Preparation method of modified activated carbon and its application, and quality improvement and modification method of low-value oils and fats

Abstract

The present invention relates to a preparation method and application of modified activated carbon, and a method for improving the quality of low-value oils and fats. The preparation method comprises the following steps: S1, contacting activated carbon with a strong oxidizing acid, heating the reaction, and obtaining pre-modified activated carbon; S2, reacting a thiol-containing compound with an epoxy compound under alkaline conditions, and then mixing the reaction system with the pre-modified activated carbon, heating and stirring, to obtain a first intermediate modified activated carbon; S3, reacting the first intermediate modified activated carbon with an organic amine under alkaline conditions to obtain a second intermediate modified activated carbon; S4, mixing the second intermediate modified activated carbon with a metal salt solution, reacting the mixture under heating conditions, and obtaining a third intermediate modified activated carbon; S5, calcining the third intermediate modified activated carbon under an inert atmosphere to obtain the modified activated carbon. The present invention introduces multiple functional groups through a multi-step synergistic modification technology, thereby improving the adsorption capacity of pollutants such as sulfides, heavy metals, and phospholipids.

Description

Technical Field

[0001] The present invention relates to the technical field of low-quality oil modification, and in particular to a preparation method of modified activated carbon and application thereof, and a method for improving the quality of low-value oil. Background Art

[0002] With the growing global demand for sustainable energy and resource utilization, the reuse of low-quality oils and fats (such as acidified oils and waste cooking oils) has become a critical challenge in the fields of environmental protection and resource recycling. These low-quality oils and fats hold considerable potential value, but inherent limitations hinder their efficient utilization. Specifically, these oils and fats often contain significant impurities, such as sulfides, heavy metals, phospholipids, and polycyclic aromatic hydrocarbons, severely limiting their use as fuels or chemical feedstocks.

[0003] Currently, common oil and fat modification methods include physical adsorption, chemical treatment, and biodegradation. Activated carbon, due to its large specific surface area, rich pore structure, and strong adsorption capacity, is widely used for oil and fat purification. However, ordinary activated carbon has limited adsorption capacity for sulfides, heavy metals, etc., making it difficult to meet the needs of deep purification of low-quality oils and fats. Load modification of activated carbon can improve its adsorption performance, but existing modified activated carbons have the following problems:

[0004] First, the functional groups introduced on activated carbon lack the ability to simultaneously adsorb pollutants such as sulfides, heavy metals, and phospholipids;

[0005] Second, impurities may be introduced during the loading modification process. For example, sulfur-containing organic amines may increase the sulfur content in oils and fats, affecting product quality.

[0006] Therefore, developing a modification method that can simultaneously enhance the adsorption capacity of activated carbon for pollutants such as sulfides, heavy metals, and phospholipids without introducing harmful impurities, with an environmentally friendly process and controllable costs, has important technical value and market prospects. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method and application of modified activated carbon, which can improve the adsorption capacity of pollutants such as sulfides, heavy metals, phospholipids, etc. without introducing harmful impurities.

[0008] The present invention also aims to provide a method for improving the quality of low-value oils and fats.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is:

[0010] One aspect of the present invention provides a method for preparing modified activated carbon, comprising the following steps:

[0011] S1, contacting the activated carbon with a strong oxidizing acid and reacting them under heating conditions to obtain pre-modified activated carbon;

[0012] S2, reacting the thiol-containing compound with the epoxy compound under alkaline conditions, and then mixing the reaction system with the pre-modified activated carbon obtained in step S1, heating and stirring to obtain a first intermediate modified activated carbon;

[0013] Wherein, the thiol-containing compound is selected from one or more of mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, and mercaptoethanol, and the epoxy compound is selected from one or more of epichlorohydrin and glycidyl methacrylate;

[0014] S3, reacting the first intermediate modified activated carbon obtained in step S2 with an organic amine under alkaline conditions to obtain a second intermediate modified activated carbon;

[0015] S4, mixing the second intermediate modified activated carbon obtained in step S3 with a metal salt solution, and reacting them under heating conditions to obtain a third intermediate modified activated carbon;

[0016] Wherein, the metal salt is selected from one or more of iron salts, manganese salts, and zinc salts;

[0017] S5. calcining the third intermediate modified activated carbon obtained in step S4 under an inert atmosphere to obtain modified activated carbon.

[0018] When strong oxidizing acids come into contact with activated carbon, they are adsorbed by it. Subsequently, under heating conditions, the strong oxidizing acid chemically reacts with the activated carbon's carbon skeleton. During this reaction, the carbon atoms on the activated carbon's surface are oxidized, forming oxygen-containing functional groups (such as carboxyl, hydroxyl, carbonyl, and quinone groups) on the surface.

[0019] Under certain conditions, the thiol groups of the thiol-containing compound react with the epoxy groups of the epoxy compound to form carbon-sulfur bonds, ultimately generating a grafted compound containing a thioether bond. Because the activated carbon surface treated with a strong oxidizing acid is rich in oxygen-containing functional groups, the grafted compound can initially be adsorbed onto the activated carbon surface through physical adsorption (such as van der Waals forces and hydrogen bonding) or electrostatic interactions. Under heating and stirring conditions, the grafted compound reacts chemically with the oxygen-containing functional groups on the activated carbon surface to form covalent bonds, achieving chemical bonding. This process firmly fixes the grafted compound to the activated carbon surface, retaining the functional groups (such as carboxyl or thiol) derived from the thiol-containing compound in the grafted compound, thereby introducing functional groups onto the activated carbon surface.

[0020] Furthermore, the modified activated carbon is reacted with an organic amine under alkaline conditions. Alkaline conditions can promote the deprotonation of the carboxyl groups on the surface of the activated carbon and enhance its reactivity. In addition, the carboxyl groups can be converted into carboxylate ions (-COO⁻), which are more likely to undergo condensation reactions with organic amines to form amide bonds, thereby achieving the introduction of amine groups. Compared with direct adsorption of organic amines, it is more solid. In addition, the oxygen-containing functional groups on the surface of the activated carbon can also act as coordinating atoms to form coordination bonds with metal ions, thereby achieving the introduction of metal ions.

[0021] Finally, calcination is used to remove volatile substances and at the same time rearrange and strengthen the chemical bonds on the activated carbon to improve the stability of the modified activated carbon.

[0022] In some embodiments, the mass ratio of the thiol-containing compound to the epoxy compound is (1-1.5):2, preferably (1.1-1.3):2, such as 1.1:2, 1.15:2, 1.2:2, 1.25:2 or 1.3:2.

[0023] In some embodiments, the mass ratio of the thiol-containing compound to the pre-modified activated carbon is (0.5-10):100, preferably (1-5):100.

[0024] In some embodiments, the alkaline condition in step S2 refers to a pH of the reaction system of 8-10.

[0025] In some embodiments, step S2 specifically includes: adding a thiol-containing compound into water and dissolving it, then slowly adding the epoxy compound dropwise, adding sodium carbonate to adjust the pH of the system to 8-10, reacting at room temperature, and adding the pre-modified activated carbon prepared in step S1 after the reaction is completed.

[0026] Furthermore, the mass ratio of the thiol-containing compound to the water is 1:(5-10), and further 1:(7-9).

[0027] In some embodiments, the heating and stirring temperature in step S2 is 60-80°C.

[0028] Furthermore, the heating and stirring time in step S2 is 1 to 3 hours.

[0029] In some embodiments, the alkaline condition in step S3 refers to a pH of the reaction system of 9.5 to 10.5.

[0030] In some embodiments, the alkaline condition in step S3 is obtained by adding ammonia water, which not only provides an alkaline environment but also provides ammonia molecules, which are beneficial for the introduction of amino groups.

[0031] In some embodiments, the organic amine is selected from one or more of diethylenetriamine, triethylenetetramine, and putrescine.

[0032] In some embodiments, the mass ratio of the first intermediate modified activated carbon to the organic amine is 1:(0.05-0.5), and more preferably 1:(0.05-0.2).

[0033] In some embodiments, the reaction temperature in step S3 is 70-90°C.

[0034] Furthermore, the reaction conditions in step S3 are 3 to 5 hours.

[0035] In some embodiments, in step S5, the calcination temperature is 300-500°C.

[0036] Furthermore, the calcination time is 1 to 3 hours.

[0037] In some embodiments, the strong oxidizing acid is nitric acid.

[0038] In some embodiments, the mass ratio of the activated carbon to the strong oxidizing acid is 1:(1-1.5).

[0039] In some embodiments, the strong oxidizing acid is fed in the form of an aqueous solution with a mass concentration of 15% to 25%.

[0040] In some embodiments, in step S1, the reaction is carried out at 60-80°C.

[0041] Furthermore, the reaction time of step S1 is 1 to 3 hours.

[0042] In some embodiments, the iron salt is selected from one or more of ferric chloride and ferric nitrate.

[0043] In some embodiments, the manganese salt is selected from one or more of manganese nitrate and manganese chloride.

[0044] In some embodiments, the zinc salt is selected from one or more of zinc chloride and zinc nitrate.

[0045] In some embodiments, the concentration of the metal salt solution is 0.1-1 mol / L.

[0046] In some embodiments, the mass ratio of the second intermediate modified activated carbon to the metal salt solution is 1:(5-10).

[0047] In some embodiments, the reaction in step S4 is carried out under alkaline conditions.

[0048] In some specific embodiments, the alkaline condition in step S4 refers to a pH of 8-10.

[0049] In some specific embodiments, ammonia water or sodium hydroxide is used to adjust the reaction system of step S4 to be alkaline.

[0050] The second aspect of the present invention is to provide an application of the modified activated carbon obtained by the preparation method as described above, wherein the application includes using the modified activated carbon for adsorption and purification of low-value oils and fats.

[0051] In some embodiments, the low-value oils and fats include one or more of acidified oils, catering waste oils and fats, bio-heavy oils, and vegetable oil residues.

[0052] In some embodiments, the application specifically includes: pre-treating low-value oils and fats, wherein the pre-treatment includes mixing the low-value oils and fats, a demulsifier, and an acidic solution; mixing the pre-treated mixed system with the modified activated carbon, adsorbing under heating conditions, and washing with water after the adsorption is completed to obtain treated oils and fats.

[0053] In some specific embodiments, the modified activated carbon accounts for 0.5% to 5% by mass of the pretreated mixed system.

[0054] In some specific embodiments, the adsorption is performed at 20-60°C.

[0055] Furthermore, the adsorption time is 3 to 6 hours.

[0056] In some specific embodiments, the mass ratio of the low-value oil to the demulsifier is 100:(0.5-3). The demulsifier is a conventional demulsifier in the art and is not specifically limited in this application.

[0057] In some specific embodiments, the mass ratio of the low-value oil to the acidic solution is 100:(1-5).

[0058] Furthermore, the acidic solution is the acidic waste liquid generated in step S1 of the preparation method as described above. Reusing the modified acidic waste liquid can achieve waste liquid recycling while effectively reducing the metal oxide content and ash content in the oil.

[0059] The third aspect of the present invention is to provide a modified activated carbon prepared by the preparation method as described above.

[0060] A fourth aspect of the present invention provides a method for improving the quality of low-value oils and fats, comprising: pretreating the low-value oils and fats, the pretreatment comprising mixing the low-value oils and fats, a demulsifier, and an acidic solution; mixing the pretreated mixture with modified activated carbon, performing adsorption under heating conditions, and washing the mixture with water after adsorption to obtain treated oils and fats; wherein the modified activated carbon is the modified activated carbon prepared by the preparation method described above. The details are as described above and will not be repeated here.

[0061] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0062] The present invention adopts a multi-step synergistic modification technology, namely: contacting activated carbon with a strong oxidizing acid and reacting it under heating conditions to form oxygen-containing functional groups on the surface of the activated carbon; chemically reacting a graft compound containing a thioether bond generated by reacting a sulfhydryl-containing compound with an epoxy compound with the oxygen-containing functional groups on the surface of the activated carbon, thereby firmly fixing the graft compound on the surface of the activated carbon and introducing functional groups such as carboxyl and sulfhydryl groups on the surface of the activated carbon; and then reacting with an organic amine under alkaline conditions and reacting with a metal salt solution to introduce amino groups and metal oxides. Thus, multiple functional groups are introduced on the surface of the activated carbon, avoiding the introduction of harmful impurities. The synergy of multiple functional groups can significantly improve the adsorption capacity of pollutants such as sulfides, heavy metals, and phospholipids.

[0063] The preparation method of the present invention has relatively mild reaction conditions and less pollution. The modified activated carbon obtained can effectively adsorb pollutants such as sulfides, heavy metals, phospholipids in low-quality oils and fats without causing an increase in the sulfur content in the oils and fats. DETAILED DESCRIPTION

[0064] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0065] Unless otherwise specified, the raw materials and instruments mentioned below are commercially available products or can be prepared by referring to existing technologies.

[0066] Example 1: This example provides a method for improving the quality of low-value oils and fats, comprising the following steps:

[0067] 1. Preparation of modified activated carbon:

[0068] 1.1. Mix activated carbon and 20% dilute nitric acid at a mass ratio of 0.15:1, stir at 60°C for 1 hour, separate and obtain pre-modified activated carbon, and collect the acidic waste liquid.

[0069] 1.2. Dissolve thioglycolic acid in water, then slowly add epichlorohydrin dropwise, and simultaneously adjust the pH of the reaction system to 8 by adding sodium carbonate. The reaction is carried out at room temperature (25±5°C). After the reaction is completed, the pre-modified activated carbon obtained in step 1.1 is added, and the mixture is stirred at 60°C for 1 hour to obtain a first intermediate modified activated carbon; wherein the amount of thioglycolic acid is 1% of the total mass of the pre-modified activated carbon; the mass ratio of thioglycolic acid to water is 1:8; and the mass ratio of thioglycolic acid to epichlorohydrin is 1.2:2.

[0070] 1.3. The first intermediate modified activated carbon obtained in step 1.2 was mixed with a mixed solution of ammonia water and diethylenetriamine with a pH of 9.5 in a mass ratio of 1:0.1, and stirred at 70°C for 3 hours to obtain a second intermediate modified activated carbon; wherein the volume ratio of ammonia water to diethylenetriamine is 0.8:1.

[0071] 1.4. The second intermediate modified activated carbon obtained in step 1.3 was mixed with a 0.1 mol / L ferric chloride aqueous solution in a mass ratio of 1:7, and the mixture was reacted at 50°C for 1 hour. During the reaction, 0.05 mol / L ammonia water was added to adjust the pH of the reaction system to 8. After that, the mixture was washed to neutrality and dried to obtain a third intermediate modified activated carbon.

[0072] 1.5. The third intermediate modified activated carbon obtained in step 1.4 is calcined at 300°C for 1 hour under the protection of inert gas (nitrogen), then washed to neutrality and dried to obtain modified activated carbon.

[0073] 2. Mix catering waste grease, demulsifier (purchased from Fengqingyang (Tianjin) Environmental Protection Technology Co., Ltd., demulsifier for oily wastewater), and the acidic waste liquid obtained in step 1.1 in a mass ratio of 100:0.5:2.

[0074] 3. The mixed system of step 2 was mixed with the modified activated carbon obtained in step 1.5 in a mass ratio of 100:3, stirred and adsorbed at 20°C for 3 hours, then washed with water again and centrifuged to obtain high-quality oil.

[0075] Example 2: This example provides a method for improving the quality of low-value oils and fats, comprising the following steps:

[0076] 1. Preparation of modified activated carbon:

[0077] Activated carbon was mixed with 20% dilute nitric acid at a mass ratio of 0.25:1, stirred at 80°C for 3h, and pre-modified activated carbon was obtained after separation, and the acidic waste liquid was collected.

[0078] 1.2. Dissolve mercaptopropionic acid in water, then slowly add glycidyl methacrylate dropwise, and simultaneously add sodium carbonate to adjust the pH of the reaction system to 10. The reaction is carried out at room temperature (25±5°C). After the reaction is completed, the pre-modified activated carbon obtained in step 1.1 is added, and the mixture is stirred at 80°C for 3 hours to obtain a first intermediate modified activated carbon; wherein the amount of mercaptopropionic acid is 5% of the total mass of the pre-modified activated carbon, the mass ratio of mercaptoacetic acid to water is 1:8, and the mass ratio of mercaptoacetic acid to glycidyl methacrylate is 1.2:2.

[0079] 1.3. The first intermediate modified activated carbon obtained in step 1.2 was mixed with a mixed solution of ammonia water and putrescine with a pH of 10.5 in a mass ratio of 1:0.1, and stirred at 90°C for 5 hours to obtain a second intermediate modified activated carbon; wherein the volume ratio of ammonia water to putrescine is 1.2:1.

[0080] 1.4. The second intermediate modified activated carbon obtained in step 1.3 was mixed with a 0.1 mol / L manganese nitrate aqueous solution in a mass ratio of 1:7, and the mixture was reacted at 100°C for 5 h. During the reaction, sodium hydroxide was added to adjust the pH of the reaction system to 10. After that, the mixture was washed to neutrality and dried to obtain a third intermediate modified activated carbon.

[0081] 1.5. The third intermediate modified activated carbon obtained in step 1.4 is calcined at 500°C for 3 h under the protection of inert gas (nitrogen), then washed to neutrality and dried to obtain modified activated carbon.

[0082] 2. Mix catering waste grease, demulsifier (purchased from Fengqingyang (Tianjin) Environmental Protection Technology Co., Ltd., oily wastewater demulsifier), and the acidic waste liquid obtained in step 1.1 in a mass ratio of 100:3:2.

[0083] 3. The mixed system of step 2 was mixed with the modified activated carbon obtained in step 1.5 in a mass ratio of 100:3, stirred and adsorbed at 60°C for 6 hours, then washed with water again and centrifuged to obtain high-quality oil.

[0084] Example 3: This example provides a method for improving the quality of low-value oils and fats, comprising the following steps:

[0085] 1. Preparation of modified activated carbon:

[0086] Activated carbon was mixed with 20% dilute nitric acid at a mass ratio of 0.2:1, stirred at 70°C for 2h, and pre-modified activated carbon was obtained after separation, and the acidic waste liquid was collected.

[0087] 1.2. Dissolve mercaptoethanol in water, then slowly add epichlorohydrin and glycidyl methacrylate dropwise, and simultaneously add sodium carbonate to adjust the pH of the reaction system to 9. The mixture is reacted at room temperature (25±5°C). After the reaction, the pre-modified activated carbon obtained in step 1.1 is added, and the mixture is stirred at 70°C for 2 hours to obtain a first intermediate modified activated carbon; wherein the amount of mercaptoethanol is 3% of the total mass of the pre-modified activated carbon, the mass ratio of thioglycolic acid to water is 1:8, and the mass ratio of thioglycolic acid to epichlorohydrin and glycidyl methacrylate is 1.2:1:1.

[0088] 1.3. The first intermediate modified activated carbon obtained in step 1.2 was mixed with a mixed solution of ammonia water and triethylenetetramine with a pH of 10 in a mass ratio of 1:0.1, and stirred at 80°C for 4 hours to obtain a second intermediate modified activated carbon; wherein the volume ratio of ammonia water to triethylenetetramine is 1:1.

[0089] 1.4. The second intermediate modified activated carbon obtained in step 1.3 was mixed with a 0.5 mol / L zinc chloride aqueous solution in a mass ratio of 1:7, and the mixture was reacted at 75°C for 3 h. During the reaction, 0.05 mol / L ammonia water was added to adjust the pH of the reaction system to 9. After that, the mixture was washed to neutrality and dried to obtain a third intermediate modified activated carbon.

[0090] 1.5. The third intermediate modified activated carbon obtained in step 1.4 is calcined at 400°C for 2 h under the protection of inert gas (nitrogen), then washed to neutrality and dried to obtain modified activated carbon.

[0091] 2. Mix catering waste grease, demulsifier (purchased from Fengqingyang (Tianjin) Environmental Protection Technology Co., Ltd., demulsifier for oily wastewater), and the acidic waste liquid obtained in step 1.1 in a mass ratio of 100:1.5:2.

[0092] 3. The mixed system of step 2 was mixed with the modified activated carbon obtained in step 1.5 in a mass ratio of 100:3, stirred and adsorbed at 40°C for 4.5 hours, then washed with water again and centrifuged to obtain high-quality oil.

[0093] Comparative Example 1: This comparative example provides a method for improving the quality of low-value oils and fats, comprising: mixing catering waste oil and a demulsifier (purchased from Fengqingyang (Tianjin) Environmental Protection Technology Co., Ltd., a demulsifier for clearing oily wastewater) in a mass ratio of 100:0.5 to obtain pretreated oil; then, mixing the pretreated oil with unmodified activated carbon in a mass ratio of 100:3, stirring and adsorbing at 20°C for 3 hours, and finally washing with water and centrifuging to obtain oil.

[0094] Comparative Example 2: This comparative example provides a method for improving the quality of low-value oils and fats, which is basically the same as Example 1, except that the activated carbon pretreatment in step 1.1 is not performed, and the activated carbon is directly mixed with the reaction solution in step 1.2.

[0095] Comparative Example 3: This comparative example provides a method for improving the quality of low-value oils and fats, which is basically the same as Example 1, except that step 1.2 is different. Step 1.2 in this example is as follows:

[0096] Thioglycolic acid, epichlorohydrin, and the pre-modified activated carbon obtained in step 1.1 were mixed in a mass ratio of 1.2:2:120, and stirred at 60° C. for 1 h to obtain a first intermediate modified activated carbon.

[0097] Comparative Example 4: This comparative example provides a method for improving the quality of low-value oils and fats, which is basically the same as Example 1, except that step 1.2 is not performed. That is, the pre-modified activated carbon obtained in step 1.1 is directly mixed with the mixed solution in step 1.3.

[0098] Comparative Example 5: This comparative example provides a method for improving the quality of low-value oils and fats, which is basically the same as Example 1, except that: in step 1.4, ammonia water is not used to adjust the pH of the reaction system during the reaction.

[0099] Comparative Example 6: This comparative example provides a method for improving the quality of low-value oils and fats, which is basically the same as Example 1, except that the calcination treatment in step 1.5 is not performed, and the third intermediate modified activated carbon obtained in step 1.4 is directly used for oil processing.

[0100] Comparative Example 7: This comparative example provides a method for improving the quality of low-value oils. This method is essentially the same as Example 1, differing only in that the pretreatment of the waste cooking oil in step 2 is omitted. Instead, the waste cooking oil is directly adsorbed by stirring using modified activated carbon. The system emulsified, making it impossible to detect indicators.

[0101] Performance testing:

[0102] The waste catering oil raw materials and the oils obtained in the examples and comparative examples were tested for sulfur, phosphorus, total metals, ash, and total sediment (thermal aging). The results are shown in Table 1 below.

[0103] Table 1

[0104]

[0105] Among them, the detection of sulfur content can refer to "GB / T 17040-2019 Petroleum and petroleum products - Determination of sulfur content - Energy dispersive X-ray fluorescence spectrometry"; the detection of phosphorus content and total metal content can refer to "IP 501-2005 Determination of aluminum, silicon, vanadium, nickel, iron, sodium, calcium, zinc and phosphorus in residual fuel oil by ashing method, fusion method and inductively coupled plasma optical emission spectrometry"; the detection of ash content can refer to "GB / T 508-1985 Petroleum products - Determination of ash content"; the detection of total sediment content can refer to "SH / T 0702-2001 Residual fuel oil - Determination of total sediment (aging method)".

[0106] As can be seen from the above table, the method for improving the quality of low-value oils and fats provided in the embodiments of the present application can significantly reduce the content of substances such as sulfur, phosphorus, total metals, and ash in the oils and fats at the same time, which is mainly due to the modified activated carbon prepared by the present invention.

[0107] Although unmodified activated carbon can reduce the content of sulfur, phosphorus, total metals, ash, and other substances in oils and fats to a certain extent, the effect is limited, as shown in Comparative Example 1. The present invention pre-modifies the activated carbon with a strong oxidizing acid to form oxygen-containing functional groups such as hydroxyl, carboxylic acid, and carbonyl groups on the activated carbon surface, thereby changing the surface chemical properties of the activated carbon, making the activated carbon surface more polar. This in turn enables an interaction mechanism with the reaction products of sulfhydryl-containing compounds and epoxy compounds, firmly anchoring the reaction products of sulfhydryl-containing compounds and epoxy compounds to the activated carbon surface. Furthermore, by introducing amine groups and metal ions into the activated carbon, the adsorption capacity for pollutants such as sulfides, phospholipids, and heavy metals is enhanced through the synergistic effect of multiple active functional groups.

[0108] During the aforementioned modification process of the activated carbon, the applicant also added ammonia during the introduction of amine groups. In addition to providing amine groups, the ammonia also promoted the deprotonation of carboxyl groups on the surface of the activated carbon, enhancing its reactivity and making it more susceptible to reaction with and adsorption of amine compounds. Referring to Example 1 and Comparative Example 5, without the use of ammonia to adjust the pH of the reaction system, the modified activated carbon exhibited a reduced adsorption capacity for pollutants such as chemicals, phospholipids, and heavy metals.

[0109] In addition, the applicant also calcined the activated carbon connected with multiple functional groups, removed volatile substances, and reconstructed the surface of the activated carbon, so that the chemical bonds of the multiple functional groups were rearranged and strengthened, further improving the adsorption effect of the modified activated carbon. Referring to Example 1 and Comparative Example 6, without calcination treatment, the adsorption capacity of the modified activated carbon for pollutants such as chemicals, phospholipids, and heavy metals decreased. Calcination temperature that is too low cannot achieve the corresponding effect, and too high a temperature will destroy the structure and function of the activated carbon. The applicant further optimized the calcination temperature to achieve the necessary chemical changes while avoiding excessive damage to the structure and function of the activated carbon.

[0110] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing modified activated carbon, characterized in that: The steps include: S1, contacting the activated carbon with a strong oxidizing acid and reacting them under heating conditions to obtain pre-modified activated carbon; S2, first reacting the thiol-containing compound with the epoxy compound under alkaline conditions, and then mixing the reaction system with the pre-modified activated carbon obtained in step S1, heating and stirring to obtain a first intermediate modified activated carbon; Wherein, the thiol-containing compound is selected from one or more of mercaptoacetic acid, mercaptopropionic acid, mercaptobutyric acid, and mercaptoethanol, and the epoxy compound is selected from one or more of epichlorohydrin and glycidyl methacrylate; S3, reacting the first intermediate modified activated carbon obtained in step S2 with an organic amine under alkaline conditions to obtain a second intermediate modified activated carbon; The organic amine is selected from one or more of diethylenetriamine, triethylenetetramine, and putrescine; the mass ratio of the first intermediate modified activated carbon to the organic amine is 1:(0.05-0.5); and the reaction temperature in step S3 is 70-90°C; S4, mixing the second intermediate modified activated carbon obtained in step S3 with a metal salt solution, and reacting them under heating conditions to obtain a third intermediate modified activated carbon; Wherein, the metal salt is selected from one or more of iron salts, manganese salts, and zinc salts, and the reaction of step S4 is carried out under alkaline conditions; S5. calcining the third intermediate modified activated carbon obtained in step S4 under an inert atmosphere to obtain modified activated carbon.

2. The method for preparing modified activated carbon according to claim 1, wherein The mass ratio of the thiol-containing compound to the epoxy compound is (1-1.5):2; and / or, the mass ratio of the thiol-containing compound to the pre-modified activated carbon is (0.5-10):100; And / or, the alkaline condition in step S2 refers to a pH of the reaction system of 8 to 10; And / or, the heating and stirring temperature in step S2 is 60-80°C.

3. The method for preparing modified activated carbon according to claim 1, wherein The alkaline condition in step S3 refers to the pH of the reaction system being 9.5-10.

5.

4. The method for preparing modified activated carbon according to claim 3, wherein The alkaline condition in step S3 is adjusted by adding ammonia water.

5. The method for preparing modified activated carbon according to claim 1, wherein In step S5, the calcination temperature is 300-500° C. and the calcination time is 1-3 hours.

6. The method for preparing modified activated carbon according to claim 1, wherein The strong oxidizing acid is nitric acid; and / or, the mass ratio of the activated carbon to the strong oxidizing acid is 1:(1-1.5); And / or, the strong oxidizing acid is fed in the form of an aqueous solution with a mass concentration of 15% to 25%; And / or, in step S1, the reaction is carried out at 60-80°C.

7. The method for preparing modified activated carbon according to claim 1, wherein The iron salt is selected from one or more of ferric chloride and ferric nitrate; And / or, the manganese salt is selected from one or more of manganese nitrate and manganese chloride; And / or, the zinc salt is selected from one or more of zinc chloride and zinc nitrate; and / or, the concentration of the metal salt solution is 0.1 to 1 mol / L; And / or, the mass ratio of the second intermediate modified activated carbon to the metal salt solution is 1:(5~10).

8. The method for preparing modified activated carbon according to claim 1, wherein The alkaline condition in step S4 refers to a pH of 8 to 10; And / or, the reaction system in step S4 is adjusted to be alkaline using ammonia water or sodium hydroxide.

9. Use of the modified activated carbon obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The application includes using the modified activated carbon for adsorption purification of low-value oils and fats.

10. The use of modified activated carbon according to claim 9, characterized in that: The low-value oils and fats include one or more of acidified oils, catering waste oils and fats, biological heavy oils, and vegetable oil residues.

11. A method for improving the quality of low-value oils and fats, characterized in that: The method comprises: Pre-treating the low-value oil, the pre-treating comprising mixing the low-value oil, a demulsifier, and an acidic solution; The pretreated mixed system is mixed with modified activated carbon, and adsorption is carried out under heating conditions. After the adsorption is completed, the system is washed with water to obtain treated oil; wherein the modified activated carbon is the modified activated carbon prepared by the preparation method according to any one of claims 1 to 8.

12. The method for improving the quality of low-value oils and fats according to claim 11, characterized in that: The modified activated carbon accounts for 0.5% to 5% of the mass content of the pretreated mixed system; and / or, adsorption is carried out at 20-60° C. for 3-6 hours; and / or, the low-value oils and fats include one or more of acidified oils, catering waste oils and fats, bio-heavy oils, and vegetable oil residues; and / or, the mass ratio of the low-value oil to the demulsifier is 100:(0.5-3); And / or, the mass ratio of the low-value oil to the acidic solution is 100:(1-5).

13. The method for improving the quality of low-value oils and fats according to claim 11, characterized in that: The acidic solution is the acidic waste liquid generated in step S1 of the preparation method according to any one of claims 1 to 8.

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