2 - remaining in water was analyzed by sampling and filtering at regular time intervals. As shown in Figure 1 , different copper salt ball-milled materials all have good removal effect, proving that aluminum can mechanically and chemically reduce Cu(II) to Cu 0 in the ball-milling process, and anions have little effect.

[0034] Example 2 Influence of ball-milling time on removal of Au(CN)2 in water by copper modified aluminum composites - Effect comparison

[0035] Micron-sized zero-valent aluminum powder was mixed with CuSO4·5H2O according to a certain molar ratio. Ball-milling was performed in a nitrogen atmosphere. Different copper modified aluminum composites were obtained by continuously ball-milling on the ball-milling machine for 0.5 h, 1 h, 2 h and 3 h respectively. Au(CN)2 - simulation water with a concentration of 20 mg / L (calculated based on gold elements) was prepared, and the initial pH of the Au(CN)2 - simulation water was adjusted to 10.5, nitrogen was used to remove dissolved oxygen in water and isolate air, then different materials were directly added and oscillated to mix uniformly and maintain a suspended state to maintain the reduction reaction, and Au(CN)2 - remaining in water was analyzed by sampling and filtering at regular time intervals. As shown in Figure 2 , shorter ball-milling time can fully exert the activity of the material.

[0036] Example 3 Influence of ball-milling speed on removal of Au(CN)2 in water by copper modified aluminum composites - Effect comparison

[0037] The micron-sized zero-valent aluminum powder is mixed with CuSO4·5H2O according to a certain molar ratio. Ball milling is performed in a nitrogen atmosphere, and the rotating speed of the ball mill is adjusted to 100 rounds, 150 rounds, 200 rounds, 250 rounds and 300 rounds respectively to obtain different copper-modified aluminum composites. Au(CN)2 - is prepared with a concentration of 20 mg / L (in terms of gold elements). The simulated water is adjusted to Au(CN)2 - at room temperature, and the initial pH of the simulated water is adjusted to 10.5. Nitrogen is used to remove dissolved oxygen in the water and isolate air, and then different materials are directly added to the water and shaken to mix uniformly and keep a suspended state to maintain the reduction reaction. Samples are taken at regular intervals for filtration and analysis of the remaining Au(CN)2 - in the water. As shown in Figure 3 , higher ball milling speed is more conducive to the performance of the material.

[0038] The preparation method of the copper-modified aluminum composite material described below is as follows: micron-sized zero-valent aluminum powder and CuSO4·5H2O are mixed according to a molar ratio of 30:1, and ball milling is performed in a nitrogen atmosphere. The rotating speed of the ball mill is maintained at 300 rounds, and the copper-modified aluminum composite material can be obtained after 1 h of ball milling.

[0039] Example 4: Effect comparison of different materials for removing Au(CN)2 - from water

[0040] Au(CN)2 - with a concentration of 20 mg / L (in terms of gold elements) is prepared. The simulated water is adjusted to Au(CN)2 - at room temperature, and the initial pH of the simulated water is adjusted to 10.5. Nitrogen is used to remove dissolved oxygen in the water and isolate air, and then the copper-modified aluminum composite material is directly added to the water and shaken to mix uniformly and keep a suspended state to maintain the reduction reaction. Samples are taken at regular intervals for filtration and analysis of the remaining Au(CN)2 - in the water. At the same time, commercial micron-sized zero-valent aluminum, micron-sized zero-valent aluminum ball-milled alone, commercial CuSO4·5H2O, CuSO4·5H2O ball-milled alone, and physical mixing of micron-sized aluminum and CuSO4·5H2O are used as controls. As shown in Figure 4 , commercial micron-sized zero-valent aluminum, micron-sized zero-valent aluminum ball-milled alone, commercial CuSO4·5H2O, CuSO4·5H2O ball-milled alone, and physical mixing of micron-sized aluminum and CuSO4·5H2O can only remove a small amount of Au(CN)2 - , but the method of the present application can efficiently decomplex Au(CN)2 - by more than 99%, proving the feasibility of the method for removing Au(CN)2 - .

[0041] Example 5: Removal of Au(CN)2by copper-modified aluminum composite under different pH conditions -

[0042] Au(CN)2with a concentration of 20 mg / L (in terms of gold element) was prepared - The simulated water was adjusted to Au(CN)2at room temperature - The initial pH of the simulated water was 9.5, 10.0, 10.5, 11.0, 11.5, and 12.0, respectively. Nitrogen was used to remove dissolved oxygen in the water and isolate air. Then, the copper-modified aluminum composite was directly added to the water and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals for filtration and analysis of the remaining Au(CN)2in the water - As shown in Figure 5 , the copper-modified aluminum composite can effectively remove Au(CN)2by decomplexation in most strongly alkaline environments - .

[0043] Example 6: Removal of Au(CN)2by copper-modified aluminum composite under different dissolved oxygen concentrations -

[0044] Au(CN)2with a concentration of 20 mg / L (in terms of gold element) was prepared - The simulated water was adjusted to Au(CN)2at room temperature - The initial pH of the simulated water was adjusted to 10.5, and three treatments were performed: nitrogen treatment, no treatment, and oxygen treatment. The initial dissolved oxygen content in the water was significantly different. Then, the copper-modified aluminum composite was directly added to the water and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals for filtration and analysis of the remaining Au(CN)2in the water - As shown in Figure 6 , this method must be performed under deoxygenated conditions to efficiently reduce and decomplex Au(CN)2 - .

[0045] Example 7: Removal of Au(CN)2by copper-modified aluminum composite with different dosages -

[0046] Au(CN)2with a concentration of 20 mg / L (in terms of gold element) was prepared at room temperature - The initial pH of the simulated water was adjusted to 10.5, and nitrogen was used to remove dissolved oxygen in the water and isolate air. Then, 0.25 g / L, 0.5 g / L, 1.0 g / L, 1.5 g / L, and 2.0 g / L of copper-modified aluminum composite were added to the water, respectively, and shaken to mix uniformly and maintain a suspended state to maintain the reduction reaction. Samples were taken at regular intervals for filtration and analysis of the remaining Au(CN)2in the water - As shown in​Figure 7 As shown, less material dosage can achieve high efficient and fast degradation of Au(CN)2 - .

[0047] Example 8 Copper-modified aluminum composite material cyclically degrading Au(CN)2 -

[0048] Au(CN)2 - was prepared at a concentration of 20 mg / L (in terms of gold element) in simulated water. Under room temperature conditions, the pH of the simulated water was adjusted to 10.5, and nitrogen was used to remove dissolved oxygen in the water and isolate air. Then, the copper-modified aluminum composite material was directly added to the simulated water and shaken to mix it evenly and keep it in a suspended state to maintain the reduction reaction. Samples were taken at regular time intervals and filtered to analyze the remaining Au(CN)2 - in the water. - After each reaction, the solid material was separated from the solution by suction filtration, and after freeze-drying, the above steps were repeated. As shown in Figure 8 , after five cycles, the copper-modified aluminum composite material still had good activity, proving that the material had a certain degree of reusability.

[0049] Example 9 Copper-modified aluminum composite material decomplexing and removing Au(CN)2 - under interference of different coexisting substances

[0050] Au(CN)2 - was prepared at a concentration of 20 mg / L (in terms of gold element) in simulated water. Different coexisting substances were added to the simulated water at the same molar concentration. Under room temperature conditions, the initial pH of the simulated water was adjusted to 10.5, and nitrogen was used to remove dissolved oxygen in the water and isolate air. Then, the copper-modified aluminum composite material was directly added to the simulated water and shaken to mix it evenly and keep it in a suspended state to maintain the reduction reaction. Samples were taken at regular time intervals and filtered to analyze the remaining Au(CN)2 - in the water. Figure 9 As shown, the copper-modified aluminum composite material could effectively shield the interference of multiple coexisting ions, proving that the copper-modified aluminum composite material had a certain anti-interference ability.

[0051] Example 10 Copper-modified aluminum composite material and Au(CN)2 - after sufficient reaction

[0052] The serum bottle after the reaction was taken out of the shaker, and solid-liquid separation was performed by suction filtration. The filter paper containing the solid powder was placed in a petri dish, and after freeze-drying, the obtained material was analyzed by X-ray electron spectroscopy. As shown in Figure 10 , Au 0 was generated on the surface of the material, i.e., the recovered Au-attached material.

Claims

1. A method for direct reduction of the complexed gold and simultaneous recovery of gold from alkaline cyanide containing gold-containing wastewater or pregnant solution of gold extraction, characterized in that, The prepared copper-modified aluminum composite material is added to the alkaline cyanide gold-containing wastewater or gold extraction liquid, the wastewater or liquid is subjected to oxygen removal operation, inert gas is continuously introduced, or after being introduced for a certain time, air is isolated and the operation is carried out in a closed condition, the dissolved oxygen concentration is maintained to be less than 0.5 mg / L; then, the copper-modified aluminum composite material and the pollutants are fully mixed through oscillation / stirring, reduction and complexation are carried out, and gold is recovered. The preparation method of the copper-modified aluminum composite material comprises the following steps: zero-valent aluminum powder and copper salt are mixed according to a molar ratio of 5-200:1, a grinding ball is used as a grinding medium, and ball milling is carried out in an inert gas protection atmosphere; the copper-modified aluminum composite material can be obtained after one-step ball milling.

2. The method of claim 1, wherein, The grinding ball is one or more of a zirconia grinding ball, a chromium alloy cast iron grinding ball, a martensitic spheroidal iron grinding ball, a steel ball and an agate ball, the copper salt includes but is not limited to one or more of CuSO4 and a hydrate thereof, CuCl2 and a hydrate thereof, Cu(NO3)2 and a hydrate thereof, and the inert gas is one or more of nitrogen, helium or argon.

3. The method of claim 1, wherein, The addition amount of the copper-modified aluminum composite material is 0.1-5 g / L.

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