Method for removing arsenic in copper smelting soot through mechanical force vulcanization

Abstract

The invention discloses a method for removing arsenic in copper smelting soot through mechanical force vulcanization. The method comprises the following steps: 1) putting the copper smelting soot and sodium sulfide into a ball mill for co-grinding; (2) a caustic soda solution is pumped into the obtained co-ground soot according to a certain flow speed, cyclic leaching is conducted, and selective separation of arsenic in the copper smelting soot is achieved; (3) after cyclic leaching, ferric chloride is added into a leaching solution, arsenic is stabilized, and a mixed solution is obtained; and 4) filtering the obtained mixed solution, collecting solids, washing, drying, and then carrying out ball milling and vacuum sintering in a protective atmosphere to obtain the arsenic-iron alloy. The method comprises the following steps: firstly, co-grinding the copper smelting soot and sodium sulfide, regulating and changing phases of arsenic and valuable metal elements in the soot by utilizing mechanical force and vulcanization, and promoting high-selectivity separation and leaching of the arsenic under mild conditions; the related recovery process is simple, convenient to operate, low in cost, high in arsenic ion selective removal efficiency and suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource utilization, and particularly relates to a method for selectively separating arsenic from copper smelting ash by wet leaching. Background Art

[0002] Copper smelting fly ash originates from the waste gas purification process during the copper smelting process. Because arsenic is often associated with copper sulfide ores and arsenic compounds have low melting points, arsenic easily accumulates in the dust removal system during the smelting process, resulting in high levels of arsenic in copper smelting fly ash (as high as 7.0-21.0%). Currently, while some fly ash is returned to the smelting furnace for reuse, the majority is stored haphazardly due to the inability to quickly and efficiently dispose of it on a large scale, posing a serious threat to the surrounding ecological environment.

[0003] Considering that copper smelting ash contains valuable metals, the traditional treatment method is to directly mix it with copper ore and then return it to the furnace; however, as the grade of copper ore decreases, the arsenic in the ash circulates and accumulates during the smelting process, which not only causes energy waste and increases the burden on the smelting furnace and flue gas purification section, but also reduces the quality of subsequent copper products. Returning to the furnace for refining has gradually been eliminated.

[0004] Currently, methods for removing arsenic from fly ash primarily include wet and pyrolysis. Traditional pyrolysis, due to its high energy consumption, severe environmental pollution, and difficult process control, has been replaced by wet leaching. Wet arsenic removal primarily involves acid leaching and alkaline leaching. Both methods require adjusting factors such as acidity, redox atmosphere, and reaction temperature to optimize arsenic leaching or precipitation efficiency, depending on the material and conditions. Common acid leaching processes include H2SO4-NaCl leaching, citrate leaching, and H2SO4 leaching. While the H2SO4-NaCl leaching system can simultaneously separate Bi and As from fly ash, it struggles to separate arsenic from valuable metals. Furthermore, process conditions are difficult to control, requiring consideration of multiple factors such as acidity, redox atmosphere, and reaction temperature. Citrate leaching, while capable of leaching valuable metals such as Pb, Cu, Ni, and Zn from fly ash, requires calcination and the high cost of citrate itself. While H2SO4 leaching technology offers low costs, it cannot separate and recover As from valuable metal elements (such as Cu and Zn). Alkaline leaching methods primarily include NaOH and NaOH+Na2S leaching systems. NaOH leaching technology is simple to operate, but the leachate composition is complex, NaOH consumption is high, the arsenic leaching rate is low, and efficient separation of arsenic from valuable metal elements is difficult to achieve. While NaOH-Na2S leaching technology can achieve selective separation of arsenic from other metals, it suffers from high reagent costs, high temperature and high pressure conditions, long processing time, high corrosion resistance requirements for equipment, and the generation of toxic gases such as hydrogen sulfide, which pollutes the environment. Summary of the Invention

[0005] The main purpose of the present invention is to address the problems of low separation efficiency of arsenic and valuable metal elements, high reagent cost, and high energy consumption in the existing double alkali method (NaOH-Na2S) for leaching copper smelting dust, and to provide a new method for removing arsenic from copper smelting dust by mechanical sulfidation. The method realizes the separation and leaching of arsenic under mild conditions, significantly reduces the consumption of caustic soda and sodium sulfide leaching reagents, and has low corrosion to equipment. In addition, the leaching process involved in the invention does not require heating treatment, can effectively reduce energy consumption, and is suitable for promotion and application.

[0006] To achieve the above object, the technical solution adopted by the present invention is: A method for removing arsenic from copper smelting ash by mechanical sulfidation comprises the following steps: 1) Place copper smelting ash and sodium sulfide into a ball mill for co-grinding; 2) Caustic soda is pumped into the resulting co-ground fly ash (in the packed column) at a constant flow rate for cyclic leaching. Arsenic in the fly ash is largely concentrated in the leachate, while valuable metal elements such as Cu, Zn, Cd, and Pb are hardly leached but are concentrated in the leaching residue in the form of sulfides. This can be directly circulated into the smelting system, thereby achieving efficient separation and leaching of arsenic in copper smelting fly ash and the reuse of valuable metal resources. 3) After the cyclic leaching, ferric chloride is added to the leachate to stabilize the arsenic and obtain a mixed solution; 4) The resulting mixed liquid is filtered, and the solid is collected, washed with water, and then dried in a freeze-drying oven. The dried solid is then ball-milled under a nitrogen atmosphere and vacuum-sintered to obtain an arsenic-iron alloy, which can be directly used as a metal additive in special alloys and electronic components.

[0007] In the above scheme, the main metal elements and their contents in the copper smelting ash include: copper 15-25 mg / g, lead 200-300 mg / g, zinc 200-300 mg / g, cadmium 20-30 mg / g, and arsenic 40-50 mg / g.

[0008] In the above solution, the particle size of the copper smelting soot is 4-20 μm.

[0009] In the above scheme, the mass ratio of copper smelting fly ash to sodium sulfide is 5.0: (3.0~3.5).

[0010] In the above scheme, the co-grinding step adopts a speed of 300-400 r / min and a time of 2 h.

[0011] In the above scheme, the concentration of the caustic soda solution is 0.01~0.10 mol / L.

[0012] In the above scheme, the solid-liquid ratio of co-ground fly ash and caustic soda solution is 1 g: (25~30) mL.

[0013] In the above scheme, the pumping speed of the caustic soda solution into the co-grinding fly ash filling column is 2-7 mL / min.

[0014] Preferably, the pumping speed of the caustic soda solution into the co-grinding fly ash filling column is 3-5 mL / min.

[0015] In the above scheme, the cycle leaching time is 0.1~3.0 h.

[0016] In the above scheme, the circulating leaching temperature condition is room temperature.

[0017] Furthermore, the circulating leaching temperature is 20-30°C.

[0018] In the above solution, the temperature used for vacuum sintering is 600-800°C.

[0019] In the above scheme, the ferric chloride used is a 30~40 wt% ferric chloride solution, the mass ratio of the introduced ferric chloride to arsenic element is 10.0:(0.5~1.2), and the pH value is adjusted to 7.0~9.0, which can effectively improve the flocculation effect of ferric chloride.

[0020] In the above scheme, the drying time in the freeze drying oven is 6.0~8.0 h.

[0021] In the above scheme, the co-grinding speed of the iron-arsenic mixture in step 4) is 600-800 r / min, and the co-grinding time is 6.0-8.0 h.

[0022] Furthermore, the arsenic-iron alloy can be directly used as a metal additive in special alloys and electronic components.

[0023] By adopting the above recovery method, the arsenic leaching rate in copper smelting ash reaches more than 90.76%, and the arsenic removal rate reaches more than 95.14%.

[0024] The present invention first grinds copper smelting ash with sodium sulfide, and uses mechanical force + sulfidation to regulate and change the physical phases of arsenic and valuable metal elements in the ash, thereby promoting the highly selective separation and leaching of arsenic under mild conditions: after the valuable metal elements Pb, Zn, Cu, and Cd in the form of sulfates in the copper smelting ash are co-grinded with sulfides, some sulfate compounds are converted into insoluble sulfides or copolymerized sulfides (such as CuFeS2, PbS, CdS, and ZnS, etc.), thereby inhibiting their leaching under alkaline conditions; at the same time, under the weakly alkaline leaching conditions of the present invention, After co-grinding with sulfide, the arsenic compounds in the fly ash can be converted into thioarsenates that are easily soluble under weak alkaline to alkaline conditions, effectively promoting the leaching of arsenic under low alkaline conditions; in addition, under the action of co-grinding, the sulfate PbSO4 in the copper smelting fly ash reacts with sodium sulfide to form sodium sulfate, and its easy solubility under alkaline conditions can promote the leaching of arsenic embedded in the fly ash to a certain extent, further promote the large-scale leaching of arsenic elements in the copper smelting fly ash, and ensure the small amount of leaching of other co-existing valuable metal elements, thereby realizing the efficient and selective leaching of arsenic and co-existing metal elements under low alkalinity and room temperature conditions.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention proposes, for the first time, to co-grind copper smelting fly ash with sodium sulfide. Under the action of mechanical force and sulfidation, the physical phases of arsenic and valuable metal elements in the fly ash are regulated and changed, thereby promoting the highly selective separation and leaching of arsenic in the copper smelting fly ash under mild conditions. 2) The present invention can effectively reduce the amount of leaching agent used, using simple and easy means to achieve efficient and selective separation and recovery of arsenic under low alkalinity and room temperature conditions. The separated valuable metal elements are mostly in the form of sulfides and can be directly introduced into the metallurgical process to extract valuable metal resources without the need for additional recovery processes. This provides a new approach to the resource utilization of solid wastes such as copper smelting ash. 3) The recovery process of the present invention is simple, easy to operate, low in cost, and has high efficiency in selectively removing arsenic ions, and is suitable for promotion and application. DETAILED DESCRIPTION

[0026] The following is a detailed description of the technical solutions used in the present invention through specific implementation examples. The description is only a part of the present invention and does not represent all embodiments. Unless otherwise specified, the experimental methods used in the present invention are conventional methods, and the instruments and equipment used are commercial products in the field of this technology.

[0027] In the following examples, the soot used in this study was obtained from the electrostatic precipitator system of a copper smelter. Testing revealed that the soot contained arsenic and major metal elements, including 44.6 mg / g arsenic, 19.3 mg / g copper, 240 mg / g lead, 217 mg / g zinc, and 21.6 mg / g cadmium. The particle size ranged from 4 to 20 μm.

[0028] Example 1 A method for selectively removing arsenic from copper smelting ash by mechanical sulfidation comprises the following steps: 1) 5.0 g of dried copper smelting fly ash and 3.0 g of sodium sulfide were added to a 500 mL ball mill and co-milled at room temperature (20°C) and a ball mill speed of 300 r / min for 2.0 h. After the reaction, the material was collected to obtain the co-milled fly ash. 2) 2 g of co-ground soot was loaded into a glass packed column. 50 mL of 0.1 mol / L caustic soda solution was pumped into the packed column at a flow rate of 3 mL / min using a peristaltic pump for cyclic leaching. The leaching process was completed after 3.0 h. 3) To 50 mL of the obtained leachate, 2 mL of a 35 wt% ferric chloride solution was added. The solution was allowed to stand for 15 min to stabilize the arsenic. The solid was then collected by filtration, washed with water, and dried in a freeze-drying oven for 6 h. The dried solid was then ball-milled at 800 r / min under a nitrogen atmosphere for 6 h. After ball-milling, the solid was vacuum-sintered at 700 °C for 3 h to obtain an arsenic-iron alloy.

[0029] Testing showed that the arsenic content in the copper smelting ash leachate obtained in this embodiment reached 0.21 g, and the leaching amounts of coexisting metal ions copper, lead, zinc, and cadmium were 0.0013, 0.0076, 0.0082, and 0.0032 g, respectively; the arsenic removal rate reached 90.8%, while the removal rates of coexisting metal ions were all less than 1%.

[0030] The arsenic-iron alloy prepared in this embodiment has the characteristics of high purity (controllable As / Fe ratio) and ultra-low impurities (extremely low heavy metal and non-metal residues), which significantly improves the resource utilization value of arsenic.

[0031] Example 2 A method for selectively removing arsenic from copper smelting ash by mechanical sulfidation comprises the following steps: 1) 5.0 g of dried copper smelting ash and 3.0 g of sodium sulfide were added to a 500 mL ball mill and co-milled at room temperature (20°C) and a ball mill speed of 300 r / min. After the co-milling reaction, the material was collected to obtain the co-milled ash; 2) 2 g of co-ground soot was loaded into a glass packed column. 50 mL of 0.1 mol / L caustic soda solution was pumped into the packed column at a flow rate of 2 mL / min using a peristaltic pump for cyclic leaching. The leaching was then completed. 3) To 50 mL of the obtained leachate, 2 mL of a 35 wt% ferric chloride solution was added. The mixture was allowed to stand for 15 min to stabilize the arsenic. The solid was then collected by filtration, washed with water, and dried in a freeze-drying oven for 6 h. The dried solid was then ball-milled at 800 r / min under a nitrogen atmosphere for 6 h. After ball-milling, the solid was vacuum-sintered at 700°C for 3 h to obtain an arsenic-iron alloy.

[0032] Testing showed that the arsenic content in the copper smelting ash leachate obtained in this example reached 0.20 g, and the leaching amounts of the coexisting metal ions copper, lead, zinc, and cadmium were 0.0021, 0.0066, 0.0072, and 0.0029 g, respectively; the arsenic removal rate reached 89.68%, while the removal rates of the coexisting metal ions were all less than 1.1%.

[0033] Example 3 A method for selectively removing arsenic from copper smelting ash by mechanical sulfidation comprises the following steps: 1) 5.0 g of dried copper smelting fly ash and 3.0 g of sodium sulfide were added to a 500 mL ball mill and co-milled at room temperature (20°C) and a ball mill speed of 300 r / min for 2.0 h. After the reaction, the material was collected to obtain the co-milled fly ash. 2) 2 g of co-ground soot was loaded into a glass packed column. 50 mL of 0.1 mol / L caustic soda solution was pumped into the packed column at a flow rate of 6 mL / min using a peristaltic pump for cyclic leaching. The leaching process was completed after 3.0 h. 3) To the obtained leachate, 2 mL of a 35 wt% ferric chloride solution was added. After standing for 15 minutes to stabilize the arsenic, the solid was collected by filtration, washed with water, and dried in a freeze-drying oven (6.0 h). The dried solid was then ball-milled under a nitrogen atmosphere (800 rpm, 6.0 h) and vacuum sintered (700°C, 3.0 h) to obtain an arsenic-iron alloy.

[0034] Testing showed that the arsenic content in the copper smelting ash leachate obtained in this embodiment reached 0.181 g, and the leaching amounts of coexisting metal ions copper, lead, zinc, and cadmium were 0.0037, 0.0064, 0.0099, and 0.0041 g, respectively; the arsenic removal rate reached 81.16%, while the removal rates of coexisting metal ions were all less than 1%.

[0035] Comparative Example 1 A method for removing arsenic from copper smelting ash by alkaline leaching, comprising the following steps: 1) Mix 5 g of dry copper smelting ash and 3 g of sodium sulfide, then take 5 g and load it into the packed column; 2) pumping 50 mL of 1 mol / L caustic soda solution into the packed column of step 1) at a flow rate of 3 mL / min for cyclic leaching; 3) After 3.0 h of cyclic leaching, the arsenic leaching rate was measured to be 74%, and the recovery rates of the coexisting metal ions copper, lead, zinc, and cadmium ions were less than 30%. The obtained arsenic ion leaching rate was low, and the leaching concentration of the coexisting valuable metal ions was high, resulting in poor selective separation and leaching of arsenic.

[0036] Comparative Example 2 A method for removing arsenic from copper smelting ash by ball milling and alkali leaching, comprising the following steps: 1) Place 5 g of dried copper smelting fly ash and 3 g of sodium sulfide in a 500 mL ball mill, grind them together (same as in Example 1), and then place 5 g of the co-ground fly ash into a packed column; 2) Pump 50 mL of 1 mol / L caustic soda solution at a flow rate of 3 mL / min into the packed column filled with co-ground fly ash for cyclic leaching; 3) After 3.0 h of cyclic leaching, the arsenic leaching rate was measured to be 81%, and the recovery rates of the coexisting metal ions copper, lead, zinc, and cadmium ions were less than 33%. The obtained arsenic ion leaching rate was low, and the leaching concentration of the coexisting valuable metal ions was not low, resulting in poor selective separation and leaching of arsenic.

[0037] Comparative Example 3 A method for removing arsenic from copper smelting ash by ball milling and alkali leaching, comprising the following steps: 1) Add 5.0 g of dry copper smelting fly ash into a 500 mL ball mill and grind it for 2.0 h at room temperature (20°C) and a ball mill speed of 300 r / min to obtain ground fly ash. 2) Mix 2 g of ground fly ash and 3.0 g of sodium sulfide and place them into a glass packed column. Use a peristaltic pump to pump 50 mL of 0.1 mol / L caustic soda solution into the packed column at a flow rate of 2 mL / min for cyclic leaching. Leaching is completed after 3.0 h.

[0038] After testing: the arsenic leaching rate was measured to be 62%, and the recovery rate of co-existing metal ions copper, lead, zinc and cadmium ions was less than 41%; the obtained arsenic ion leaching rate was low, and the leaching concentration of co-existing valuable metal ions was not low, and the selective separation and leaching effect of arsenic was poor.

[0039] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.

Claims

1. A method for removing arsenic from copper smelting ash by mechanical sulfidation, characterized in that: The steps include: 1) Place copper smelting ash and sodium sulfide into a ball mill for co-grinding; 2) Pumping caustic soda solution into the obtained co-ground fly ash at a certain flow rate for cyclic leaching; 3) After the cyclic leaching, ferric chloride is added to the leachate to stabilize the arsenic and obtain a mixed solution; 4) The resulting mixed solution is filtered, and the solid is collected, washed, and dried, and then ball-milled under a protective atmosphere and vacuum-sintered to obtain an arsenic-iron alloy.

2. The method according to claim 1, characterized in that The main metal elements and their contents in the copper smelting ash include: 15-25 mg / g copper, 200-300 mg / g lead, 200-300 mg / g zinc, 20-30 mg / g cadmium, and 40-50 mg / g arsenic.

3. The method according to claim 1, characterized in that The particle size of the copper smelting soot is 4-20 μm.

4. The method according to claim 1, wherein The mass ratio of copper smelting ash to sodium sulfide is 5.0:(3.0~3.5).

5. The method according to claim 1, wherein The co-grinding step adopts a speed of 300-400 r / min and a time of 1.0-3.0 h.

6. The method according to claim 1, characterized in that The concentration of the caustic soda solution is 0.01-0.10 mol / L.

7. The method according to claim 1, characterized in that The solid-liquid ratio of co-ground fly ash and caustic soda is 1 g: (25~30) mL.

8. The method according to claim 1, characterized in that The caustic soda solution is pumped into the co-ground fly ash filling column at a pumping speed of 2-7 mL / min; and the circulation leaching time is 0.1-3.0 h.

9. The method according to claim 1, characterized in that The temperature used in the vacuum sintering is 600-800°C.

10. The method according to claim 1, characterized in that Step 3) The pH value of the stabilization step is regulated to be 7.0-9.0.