Method for removing cyanide in cyanidation tailings through oxidation of metal activated persulfate

Abstract

The invention belongs to the technical field of solid pollutant treatment, and particularly relates to a method for removing cyanide in cyanidation tailings through metal activated persulfate oxidation. The problems that different cyanide removal mechanisms are different, the removal efficiency is low, the cost is high, secondary pollution is easily caused and the like exist in treatment of the cyanidation tailings. The tailings are subjected to cyanogen reduction treatment by adopting a stage treatment method. The method comprises the following steps: firstly, crushing the tailings to prepare a charcoal-loaded metal composite material Me / BC; when free cyanide in the tailings is smaller than or equal to 50 mg / kg, Me / BC activated persulfate is used for conducting cyanide reduction treatment on the tailings; when the tailings contain free cyanide gt; when the concentration is 50 mg / kg, free cyanides in the tailings are removed through leaching, and then Me / BC is used for activating persulfate to degrade strong complex state cyanides in the tailings. By adopting the method, the problems that complex cyanide is difficult to remove by a single leaching method and persulfate is large in dosage and high in cost in a single oxidation method can be solved, and the cascade cyanogen removal method is efficient, low in cost and free of secondary pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of solid pollutant treatment, and in particular relates to a method for removing cyanide in cyanide tailings by metal-activated persulfate oxidation. Background Art

[0002] Cyanide tailings contain a large amount of highly toxic cyanide. Milligrams of cyanide can cause animal poisoning and death and crop yield reduction in a short period of time, and are a type of hazardous waste. The gold industry produces about 100 million tons of cyanide tailings each year, including 70 million tons of low-grade cyanide heap leaching tailings. They are mainly disposed of by open-air stacking and tailings pond storage, which not only occupies a large amount of land, but also produces a large amount of cyanide-containing wastewater after being washed by rainwater, posing a great threat to the surrounding environment.

[0003] At present, the treatment methods of cyanide in cyanide tailings are mainly physical, chemical and biological methods. Among them, the physical method mainly includes natural degradation, backfilling and other methods. Natural degradation refers to the decomposition of cyanide by spontaneous physical and chemical methods such as natural oxidation, volatilization and sunlight decomposition. This method is inexpensive but will be affected by many factors, such as the type and concentration of cyanide, pH value, temperature, sunlight, etc. Therefore, it is difficult to ensure safety and the degree of slag degradation. Biological method refers to the method of using the metabolism of microorganisms to convert cyanide in wastewater into harmless or low-toxic substances, mainly including biological oxidation, biological adsorption and biological transformation, but it has the disadvantages of low treatment efficiency, poor adaptability and strict operating conditions. Chemical method refers to the separation of cyanide from cyanide tailings by changing the chemical form of cyanide through chemical reactions, including alkaline chlorination method, Inco method, persulfate oxidation method, etc.

[0004] The leaching method mainly uses high-pressure water flow to transfer the free cyanide attached to the surface of the cyanide tailings from the solid phase to the liquid phase, thereby reducing the total cyanide content in the tailings. It has the advantages of low cost and convenient operation. However, the leaching method is difficult to remove complexed cyanide.

[0005] The persulfate oxidation method mainly utilizes sulfate radicals generated after persulfate activation to oxidize and remove strongly complexed cyanide. The persulfate oxidation method has high removal efficiency, low cost, and no secondary pollution. However, due to the free cyanide attached to the surface of cyanide residue, the amount of persulfate used is large, the cyanide reduction efficiency is reduced, and the cost is increased. Therefore, it is of practical significance to develop an efficient, low-cost and secondary pollution-free method for removing cyanide from cyanide tailings. Summary of the invention

[0006] Aiming at the problems that different cyanides in cyanide tailings have different removal mechanisms, low removal efficiency, high cost, and easy secondary pollution, the present invention provides a metal-activated persulfate oxidation decyanation method, which can effectively remove different types of cyanides in cyanide tailings, and at the same time has high removal efficiency, low cost, and no secondary pollution.

[0007] The method for removing cyanide from cyanide tailings by metal-activated persulfate oxidation is achieved by the following technical scheme:

[0008] (1) analyzing the types of cyanide (i.e., free cyanide and complexed cyanide) and the content of free cyanide in the cyanide tailings; crushing the cyanide tailings to obtain cyanide tailings powder;

[0009] (2) Preparation of Me / BC composite material: crushing forestry or agricultural waste and mixing with metal source, and pyrolyzing to prepare biochar-loaded metal composite material Me / BC; the metal source includes nano zero-valent iron particles and nano zero-valent copper particles;

[0010] (3) After mixing the cyanide tailings powder with water, Me / BC and persulfate are added to carry out cyanide reduction reaction;

[0011] (4) After the reaction is completed, the reaction system is quenched, and the solid-liquid separation of the reaction system is carried out to obtain cyanide removal tailings and cyanide removal liquid.

[0012] In step (1), the cyanide tailings are crushed to 30-100 meshes.

[0013] In step (2), the mass ratio of forestry or agricultural waste to metal source is 100:(0.5-5), and pyrolysis is carried out at 300°C-900°C for 2-5 hours. The pyrolysis process is carried out in an anaerobic environment. The forestry or agricultural waste includes stumps, fallen leaves, weeds, straw, sawdust, shrubs, etc.

[0014] In step (3), the cyanide tailings powder and water are uniformly mixed according to a solid-liquid ratio of 1:1 to 1:20, the mass ratio of Me / BC to persulfate is (0.05:1) to (1:1) (for example, the mass ratio is 0.05:1, 0.1:1, 0.2:1, 0.5:1, etc.), and the amount of persulfate added is 1% to 20% of the mass of the cyanide tailings (for example, 2.5%, 5%, 7.5%, 10%, 20%, etc.);

[0015] The temperature of the cyanide reduction reaction is 30° C. to 50° C., and the reaction time is 2 hours to 12 hours.

[0016] Step (4) comprises the following contents: after the reaction is completed, the temperature is lowered to room temperature and the reaction system is quenched, the reaction system is subjected to a solid-liquid separation to obtain a solid phase and a liquid phase, 5% to 20% deionized water is added to the solid phase for mixing and washing, solid-liquid separation is performed again to obtain a cyanide removal residue and a washing liquid, the washing liquid is mixed with the liquid phase to obtain a cyanide removal liquid; and the cyanide contents in the cyanide removal residue and the cyanide removal liquid are respectively determined.

[0017] Preferably, in step (1), when the content of free cyanide in the cyanide tailings is ≤50 mg / kg, the above-mentioned metal activated persulfate oxidation method can be directly used to remove cyanide in the cyanide tailings;

[0018] When the content of free cyanide in the cyanide tailings exceeds 50 mg / kg, the free cyanide in the cyanide tailings is first removed by elution, and then the cyanide tailings are subjected to cyanide reduction treatment using the above-mentioned metal activated persulfate oxidation method to remove the strongly complexed cyanide in the cyanide tailings.

[0019] The elution includes the following contents:

[0020] (1.1) mixing the cyanide tailings powder with water at a solid-liquid ratio of 1:1 to 1:10, stirring and eluting for 10 to 60 minutes at a stirring speed of 100 to 600 rpm, centrifugally filtering after shaking, and drying the obtained filter residue to constant weight;

[0021] (1.2) After repeating step (1.1) for 2 to 3 times, the mud-water mixture is separated by centrifugation at a centrifugal speed of 4000 to 6000 rpm for 3 to 5 minutes. The supernatant is returned to step (1.1). The mud cake is placed in an oven and dried at 40° C. to 70° C. for 6 to 12 hours to obtain a fully dried washed cyanide tailings powder.

[0022] Advantages of the invention

[0023] Compared with the prior art, the present invention can achieve the removal of cyanide in cyanide tailings. In the present invention, leaching and cyanide removal is mainly to remove free cyanide attached to the surface of cyanide slag. After elution with distilled water, 40% to 60% of free cyanide can be removed. This type of cyanide can slowly hydrolyze to form ammonium salt and formate at room temperature. The increase in the number of leaching times and the extension of the leaching time can fully remove the free cyanide attached to the surface of cyanide slag. Metal-activated persulfate cyanide removal is to activate persulfate by the electron transfer process of transition metals such as iron, copper, manganese, zinc, cobalt, and molybdenum. Among them, iron is most used as an efficient activator because of its environmental friendliness and low cost. Highly active sulfate anion radicals are generated through the chemical activation of iron ions to destroy persistent and non-volatile inorganic pollutants in cyanide slag and convert them into thiocyanate. Cyanide is oxidized to thiocyanate by persulfate in the presence of trivalent iron ions. Thiocyanate can be used for mine remediation because stricter environmental regulations are implemented to limit the discharge of thiocyanate into tailings dams. This can also serve as a cost-effective method to minimize and recover cyanide in mining facilities.

[0024] The present invention adopts a metal-activated persulfate oxidation method to remove cyanide when the free cyanide content of the tailings is ≤50 mg / kg; when the free cyanide content of the tailings is >50 mg / kg, free cyanide in the tailings is first removed by leaching, and then Me / BC-activated persulfate is used to degrade the strongly complexed cyanide in the tailings, and leaching and metal-activated persulfate oxidation are used to collaboratively treat and remove cyanide. The present invention performs step-by-step removal for different types of cyanide, which can not only solve the problem of complexed cyanide that is difficult to remove by a single leaching method, but also solve the problem of large persulfate usage and high cost in a single oxidation method, thereby improving reaction efficiency, reducing processing costs, and having no secondary pollution, and having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of removing cyanide from cyanide tailings by metal activated persulfate oxidation. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention is clearly and completely described below in conjunction with the embodiments and the accompanying drawings. It should be pointed out that the embodiments described in the present invention are only used to further explain and illustrate, rather than to limit the scope of application. Based on the present invention, all other embodiments obtained by those skilled in the art without making creative work belong to the protection scope of the present invention.

[0027] The free cyanide content in the sample is determined by isonicotinic acid-barbituric acid spectrophotometry. The process of removing cyanide from cyanide tailings by metal activated persulfate oxidation of the present invention is as follows: Figure 1 shown.

[0028] Example 1

[0029] Leaching + metal activation persulfate oxidation method

[0030] (1) The cyanide tailings produced by a gold smelting enterprise in Shandong were collected, and the free cyanide content was 65.03 mg / kg. The free cyanide in the cyanide tailings was firstly removed by elution, and then the strongly complexed cyanide in the cyanide tailings was removed by oxidation with metal-activated persulfate; the cyanide tailings were crushed into 30 meshes to obtain cyanide tailings powder;

[0031] (1.1) mixing the cyanide tailings powder with water at a solid-liquid ratio of 1:5, stirring and eluting for 30 minutes at a stirring speed of 600 rpm; centrifuging and filtering after shaking, and drying the obtained filter residue to constant weight;

[0032] (1.2) After repeating the rinsing operation in step (1.1) twice, the mud-water mixture was centrifuged at a centrifugal speed of 5000 rpm for 3 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven at 60° C. and dried for 6 hours to obtain a fully dried washed cyanide tailings powder;

[0033] (2) Preparation of Fe 0 / BC composite material: The straw was crushed and mixed with nano zero-valent iron particles at a mass ratio of 100:0.5, and pyrolyzed at 500℃ for 2 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0034] (3) Weigh 10 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:5, and place it in a 50 ml centrifuge tube; add sodium persulfate in an amount of 10% of the mass of the cyanide tailings, Fe 0 The mass ratio of BC to sodium persulfate is 0.25:1. Sodium persulfate and Fe are added. 0 / BC. Place the centrifuge tube in a constant temperature oscillator to avoid light and react at 30°C for 6 hours;

[0035] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 4000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 5% deionized water is added to the solid phase, mixed and washed with water. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0036] The total cyanide content in the decyanide tailings and decyanide liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanide tailings after leaching and metal-activated persulfate oxidation treatment was 11.382 mg / kg, and the total cyanide concentration in the decyanide liquid was 0.046 mg / L, which was lower than 0.1 mg / L, meeting the toxicity leaching requirements of the "Technical Specifications for Cyanide Slag Pollution Control in the Gold Industry" (HJ943-2018).

[0037] Example 2

[0038] Leaching + metal activation persulfate oxidation method

[0039] (1) collecting cyanide tailings produced by the gold smelting industry, with a free cyanide content of 102.71 mg / kg, first eluting to remove the free cyanide in the cyanide tailings, and then using metal-activated persulfate oxidation to remove the strongly complexed cyanide in the cyanide tailings; crushing the cyanide tailings into 30 meshes to obtain cyanide tailings powder;

[0040] (1.1) The cyanide tailings powder was mixed with water at a solid-liquid ratio of 1:10, stirred and rinsed for 60 minutes at a stirring speed of 350 rpm; centrifuged and filtered after shaking, and the obtained filter residue was dried to constant weight;

[0041] (1.2) After repeating the rinsing operation in step (1.1) twice, the mud-water mixture was centrifuged at a speed of 4000 rpm for 5 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven at 50° C. and dried for 6 hours to obtain a fully dried washed cyanide tailings powder;

[0042] (2) Preparation of Fe 0 / BC composite material: The tree stumps were crushed and mixed with nano zero-valent iron particles at a mass ratio of 100:1, and pyrolyzed at 600℃ for 3 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0043] (3) Weigh 2 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:10, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 5% of the mass of the cyanide tailings, Fe 0 The mass ratio of BC to sodium persulfate is 0.5:1. Sodium persulfate and Fe are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at a temperature of 35°C for 8 hours;

[0044] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 6000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0045] The total cyanide content in the decyanide tailings and decyanide liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanide tailings after leaching and metal-activated persulfate oxidation treatment was 17.571 mg / kg, and the total cyanide concentration in the decyanide liquid was 0.067 mg / kg, which was lower than 0.1 mg / L, meeting the toxicity leaching requirements of the "Technical Specifications for Cyanide Slag Pollution Control in the Gold Industry" (HJ943-2018).

[0046] Example 3

[0047] Leaching + metal activation persulfate oxidation method

[0048] (1) The cyanide tailings produced by a gold smelting enterprise were collected, and the free cyanide content was 63.81 mg / kg. The free cyanide in the cyanide tailings was firstly removed by elution, and then the strongly complexed cyanide in the cyanide tailings was removed by oxidation with metal-activated persulfate; the cyanide tailings were crushed into 100 meshes to obtain cyanide tailings powder;

[0049] (1.1) The cyanide tailings powder was mixed with water at a solid-liquid ratio of 1:5, stirred and rinsed for 60 minutes at a stirring speed of 600 rpm, centrifuged and filtered after shaking, and the obtained filter residue was dried to constant weight;

[0050] (1.2) After repeating the rinsing operation in step (1.1) for 3 times, the mud-water mixture was centrifuged at a speed of 6000 rpm for 3 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven and dried at 40°C for 10 hours to obtain a fully dried washed cyanide tailings powder; (2) Preparation of Fe 0 / BC composite material: The fallen leaves and weeds were crushed and mixed with nano zero-valent iron particles in a mass ratio of 100:5, and pyrolyzed at 800℃ for 4 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0051] (3) Weigh 3 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:15, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 1% of the mass of the cyanide tailings, Fe 0The mass ratio of BC to sodium persulfate is 1:1. Sodium persulfate and Fe are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at 40°C for 4 hours;

[0052] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 6000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0053] The total cyanide content in the decyanide tailings and decyanide liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanide tailings after leaching and metal-activated persulfate oxidation treatment was 13.751 mg / kg, and the total cyanide concentration in the decyanide liquid was 0.059 mg / kg, which was lower than 0.1 mg / L, meeting the toxicity leaching requirements of the "Technical Specifications for Cyanide Slag Pollution Control in the Gold Industry" (HJ943-2018).

[0054] Example 4

[0055] Metal-activated persulfate oxidation

[0056] (1) The cyanide tailings of a certain abandoned tailings pond were collected, and the free cyanide content was 41.82 mg / kg. The free cyanide content was low, and the free cyanide and strongly complexed cyanide in the cyanide tailings could be directly removed by oxidation with metal-activated persulfate without leaching; the cyanide tailings were crushed into 30 meshes to obtain cyanide tailings powder;

[0057] (2) Preparation of Fe 0 / BC composite material: Sawdust was crushed and mixed with nano zero-valent iron particles in a mass ratio of 100:2.5, and pyrolyzed at 700℃ for 4 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0058] (3) Weigh 2 g of cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:20, and place it in a 50 ml centrifuge tube; add sodium persulfate in an amount of 7.5% of the mass of the cyanide tailings, Fe 0 The mass ratio of BC to sodium persulfate is 0.75:1. Sodium persulfate and Fe are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at a temperature of 45°C for 4 hours;

[0059] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 6000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 15% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide-removing tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide-removing liquid.

[0060] The total cyanide content in the decyanide tailings and decyanide liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanide tailings after treatment with metal-activated persulfate oxidation method was 10.271 mg / kg, and the total cyanide concentration in the decyanide liquid was 0.039 mg / kg, which was lower than 0.1 mg / L, meeting the toxicity leaching requirements of the "Technical Specifications for Cyanide Slag Pollution Control in the Gold Industry" (HJ943-2018).

[0061] Example 5

[0062] Leaching + metal activation persulfate oxidation method

[0063] (1) Collecting cyanide tailings accumulated in a gold smelter, the free cyanide content is 88.21 mg / kg, first eluting to remove the free cyanide in the cyanide tailings, and then using metal-activated persulfate oxidation to remove the strongly complexed cyanide in the cyanide tailings; crushing the cyanide tailings into 50 meshes to obtain cyanide tailings powder;

[0064] (1.1) mixing the cyanide tailings powder with water at a solid-liquid ratio of 1:10, stirring and eluting for 30 minutes at a stirring speed of 400 rpm, centrifuging and filtering after shaking, and drying the obtained filter residue to constant weight;

[0065] (1.2) After repeating the rinsing operation in step (1.1) for 3 times, the mud-water mixture was centrifuged at a speed of 5000 rpm for 5 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven and dried at 70°C for 6 hours to obtain a fully dried washed cyanide tailings powder; (2) Preparation of Cu 0 / BC composite material: corn stalks were crushed and mixed with nano zero-valent copper particles at a mass ratio of 100:2, and pyrolyzed at 400°C for 12 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain biochar-loaded nano zero-valent copper composite material Cu 0 / BC;

[0066] (3) Weigh 5 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:5, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 5% of the mass of the cyanide tailings, Cu 0The mass ratio of BC to sodium persulfate is 0.2:1. Sodium persulfate and Cu are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at a temperature of 35°C for 6 hours;

[0067] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 5000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% ml of deionized water is added to the solid phase to mix and wash. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0068] The total cyanide content in the decyanide tailings and decyanide liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanide tailings after leaching and metal-activated persulfate oxidation treatment was 25.137 mg / kg, and the total cyanide concentration in the decyanide liquid was 0.082 mg / kg, which was lower than 0.1 mg / L, meeting the toxicity leaching requirements of the "Technical Specifications for Cyanide Slag Pollution Control in the Gold Industry" (HJ943-2018).

[0069] Comparative Example 1

[0070] The cyanide tailings collected and the method for removing cyanide are the same as those in Example 1, except that in step (3), the cyanide tailings after leaching are oxidized and removed by alkali-activated persulfate.

[0071] (1) The cyanide tailings produced by a gold smelting enterprise in Shandong were collected, and the free cyanide content was 65.03 mg / kg. The free cyanide in the cyanide tailings was firstly removed by elution, and then the strongly complexed cyanide in the cyanide tailings was removed by oxidation with alkali-activated persulfate; the cyanide tailings were crushed into 30 meshes to obtain cyanide tailings powder;

[0072] (1.1) The cyanide tailings powder was mixed with water at a solid-liquid ratio of 1:5, stirred and rinsed for 30 minutes at a stirring speed of 600 rpm; centrifuged and filtered after shaking, and the obtained filter residue was dried to constant weight;

[0073] (1.2) After repeating the rinsing operation in step (1.1) twice, the mud-water mixture was centrifuged at a centrifugal speed of 5000 rpm for 3 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven at 60° C. and dried for 6 hours to obtain a fully dried washed cyanide tailings powder;

[0074] (2) No prepared Fe 0 / BC composite steps;

[0075] (3) Weigh 10 grams of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:5, and place it in a 50 ml centrifuge tube; add sodium hydroxide and sodium persulfate at a sodium persulfate addition amount of 10% of the mass of the cyanide tailings and a mass ratio of sodium hydroxide to sodium persulfate of 0.25:1. Place the centrifuge tube in a constant temperature oscillator to avoid light for reaction, the reaction temperature is 30°C, and the reaction time is 6 hours;

[0076] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 4000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 5% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0077] The total cyanide content in the decyanation tailings and decyanation liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanation tailings after coordinated treatment with elution and alkaline-activated persulfate oxidation was 22.157 mg / kg, and the total cyanide concentration in the decyanation liquid was 0.075 mg / kg.

[0078] Compared with the results of Example 1, it can be seen that the efficiency of cyanide degradation by alkali-activated persulfate is lower than that by metal-activated persulfate method, which may be due to the fact that the amount of sodium hydroxide used is too small and the optimal amount of activated persulfate is not reached. That is, for the same tailings conditions and drug dosage, the metal-activated persulfate oxidation method of the present invention can significantly improve the cyanide removal effect of tailings.

[0079] Comparative Example 2

[0080] The cyanide tailings raw material and the decyanation method are the same as those in Example 2, except that in step (1), the cyanide tailings raw material is directly decyanated without crushing, and the particle size of the cyanide tailings raw material is 0.1 mm to 10 mm.

[0081] (1) Collect the cyanide tailings from the gold smelting industry, the free cyanide content is 102.71 mg / kg, first remove the free cyanide in the cyanide tailings by elution, and then use metal-activated persulfate oxidation to remove the strongly complexed cyanide in the cyanide tailings;

[0082] (1.1) The cyanide tailings powder was mixed with water at a solid-liquid ratio of 1:10, stirred and rinsed for 60 minutes at a stirring speed of 350 rpm; centrifuged and filtered after shaking, and the obtained filter residue was dried to constant weight;

[0083] (1.2) After repeating the rinsing operation in step (1.1) twice, the mud-water mixture was centrifuged at a speed of 4000 rpm for 5 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven at 50° C. and dried for 6 hours to obtain a fully dried washed cyanide tailings powder;

[0084] (2) Preparation of Fe 0 / BC composite material: The tree stumps were crushed and mixed with nano zero-valent iron particles at a mass ratio of 100:1, and pyrolyzed at 600℃ for 3 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0085] (3) Weigh 2 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:10, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 5% of the mass of the cyanide tailings, Fe 0 The mass ratio of BC to sodium persulfate is 0.5:1. Sodium persulfate and Fe are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at a temperature of 35°C for 8 hours;

[0086] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 6000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0087] The total cyanide content in the decyanation tailings and decyanation liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanation tailings after the uncrushed tailings were eluted and treated with metal-activated persulfate oxidation method was 30.016 mg / kg, and the total cyanide concentration in the decyanation liquid was 0.089 mg / kg.

[0088] Compared with the results of Example 2, it can be seen that for the same tailings conditions and cyanide removal method, the cyanide inside the tailings can be exposed after crushing, and the contact area is increased. Combined with leaching and metal-activated persulfate oxidation method, the cyanide removal effect is significantly improved.

[0089] Comparative Example 3

[0090] The cyanide tailings collected and the cyanide removal method are the same as those in Example 3, except that the cyanide tailings after crushing in step (1) are not rinsed, but are directly oxidized and decyanated using metal-activated persulfate.

[0091] (1) The cyanide tailings produced by a gold smelting enterprise were collected, and the free cyanide content was 63.81 mg / kg. The free cyanide and strongly complexed cyanide in the cyanide tailings were directly removed by oxidation with metal-activated persulfate; the cyanide tailings were crushed into 100 meshes to obtain cyanide tailings powder;

[0092] (2) Preparation of Fe 0 / BC composite material: The fallen leaves and weeds were crushed and mixed with nano zero-valent iron particles in a mass ratio of 100:5, and pyrolyzed at 800℃ for 4 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent iron composite material Fe 0 / BC;

[0093] (3) Weigh 3 g of cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:15, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 1% of the mass of the cyanide tailings, Fe 0 The mass ratio of BC to sodium persulfate is 1:1. Sodium persulfate and Fe are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at 40°C for 4 hours;

[0094] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 6000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% of ionized water is added to the solid phase, mixed and washed with water, and after a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0095] The total cyanide content in the decyanation tailings and decyanation liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanation tailings treated only by metal-activated persulfate oxidation method was 20.182 mg / kg, and the total cyanide concentration in the decyanation liquid was 0.071 mg / kg.

[0096] Compared with the results of Example 3, it can be seen that when the free cyanide content in the cyanidation tailings is high, with the same tailings conditions and drug dosage, the coordinated treatment of leaching and metal-activated persulfate oxidation can significantly reduce the cyanide content in the decyanidation tailings.

[0097] Comparative Example 4

[0098] The cyanide tailings collected and the cyanide removal method are the same as those in Example 5, except for the preparation of the composite material in step (2).

[0099] (1) Collecting cyanide tailings accumulated in a gold smelter, the free cyanide content is 88.21 mg / kg, first eluting to remove the free cyanide in the cyanide tailings, and then using metal-activated persulfate oxidation to remove the strongly complexed cyanide in the cyanide tailings; crushing the cyanide tailings into 50 meshes to obtain cyanide tailings powder;

[0100] (1.1) mixing the cyanide tailings powder with water at a solid-liquid ratio of 1:10, stirring and eluting for 30 minutes at a stirring speed of 400 rpm, centrifuging and filtering after shaking, and drying the obtained filter residue to constant weight;

[0101] (1.2) After repeating the rinsing operation in step (1.1) for 3 times, the mud-water mixture was centrifuged at a speed of 5000 rpm for 5 minutes, and the supernatant was returned to step (1.1). The mud cake was placed in an oven and dried at 70°C for 6 hours to obtain a fully dried washed cyanide tailings powder; (2) Preparation of Mn 0 / BC composite material: The corn stalks were crushed and mixed with nano zero-valent manganese particles in a mass ratio of 100:2, and pyrolyzed at 400 °C for 12 hours. The pyrolysis process was carried out in an oxygen-free environment to obtain the biochar-loaded nano zero-valent manganese composite material Mn 0 / BC;

[0102] (3) Weigh 5 g of fully dried washed cyanide tailings powder, mix it with water at a solid-liquid ratio of 1:5, and place it in a 50 ml centrifuge tube; add sodium persulfate at an amount of 5% of the mass of the cyanide tailings, Mn 0 The mass ratio of BC to sodium persulfate is 0.2:1. Sodium persulfate and Mn are added. 0 / BC; place the centrifuge tube in a constant temperature oscillator to avoid light and react at a temperature of 35°C for 6 hours;

[0103] (4) After the reaction is completed, the centrifuge tube is placed in an ice bath. After the temperature drops to 25° C., 5 ml of methanol is added to the centrifuge tube to quench the free radicals remaining in the system. The centrifuge tube is placed in a centrifuge for solid-liquid separation at 5000 rpm for 10 minutes. After a solid-liquid separation, a solid phase and a liquid phase are obtained. 10% deionized water is added to the solid phase and mixed and washed. After a solid-liquid separation, a cyanide removal tail and a washing liquid are obtained. The washing liquid is mixed with the liquid phase of the first solid-liquid separation to obtain a cyanide removal liquid.

[0104] The total cyanide content in the decyanation tailings and decyanation liquid was determined by isonicotinic acid-barbituric acid spectrophotometry. The results showed that the total cyanide content in the decyanation tailings after leaching and metal-activated persulfate oxidation treatment was 37.125 mg / kg, and the total cyanide concentration in the decyanation liquid was 0.094 mg / kg.

[0105] Compared with the results of Example 5, it can be seen that Mn 0The efficiency of persulfate activation by BC in degrading cyanide is lower than that of Cu 0 / BC activation persulfate method, the reason may be that Mn 0 The effect of loading biochar is not as good as zero-valent copper, which leads to the failure of fully activating persulfate. That is, for the same tailings and drug dosage, the Fe 0 / BC or Cu 0 / BC activated persulfate oxidation method can significantly improve the cyanide removal effect of tailings.

Claims

1. A method for removing cyanide from cyanide tailings by metal-activated persulfate oxidation, characterized in that: Includes the following: (1) analyzing the free cyanide content in the cyanidation tailings, crushing the cyanidation tailings to obtain cyanidation tailings powder; (2) Preparation of Me / BC composite material: crushing forestry or agricultural waste and mixing with metal source, and pyrolyzing to prepare biochar-loaded metal composite material Me / BC; the metal source includes nano zero-valent iron particles and nano zero-valent copper particles; (3) After mixing the cyanide tailings powder with water, Me / BC and persulfate are added to carry out cyanide reduction reaction; (4) After the reaction is completed, the reaction system is quenched, and the solid-liquid separation of the reaction system is carried out to obtain cyanide removal tailings and cyanide removal liquid.

2. The method for removing cyanide from cyanide tailings by metal activated persulfate oxidation according to claim 1, characterized in that: In step (1), the cyanide tailings are crushed to 30-100 meshes.

3. The method for removing cyanide from cyanide tailings by metal activated persulfate oxidation according to claim 1, characterized in that: In step (2), the mass ratio of forestry or agricultural waste to metal source is 100:(0.5-5), and pyrolysis is carried out at 300°C-900°C for 2 hours-5 hours, and the pyrolysis process is carried out in an oxygen-free environment.

4. The method for removing cyanide from cyanide tailings by metal activated persulfate oxidation according to claim 1, characterized in that: In step (3), the cyanide tailings powder is mixed with water at a solid-liquid ratio of 1:1 to 1:20, the mass ratio of Me / BC to persulfate is (0.05:1) to (1:1), and the amount of persulfate added is 1% to 20% of the mass of the cyanide tailings.

5. The method for removing cyanide from cyanide tailings by metal activated persulfate oxidation according to claim 1, characterized in that: The temperature of the cyanide reduction reaction in step (3) is 30° C. to 50° C., and the reaction time is 2 hours to 12 hours.

6. The method for removing cyanide from cyanide tailings by metal activated persulfate oxidation according to claim 1, characterized in that: Step (4) comprises the following contents: after the reaction is completed, the temperature is lowered to room temperature and the reaction system is quenched, the reaction system is subjected to a solid-liquid separation to obtain a solid phase and a liquid phase, 5% to 20% deionized water is added to the solid phase for mixing and washing, solid-liquid separation is performed again to obtain a cyanide removal tailing and a washing liquid, and the washing liquid is mixed with the liquid phase to obtain a cyanide removal liquid.

7. The method for removing cyanide from cyanide tailings by metal-activated persulfate oxidation according to any one of claims 1 to 6, characterized in that: The content of free cyanide in the cyanidation tailings is ≤50 mg / kg.

8. The method for removing cyanide from cyanide tailings by metal-activated persulfate oxidation according to any one of claims 1 to 6, characterized in that: When the content of free cyanide in the cyanide tailings exceeds 50 mg / kg, the free cyanide in the cyanide tailings is firstly removed by elution, and then the cyanide reduction treatment of the cyanide tailings is carried out by metal activated persulfate oxidation method.

9. The method for removing cyanide from cyanide tailings by metal-activated persulfate oxidation according to claim 8, characterized in that: The elution includes the following contents: (1.1) mixing the cyanide tailings powder with water at a solid-liquid ratio of 1:1 to 1:10, stirring and eluting for 10 to 60 minutes at a stirring speed of 100 to 600 rpm, centrifugally filtering after shaking, and drying the obtained filter residue to constant weight; (1.2) After repeating step (1.1) for 2 to 3 times, the mud-water mixture is separated by centrifugation at a centrifugal speed of 4000 to 6000 rpm for 3 to 5 minutes. The supernatant is returned to step (1.1). The mud cake is placed in an oven and dried at 40° C. to 70° C. for 6 to 12 hours to obtain a fully dried washed cyanide tailings powder.

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