A cyanide removing agent and a method for preparing the same

Abstract

The application belongs to the technical field of wastewater treatment, and particularly relates to a cyanide removal agent and a preparation method thereof. The application discloses a preparation method of a cyanide removal agent, which comprises the following steps: uniformly mixing hydroxyapatite and starch, and then ultrasonically dispersing the mixture in an organic alcohol solution; adding 4-vinylpyridine and an initiator into the mixture, and stirring; adding a crosslinking agent into the mixture, and continuing to stir; obtaining modified hydroxyapatite; mixing the modified hydroxyapatite with an alkali solution, and stirring uniformly; heating the system to react; filtering the system after the reaction is completed; freezing the obtained product; obtaining a freeze-dried product; calcining the freeze-dried product under a nitrogen atmosphere; cooling the product to room temperature after the calcination is completed; crushing, grinding and sieving the product; and obtaining porous modified hydroxyapatite, which is the cyanide removal agent. The cyanide removal agent can not only remove small-molecule substances such as cyanide in wastewater, but also cooperatively reduce the content of metal ions such as copper, zinc and iron in water, and the effect is obvious, and the effluent water quality is good.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wastewater treatment, and particularly relates to a cyanide removal agent and a preparation method thereof. BACKGROUND

[0002] Cyanide refers to a compound containing cyanide (CN-), including organic cyanide and inorganic cyanide. Among them, common inorganic cyanides are sodium cyanide (NaCN), potassium cyanide (KCN) and the like; common organic cyanides are acrylonitrile, ethanedinitrile and the like. Cyanide is widely used in industrial production, and at the same time, a large amount of cyanide-containing wastewater is generated. The cyanide-containing wastewater mainly comes from the mining and refining of minerals, photographic printing, coke oven wastewater, electroplating plants, metal surface treatment plants, gas plants, dye plants, tanneries, plastic plants, synthetic fibers, surface quenching of steel ingots, and industrial gas washing, etc.

[0003] According to incomplete statistics, there are more than 20 kinds of cyanide-containing wastewater treatment technologies at present. The key to cyanide-containing wastewater treatment lies in the deep degradation of CN - and the removal of coexisting metal ions such as copper, zinc and iron. The early cyanide-containing wastewater treatment methods mainly include chloro-oxidation method, sulfur dioxide-air method, acidification recovery method, Fenton oxidation method, metal ion complexation method and the like. In recent years, new technologies such as radiation method, ultrasonic oxidation method, supercritical water oxidation method, biological oxidation method and photocatalytic oxidation method have been developed. These treatment methods each have their own characteristics. The acidification recovery method can maximize the recovery of cyanide, but due to the risk of hydrogen cyanide overflow, it not only requires a fully closed system, but also has complex operation. The most critical is that the cyanide-containing residual liquid after one-time treatment of this method is difficult to meet the discharge standard, and can only be used as a primary treatment technology. The chloro-oxidation method, sulfur dioxide-air method, Fenton oxidation method, ultrasonic oxidation method, supercritical water oxidation method and biological oxidation method, these methods are basically based on strong oxidizing agents to oxidize and decompose CN - , but the zinc and copper concentrations in wastewater are high, and the metal ions form very stable complexes with CN - , which are difficult to completely degrade and are prone to secondary pollution. The photocatalytic oxidation method can completely eliminate CN - in wastewater, but the performance of the catalyst is still a problem faced at present. In addition, there are, for example, extraction method, ion exchange method, membrane method and the like, which have not been widely applied due to harsh conditions or high cost.

[0004] Hydroxyapatite is abbreviated as HAP, and its chemical formula is Ca sHydroxyapatite (PO4)3(OH) has good bioactivity and is the main inorganic component of human and animal bones. Hydroxyapatite can participate in metabolism in vivo, stimulate or induce hyperosteosis, and promote the repair of damaged tissues. Therefore, hydroxyapatite can be used as a bone substitute material, a calcium supplement and an orthopedic material, and is widely used in the fields of medical materials and bone tissue regeneration.

[0005] In addition, hydroxyapatite has a porous structure and thus has good adsorption performance. In the field of wastewater treatment, hydroxyapatite is an environmentally friendly mineral material and has broad-spectrum and open properties in the treatment of various toxic metal ion-containing wastewater. This widely replaceable feature allows it to accommodate various types of metal ions with different radii and different electric charges in its structure, especially in the removal of heavy metal ions, which has the advantages of high quality, high efficiency, low cost and low secondary pollution. The effect is particularly remarkable in the treatment of wastewater containing highly toxic heavy metal ions such as lead, cadmium and mercury. However, the actual application effect of natural hydroxyapatite in wastewater treatment is not ideal based on its own physical and chemical properties, especially when both cyanide and heavy metal ions in water need to be removed, the effect is far lower than the theoretical value.

[0006] Therefore, a modified hydroxyapatite composite material that can simultaneously reduce the content of cyanide and metal ions in wastewater is expected. SUMMARY

[0007] The present application aims to overcome the problems in the prior art and provides a cyanide removal agent and a preparation method thereof. The cyanide removal agent of the present application can not only remove small molecular substances such as cyanide in wastewater, but also cooperatively reduce the content of metal ions such as copper, zinc and iron in water, and has obvious effect and good effluent quality.

[0008] The object and technical problem of the present application are achieved by the following technical solutions.

[0009] One aspect of the present application provides a preparation method of a cyanide removal agent, which comprises the following steps:

[0010] Hydroxyapatite and starch are mixed uniformly and then ultrasonically dispersed in an organic alcohol solution with a volume fraction of 60-80%, and then 4-vinylpyridine and an initiator are added and stirred at 50-100°C for 4-8h, then the temperature is kept unchanged, a crosslinking agent is added and stirred for 1-5h, and then the reaction is completed, the obtained solid product is filtered, washed and dried to obtain modified hydroxyapatite;

[0011] The modified hydroxyapatite is mixed with 1-5 wt% acid solution according to the mass-volume ratio of 1 g: 50-100 mL and stirred uniformly, then the system is heated to 100-150 °C and stirred for 1-3 h, after the reaction is completed, the product is filtered, and the obtained product is frozen at -40 to -20 °C for 8-12 h to obtain a freeze-dried product;

[0012] The freeze-dried product is calcined at 400-1000 °C for 2-6 h under a nitrogen atmosphere, after the calcination is completed, the product is cooled to room temperature, and then the product is crushed, ground and sieved through a 40-100 mesh sieve to obtain porous modified hydroxyapatite, which is a cyanide removal agent.

[0013] In a preferred embodiment of the present application, the starch is selected from any one or a mixture of two or more of cassava starch, corn starch, sweet potato starch, and potato starch.

[0014] In a preferred embodiment of the present application, the organic alcohol is selected from any one or a mixture of two or more of ethanol, ethylene glycol, 1-propanol, 1-butanol, 1-hexanol, and 1-pentanol.

[0015] In a preferred embodiment of the present application, the hydroxyapatite, starch, and organic alcohol solution are added in an amount of 1 g: 0.5-1 g: 10-50 mL according to the mass-volume ratio.

[0016] In a preferred embodiment of the present application, the ultrasonic conditions are: power 600-800 W, and time 30-60 min.

[0017] In a preferred embodiment of the present application, the 4-vinylpyridine is added in an amount of 1-3 mL: 1 g according to the volume-mass ratio.

[0018] In a preferred embodiment of the present application, the initiator is selected from any one of ammonium persulfate and potassium persulfate; and the initiator is added in an amount of 0.1-0.5: 1 according to the mass ratio with the starch.

[0019] In a preferred embodiment of the present application, the crosslinking agent is selected from any one of catechol, hydroquinone, and resorcinol; and the crosslinking agent is added in an amount of 0.01-0.05: 1 according to the mass ratio with the starch.

[0020] In a preferred embodiment of the present application, the base is selected from any one or a mixture of two or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0021] Another aspect of the present application also provides a cyanide removal agent prepared according to the method as described above.

[0022] By means of the above technical solution, the present application has at least the following advantages:

[0023] 1. This invention uses hydroxyapatite as raw material, starch as polymer carrier, and 4-vinylpyridine as functional monomer. A free radical polymerization reaction is initiated under the action of an initiator to obtain 4-vinylpyridine-grafted modified starch. Finally, under the action of a crosslinking agent, the 4-vinylpyridine-grafted modified starch undergoes a crosslinking reaction, coating the surface of hydroxyapatite in the presence of hydroxyapatite, resulting in a hydroxyapatite composite coated with 4-vinylpyridine-grafted modified starch. The obtained hydroxyapatite composite coated with 4-vinylpyridine-grafted modified starch is heated in an alkaline solution. The alkaline solution provides an alkaline environment for the system, causing a certain number of negative charges to adhere to the surface of the composite. Finally, the composite is freeze-dried to increase its volume and the number of porous structures. After calcination, further pore formation is achieved, resulting in porous modified hydroxyapatite powder. The porous modified hydroxyapatite powder of this invention not only possesses a porous structure but also has negative charges and multiple coordinating atoms on its surface, making the composite not only adsorbent but also capable of complexing metal ions and binding CN. - The ability to remove CN from wastewater - The purpose of metal ions.

[0024] 2. The cyanide removal agent of this invention is obtained through calcination, has a stable structure, can be recycled, and is energy-saving and environmentally friendly. The preparation process of the cyanide removal agent of this invention is simple and suitable for industrial production.

[0025] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Detailed Implementation

[0026] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods.

[0028] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0029] Example 1:

[0030] Hydroxyapatite and cassava starch were mixed uniformly and dispersed in a 70% volume fraction of ethylene glycol solution under ultrasonic treatment at 700 W for 45 min, then 4-vinylpyridine (added in an amount of 2 mL: 1 g in terms of volume: mass ratio of cassava starch) and potassium persulfate (added in an amount of 0.3: 1 in terms of mass ratio of cassava starch) were added, and the mixture was stirred at 75°C for 6 h, then catechol (added in an amount of 0.03: 1 in terms of mass ratio of cassava starch) was added while maintaining the temperature, and the mixture was stirred for another 3 h, after the reaction was completed, the mixture was filtered, and the obtained solid product was washed and dried to obtain modified hydroxyapatite; in the above reaction process, hydroxyapatite, cassava starch, and ethylene glycol solution were added in an amount of 1 g: 0.75 g: 30 mL in terms of mass: volume ratio.

[0031] The modified hydroxyapatite was mixed with a 3% by weight sodium hydroxide solution in a mass: volume ratio of 1 g: 75 mL and stirred uniformly, then the system was heated to 125°C and stirred for 2 h, after the reaction was completed, the mixture was filtered, and the obtained product was frozen at -30°C for 10 h to obtain a freeze-dried product.

[0032] Under a nitrogen atmosphere, the obtained freeze-dried product was calcined at 700°C for 4 h, after the calcination was completed, the product was cooled to room temperature, and the product was crushed, ground, and passed through a 70-mesh sieve to obtain a de-cyanogen agent.

[0033] Example 2:

[0034] Hydroxyapatite and corn starch were mixed uniformly and dispersed in a 60% volume fraction of ethanol solution under ultrasonic treatment at 800 W for 30 min, then 4-vinylpyridine (added in an amount of 3 mL: 1 g in terms of volume: mass ratio of corn starch) and potassium persulfate (added in an amount of 0.5: 1 in terms of mass ratio of corn starch) were added, and the mixture was stirred at 50°C for 8 h, then catechol (added in an amount of 0.01: 1 in terms of mass ratio of corn starch) was added while maintaining the temperature, and the mixture was stirred for another 5 h, after the reaction was completed, the mixture was filtered, and the obtained solid product was washed and dried to obtain modified hydroxyapatite; in the above reaction process, hydroxyapatite, corn starch, and ethanol solution were added in an amount of 1 g: 1 g: 50 mL in terms of mass: volume ratio.

[0035] The modified hydroxyapatite was mixed with a 1% by weight potassium hydroxide solution in a mass: volume ratio of 1 g: 50 mL and stirred uniformly, then the system was heated to 150°C and stirred for 1 h, after the reaction was completed, the mixture was filtered, and the obtained product was frozen at -20°C for 12 h to obtain a freeze-dried product.

[0036] Under a nitrogen atmosphere, the obtained freeze-dried product was calcined at 400°C for 6 h, after the calcination was completed, the product was cooled to room temperature, and the product was crushed, ground, and passed through a 40-mesh sieve to obtain a de-cyanogen agent.

[0037] Example 3:

[0038] The hydroxyapatite and sweet potato starch were mixed uniformly and dispersed in a 80% volume fraction of ethylene glycol solution under ultrasonic at 600W for 60min, then 4-vinylpyridine (added according to the volume mass ratio of 1mL:1g with the sweet potato starch) and potassium persulfate (added according to the mass ratio of 0.1:1 with the sweet potato starch) were added, stirred at 100℃ for 4h, then the temperature was kept unchanged, hydroquinone (added according to the mass ratio of 0.05:1 with the sweet potato starch) was added and stirred for 1h, after the reaction was completed, the solid product was filtered, washed, dried to obtain modified hydroxyapatite; in the above reaction process, the hydroxyapatite, sweet potato starch and ethylene glycol solution were added according to the mass volume ratio of 1g:0.5g:10mL.

[0039] The modified hydroxyapatite was mixed with 5wt% lithium hydroxide solution according to the mass volume ratio of 1g:100mL and stirred uniformly, then the system was heated to 100℃ and stirred for 3h, after the reaction was completed, the product was filtered, frozen at-40℃ for 8h to obtain a freeze-dried product.

[0040] The freeze-dried product was calcined at 1000℃ for 2h under nitrogen atmosphere, after the calcination was completed, the product was cooled to room temperature, crushed, ground and passed through a 100 mesh sieve to obtain a cyanide removal agent.

[0041] Example 4:

[0042] The hydroxyapatite and potato starch were mixed uniformly and dispersed in a 75% volume fraction of 1-hexanol solution under ultrasonic at 700W for 40min, then 4-vinylpyridine (added according to the volume mass ratio of 2mL:1g with the potato starch) and ammonium persulfate (added according to the mass ratio of 0.2:1 with the potato starch) were added, stirred at 60℃ for 7h, then the temperature was kept unchanged, hydroquinone (added according to the mass ratio of 0.04:1 with the potato starch) was added and stirred for 2h, after the reaction was completed, the solid product was filtered, washed, dried to obtain modified hydroxyapatite; in the above reaction process, the hydroxyapatite, potato starch and 1-hexanol solution were added according to the mass volume ratio of 1g:0.6g:40mL.

[0043] The modified hydroxyapatite was mixed with 4wt% lithium hydroxide solution according to the mass volume ratio of 1g:90mL and stirred uniformly, then the system was heated to 140℃ and stirred for 2h, after the reaction was completed, the product was filtered, frozen at-35℃ for 9h to obtain a freeze-dried product.

[0044] The freeze-dried product was calcined at 500℃ for 5h under nitrogen atmosphere, after the calcination was completed, the product was cooled to room temperature, crushed, ground and passed through an 80 mesh sieve to obtain a cyanide removal agent.

[0045] Example 5:

[0046] Hydroxyapatite and cassava starch were mixed uniformly and dispersed in a 1-propanol solution with a volume fraction of 65% under ultrasonic waves at 600 W for 50 min, then 4-vinylpyridine (added in an amount of 1 mL: 1 g in terms of volume: mass ratio of cassava starch) and ammonium persulfate (added in an amount of 0.4: 1 in terms of mass ratio of cassava starch) were added, and stirring was performed at 90°C for 5 h, then the temperature was kept unchanged, resorcinol (added in an amount of 0.02: 1 in terms of mass ratio of cassava starch) was added, and stirring was continued for 2 h, after the reaction was completed, filtration was performed, and the obtained solid product was washed and dried to obtain modified hydroxyapatite; in the above reaction process, hydroxyapatite, cassava starch, and the 1-propanol solution were added in an amount of 1 g: 0.9 g: 20 mL in terms of mass: volume ratio.

[0047] The modified hydroxyapatite was mixed with a 2wt% potassium hydroxide solution in a mass: volume ratio of 1 g: 60 mL and stirred uniformly, then the system was heated to 110°C and stirring was performed for 3 h, after the reaction was completed, filtration was performed, and the obtained product was frozen at -25°C for 11 h to obtain a freeze-dried product.

[0048] The obtained freeze-dried product was calcined at 900°C for 3 h under a nitrogen atmosphere, after the calcination was completed, the product was cooled to room temperature, and the product was crushed, ground, and passed through a 50-mesh sieve to obtain a cyanide removal agent.

[0049] Example 6:

[0050] Hydroxyapatite and corn starch were mixed uniformly and dispersed in a 1-butanol solution with a volume fraction of 80% under ultrasonic waves at 800 W for 50 min, then 4-vinylpyridine (added in an amount of 3 mL: 1 g in terms of volume: mass ratio of corn starch) and ammonium persulfate (added in an amount of 0.4: 1 in terms of mass ratio of corn starch) were added, and stirring was performed at 70°C for 6 h, then the temperature was kept unchanged, resorcinol (added in an amount of 0.02: 1 in terms of mass ratio of corn starch) was added, and stirring was continued for 3 h, after the reaction was completed, filtration was performed, and the obtained solid product was washed and dried to obtain modified hydroxyapatite; in the above reaction process, hydroxyapatite, corn starch, and the 1-butanol solution were added in an amount of 1 g: 0.8 g: 20 mL in terms of mass: volume ratio.

[0051] The modified hydroxyapatite was mixed with a 2wt% sodium hydroxide solution in a mass: volume ratio of 1 g: 80 mL and stirred uniformly, then the system was heated to 120°C and stirring was performed for 2 h, after the reaction was completed, filtration was performed, and the obtained product was frozen at -30°C for 10 h to obtain a freeze-dried product.

[0052] The obtained freeze-dried product was calcined at 600°C for 5 h under a nitrogen atmosphere, after the calcination was completed, the product was cooled to room temperature, and the product was crushed, ground, and passed through a 60-mesh sieve to obtain a cyanide removal agent.

[0053] Comparative Example 1

[0054] The hydroxyapatite was mixed with a 3wt% sodium hydroxide solution at a mass-volume ratio of 1g:75mL and stirred uniformly, then the system was heated to 125°C and stirred for 2h of reaction. After the reaction was completed, the product was filtered, frozen at -30°C for 10h, and then lyophilized to obtain a lyophilizate.

[0055] The lyophilizate was calcined at 700°C for 4h under a nitrogen atmosphere, and after the calcination was completed, the product was cooled to room temperature, crushed, ground, and then sieved through a 70-mesh screen to obtain a cyanide removal agent.

[0056] Comparative Example 2

[0057] The hydroxyapatite and cassava starch were mixed uniformly and dispersed in a 70% volume fraction of a glycol solution under ultrasonication at 700W for 45min. Then, 4-vinylpyridine (added at a volume-mass ratio of 2mL:1g of cassava starch) and potassium persulfate (added at a mass ratio of 0.3:1 of cassava starch) were added, and the mixture was stirred at 75°C for 6h. Subsequently, the temperature was maintained, catechol (added at a mass ratio of 0.03:1 of cassava starch) was added, and the mixture was stirred for another 3h. After the reaction was completed, the solid product was washed, dried, crushed, ground, and then sieved through a 70-mesh screen to obtain modified hydroxyapatite, which was used as a cyanide removal agent. In the above reaction process, the hydroxyapatite, cassava starch, and glycol solution were added at a mass-volume ratio of 1g:0.75g:30mL.

[0058] Comparative Example 3

[0059] The hydroxyapatite and cassava starch were mixed uniformly and dispersed in a 70% volume fraction of a glycol solution under ultrasonication at 700W for 45min. After the reaction was completed, the solid product was washed, dried, and then sieved through a 70-mesh screen to obtain modified hydroxyapatite. In the above reaction process, the hydroxyapatite, cassava starch, and glycol solution were added at a mass-volume ratio of 1g:0.75g:30mL.

[0060] The modified hydroxyapatite was mixed with a 3wt% sodium hydroxide solution at a mass-volume ratio of 1g:75mL and stirred uniformly, then the system was heated to 125°C and stirred for 2h of reaction. After the reaction was completed, the product was filtered, frozen at -30°C for 10h, and then lyophilized to obtain a lyophilizate.

[0061] The lyophilizate was calcined at 700°C for 4h under a nitrogen atmosphere, and after the calcination was completed, the product was cooled to room temperature, crushed, ground, and then sieved through a 70-mesh screen to obtain a cyanide removal agent.

[0062] Comparative Example 4

[0063] Hydroxyapatite is dispersed in a 70% volume fraction of ethylene glycol solution under ultrasonic waves at 700 W for 45 min, then 4-vinylpyridine (added in an amount of 2 mL: 1 g in terms of volume: mass ratio of hydroxyapatite) and potassium persulfate (added in an amount of 0.3: 1 in terms of mass ratio of hydroxyapatite) are added, and the mixture is stirred at 75°C for 6 h, then the temperature is kept unchanged, catechol (added in an amount of 0.03: 1 in terms of mass ratio of hydroxyapatite) is added, and the mixture is stirred for another 3 h, after the reaction is completed, the mixture is filtered, and the obtained solid product is washed, dried, and then modified hydroxyapatite is obtained; in the above reaction process, the hydroxyapatite and the ethylene glycol solution are added in an amount of 1 g: 30 mL in terms of mass: volume ratio.

[0064] The modified hydroxyapatite is mixed with a 3% sodium hydroxide solution in a mass: volume ratio of 1 g: 75 mL and stirred uniformly, then the system is heated to 125°C and stirred for 2 h, after the reaction is completed, the mixture is filtered, and the obtained product is frozen at -30°C for 10 h to obtain a freeze-dried product.

[0065] The freeze-dried product is calcined at 700°C for 4 h under a nitrogen atmosphere, after the calcination is completed, the product is cooled to room temperature, and then the product is crushed, ground, and passed through a 70-mesh sieve to obtain a cyanide removal agent.

[0066] Test Example: Detection of the removal effects of different cyanide removal agents on cyanide and metal ions in wastewater

[0067] Test objects: cyanide removal agents of Examples 1-6 and Comparative Examples 1-4.

[0068] Test method:

[0069] 1. The concentrations of copper, iron, and zinc ions in the solution are measured by atomic absorption spectrophotometry (AAS: TAS-990), and the total cyanide concentration in the solution is measured by silver nitrate titration according to the national standard “HJ 484-2009 Determination of Cyanide in Water by Volumetric and Spectrophotometric Methods”.

[0070] 2. The cyanide-containing wastewater used in the experiment is wastewater discharged by a gold smelting enterprise in Hebei Province, and the pollutants and indicators in the wastewater are as follows: the total cyanide concentration is 458 mg / L, the copper concentration is 36 mg / L, the zinc concentration is 28 mg / L, and the iron concentration is 76 mg / L.

[0071] 3. The above wastewater 10 L is evenly divided into 10 groups, each group being 1 L, and numbered as groups 1-10; 100 mg of the cyanide removal agents of Examples 1-6 and Comparative Examples 1-4 is added to each group of wastewater, and the mixture is stirred at a speed of 400 rpm for 10 min and then left to stand for 2 h, after which the supernatant is taken to detect the concentrations of various pollutants, and the removal rates of various pollutants are calculated.

[0072] Removal rate = (initial pollutant concentration - pollutant concentration after treatment) / initial pollutant concentration x 100%.

[0073] Experimental results: see Table 1.

[0074] As can be seen from the results in Table 1, the cyanide removal agent prepared according to the methods of the embodiments 1-6 of the present application has a significantly higher removal rate of cyanide in wastewater than the cyanide removal agents of the comparative embodiments 1-4, and the cyanide removal agent prepared according to the methods of the embodiments 1-6 of the present application also has a significantly higher removal rate of metal ions such as copper, iron and zinc in wastewater than the cyanide removal agents of the comparative embodiments 1-4. This shows that the cyanide removal agent of the present application not only has a good cyanide removal effect, but also can remove metal ions in wastewater, thereby achieving the purpose of improving water quality.

[0075] Table 1 removal rates of different groups of pollutants

[0076]

[0077] The above description is only the preferred embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed methods and technical contents to make equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application, which does not depart from the technical solution of the present application, still belongs to the scope of the technical solution of the present application.

Claims

1. A method for preparing a cyanide removal agent, characterized in that, The method includes the following steps: Hydroxyapatite and starch were mixed evenly and then ultrasonically dispersed in an organic alcohol solution with a volume fraction of 60-80%. Then, 4-vinylpyridine and an initiator were added and stirred at 50-100°C for 4-8 hours. Then, while keeping the temperature constant, a crosslinking agent was added and stirring was continued for 1-5 hours. After the reaction was completed, the mixture was filtered, and the resulting solid product was washed and dried to obtain modified hydroxyapatite. Modified hydroxyapatite was mixed with 1-5 wt% alkaline solution at a mass-volume ratio of 1 g: 50-100 mL and stirred until homogeneous. The system was then heated to 100-150 °C and stirred for 1-3 h. After the reaction was completed, the mixture was filtered and the resulting product was frozen at -40 to -20 °C for 8-12 h to obtain lyophilized product. Under a nitrogen atmosphere, the obtained freeze-dried product is calcined at 400-1000℃ for 2-6 hours. After calcination, it is cooled to room temperature. The product is then crushed, ground, and passed through a 40-100 mesh sieve to obtain porous modified hydroxyapatite, which is the cyanide removal agent.

2. The preparation method according to claim 1, characterized in that, The starch is selected from any one or a mixture of two or more of the following: tapioca starch, corn starch, sweet potato starch, and potato starch.

3. The preparation method according to claim 1, characterized in that, The organic alcohol is selected from any one or a mixture of two or more of ethanol, ethylene glycol, 1-propanol, 1-butanol, 1-hexanol, and 1-pentanol.

4. The preparation method according to claim 1, characterized in that, The hydroxyapatite, starch, and organic alcohol solution are added in a mass-volume ratio of 1g:0.5-1g:10-50mL.

5. The preparation method according to claim 1, characterized in that, The ultrasonic conditions are: power 600-800W, time 30-60min.

6. The preparation method according to claim 1, characterized in that, The 4-vinylpyridine was added at a volume-to-mass ratio of 1 to 3 mL to 1 g of starch.

7. The preparation method according to claim 1, characterized in that, The initiator is selected from either ammonium persulfate or potassium persulfate; the initiator is added at a mass ratio of 0.1 to 0.5:1 with starch.

8. The preparation method according to claim 1, characterized in that, The crosslinking agent is selected from any one of catechol, hydroquinone, and resorcinol; the crosslinking agent is added in an amount of 0.01 to 0.05:1 by mass of starch.

9. The preparation method according to claim 1, characterized in that, The alkali is selected from any one or a mixture of two or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

10. A cyanide removal agent, characterized in that, Prepared by the method according to any one of claims 1 to 9.

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