Method for recovering copper-iron alloy based on coconut shell biochar loaded nano zero-valent iron

Abstract

The present application belongs to the field of wastewater treatment and heavy metal recovery, and particularly relates to a method for recovering copper-iron alloy based on coconut shell biochar loaded with nano zero-valent iron. The material is prepared by liquid phase reduction method. Biomass pyrolyzed at 800-900 DEG C, ground, sieved and impregnated with hydrochloric acid is used as active biochar. Under nitrogen protection, the biochar is reacted with ferrous salt FeCl2.4H2O and reducing agent Na2S2O4 in an oil bath multi-neck flask containing NaOH solution to prepare biochar loaded with nano zero-valent iron (nZVI@HBC). The nZVI@HBC is added to copper-containing wastewater, and the treated wastewater is subjected to magnetic separation to obtain copper-containing waste residue. The waste residue is recovered to produce copper-iron alloy by adopting the process of primary reduction roasting + sulfation roasting, secondary acid leaching of copper and electrolysis, which is helpful to environmental protection, resource saving and green development.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment and heavy metal recovery, specifically relating to a method for recovering and producing copper-iron alloys from coconut shell biochar-supported nano-zero-valent iron. Background Technology

[0002] Wastewater generated during many industrial production processes contains large amounts of the heavy metal copper. If this copper-containing industrial wastewater is discharged into water bodies without effective treatment, it will cause serious harm to human health and the ecological environment, and will also hinder the sustainable use of water resources. Furthermore, copper is an important non-ferrous metal resource, widely used in electronics, electrical engineering, construction, transportation, machinery, and other fields. Therefore, taking measures to treat and recycle heavy metal copper from industrial wastewater is essential and will help protect the environment, conserve resources, and promote green development.

[0003] In the prior art, for example, Chinese Patent Publication No. CN113262764A discloses the use of an iron-based cellulose nanocomposite material in an aquatic environment. This iron-based cellulose nanocomposite material has a three-dimensional network structure composed of nanocellulose and nano-zero-valent iron. This material has a large specific surface area and high adsorption and reduction capacity for heavy metals. However, the raw material NaBH4 used in this invention is a toxic reagent and is expensive. Chinese Patent Publication No. CN114950357A discloses a one-step method for preparing activated carbon-supported sulfurized nano-zero-valent iron composite material. This method involves impregnating and loading biochar with an iron-containing precursor and a sulfur precursor to prepare the composite material. However, this patent does not treat actual wastewater, nor does it recycle the treated wastewater. Summary of the Invention

[0004] This invention provides a method for recovering and producing copper-iron alloys from coconut shell biochar-supported nano-zero-valent iron, overcoming the problems of expensive and toxic NaBH4 reducing agent, and realizing the recovery and utilization of copper in wastewater to produce copper-iron alloys, which helps to protect the environment, save resources, and promote economic development.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for producing copper-iron alloys based on coconut shell biochar-supported nano-zero-valent iron, specifically including the following steps:

[0006] S1. Prepare raw biochar by pyrolysis carbonization of biomass coconut shells, and then soak, rinse and dry the raw biochar in sufficient hydrochloric acid solution to obtain activated biochar.

[0007] S2. Under nitrogen protection, activated biochar is added to a mixed solution of ferrous salt FeCl2·4H2O, reducing agent Na2S2O4, and NaOH. The reaction is carried out in an oil bath at 150-160℃ for 0.5-1.5 hours. After the reaction is completed, the precipitate is separated by centrifugation, washed, and dried to obtain activated biochar loaded with nano-zero valent iron, abbreviated as nZVI@HBC.

[0008] S3. Adjust the pH of the copper-containing wastewater to ≥5.5 and heat it to 50-60℃. Add the prepared nZVI@HBC to the copper-containing wastewater at a dosage of 0.4-0.6 g / L. The Cu in the copper-containing wastewater... 2+ The concentration of the substance is 0.01-0.1 mol / L. After thorough stirring, magnetic separation is performed. The separated waste residue is then subjected to reduction roasting + sulfation roasting process, acid leaching copper process and electrolysis process to recover copper and iron, and produce copper-iron alloy.

[0009] As a further improvement to the method of producing copper-iron alloys based on coconut shell biochar-supported nano-zero-valent iron:

[0010] Preferably, in step S1, the temperature for biomass coconut shell pyrolysis carbonization is 800-900℃, the time is 1-2h, the heating rate is 5℃ / min, and then the raw biochar is obtained by passing it through a 100-120 mesh sieve.

[0011] Preferably, the concentration of the hydrochloric acid solution in step S1 is 0.9-1.1 mol·L⁻¹. -1 The soaking time is 20-24 hours. After soaking, rinse with deionized water and dry at 80-90℃ for 20-24 hours.

[0012] Preferably, the concentration of ferrous salt FeCl2·4H2O in the mixed solution described in step S2 is 0.2-0.25 mol·L. -1 The concentration of the reducing agent Na2S2O4 is 0.2-0.25 mol·L⁻¹. -1 The concentration of NaOH is 0.5-0.7 mol·L⁻¹. -1 .

[0013] Preferably, in step S2, the centrifugation speed is 6000-7000 r / min, and the separated precipitate is washed sequentially with oxygen-free water and anhydrous ethanol in an oxygen-free atmosphere until the pH of the supernatant is neutral.

[0014] Preferably, in step S2, the precipitate is washed and then vacuum dried at 60-70°C for 5-6 hours to obtain nZVI@HBC.

[0015] Preferably, in step S3, after nZVI@HBC is added to the copper-containing wastewater, it is stirred at a speed of 200-300 r / min for 100-250 min.

[0016] Preferably, the specific steps of the reduction roasting + sulfation roasting process in step S3 are as follows: the separated waste residue is mixed with sulfuric acid at a solid-liquid ratio of 1:(2-4) and added to the sulfation roasting device. The sulfation roasting device is placed in a muffle furnace at 600-700℃ for roasting. The furnace door is partially opened and the mixture is stirred every 10-20 minutes. The roasting time is 0.8-2 hours.

[0017] Preferably, the specific steps of the acid leaching copper process in step S3 are as follows: the product after reduction roasting + sulfation roasting is added to a sulfuric acid solution with a concentration of 15-25 g / L, and then placed in an XJT type leaching mixer for acid leaching. The stirring speed is 300-400 r / min, the leaching temperature is 80-90℃, and the leaching time is 1-2 h.

[0018] Preferably, the specific steps of the electrolysis process in step S3 are as follows: using the leaching solution from the acid leaching copper process as the electrolyte, a carbon rod as the anode, and an iron sheet as the cathode, the electrolysis time is 0.5-1h, and a mixture of metallic copper and iron is deposited on the cathode to prepare a copper-iron alloy.

[0019] The advantages of this invention compared to the prior art are as follows:

[0020] 1) This invention provides a liquid-phase reduction synthesis method for nZVI composite materials without the need for NaBH4. The raw materials are inexpensive, and the byproducts are only common natural salts. The produced copper-iron alloy reduces waste emissions and enables the recovery of copper and iron from wastewater, achieving efficient resource utilization. The reducing agent used in this invention is Na2S2O4, which solves the problem of the high price of NaBH4. The resulting composite material can be used for wastewater treatment to recover the waste residue after heavy metal adsorption, achieving a recovery rate of over 80%, thus realizing resource recycling and avoiding secondary pollution.

[0021] 2) In this invention, biomass is first pyrolyzed and carbonized to generate pyrolysis gas and carbon residue, i.e., original biochar. After activation by hydrochloric acid impregnation, the surface of the biochar has more microporous structures. These pores provide a lot of space for the attachment of nano-zero valent iron, and the more sites significantly reduce the agglomeration and aggregation of nano-zero valent iron.

[0022] Under nitrogen protection, activated biochar was added to a mixed solution of ferrous salt FeCl2·4H2O, reducing agent Na2S2O4, and NaOH, and the reaction occurred in an oil bath: Fe 2+ (aq)+S2O4 2- +4OH -→Fe 0 +2SO3 2- +2H2O, washing and drying to obtain activated biochar loaded with nano-zero valent iron;

[0023] The pH of the copper-containing wastewater was adjusted, and the prepared nZVI@HBC was added to the wastewater and stirred thoroughly. The stirred wastewater was then subjected to magnetic separation. The waste residue was processed sequentially using a reduction roasting + sulfation roasting process, an acid leaching copper process, and an electrolysis process. During the reduction roasting process, the copper-containing compounds in the waste residue were reduced to metallic copper. During the sulfation roasting process, the metallic copper was oxidized to copper ions and reacted with sulfuric acid to form copper sulfate. Other impurities in the waste residue were removed through oxidation and decomposition. In the electrolysis process, the anode reaction is: 2H₂O(l) → O₂(g) + 4H₂O + (aq)+4e - Cathode reaction: Fe 2+ (aq)+2e - →Fe(s); Cu 2+ (aq)+2e - →Cu(s). Attached Figure Description

[0024] Figure 1 This is a flowchart of the process for producing copper-iron alloys based on the recovery of nano-zero-valent iron supported by coconut shell biochar according to the present invention;

[0025] Figure 2 The image is an SEM image of nZVI@HBC obtained in Embodiment 1 of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] To avoid repetition, the raw materials for preparing nZVI@HBC are described below, and will not be repeated in the examples: coconut shell, FeCl2·4H2O, Na2S2O4 as reducing agent, NaOH solution, and N2.

[0028] Example 1

[0029] This embodiment provides a method for recovering and producing copper-iron alloys based on coconut shell biochar-supported nano-zero-valent iron, the process of which is as follows: Figure 1 As shown, the specific steps include the following:

[0030] S1. Place the coconut shell in a muffle furnace and calcine it at 800℃ for 2 hours at a heating rate of 5℃ / min. After pyrolysis, grind it through a 120-mesh sieve to obtain raw biochar. The raw biochar is then subjected to pyrolysis at 0.9 mol·L⁻¹. -1 The activated biochar was obtained by immersing the biochar in hydrochloric acid for 24 hours, rinsing it three times with deionized water, and drying it in an 80℃ drying oven for 24 hours.

[0031] 500g of dried activated biochar was added to a 1000mL mixed solution of ferrous salt FeCl2·4H2O, reducing agent Na2S2O4, and NaOH. The concentration of ferrous salt FeCl2·4H2O in the mixed solution was 0.2mol·L⁻¹. -1 The concentration of the reducing agent Na2S2O4 is 0.2 mol·L⁻¹. -1 The concentration of NaOH is 0.6 mol·L⁻¹ -1 The reaction was carried out in a multi-necked flask with an oil bath at 150℃ for 0.5 h. After the reaction, the precipitate was separated by centrifugation at 6000 r / min using a high-speed centrifuge. The precipitate was washed three times with anoxic water and twice with anhydrous ethanol in a glove box. The supernatant after washing was neutral in pH. After drying in a vacuum drying oven at 60℃ for 5 h, activated biochar nZVI@HBC loaded with nano-zero valent iron was obtained.

[0032] S2. The wastewater to be treated was taken from copper-containing electroplating wastewater generated by an electroplating factory in East China. The pH was measured to be 8, and the copper ion concentration in the copper-containing wastewater was measured to be 0.040 mol / L. The nZVI@HBC prepared in step S1 was added to the copper-containing wastewater at a dosage of 0.5 g / L, heated to 50°C and kept at that temperature, and stirred at 200 r / min for 125 min.

[0033] S3. The treated waste liquid is subjected to magnetic separation. The separated waste residue is dried, and 500g of the dried waste residue is weighed and mixed with sulfuric acid in a sulfation roasting apparatus at a solid-liquid ratio of 1:2. When the muffle furnace temperature reaches 600℃, the roasting apparatus is transferred to the muffle furnace, and the sample is stirred and roasted every 20 minutes with the furnace door partially open for 2 hours. After roasting, the product is added to a 20g / L sulfuric acid solution at a solid-liquid ratio of 1:2.5 and acid leaching is carried out in an XJT type leaching mixer at a leaching temperature of 80℃, a leaching time of 2 hours, and a stirring speed of 300r / min. The leaching solution from the acid leaching copper process is used as the electrolyte, a carbon rod as the anode, and an iron sheet as the cathode. The electrolysis time is 0.5 hours, and a mixture of metallic copper and iron is deposited on the cathode to prepare a copper-iron alloy.

[0034] Example 2

[0035] This embodiment provides a method for recovering and producing copper-iron alloys based on coconut shell biochar-supported nano-zero-valent iron, the process of which is as follows: Figure 1As shown, the specific steps include the following:

[0036] S1. Place the coconut shell in a muffle furnace, heat at a rate of 5℃ / min, and calcine at 800℃ for 2 hours. After pyrolysis, grind the shell through a 110-mesh sieve to obtain raw biochar. Then, heat the raw biochar at 1 mol·L⁻¹... -1 The activated biochar was obtained by immersing the biochar in hydrochloric acid for 24 hours, rinsing it three times with deionized water, and drying it in an 80℃ drying oven for 24 hours.

[0037] 500g of dried activated biochar was added to a 1000mL mixed solution of ferrous salt FeCl2·4H2O, reducing agent Na2S2O4, and NaOH. The concentration of ferrous salt FeCl2·4H2O in the mixed solution was 0.2mol·L⁻¹. -1 The concentration of the reducing agent Na2S2O4 is 0.25 mol·L⁻¹. -1 The concentration of NaOH is 0.6 mol·L⁻¹ -1 The reaction was carried out in a multi-necked flask in an oil bath at 150℃ for 1 hour. After the reaction, the precipitate was separated by centrifugation at 6500 r / min using a high-speed centrifuge. The precipitate was washed twice with anoxic water and three times with anhydrous ethanol in a glove box until the pH of the supernatant was neutral. After drying in a vacuum drying oven at 60℃ for 5 hours, activated biochar nZVI@HBC loaded with nano-zero valent iron was obtained.

[0038] S2. The wastewater to be treated was acidic wastewater generated by an electroplating factory in East China. The pH was measured to be 3, and the pH was adjusted to 5.5. The copper ion concentration in the copper-containing wastewater was measured to be 0.050 mol / L. The nZVI@HBC prepared in step S1 was added to the copper-containing wastewater at a dosage of 0.5 g / L, heated to 55°C and kept at that temperature, and stirred at 300 r / min for 120 min.

[0039] S3. The treated waste liquid is subjected to magnetic separation. The separated waste residue is dried, and 500g of the dried waste residue is weighed and mixed with sulfuric acid in a sulfation roasting apparatus at a solid-liquid ratio of 1:3. When the muffle furnace temperature reaches 600℃, the roasting apparatus is transferred into the muffle furnace, and the furnace door is partially opened. The sample is stirred and roasted every 15 minutes for a total roasting time of 1.5 hours. Afterward, the roasted product is added to a 20g / L sulfuric acid solution at a solid-liquid ratio of 1:3 and acid leaching is carried out in an XJT type leaching mixer at a leaching temperature of 80℃, a leaching time of 1.5 hours, and a stirring speed of 350r / min. The leaching solution from the acid leaching copper process is used as the electrolyte, a carbon rod as the anode, and an iron sheet as the cathode. The electrolysis time is 0.5 hours. A mixture of metallic copper and iron is deposited on the cathode to prepare a copper-iron alloy.

[0040] Example 3

[0041] This embodiment provides a method for recovering and producing copper-iron alloys based on coconut shell biochar-supported nano-zero-valent iron, the process of which is as follows: Figure 1 As shown, the specific steps include the following:

[0042] S1. Place the coconut shell in a muffle furnace and calcine it at 800℃ for 2 hours at a heating rate of 5℃ / min. After pyrolysis, grind it through a 100-mesh sieve to obtain raw biochar. The raw biochar is then heated to 1.1 mol·L⁻¹. -1 The activated biochar was obtained by immersing the biochar in hydrochloric acid for 24 hours, rinsing it three times with deionized water, and drying it in an oven at 80°C for 24 hours.

[0043] 500g of dried activated biochar was added to 1000mL of a mixed solution of ferrous salt FeCl2·4H2O, reducing agent Na2S2O4, and NaOH. The concentration of ferrous salt FeCl2·4H2O in the mixed solution was 0.25mol·L⁻¹. -1 The concentration of the reducing agent Na2S2O4 is 0.25 mol·L⁻¹. -1 The concentration of NaOH is 0.6 mol·L⁻¹ -1 The reaction was carried out in a multi-necked flask in an oil bath at 150℃ for 1.5 h. After the reaction, the precipitate was separated by centrifugation at 7000 r / min using a high-speed centrifuge. The precipitate was washed three times with anoxic water and three times with anhydrous ethanol in a glove box to make the pH of the supernatant neutral. After drying in a vacuum drying oven at 60℃ for 5 h, activated biochar nZVI@HBC loaded with nano-zero valent iron was obtained.

[0044] S2. The wastewater to be treated was copper-containing wastewater generated by an electroplating factory in East China. The pH was measured to be 8.1 and the copper ion concentration was measured to be 0.033 mol / L. The nZVI@HBC prepared in step S1 was added to the copper-containing wastewater at a dosage of 0.5 g / L, heated to 60°C and kept at that temperature, and stirred at 250 r / min for 240 min.

[0045] S3. The treated waste liquid is subjected to magnetic separation. The separated waste residue is dried, and 500g of the dried residue is weighed and mixed with sulfuric acid in a sulfation roasting apparatus at a solid-liquid ratio of 1:4. When the muffle furnace temperature reaches 600℃, the roasting apparatus is transferred to the muffle furnace, and the sample is stirred and roasted every 10 minutes with the furnace door partially open for 0.8 hours. Afterward, the roasted product is added to a 20g / L sulfuric acid solution at a solid-liquid ratio of 1:3.5, and acid leaching is carried out in an XJT type leaching mixer at a leaching temperature of 80℃, a leaching time of 1 hour, and a stirring speed of 400r / min. The leaching solution from the acid leaching copper process is used as the electrolyte, a carbon rod as the anode, and an iron sheet as the cathode. The electrolysis time is 0.5 hours, and a mixture of metallic copper and iron is deposited on the cathode to prepare a copper-iron alloy.

[0046] In Examples 1 and 2, nZVI@HBC achieved optimal copper removal efficiency at 125 min, with removal rates of 93.12% and 87.63%, respectively, and recovery rates of 86.61% and 87.32%. In Example 3, nZVI@HBC achieved maximum copper removal efficiency at 240 min, with a removal rate of 76.32% and a recovery rate of 90.87%.

[0047] Figure 2 The SEM image of nZVI@HBC obtained in Embodiment 1 of the present invention is shown below. Figure 2 It can be seen that the acid-leached coconut shell biochar provides more attachment sites for nano-zero-valent iron compared to untreated coconut shell biochar, reducing the aggregation and agglomeration of nano-zero-valent iron and improving the efficiency of removing heavy metal copper from wastewater. Furthermore, this invention employs a primary reduction roasting + sulfation roasting, a secondary acid leaching copper process, and electrolysis to treat waste residue and form a copper-iron alloy, which can effectively reduce waste emissions, contributing to environmental protection, resource conservation, cost reduction, and economic development. In addition, the preparation and application of this material provide new ideas and methods for wastewater treatment in my country, possessing significant theoretical and practical value.

[0048] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for recovering copper-iron alloy production based on coconut shell biochar loaded nano zero-valent iron, characterized by, Specifically comprising the following steps: S1, the biomass coconut shell is carbonized by pyrolysis, the pyrolysis carbonization temperature is 800-900 DEG C, the time is 1-2 h, the temperature rising rate is 5 DEG C / min, then the original biochar is obtained by passing through 100-120 mesh sieve;The original biochar is immersed, washed and dried in sufficient hydrochloric acid solution to obtain active biochar;The concentration of the hydrochloric acid solution is 0.9-1.1 mol·L -1 , the immersion time is 20-24 h, the immersion is washed with deionized water, the drying temperature is 80-90 DEG C, and the drying time is 20-24 h; S2, under the protection of nitrogen, active biochar is added to ferrous salt FeCl2 4H2O, a reducing agent Na2S2O4, and NaOH, and the mixture is reacted at 150-160°C in an oil bath for 0.5-1.5 h. After the reaction is completed, the precipitate is separated by centrifugation, washed, and dried to obtain active biochar loaded with nano zero-valent iron, referred to as nZVI@HBC; the concentration of ferrous salt FeCl2 4H2O in the mixed solution is 0.2-0.25 mol·L -1 ; the concentration of the reducing agent Na2S2O4 is 0.2-0.25 mol·L -1 ; and the concentration of NaOH is 0.5-0.7 mol·L -1 . S3, adjust the pH of the copper-containing wastewater to be greater than or equal to 5.5 and heat to 50-60°C, add the nZVI@HBC prepared above to the copper-containing wastewater at a dosage of 0.4-0.6 g / L, the concentration of Cu 2+ in the copper-containing wastewater is 0.01-0.1 mol / L, after sufficient stirring, magnetic separation is performed, the separated waste residue is sequentially subjected to reduction roasting + sulfuric acid roasting process, acid leaching copper process and electrolysis process to recover copper and iron, and a copper-iron alloy is produced; The specific steps of the reduction roasting + sulfuric acid roasting process are as follows: the separated waste residue is mixed with sulfuric acid at a solid-liquid ratio of 1: (2-4), and then added to a sulfuric acid roasting device, the sulfuric acid roasting device is placed in a muffle furnace at 600-700 DEG C, the furnace door is half opened and stirred every 10-20 min, and the roasting time is 0.8-2 h; The specific steps of the acid leaching copper process are as follows: the product after the reduction roasting + sulfuric acid roasting process is added to a sulfuric acid solution with a concentration of 15-25 g / L, and then placed in an XJT type leaching stirrer for acid leaching, the stirring speed is 300-400 r / min, the leaching temperature is 80-90 DEG C, and the leaching time is 1-2 h; The specific steps of the electrolysis process are as follows: the leaching solution of the acid leaching copper process is used as the electrolyte, a carbon rod is used as the anode, and an iron sheet is used as the cathode, the electrolysis time is 0.5-1 h, a copper-iron alloy is prepared by depositing a mixture of metal copper and iron on the cathode.

2. The method for recovering copper-iron alloy production based on coconut shell biochar loaded nano zero-valent iron according to claim 1, characterized in that, The centrifugal separation speed in step S2 is 6000-7000 r / min, and the separated precipitate is washed with oxygen-free water and anhydrous ethanol in an oxygen-free atmosphere, and the washing is continued until the supernatant is neutral.

3. The method for recovering copper-iron alloy production based on coconut shell biochar loaded nano zero-valent iron according to claim 1 or 2, characterized in that, The precipitate in step S2 is vacuum dried at 60-70 DEG C for 5-6 h after washing to obtain nZVI@HBC.

4. The method for recovering copper-iron alloy production based on coconut shell biochar loaded nano zero-valent iron according to claim 1, characterized in that, In step S3, the nZVI@HBC is added to the copper-containing wastewater and stirred at a speed of 200-300 r / min for 100-250 min.

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