Environment-friendly recovery method of carbon and heavy metal elements in gasification ash and application thereof

Abstract

This invention belongs to the field of resource recycling technology, and more specifically, relates to an environmentally friendly method for the recovery of carbon and heavy metal elements from gasification ash and its application. The gasification ash is ground and sieved to a particle size <100μm. The ground ash is then slurried with water, and a betaine-type surfactant solution is added to obtain a gasification ash slurry. The pH of the slurry is adjusted to 7-9. An oxidant solution is added, and the mixture is ultrasonically reacted at a frequency of 200 Hz for 10-30 minutes at a temperature of 40-100℃. Further acid leaching is performed for 60-180 minutes at a temperature of 60-100℃. The resulting acid leaching slurry is subjected to solid-liquid separation to obtain an acid leaching filtrate and a filter cake. The leaching rate of heavy metals vanadium, iron, nickel, and aluminum from the gasification ash is greater than 90%. The filter cake is washed until neutral and dried to obtain powdered activated carbon. This activated carbon is used for decolorization and COD removal from wastewater absorbed by pyrolysis tail gas. The activated carbon dosage is 0.1-5%, the stirring time is 30-90 min, the decolorization rate of the pyrolysis wastewater is 100%, and the COD removal rate of the pyrolysis wastewater is over 80%. The acid leaching solution is treated with a two-way precipitation-selective extraction coupling method for gradient separation and recovery of heavy metals in the acid leaching filtrate.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology and relates to an environmentally friendly method for recycling carbon and heavy metal elements in gasification ash and its application. Background Technology

[0002] With rapid economic growth, petroleum resources are dwindling, and the quality and density of crude oil are increasing, leading to a rise in the proportion of residue oil fractions. Coking is currently the main residue oil processing technology, with very low requirements for raw materials, low investment costs, and mature technology. However, it suffers from significant environmental pollution and low light oil yield. With increasingly stringent environmental requirements and the urgent need for oil product upgrading, it is becoming increasingly difficult to meet the actual needs of refineries. Therefore, efficient residue oil conversion is crucial for cracking enterprises. Residue oil decarbonization and hydrotreating are typical mid-oil processing technologies. Decarbonization, represented by delayed coking, features low investment, flexible operation, and low transportation costs, but also suffers from low light oil yield and poor quality. Furthermore, with increasingly stringent policies and regulations, the market circulation of high-sulfur petroleum coke is gradually being prohibited, severely limiting delayed coking technology. Residue oil hydrotreating technology is an environmentally friendly residue oil processing technology with high resource utilization and good product quality, belonging to clean production processes, but with high operating costs. Furthermore, the issue of disposing of unconverted oil after residue hydrotreating has always been a major obstacle to the widespread application of residue hydrotreating technology. Gasification ash is an unavoidable byproduct, and because it is enriched with toxic heavy metals such as vanadium and nickel from crude oil, and also contains a high concentration of sulfur, residue gasification ash is mostly hazardous waste.

[0003] Currently, the treatment of gasification ash typically involves roasting and decarburization to recover valuable metals such as vanadium and nickel. CN112795780A discloses a method for treating petroleum coke gasification ash, which first involves oxidative decarburization. Effective metal leaching is only achieved after the decarburized ash is subjected to high-concentration acid (20-60%) and high-temperature conditions (100-200℃). CN112661162A discloses a method for treating petroleum coke gasification ash and a mesoporous silica material, which first involves oxidative decarburization, followed by alkali and acid treatment of the decarburized ash to achieve effective metal recovery. While these methods aim to recover valuable metal elements from the ash, carbon is not effectively utilized. Furthermore, because the gasification ash contains a certain amount of sulfur and heavy metals such as vanadium and nickel, a large amount of sulfur dioxide gas is generated during roasting, polluting the environment. Additionally, the presence of heavy metals readily forms low-melting-point compounds at high temperatures, leading to ash sintering and affecting the recovery efficiency of heavy metals. Therefore, the roasting process requires strict control of process parameters and cannot achieve effective utilization of carbon resources.

[0004] Therefore, the clean utilization and resource recovery of gasification ash residue, achieving comprehensive recycling and reuse of carbon and valuable metal elements, and realizing the full-scale application of resources, has both environmental and economic significance. In the crude oil cracking process, the absorption wastewater from the cracking tail gas is weakly alkaline and contains a high concentration of organic matter, exhibiting a dark color and high COD. Furthermore, some of the organic matter exists in the form of emulsified oil, making its treatment difficult. Fully recovering carbon and valuable metal elements from the gasification ash residue, and obtaining corresponding products through gradient separation of the valuable metal leachate; the residual carbon after oxidative leaching is prepared into high-quality activated carbon, which is used for decolorization treatment of cracking wastewater and removal of organic pollutants. This achieves effective resource utilization and the goal of treating waste with waste, possessing significant economic and social importance. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the primary objective of this invention is to provide an environmentally friendly method for the recovery of carbon and heavy metal elements from gasification ash and its application.

[0006] This invention first involves mixing crushed gasification ash with a betaine-type amphoteric surfactant. The excellent acid and alkali resistance, emulsifying properties, and dispersing properties of the betaine-type surfactant reduce the interfacial tension between the ash and the solution, increasing the hydrophilicity of the ash. This facilitates the penetration of the oxidant solution into the ash pores, ensuring sufficient interfacial contact. Simultaneously, the betaine-type surfactant's good acid and alkali resistance helps maintain stability during subsequent oxidation and acid leaching processes, preserving the hydrophilic effect of the gasification ash. Then, by adding an oxidant under weakly alkaline conditions, the reduced sulfur in the ash is oxidized, converting sulfur compounds into soluble sulfates. This prevents the escape of hydrogen sulfide during subsequent acid leaching for heavy metal extraction, reducing harm to the environment and human health. During the oxidation process, the complex metal ion system in the gasification ash can act as a catalyst, effectively catalyzing and activating the oxidant to accelerate the oxidation of low-valence metals. On the other hand, the introduction of the oxidant increases the hydrophilic functional groups in the gasification ash, further enhancing the hydrophilicity of the activated carbon, which is beneficial for improving the extraction rate of heavy metals during subsequent acid leaching. The introduction of ultrasound during the oxidation process provides energy, increasing the depth of sulfur oxidation. After the oxidation reaction, heavy metals in the ash are further extracted by acid leaching. Since sulfur has been deeply oxidized, no hydrogen sulfide is released during acid leaching, ensuring the safety of the wet acid leaching process. High-quality activated carbon products are obtained through solid-liquid separation, washing, and drying. This activated carbon product can be directly used for decolorization of pyrolysis wastewater and removal of COD from wastewater. The acid leaching solution utilizes a two-way precipitation-selective extraction coupling method to achieve gradient separation and recovery of valuable metals and prepare corresponding products.

[0007] To achieve the above objectives, the present invention specifically includes the following steps: S1. Crush, grind, and sieve the gasification ash residue to a particle size of <100μm; add water to the finely ground gasification ash residue to make a slurry, add a betaine-type surfactant solution with a concentration of 0.5~3%, and adjust the pH value of the gasification ash residue slurry to 7~9; S2. Add one or more of sodium hypochlorite, calcium hypochlorite, sodium persulfate, and potassium persulfate to the gasified ash slurry in S1 as oxidants to carry out an oxidation reaction. The reaction is carried out by ultrasonication for 10 to 30 minutes, the ultrasonic frequency is 200 Hz, and the reaction temperature is 40 to 100℃. S3. Sulfuric acid is added to the ash slurry after the S2 oxidation reaction for acid leaching. The leaching time is 60-180 min, and the leaching temperature is 60-100℃. The acid leaching slurry after the reaction is subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rate of heavy metals vanadium, iron, nickel, and aluminum in the gasification ash slurry is greater than 90%. S4. The acid leaching filtrate obtained in S3 is subjected to a two-way precipitation-selective extraction coupled method for gradient separation and recovery of heavy metals. First, two-way precipitation is used at a pH of 2-3 to separate vanadium and iron through co-precipitation. The precipitate slurry is filtered to obtain ferrovanadium filter cake and precipitate filtrate. The filter cake is washed to obtain ferric vanadate precipitate. The precipitate filtrate is then subjected to nickel selective extraction to separate and recover nickel and aluminum. The extraction pH is 2.5-3.5, and sulfuric acid is used as the back-extraction agent to obtain nickel sulfate. The raffinate is precipitated with liquid alkali to obtain aluminum hydroxide and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. This method achieves gradient separation of heavy metals and produces high-value-added products. S5. The filter cake obtained in S3 is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of less than 0.5% and a specific surface area greater than 1000 μm. 2 The activated carbon exhibits an adsorption value greater than 180 mg / g for methylene blue and greater than 900 mg / g for iodine. It is used for decolorization and COD removal of crude oil pyrolysis tail gas absorption wastewater. The activated carbon dosage is 0.1–5%, the stirring time is 30–90 min, and the decolorization rate of the pyrolysis wastewater is 100%, while the COD removal rate exceeds 80%.

[0008] Furthermore, the liquid-to-solid ratio of the pulping process described in S1 is 10:1 to 50:1; Furthermore, the betaine-type surfactant described in S1 is one or a combination of two of lauramidopropyl hydroxysulfonate betaine, cocamidopropyl hydroxysulfonate betaine, alkyl dimethyl hydroxypropyl phosphate betaine, and alkyl dimethyl betaine. Furthermore, the dosage of the betaine-type surfactant in S1 is in the mass ratio of (1~10) mL: 100 g; Furthermore, the amount of oxidant used in S2 is 2 to 5 times the theoretical molar amount for the sulfur oxidation reaction in the gasification ash; Furthermore, the acid concentration used in the acid leaching reaction described in S3 is 30~90g / L.

[0009] Compared with the prior art, the present invention has the following advantages: (1) This invention achieves the full and effective resource recovery and reuse of carbon and valuable metal elements in gasification ash residue through oxidation-leaching-gradient separation and recovery, and prepares them into corresponding high value-added products. (2) This invention solves the problem of hydrogen sulfide release caused by direct acid leaching by introducing an oxidant under weakly alkaline conditions, thus ensuring the process safety of wet acid leaching. At the same time, the oxidation further introduces hydrophilic groups, effectively improving the leaching rate of heavy metals. Attached Figure Description

[0010] Figure 1 Hydrogen sulfide release curves during acid leaching before and after oxidation treatment Figure 2 The effect of the prepared activated carbon on the decolorization of pyrolysis wastewater (Figure 1) Detailed Implementation

[0011] The present invention will be further described in detail below with reference to specific embodiments, so that those skilled in the art can implement it based on the description. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0012] Example 1

[0013] An environmentally friendly method for recovering carbon and heavy metals from gasification ash and its application, characterized by the following steps: S1. The gasification ash residue is crushed, ground, and sieved to a particle size of <100μm; the ground gasification ash residue is mixed with water to form a slurry with a liquid-to-solid ratio of 25:1. A 1% lauramide propyl hydroxysulfonic acid betaine surfactant solution is added to adjust the pH of the gasification ash residue slurry to 7~9. The dosage of the betaine surfactant is 5mL:100g of gasification ash residue. S2. Add sodium hypochlorite solution to the gasification ash slurry in S1, and sonicate for 30 minutes at an ultrasonic frequency of 200 Hz and a reaction temperature of 60°C. The amount of sodium hypochlorite used is twice the sulfur content in the gasification ash. S3. Sulfuric acid was added to the ash slurry after the oxidation reaction in S2 for acid leaching. The leaching time was 120 min and the leaching temperature was 90℃. No hydrogen sulfide release was detected during the leaching process. The leached slurry after the reaction was subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rates of heavy metals vanadium, iron, nickel, and aluminum in the gasification ash slag were all greater than 91.5%. S4. The acid leaching filtrate obtained in S3 is subjected to gradient separation and recovery of heavy metals using a two-way precipitation-selective extraction coupled method. First, vanadium and iron are co-precipitated and separated using a two-way precipitation method at a pH of 2.5. The precipitate slurry is filtered to obtain a filter cake and ferrovanadate filtrate. The filter cake is washed to obtain ferrovanadate precipitate. The ferrovanadate filtrate is subjected to selective extraction and back-extraction of nickel at a pH of 3.0 to prepare nickel sulfate product. The raffinate is precipitated to obtain aluminum hydroxide product and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. S5. The filter cake is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of 0.4% and a specific surface area of ​​1150 μm. 2 The activated carbon had an adsorption value of 185 mg / g for methylene blue and 925 mg / g for iodine. This activated carbon was used for decolorization and COD removal of pyrolysis tail gas absorption wastewater. With an activated carbon dosage of 2% and a stirring time of 30 min, the decolorization rate of the pyrolysis wastewater was 100%, and the COD removal rate reached 83%.

[0014] Example 2

[0015] An environmentally friendly method for recovering carbon and heavy metals from gasification ash and its application, characterized by the following steps: S1. The gasification ash residue is crushed, ground, and sieved to a particle size of <100μm; the ground gasification ash residue is mixed with water to form a slurry with a liquid-to-solid ratio of 25:1. A 3% lauramide propyl hydroxysulfonic acid betaine surfactant solution is added to adjust the pH of the gasification ash residue slurry to 7-9. The dosage of the betaine surfactant is 1mL:100g of gasification ash residue. S2. Add calcium hypochlorite solution to the gasification ash slurry in S1, and sonicate for 30 minutes at an ultrasonic frequency of 200 Hz and a reaction temperature of 60 ℃. The amount of calcium hypochlorite used is 3 times the sulfur content in the gasification ash. S3. Acid was added to the ash slurry after the oxidation reaction in S2 for acid leaching. The leaching time was 180 min and the leaching temperature was 95℃. No hydrogen sulfide release was detected during the leaching process. The leached slurry was then subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rate of heavy metals vanadium, iron, nickel, and aluminum in the gasified ash slag was greater than 90.7%. S4. The acid leaching filtrate obtained in step S3 is subjected to gradient separation and recovery of heavy metals using a two-dimensional precipitation-selective extraction coupled method. First, two-dimensional precipitation is used at pH 2.5 to separate vanadium and iron through co-precipitation. The precipitate slurry is filtered to obtain a filter cake and ferrovanadium precipitate filtrate. The filter cake is washed to obtain ferrovanadate precipitate. Then, selective extraction is used at pH 3.0 to selectively extract and back-extract nickel to prepare nickel sulfate product. The raffinate is precipitated to obtain aluminum hydroxide product and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. The distilled water is collected and returned to the ash slurry process. S5. The filter cake is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of 0.45% and a specific surface area of ​​1050 μm. 2 The activated carbon had an adsorption value of 180 mg / g for methylene blue and 910 mg / g for iodine. This activated carbon was used for decolorization and COD removal of pyrolysis tail gas absorption wastewater. When the activated carbon dosage was 4% and the stirring time was 30 min, the decolorization rate of the pyrolysis wastewater was 100%, and the COD removal rate reached 81%.

[0016] Example 3

[0017] An environmentally friendly method for recovering carbon and heavy metals from gasification ash and its application, characterized by the following steps: S1. The gasification ash residue is crushed, ground, and sieved to a particle size of <100μm; the ground gasification ash residue is mixed with water to form a slurry with a liquid-to-solid ratio of 40:1. A 0.5% lauramide propyl hydroxysulfonic acid betaine surfactant solution is added to adjust the pH of the gasification ash residue slurry to 7-9. The dosage of the betaine surfactant is 10mL:100g by mass of the gasification ash residue. S2. Add sodium persulfate solution to the above gasification ash slurry, and sonicate for 30 minutes at an ultrasonic frequency of 200 Hz and a reaction temperature of 90 ℃. The amount of sodium persulfate is 5 times the sulfur content in the gasification ash. S3. Acid was added to the ash slurry after the above oxidation reaction for acid leaching. The acid leaching time was 180 min and the acid leaching temperature was 90℃. No hydrogen sulfide release was detected during the acid leaching process. The acid leaching slurry after the reaction was subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rate of heavy metals vanadium, iron, nickel and aluminum in the gasification ash slag was greater than 90.5%. S4. The acid leaching filtrate obtained in step S3 is subjected to gradient separation and recovery of heavy metals using a two-dimensional precipitation-selective extraction coupled method. First, two-dimensional precipitation is used at pH 2.5 to separate vanadium and iron through co-precipitation. The precipitate slurry is filtered to obtain a filter cake and ferrovanadium precipitate filtrate. The filter cake is washed to obtain ferrovanadate precipitate. Then, selective extraction is used at pH 3.0 to selectively extract and back-extract nickel to prepare nickel sulfate product. The raffinate is precipitated to obtain aluminum hydroxide product and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. The distilled water is collected and returned to the ash slurry process. S5. The filter cake is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of 0.3% and a specific surface area of ​​1300 μm. 2 The adsorption value of methylene blue was 192 mg / g, and the adsorption value of iodine was 937 mg / g. The activated carbon was used for decolorization and COD removal of pyrolysis tail gas absorption wastewater. When the activated carbon dosage was 1% and the stirring time was 30 min, the decolorization rate of the pyrolysis wastewater was 100%, and the COD removal rate reached 85%.

[0018] Example 4

[0019] An environmentally friendly method for recovering carbon and heavy metals from gasification ash and its application, characterized by the following steps: S1. The gasification ash residue is crushed, ground, and sieved to a particle size of <100μm; the ground gasification ash residue is mixed with water to form a slurry with a liquid-to-solid ratio of 25:1. A 1% lauramide propyl hydroxysulfonic acid betaine surfactant solution is added to adjust the pH of the gasification ash residue slurry to 7-9. The dosage of the betaine surfactant is 5mL:100g of gasification ash residue. S2. Add potassium persulfate solution to the gasification ash slurry in S1, and sonicate for 30 minutes at an ultrasonic frequency of 200 Hz and a reaction temperature of 60 ℃. The amount of potassium persulfate used is 4 times the sulfur content in the gasification ash. S3. Acid was added to the ash slurry after the oxidation reaction in S2 for acid leaching. The leaching time was 120 min and the leaching temperature was 90℃. No hydrogen sulfide release was detected during the leaching process. The leached slurry after the reaction was subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rates of heavy metals vanadium, iron, nickel, and aluminum in the gasification ash slag were all greater than 91.5%. S4. The acid leaching filtrate obtained in S3 is subjected to gradient separation and recovery of heavy metals using a two-dimensional precipitation-selective extraction coupled method. First, two-dimensional precipitation is used at pH 2.5 to separate vanadium and iron through co-precipitation. The precipitate slurry is filtered to obtain a filter cake and ferrovanadium precipitate filtrate. The filter cake is washed to obtain ferrovanadate precipitate. Then, selective extraction is used at pH 3.0 to selectively extract and back-extract nickel to prepare nickel sulfate product. The raffinate is precipitated to obtain aluminum hydroxide product and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. The distilled water is collected and returned to the ash slurry process. S5. The filter cake is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of 0.4% and a specific surface area of ​​1150 μm. 2 The adsorption value of methylene blue was 185 mg / g, and the adsorption value of iodine was 925 mg / g. The activated carbon was used for decolorization and COD removal of pyrolysis tail gas absorption wastewater. When the activated carbon dosage was 2% and the stirring time was 30 min, the decolorization rate of the pyrolysis wastewater was 100%, and the COD removal rate reached 83%.

[0020] Comparative Example 1 Compared with Example 1, the difference is that the oxidation treatment in step S2 was not performed, while the remaining steps and parameters were the same. Hydrogen sulfide release was detected during the acid leaching process in step S3, with a maximum concentration of 12 mg / L. The activated carbon ash obtained in step S5 had a content of 1.2% and a specific surface area of ​​920 μm. 2 / g, methylene blue adsorption value is 162 mg / g, iodine adsorption value is 896 mg / g. The decolorization rate of the pyrolysis wastewater is 100%, but the COD removal rate is only 65%.

[0021] Comparative Example 2 Compared with Example 1, the difference is that no surfactant was added in step S1, while the other steps and parameters were the same. Hydrogen sulfide release was detected during the acid leaching process in step S3, with a maximum concentration of 8 mg / L. The activated carbon ash obtained in step S5 had a content of 2.1% and a specific surface area of ​​480 μm. 2 / g, methylene blue adsorption value is 85 mg / g, iodine adsorption value is 320 mg / g. The decolorization rate of the pyrolysis wastewater is 80%, but the COD removal rate is only 35%.

[0022] Comparative Example 3 Compared with Example 2, the difference is that the amount of oxidant used in step S2 is 1 times the amount of sulfur, while the other steps and parameters are the same. Hydrogen sulfide release was detected during the acid leaching process in step S3, with a maximum concentration of 4 mg / L. The activated carbon ash obtained in step S5 has a content of 1.0% and a specific surface area of ​​880 μm. 2 / g, methylene blue adsorption value is 158mg / g, iodine adsorption value is 900mg / g. The decolorization rate of the pyrolysis wastewater is 80%, and the COD removal rate is 70%.

[0023] Comparative Example 4 Compared with Example 3, the difference is that 0.5% surfactant is added in step S1, wherein the amount of betaine-type surfactant added is 0.5 mL: 100 g in mass ratio to gasification ash. The remaining steps and parameters are the same. Hydrogen sulfide release was detected during acid leaching in step S3, with a maximum concentration of 8 mg / L. The activated carbon ash obtained in step S5 has a content of 1.8% and a specific surface area of ​​658 μm. 2 / g, methylene blue adsorption value is 120 mg / g, iodine adsorption value is 750 mg / g. The decolorization rate of the pyrolysis wastewater is 85%, but the COD removal rate is only 46%.

[0024] The results of Examples 1-4 and Comparative Examples 1-4 are shown in the table below: hydrogen sulfide concentration mg / L 0 0 0 0 12 8 4 6 Specific surface area <![CDATA[m 2 / g]]> 1150 1050 1300 1230 920 480 880 658 methylene blue adsorption value mg / g 185 180 192 195 162 85 158 120 Iodine adsorption value mg / g 925 910 937 982 816 320 780 750 Decolorization rate % 100 100 100 100 100 80 80 85 COD removal rate % 83 81 85 84 55 35 70 46 The difference between Comparative Example 1 and Example 1 is that no oxidation reaction was performed before acid leaching. The comparison results show that direct acid leaching leads to the release of hydrogen sulfide, threatening the environment and human health. Oxidation effectively eliminates the release of hydrogen sulfide, ensuring process safety. The difference between Comparative Example 2 and Example 1 is that no betaine-type amphoteric surfactant was added. Betaine-type surfactants can effectively reduce the interfacial tension of the system and increase the hydrophilicity of carbon, thus benefiting oxidation and leaching effects, and facilitating the preparation of high-performance activated carbon. The lack of surfactant in Comparative Example 2 resulted in poor hydrophilicity of the gasified ash, insufficient oxidation effect, and poor acid leaching effect. It failed to achieve effective sulfur oxidation and metal leaching, leading to the continued release of hydrogen sulfide during the acid leaching process. The resulting activated carbon had high ash content and slightly inferior performance, ultimately resulting in poor COD removal and decolorization rates. The difference between Comparative Example 3 and Example 2 lies in the insufficient amount of oxidant, resulting in poor sulfur oxidation and residual sulfur. Hydrogen sulfide is released during acid leaching. The difference between Comparative Example 4 and Example 3 lies in the insufficient amount of surfactant, leading to slightly lower hydrophilicity of the gasification ash. This results in poor sulfur oxidation and metal leaching, and hydrogen sulfide release is detected during acid leaching. The poor metal leaching leads to poor performance of the resulting activated carbon, resulting in slightly poorer decolorization and COD removal effects on the pyrolysis wastewater.

[0025] In summary, the method provided by this invention increases the hydrophilicity of carbon by using a betaine-type amphoteric surfactant, and then achieves sulfur oxidation through wet oxidation, with no release of hydrogen sulfide during acid leaching; the resulting activated carbon has good decolorization and COD removal performance.

[0026] The applicant declares that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above detailed methods, that is, it does not mean that the present invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that equivalent substitutions of the raw materials for the products of the present invention, the addition of auxiliary components, and the selection of specific methods all fall within the protection and disclosure scope of the present invention.

Claims

1. An environmentally friendly method for recovering carbon and heavy metal elements from gasification ash and its application, characterized in that, The method is as follows: S1. Crush, grind, and sieve the gasification ash residue to a particle size of <100μm; add water to the finely ground gasification ash residue to make a slurry, add a betaine-type surfactant solution with a concentration of 0.5~3%, and adjust the pH value of the gasification ash residue slurry to 7~9; S2. Add one or more of sodium hypochlorite, calcium hypochlorite, sodium persulfate, and potassium persulfate to the gasified ash slurry in S1 as oxidants to carry out an oxidation reaction. The reaction is carried out by ultrasonication for 10 to 30 minutes, the ultrasonic frequency is 200 Hz, and the reaction temperature is 40 to 100℃. S3. Add sulfuric acid to the ash slurry after the S2 oxidation reaction for acid leaching. The leaching time is 60-180 min, and the leaching temperature is 60-100℃. The acid leaching slurry after the reaction is subjected to solid-liquid separation to obtain acid leaching filtrate and filter cake. The leaching rate of heavy metals vanadium, iron, nickel, and aluminum in the gasification ash slurry is greater than 90%. S4. The acid leaching filtrate obtained in S3 is subjected to a two-way precipitation-selective extraction coupled method for gradient separation and recovery of heavy metals. First, two-way precipitation is used at a pH of 2-3 to separate vanadium and iron through co-precipitation. The precipitate slurry is filtered to obtain ferrovanadium filter cake and precipitate filtrate. The filter cake is washed to obtain ferric vanadate precipitate. The precipitate filtrate is then subjected to nickel selective extraction to separate and recover nickel and aluminum. The extraction pH is 2.5-3.5, and sulfuric acid is used as the back-extraction agent to obtain nickel sulfate. The raffinate is precipitated with liquid alkali to obtain aluminum hydroxide and high-salt wastewater. The high-salt wastewater is evaporated and crystallized to obtain sodium sulfate. This method achieves gradient separation of heavy metals and produces high-value-added products. S5. The filter cake obtained in S3 is washed until neutral and then dried to obtain powdered activated carbon. This activated carbon has an ash content of less than 0.5% and a specific surface area greater than 1000 μm. 2 The activated carbon exhibits an adsorption value greater than 180 mg / g for methylene blue and greater than 900 mg / g for iodine. It is used for decolorization and COD removal of crude oil pyrolysis tail gas absorption wastewater. The activated carbon dosage is 0.1–5%, the stirring time is 30–90 min, and the decolorization rate of the pyrolysis wastewater is 100%, while the COD removal rate exceeds 80%.

2. The environmentally friendly method for recovering carbon and heavy metal elements from gasification ash slag according to claim 1 and its application, characterized in that: The liquid-to-solid ratio for pulping described in S1 is 10:1 to 50:

1.

3. The environmentally friendly method for recovering carbon and heavy metal elements from gasification ash as described in claim 1, and its application, is characterized in that: The betaine-type surfactant described in S1 is one or a combination of two of the following: lauramidopropyl hydroxysulfonate betaine, cocamidopropyl hydroxysulfonate betaine, alkyl dimethyl hydroxypropyl phosphate betaine, and alkyl dimethyl betaine.

4. The environmentally friendly method for recovering carbon and heavy metal elements from gasification ash as described in claim 1, and its application, is characterized in that: The dosage of the betaine-type surfactant described in S1 is in the mass ratio of (1~10) mL:100g to the gasification ash residue.

5. The environmentally friendly method for recovering carbon and heavy metal elements from gasification ash slag according to claim 1 and its application, characterized in that: The amount of oxidant used in S2 is 2 to 5 times the theoretical molar amount for the sulfur oxidation reaction in the gasified ash.

6. The environmentally friendly method for recovering carbon and heavy metal elements from gasification ash slag according to claim 1 and its application, characterized in that: The acid concentration used in the acid leaching reaction described in S3 is 30~90g / L.

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