Method for purifying carbon black in alkaline industrial waste residue

Abstract

This invention discloses a method for purifying carbon black from alkaline industrial waste residue, belonging to the field of solid waste resource utilization and carbon material purification technology. This method achieves high-purity carbon black recovery through a multi-stage synergistic process of "CO2 carbonization regulation – flotation separation – acid washing purification". Ammonia is removed by bubbling stripping, and CaCO3 precipitate is generated by the reaction of CO2 gas with Ca(OH)2. The pH of the slurry is adjusted to 7-9 to improve the flotation environment. A combination system of collector, frother, and inhibitor is used to selectively enrich carbon phase particles. The concentrate obtained from flotation is subjected to two-step acid leaching with hydrochloric acid and hydrofluoric acid to remove metal oxides and silicate impurities, resulting in a carbon content exceeding 99%. This method combines alkali reduction, phytotoxicity removal, and purification functions. The process is simple, low-pollution, and suitable for the resource utilization of carbon black from alkaline waste residue.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and carbon material purification technology, specifically relating to a method for purifying carbon black from alkaline industrial waste residue. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Highly alkaline solid waste residue is an alkaline solid or semi-solid waste discharged during industrial production processes such as chemical, metallurgical, and nitrogen fertilizer production. It has a complex composition and poses a high environmental risk. Its characteristics include a pH value often higher than 12, abundant alkaline compounds such as calcium hydroxide, and trace amounts of organic residues and metallic impurities. This type of waste residue contains approximately 11% fixed carbon, mainly in the form of carbon black, exhibiting a certain degree of graphitization and electrical conductivity potential, demonstrating high resource recovery value. If the carbonaceous components can be efficiently separated and purified to industrial-grade standards, it can significantly reduce the waste residue disposal load and environmental risk, and partially replace petrochemical-derived carbon black or natural graphite, thereby alleviating the shortage of high-quality carbon materials.

[0004] Recovering carbon black from high-calcium, high-alkalinity industrial waste is an important direction for resource utilization, but existing technologies have significant limitations. The high-calcium, high-alkalinity environment of alkaline slag causes carbon black to form stable agglomerates with alkaline substances (such as calcium carbonate and hydroxides). Conventional physical sieving, water washing, or acid washing is insufficient to effectively dissociate carbon black particles; instead, it easily leads to gelation due to the alkaline medium, reducing carbon black recovery rates, consuming large amounts of water / acid, generating high-salt wastewater, resulting in high treatment costs and low efficiency. Direct flotation is affected by Ca... 2+ With OH - Interference, poor selectivity, and high reagent consumption make it difficult to obtain high-purity carbon black. While high-temperature or strong oxidation methods can improve purity, they easily damage the microstructure and electrical properties of carbon black, limiting its application in high-value-added materials. Existing methods rarely consider the targeted control of carbon black purification based on the characteristics of alkali slag components, and lack a stepwise removal design for multi-stage impurities, resulting in low purity of the final product that fails to meet industrial application standards. These shortcomings collectively limit the high-value utilization pathway of alkali slag-based carbon black. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for purifying carbon black from alkaline industrial waste. Following the technical principle of "reducing hazards first, then purifying," this invention proposes a green and efficient flotation purification technology route suitable for highly alkaline, high-calcium-based industrial waste. This solves the adverse effects of the highly alkaline environment caused by the high calcium hydroxide content in the system on the flotation behavior of carbon phase particles, thereby achieving efficient separation and recovery of carbon black and ensuring the stabilization and harmless disposal of tailings.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] The first aspect of this invention provides a method for purifying carbon black from alkaline industrial waste, comprising:

[0008] Alkaline industrial waste residue is ground and mixed with solvent to obtain a slurry, and ammonia is removed; the first filter residue is obtained by filtration, dissolved in water, and carbon dioxide is introduced to adjust the pH of the slurry to 7-9, and then filtered to obtain the second filter residue.

[0009] The second filter residue is dissolved in water to obtain a slurry. A collector, frother, and depressant are added and mixed well for a first roughing process. A collector is added to the slurry obtained from the roughing process, and two scavenging processes are performed. A collector and frother are added to the slurry obtained from the scavenging process, and a finer process is performed to obtain carbon black.

[0010] The obtained carbon black was washed successively with hydrochloric acid and water until neutral, then washed with hydrofluoric acid and water until neutral, and dried to obtain carbon black concentrate.

[0011] In some embodiments of the present invention, the alkaline industrial waste residue contains 10-15 wt% carbon, 35-40 wt% calcium, 3-5 wt% silicon, 2-4 wt% aluminum, 1-2 wt% iron, 0.1-0.2 wt% magnesium, and 0.1-0.2 wt% titanium; the balance is water.

[0012] In some embodiments of the present invention, the removal of ammonia is performed by: introducing gas and bubbling to remove ammonia; or introducing ammonia-containing gas into an acidic medium to recover the ammonia source.

[0013] Preferably, the slurry is heated and gas is introduced.

[0014] Preferably, the gas is air.

[0015] Preferably, the acidic medium is a phosphoric acid solution or a sulfuric acid solution.

[0016] In some embodiments of the present invention, the second filter residue is dissolved in water to obtain a slurry with a concentration of 15% to 20%.

[0017] In some embodiments of the present invention, the second filter residue is dissolved in water to obtain a slurry, and a collector, a frother and an inhibitor are added. The amount of collector added is 500~1000 g / t, the amount of frother added is 200~500 g / t, and the amount of inhibitor added is 0.2~0.5 g.

[0018] In some embodiments of the present invention, 250-500 g / t of collector is added to the roughing pulp and two scavenging processes are performed.

[0019] In some embodiments of the present invention, the addition of collector and frother to the slurry obtained by scavenging for fine selection specifically involves: adding 250-500 g / t of collector and 100-250 g / t of frother for the first fine selection, followed by multiple fine selections, with 250-500 g / t of collector added each time.

[0020] The best ones are selected, and then two more rounds of selection are made.

[0021] In some embodiments of the present invention, the collector is any one or more of kerosene, emulsified kerosene, diesel oil, and emulsified diesel oil; the foaming agent is any one or more of pine oil, polypropylene glycol, fatty alcohol, and methyl isobutyl methanol; and the inhibitor is sodium hexametaphosphate.

[0022] In some embodiments of the present invention, the collector is kerosene, the foaming agent is pine oil, and the inhibitor is sodium hexametaphosphate.

[0023] In some embodiments of the present invention, the concentration of hydrochloric acid is 1-5 mol / L, and the mass of the hydrochloric acid solution is 1-1.2 times the mass of carbon black; the washing with hydrochloric acid involves immersing the carbon black in the hydrochloric acid solution, stirring for 5-10 min, and sonicating for 30-60 min.

[0024] In some embodiments of the present invention, the concentration of hydrofluoric acid is 1-5 mol / L, and the mass of the hydrofluoric acid solution is 0.5 to 1 times the mass of carbon black; the washing with hydrofluoric acid involves immersing the carbon black in the hydrofluoric acid solution for 5-10 min and then sonicating for 30-60 min.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention employs a multi-stage synergistic purification mechanism to extract carbon black from alkaline industrial waste. Through a unique combination of pretreatment and multi-stage flotation processes, it effectively overcomes the adverse effects of high-calcium and high-alkalinity environments on carbon black recovery. This results in improved carbon black recovery rate and purity, reduced processing costs, and promotion of solid waste resource utilization. A pretreatment combination process of "grinding-heating bubbling stripping-carbon dioxide carbonization" is used. Heating and bubbling stripping effectively remove volatile ammonia nitrogen components from the waste residue, reducing the potential interference of ammonia gas on the operating environment and flotation reagents in subsequent processes. Next, carbon dioxide is introduced for carbonization adjustment, which not only precisely lowers the slurry pH to the optimal range for flotation (neutral to weakly alkaline, 7-9), but more importantly, carbon dioxide reacts with a large number of calcium ions in the waste residue to form calcium carbonate precipitate. This largely solves the problem of co-precipitation or encapsulation of carbon black and calcium salts in high-calcium environments, creating more favorable conditions for subsequent flotation. Under optimized flotation conditions, a multi-stage flotation process of "roughing-scavenging-cleaning" is adopted, with precise addition of collectors, frothers, and depressants at different stages. This significantly enhances the selective separation efficiency of carbon black particles. On the one hand, it maximizes the extraction of carbon black from the complex waste matrix, contributing to improved carbon black recovery. On the other hand, multiple cleaning and scavenging stages better separate carbon black from residual inorganic mineral impurities (such as silicon-aluminum components), thus helping to obtain carbon black products with higher purity. The entire process demonstrates excellent synergy. The carbon dioxide used in the pretreatment stage can be derived from industrial waste gas, achieving low-cost utilization of carbon resources. The precise pH control and calcium fixation during pretreatment reduce the difficulty of treating strongly alkaline wastewater and the excessive consumption of chemical reagents in subsequent flotation processes, lowering operating costs. Simultaneously, this method transforms difficult-to-dispose-of alkaline industrial waste into valuable resources, achieving high-value utilization of waste and possessing both environmental and economic benefits.

[0027] Furthermore, this invention achieves efficient separation and deep purification of carbon black from alkaline waste residue through a three-stage synergistic process of "CO2 carbonization regulation - flotation separation - acid washing purification". CO2 gas reacts with Ca(OH)2 to generate CaCO3 precipitate, effectively reducing the alkalinity of the system and improving the adsorption conditions of the flotation reagents. After two-step acid leaching with HCl and HF, the carbon black purity can reach 99.39%, demonstrating significant purification effect and recovery efficiency.

[0028] The method provided by this invention is green and low-consumption, and has the dual benefits of reducing alkali and utilizing resources. This method does not require high temperature or strong oxidation conditions, avoids the large amount of high-salt wastewater and secondary pollution generated by traditional water washing methods, and realizes the resource utilization of CO2 tail gas and the recovery and regeneration of ammonia, thus achieving the effects of energy saving, emission reduction and resource recycling.

[0029] The method provided by this invention has strong applicability and potential for engineering and industrial application. The process is simple, operates under mild conditions, and has controllable parameters, making it suitable for various high-calcium and high-alkalinity industrial waste systems. The resulting carbon black has high purity, intact structure, and excellent electrical conductivity, and can partially replace petrochemical carbon black or graphite materials, resulting in significant comprehensive economic and environmental benefits. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 This is a schematic flowchart of the method for purifying carbon black from alkaline industrial waste residue according to Example 1 of the present invention. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a method for purifying carbon black from alkaline industrial waste residue, comprising the following steps: grinding and mixing the alkaline industrial waste residue with a solvent to obtain a slurry, and stripping ammonia gas; filtering to obtain a first filter residue, dissolving it in water, introducing carbon dioxide to adjust the pH of the slurry to 7-9, and filtering to obtain a second filter residue; dissolving the second filter residue in water to obtain a slurry, adding a collector, a frother, and an inhibitor, mixing well, and performing a roughing process; adding a collector to the slurry obtained from the roughing process, and performing two scavenging processes; adding a collector and a frother to the slurry obtained from the scavenging process, and performing a fine cleaning process to obtain carbon black; washing the obtained carbon black sequentially with hydrochloric acid and water until neutral, washing with hydrofluoric acid and water until neutral, and drying to obtain carbon black concentrate.

[0034] See Figure 1 , Figure 1 This is a schematic flowchart of the method for purifying carbon black from alkaline industrial waste provided by the present invention.

[0035] In this invention, there are no special restrictions on the source of any raw materials; they can be commercially available.

[0036] In this invention, the alkaline industrial waste residue can be any high-calcium, high-alkaline industrial waste residue known to those skilled in the art, and there are no special limitations. Preferably, the chemical composition of the alkaline industrial waste residue is: carbon content 10-15 wt%, calcium content 35-40 wt%, silicon content 3-5 wt%, aluminum content 2-4 wt%, iron content 1-2 wt%, magnesium content 0.1-0.2 wt%, titanium content 0.1-0.2 wt%, with the balance being water. This alkaline industrial waste residue has a fixed carbon content of approximately 10-15 wt%, mainly existing in the carbon black phase, possessing a certain degree of graphitization and electrical conductivity potential, showing high resource recovery value.

[0037] Alkaline industrial waste residue is ground and mixed with a solvent to obtain a slurry; the solvent is water or a finely selected mineral slurry. The preferred mass ratio of the alkaline industrial waste residue to the solvent is (1~4):(1~10), more preferably (1~4):(1~6), even more preferably (1~3):(1~4), and most preferably 1:(2~3). The amount of solvent will affect subsequent steps. Too little solvent will cause the slurry viscosity to increase significantly, increase the resistance to stirring and aeration, and make it difficult for bubbles to disperse evenly, thus reducing the deammoniation efficiency; too much solvent will cause the ammonia to be diluted by a large amount of water, requiring a longer time or a larger air flow rate to achieve the same deammoniation effect during stripping, increasing energy consumption. The preferred mixing method is mechanical stirring, ball milling, or grinding mill stirring, more preferably grinding mill stirring. The preferred rotation speed of the grinding mill is ... r / min. The preferred mixing time is 5~30 min, more preferably 5~20 min, and even more preferably 5~15 min. The grinding mill can fully crush alkaline industrial waste residue and reduce the inorganic phase on the surface of carbon black particles. If the time is too short, the subsequent reaction time will be correspondingly longer. Extending the time and increasing the rotation speed can accelerate the crushing process.

[0038] According to the present invention, ammonia is removed from the slurry. The preferred method for ammonia removal is stripping, and more preferably, bubbling stripping with gas introduced into the slurry. Air is preferred as the gas. To further improve the ammonia removal efficiency, the slurry can be heated to increase the ammonia volatilization rate. The heating method is preferably water bath heating; the water bath heating temperature is preferably 40-70°C, more preferably 40-60°C, and even more preferably 45-55°C. A porous gas washing bottle is preferably used for stripping to remove ammonia, and the resulting ammonia-containing gas is directly passed into an acidic medium to recover the ammonia source. Water containing phenolphthalein indicator is preferably used to replace the absorbent to observe the ammonia removal endpoint.

[0039] The acidic medium is preferably a phosphoric acid solution or a sulfuric acid solution.

[0040] After stripping, the slurry is filtered, and the supernatant is recovered for subsequent carbon black purification. The first filter residue is dissolved in water again, and excess carbon dioxide gas is introduced to adjust the pH of the slurry to 7-9. The CO2 gas reacts with Ca(OH)2 to form CaCO3 precipitate, effectively reducing the alkalinity of the system and improving the adsorption conditions of the flotation reagents. The slurry is then filtered again to obtain the second filter residue. The obtained second filter residue is used for flotation.

[0041] According to this invention, the second filter residue is dissolved in water to obtain a slurry with a concentration of 15% to 20%. The slurry concentration affects subsequent flotation steps. Too high a concentration leads to a viscous slurry, poor aeration conditions, difficulty in bubble dispersion, and deterioration of the flotation machine's operating conditions, resulting in decreased recovery rate, reduced concentrate quality, poor selectivity, and increased entrainment of impurities. Too low a concentration reduces the probability of particle-bubble collisions, slows flotation speed, lowers recovery rate, increases costs, and increases water and electricity consumption. A collector, frother, and depressant are added to the slurry, and after thorough mixing, a roughing stage is performed.

[0042] According to the present invention, the second filter residue is dissolved in water to obtain a slurry, and a collector, a frother and an inhibitor are added. The preferred amount of collector is 500~1000 g / t, the preferred amount of frother is 200~500 g / t, and the preferred amount of inhibitor is 0.2~0.5 g.

[0043] After roughing, 250-500 g / t collector is added to the roughing pulp, and two scavenging processes are performed. After the two scavenging processes, a collector and a frother are added to the scavenged pulp, and multiple cleaning processes are performed. Specifically, the cleaning process involves: adding 250-500 g / t collector and 100-250 g / t frother for the first cleaning, followed by multiple cleaning processes, each time adding 250-500 g / t collector. The cleaning process is preferably performed three or four times, and more preferably three times.

[0044] According to the present invention, a process of "coarse selection, sweep selection, and multiple fine selection" is adopted for selective separation.

[0045] According to the present invention, the collector is any one or more of kerosene, emulsified kerosene, diesel oil, and emulsified diesel oil; the foaming agent is any one or more of pine oil, polypropylene glycol, fatty alcohol, and methyl isobutyl methanol; and the inhibitor is sodium hexametaphosphate.

[0046] According to this invention, the collector is kerosene, the frother is pine oil, and the depressant is sodium hexametaphosphate. Single-factor experiments determined that kerosene is the collector, pine oil the frother, and sodium hexametaphosphate the depressant. Kerosene adsorbs onto the carbon black surface, enhancing its hydrophobicity and laying the foundation for bubble binding; pine oil generates stable microbubbles, serving as a "carrier" for the carbon black particles to float; sodium hexametaphosphate adsorbs onto the surface of hydrophilic inorganic impurities (such as calcium and magnesium oxides and silicates), enhancing their hydrophilicity and preventing them from binding with bubbles, ultimately achieving the separation effect of selectively floating carbon black while retaining impurities in the slurry. The synergistic effect of these three components greatly improves the flotation efficiency.

[0047] According to the present invention, after the selection is completed, the obtained carbon black can be deeply purified. The carbon black obtained by flotation is reconstituted into a slurry with a small amount of deionized water, washed with hydrochloric acid, mechanically stirred and ultrasonically vibrated, washed with water until neutral, washed with hydrofluoric acid, mechanically stirred and ultrasonically vibrated, washed with water until neutral, filtered and dried to obtain carbon black concentrate.

[0048] According to the present invention, the concentration of hydrochloric acid is 1-5 mol / L, and the mass of the hydrochloric acid solution is 1-1.2 times the mass of carbon black; the washing with hydrochloric acid involves immersing the carbon black in the hydrochloric acid solution, stirring for 5-10 min, and sonicating for 30-60 min.

[0049] According to the present invention, the concentration of hydrofluoric acid is 1-5 mol / L, and the mass of the hydrofluoric acid solution is 0.5-1 times the mass of carbon black; the washing with hydrofluoric acid involves immersing the carbon black in the hydrofluoric acid solution for 5-10 min and then sonicating for 30-60 min.

[0050] According to the present invention, carbon black concentrate can be dried in an oven at a temperature of 100~110℃ for 1.5~2.5 h.

[0051] This invention achieves efficient separation and deep purification of carbon black from alkaline waste residue through a three-stage synergistic process of "CO2 carbonization regulation - flotation separation - acid washing purification". CO2 gas reacts with Ca(OH)2 to form CaCO3 precipitate, effectively reducing the alkalinity of the system and improving the adsorption conditions of flotation reagents. After two-step acid leaching with HCl and HF, the carbon black purity can reach 99.39%, demonstrating significant purification effect and recovery efficiency.

[0052] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0053] In the following examples, the alkaline industrial waste samples used contained 11.56 wt% carbon, 35-40 wt% calcium, 3-5 wt% silicon, 2-4 wt% aluminum, 1-2 wt% iron, 0.1-0.2 wt% magnesium, and 0.1-0.2 wt% titanium; the balance was water.

[0054] Example 1

[0055] This embodiment provides a method for purifying carbon black from alkaline industrial waste, comprising the following steps:

[0056] A sample of alkaline industrial waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle and air (supplied by an air compressor) was introduced into the slurry at 50°C in a water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification. The remaining solids were dissolved again in deionized water, and excess CO2 gas was introduced to adjust the pH of the slurry to 7-9. The filtered solids were then used for flotation.

[0057] The pretreated waste residue is poured into the flotation cell, and the pulp concentration is adjusted to 15%~20%. 500 g / t kerosene, 200 g / t pine oil, and 0.2 g sodium hexametaphosphate are added. After stirring in the flotation machine for 20~30 min, a roughing process is performed. The pulp obtained from the roughing process is then subjected to two scavenging processes with the addition of 250 g / t kerosene. The scavenging pulp is returned to the flotation cell for further cleaning. The first cleaning process involves the addition of 250 g / t kerosene and 100 g / t pine oil, followed by two more cleaning processes with the addition of 250 g / t kerosene each time. After solid-liquid filtration separation, a carbon black concentrate with a carbon content of 80.91% is obtained. The roughing tailings and the scavenging tailings are combined and disposed of in a harmless manner.

[0058] The carbon black concentrate obtained from flotation was subjected to deep purification treatment. A 5 mol / L hydrochloric acid solution was added to the sample to remove Ca. 2+ Fe 2+ After removing residual metal ions, the mixture was stirred for 5 minutes, then ultrasonically cleaned for 30 minutes, and repeatedly washed with deionized water until the filtrate was neutral. Subsequently, silicate impurities were removed using hydrofluoric acid solution, and the same washing process was repeated. The sample was dried in a 105℃ constant temperature drying oven to constant weight, and the final carbon black concentrate grade reached 99.39%.

[0059] Comparative Example 1

[0060] This comparative example provides a method for purifying carbon black from alkaline industrial waste residue. The difference from Example 1 is that CO2 gas is not introduced and acid washing is not performed. Specifically, the method includes the following steps:

[0061] A sample of alkaline industrial waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle, and air (supplied by an air compressor) was introduced into the slurry at 50°C in a water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification; the solid obtained after filtration was used for flotation.

[0062] The pretreated waste residue is poured into the flotation cell, and the pulp concentration is adjusted to 15%~20%. 500 g / t kerosene, 200 g / t pine oil, and 0.2 g sodium hexametaphosphate are added. After stirring in the flotation machine for 20~30 min, a roughing process is performed. The pulp obtained from the roughing process is then subjected to two scavenging processes with the addition of 250 g / t kerosene. The scavenging pulp is returned to the flotation cell for further cleaning. In the first cleaning process, 250 g / t kerosene and 100 g / t pine oil are added, followed by two more cleaning processes with the addition of 250 g / t kerosene each time. After solid-liquid filtration separation, a carbon black concentrate with a carbon content of 65.07% is obtained. The roughing tailings and the scavenging tailings are combined and disposed of in a harmless manner.

[0063] Comparative Example 2

[0064] This comparative example provides a method for purifying carbon black from alkaline industrial waste. The difference from Example 1 is that the collector is diesel oil and no acid washing is performed. The specific steps include:

[0065] A sample of alkaline industrial waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle and air (supplied by an air compressor) was introduced into the slurry at 50°C in a water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification. The remaining solids were dissolved again in deionized water, and excess CO2 gas was introduced to adjust the pH of the slurry to 7-9. The filtered solids were then used for flotation.

[0066] Pretreated waste residue is added to the flotation cell, and the pulp concentration is adjusted to 15%–20%. 500 g / t diesel oil, 200 g / t pine oil, and 0.2 g sodium hexametaphosphate are added, and the mixture is stirred in the flotation machine for 20–30 minutes for roughing. The pulp obtained from roughing is then subjected to two scavenging processes with the addition of 250 g / t diesel oil. The scavenged pulp is returned to the flotation cell for further cleaning. The first cleaning process involves the addition of 250 g / t diesel oil and 100 g / t pine oil, followed by two more cleaning processes with the addition of 250 g / t diesel oil each time. After solid-liquid filtration separation, a carbon black concentrate with a carbon content of 68.65% is obtained. The roughing tailings and scavenging tailings are combined and disposed of in a harmless manner.

[0067] Comparative Example 3

[0068] This comparative example provides a method for purifying carbon black from alkaline industrial waste. The difference from Example 1 is that the foaming agent is polypropylene glycol and no acid washing is performed. The specific steps include:

[0069] A sample of alkaline industrial waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle and air (supplied by an air compressor) was introduced into the slurry at 50°C in a water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification. The remaining solids were dissolved again in deionized water, and excess CO2 gas was introduced to adjust the pH of the slurry to 7-9. The filtered solids were then used for flotation.

[0070] Pretreated waste residue is added to the flotation cell, and the pulp concentration is adjusted to 15%–20%. 500 g / t kerosene, 200 g / t polypropylene glycol, and 0.2 g sodium hexametaphosphate are added, and the mixture is stirred in the flotation machine for 20–30 min for roughing. The pulp obtained from roughing is then subjected to two scavenging processes with the addition of 250 g / t kerosene. The scavenged pulp is returned to the flotation cell for further cleaning. The first cleaning process involves the addition of 250 g / t kerosene and 100 g / t polypropylene glycol, followed by two more cleaning processes with the addition of 250 g / t kerosene each time. After solid-liquid filtration, a carbon black concentrate with a carbon content of 59.5% is obtained. The roughing tailings and scavenging tailings are combined and disposed of in a harmless manner.

[0071] Comparative Example 4

[0072] This comparative example provides a method for purifying carbon black from alkaline industrial waste. The difference from Example 1 is that the foaming agent is a fatty alcohol and no acid washing is performed. The specific steps include:

[0073] A sample of alkaline industrial waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle and air (supplied by an air compressor) was introduced into the slurry at 50°C in a water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification. The remaining solids were dissolved again in deionized water, and excess CO2 gas was introduced to adjust the pH of the slurry to 7-9. The filtered solids were then used for flotation.

[0074] Pretreated waste residue is added to the flotation cell, and the pulp concentration is adjusted to 15%–20%. 500 g / t kerosene, 200 g / t fatty alcohol, and 0.2 g sodium hexametaphosphate are added, and the mixture is stirred in the flotation machine for 20–30 minutes for roughing. The pulp obtained from the roughing is then subjected to two scavenging processes with the addition of 250 g / t kerosene. The scavenged pulp is returned to the flotation cell for further cleaning. The first cleaning process involves the addition of 250 g / t kerosene and 100 g / t fatty alcohol, followed by two more cleaning processes with the addition of 250 g / t kerosene each time. After solid-liquid filtration, a carbon black concentrate with a carbon content of approximately 63% is obtained. The roughing tailings and the scavenging tailings are combined and disposed of in a harmless manner.

[0075] Comparative Example 5

[0076] This comparative example provides a method for purifying carbon black from alkaline industrial waste residue. The difference from Example 1 is that the carbon black slag is not acid-washed. The specific steps include the following:

[0077] A sample of alkaline waste residue was ground in a planetary mill for 10 minutes and then thoroughly mixed with an equal mass of deionized water to prepare a homogeneous slurry with a mass fraction of 50%. The resulting slurry was placed in a porous gas washing bottle and air (supplied by an air compressor) was introduced into the phosphate absorbent at a 50°C water bath. The airflow passed through the other end into the phosphoric acid absorbent, and bubbling was continued until ammonia was completely removed. The absorbent was then replaced with water containing phenolphthalein indicator to observe the endpoint of ammonia removal. After stripping, the slurry was filtered, and the supernatant was recovered for subsequent purification. The remaining solids were dissolved again in deionized water, and excess CO2 gas was introduced to adjust the pH of the slurry to 7-9. The filtered solids were then used for flotation.

[0078] Pretreated waste residue is added to the flotation cell, and the pulp concentration is adjusted to 15%–20%. 500 g / t kerosene, 200 g / t pine oil, and 0.2 g sodium hexametaphosphate are added, and the mixture is stirred in the flotation machine for 20–30 min before a roughing process. The pulp obtained from the roughing process is then subjected to two scavenging processes with the addition of 250 g / t kerosene. The scavenged pulp is returned to the flotation cell for further cleaning. The first cleaning process involves the addition of 250 g / t kerosene and 100 g / t pine oil, followed by two more cleaning processes with the addition of 250 g / t kerosene each time. After solid-liquid filtration, a carbon black concentrate with a carbon content of 80.91% is obtained. The roughing tailings and the scavenging tailings are combined and disposed of in a harmless manner.

[0079] In summary, the carbon black grade and recovery rate obtained in Example 1 and Comparative Examples 1-5 are shown in Table 1.

[0080] Table 1. Carbon black grade and recovery rate obtained from the examples and comparative examples

[0081]

[0082] Note: The carbon black content in the raw material is 11.56%.

[0083] As shown in Table 1, after neutralization with CO2 gas to adjust pH, flotation enrichment, and acid washing purification in the examples, the carbon black purity was significantly improved to 99.39%, far exceeding that of the comparative examples. The results indicate that CO2 neutralization effectively optimizes the flotation system environment, the rational selection of reagents can significantly promote the selective enrichment of carbon phase particles, and the acid washing step can thoroughly remove inorganic impurities such as calcium and silicon. The synergistic effect of these three steps is key to achieving efficient extraction of high-purity carbon black.

[0084] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for purifying carbon black from alkaline industrial waste residue, characterized in that, include: Alkaline industrial waste residue is ground and mixed with solvent to obtain a slurry, which removes ammonia gas. The first filter residue was obtained by filtration, dissolved in water, and carbon dioxide was introduced to adjust the pH of the slurry to 7-9. The second filter residue was then obtained by filtration. The second filter residue is dissolved in water to obtain a slurry. Collector, frother and depressant are added, mixed and subjected to a first roughing process. Collector is added to the slurry obtained from the roughing process and subjected to two scavenging processes. Collector and frother are added to the slurry obtained from the scavenging process and subjected to a fine cleaning process to obtain carbon black. The obtained carbon black was washed successively with hydrochloric acid and water until neutral, then washed with hydrofluoric acid and water until neutral, and dried to obtain carbon black concentrate; The alkaline industrial waste residue contains 10-15 wt% carbon, 35-40 wt% calcium, 3-5 wt% silicon, 2-4 wt% aluminum, 1-2 wt% iron, 0.1-0.2 wt% magnesium, and 0.1-0.2 wt% titanium; the balance is water. The second filter residue is dissolved in water to obtain a slurry with a concentration of 15% to 20%. The collector is kerosene, the foaming agent is pine oil, and the depressant is sodium hexametaphosphate.

2. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The ammonia removal process involves: introducing gas and bubbling to remove ammonia; and introducing ammonia-containing gas into an acidic medium to recover the ammonia source.

3. The method for purifying carbon black from alkaline industrial waste as described in claim 2, characterized in that, The slurry is heated and gas is introduced to remove ammonia through bubbling.

4. The method for purifying carbon black from alkaline industrial waste as described in claim 2, characterized in that, The gas is air.

5. The method for purifying carbon black from alkaline industrial waste as described in claim 2, characterized in that, The acidic medium is a phosphoric acid solution or a sulfuric acid solution.

6. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The second filter residue is dissolved in water to obtain a slurry. A collector, a frother, and an inhibitor are then added. The amount of collector added is 500~1000 g / t, the amount of frother added is 200~500 g / t, and the amount of inhibitor added is 0.2~0.5 g.

7. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The collector is added to the roughing pulp at a rate of 250-500 g / t, and the pulp is then scavenged twice.

8. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The process of adding collectors and frothers to the slurry obtained from scavenging for fine cleaning specifically involves: adding 250-500 g / t of collector and 100-250 g / t of frother for the first fine cleaning, followed by two more fine cleaning processes, each time adding 250-500 g / t of collector.

9. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The concentration of hydrochloric acid is 1-5 mol / L, and the mass of the hydrochloric acid solution is 1-1.2 times the mass of carbon black; the washing with hydrochloric acid involves immersing the carbon black in the hydrochloric acid solution, stirring for 5-10 min, and then sonicating for 30-60 min.

10. The method for purifying carbon black from alkaline industrial waste as described in claim 1, characterized in that, The concentration of hydrofluoric acid is 1-5 mol / L, and the mass of the hydrofluoric acid solution is 0.5-1 times the mass of carbon black; the washing with hydrofluoric acid involves immersing the carbon black in the hydrofluoric acid solution, stirring for 5-10 min, and sonicating for 30-60 min.

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