A pyrolysis biochar adsorption material and its preparation method and application

Abstract

The present invention provides a pyrolytic biochar adsorption material, a preparation method and an application thereof. The pyrolytic biochar adsorption material of the present invention comprises a pyrolytic biochar carrier, and amino functional groups are distributed on the pyrolytic biochar carrier. The pyrolytic biochar adsorption material of the present invention can achieve the complete detoxification and resource utilization of chromium slag and the resource utilization of municipal sludge pyrolysis carbon residue. The chromium slag can be completely detoxified without the risk of secondary pollution. The investment cost of the material is low and has good economy. The pyrolytic biochar adsorption material of the present invention has amino functional groups distributed on the pyrolytic biochar carrier, which can improve its adsorption and deposition capacity for metal ions. The present invention also provides a preparation method and an application of the pyrolytic biochar adsorption material.

Description

Technical Field

[0001] The present invention belongs to the technical field of heavy metal treatment, and in particular relates to a pyrolysis biochar adsorption material and a preparation method and application thereof. Background Art

[0002] As the level of municipal infrastructure services in modern cities continues to improve, the amount of municipal sludge generated is gradually increasing. Among the various methods for sludge resource utilization, sludge pyrolysis is gaining increasing attention due to its advantages such as rapid treatment, thorough harmless treatment, good stability of treated sludge, and energy recovery.

[0003] Chromium slag is a byproduct of dichromate production. Its chemical composition is as follows: 4-30% silicon dioxide, 5-10% aluminum oxide, 26-44% calcium oxide, 8-36% magnesium oxide, 2-11% iron oxide, 0.6-0.8% chromium hexaoxide (Cr2O6), and approximately 1% sodium dichromate (Na2Cr2O7). The main minerals in chromium slag include periclase (MgO), calcium silicate (2CaO·SiO2), brüderite (4CaO·Al2O3·Fe2O3), and 1-10% residual chromite. Chromium slag contains water-soluble hexavalent chromium, making it extremely toxic. If left untreated and dumped in the open air, it can cause varying degrees of contamination of groundwater, rivers, or oceans, seriously endangering human health and the growth of plants and animals.

[0004] The current detoxification methods for chromium slag (i.e., converting highly toxic hexavalent chromium into trivalent chromium) are divided into two categories: wet detoxification and dry detoxification. The wet method is to reduce the Cr in the chromium slag by adding a reducing agent. 6+ In liquid phase reduction detoxification, this method consumes a lot of reagents and is high in cost, and is currently difficult to use on a large scale to treat chromium slag.

[0005] Dry detoxification is to reduce hexavalent chromium in chromium slag to trivalent chromium through the strong reducing effect of high temperature reducing atmosphere to achieve the purpose of detoxification. The traditional dry treatment uses carbon as a reducing agent, and heats to about 1000℃ in a reducing atmosphere to reduce the toxic Cr 6+ Reduced to non-toxic Cr 3+ This method has been widely used in the treatment of chromium slag. Although it has certain economic benefits, the treatment process is accompanied by secondary dust pollution, high investment cost and high energy consumption.

[0006] Therefore, a new chromium removal material still needs to be developed. Summary of the Invention

[0007] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention provides a pyrolysis biochar adsorption material that can thoroughly decompose and recycle chromium slag.

[0008] The present invention also provides a method for preparing the pyrolysis biochar adsorption material.

[0009] The present invention also provides an application of the pyrolysis biochar adsorption material.

[0010] A first aspect of the present invention provides a pyrolyzed biochar adsorption material, comprising a pyrolyzed biochar carrier, wherein amino functional groups are distributed on the pyrolyzed biochar carrier.

[0011] One of the technical solutions of the present invention regarding the pyrolysis biochar adsorption material has at least the following beneficial effects:

[0012] The pyrolytic biochar adsorption material of the present invention can achieve complete detoxification and resource utilization of chromium slag, as well as resource utilization of municipal sludge pyrolysis carbon residue. It can completely detoxify chromium slag without the risk of secondary pollution, and the material has low investment cost and good economic benefits.

[0013] The pyrolysis biochar adsorption material of the present invention has amino functional groups distributed on the pyrolysis biochar carrier, which can improve its adsorption and deposition capabilities for metal ions.

[0014] According to some embodiments of the present invention, the raw material for preparing the pyrolysis biochar carrier includes municipal sludge.

[0015] The second aspect of the present invention provides a method for preparing the pyrolyzed biochar adsorption material, comprising the following steps:

[0016] S1: immersing municipal sludge powder in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate to obtain modified municipal sludge powder;

[0017] S2: pyrolyzing the modified municipal sludge powder under a protective atmosphere to obtain sludge-based biochar;

[0018] S3: dispersing the sludge-based biochar into water, adding a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate to carry out an amination reaction to obtain the pyrolysis biochar adsorption material.

[0019] A technical solution in the method for preparing pyrolysis biochar adsorption material of the present invention has at least the following beneficial effects:

[0020] In steps S1 and S2, the dried sludge powder is impregnated with a mixed solution of ammonium bifluoride and ammonium aluminum carbonate and then pyrolyzed. Compared with general reagent impregnation, the ammonia, carbon dioxide and hydrogen fluoride gas generated during the pyrolysis of the dried sludge after impregnation with the mixed solution of ammonium bifluoride and ammonium aluminum carbonate can not only change the pore size, pore volume and other structures of the pyrolytic carbon, but the presence of fluorine atoms can also increase the affinity of the pyrolytic carbon for heavy metals such as hexavalent chromium, which can deeply remove a variety of heavy metals and has a large adsorption capacity.

[0021] The preparation method of the present invention does not require expensive equipment and complicated process control, has undemanding reaction conditions, has readily available raw materials, has low production costs, and is easy to industrialize.

[0022] According to some embodiments of the present invention, in step S1, the municipal sludge powder is a dried powder obtained by dehydrating, drying and crushing municipal sludge.

[0023] According to some embodiments of the present invention, in step S1, the solid-liquid ratio of the municipal sludge powder to the mixed solution is 1:1-20.

[0024] According to some embodiments of the present invention, in the mixed solution of ammonium bifluoride and ammonium aluminum carbonate, the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 1:3-1.

[0025] According to some embodiments of the present invention, the municipal sludge powder is immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate for 2 to 24 hours.

[0026] According to some embodiments of the present invention, after impregnation, the mixture is dried at 105°C to 120°C.

[0027] According to some embodiments of the present invention, in step S2, the pyrolysis temperature is 450°C to 650°C.

[0028] According to some embodiments of the present invention, the holding time of the pyrolysis is 30 to 50 minutes.

[0029] According to some embodiments of the present invention, the heating rate of the pyrolysis is 10-15°C / min.

[0030] According to some embodiments of the present invention, the protective atmosphere is nitrogen, argon or other inert gases with a mass fraction of more than 99%.

[0031] According to some embodiments of the present invention, after pyrolysis, the mixture is naturally cooled to room temperature.

[0032] According to some embodiments of the present invention, in step S3, the sludge-based biochar is washed to neutrality before being dispersed into water.

[0033] According to some embodiments of the present invention, in step S3, the solid-to-liquid ratio of the mixed solution of the sludge-based biochar, hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate is 1 g:1-5 mL.

[0034] According to some embodiments of the present invention, in the mixed solution of cetyltrimethylammonium acetate and cetyltrimethylammonium sulfate, the volume ratio of cetyltrimethylammonium acetate to cetyltrimethylammonium sulfate is 1:3-1.

[0035] Hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate can synergistically improve the amination effect of biochar. During impregnation modification, the synergistic effect of the two can be distributed more evenly inside and on the surface of the biochar, and the amination modification of the biochar is more thorough. If only one is used, the biochar modification may not be thorough. If the modification is not thorough, it will affect the subsequent adsorption and deposition effects of metal ions.

[0036] There are lone pairs of electrons on the nitrogen atom of the amino group, which are easy to combine with metal cations. The reaction of the material containing amino functional groups to adsorb metal ions is a chelation reaction. The material rich in amino functional groups can form a chelate structure with heavy metals. 3+ 、Al 3 + 、C r6+ Metal ions can quickly complex and coordinate with these functional groups to form coordination compounds with a specific structure. Increasing the content of amino functional groups on biochar materials can create more coordination sites, thereby improving their ability to adsorb and deposit metal ions.

[0037] According to some embodiments of the present invention, the temperature of the amination reaction is 40°C to 60°C.

[0038] According to some embodiments of the present invention, the amination reaction time is 3 to 6 hours.

[0039] A third aspect of the present invention provides a method for removing chromium from chromium slag, comprising the following steps:

[0040] (1): Leaching the chromium slag fine material with potassium permanganate acid solution, separating the solid and liquid, and obtaining acid-leached chromium slag and acid leaching solution;

[0041] (2): The pyrolysis biochar adsorption material of the present invention is added to the acid leaching solution to carry out a precipitation reaction.

[0042] The present invention relates to a technical solution for a method for removing chromium from chromium slag, which has at least the following beneficial effects:

[0043] The chromium slag is directly oxidized and leached by potassium permanganate acid solution, and the Cr in the chromium slag can be 3+ Oxidized to Cr 6+The chromium slag leachate also contains a large amount of metal ions such as iron and aluminum ions. The existing technology mainly purifies and removes these metal ions as pollutants. The technical solution of the present invention cleverly uses pyrolysis carbon residue as a carrier. After the surface polarity of the carbon residue is modified, it can be used as a carrier material to efficiently adsorb and precipitate iron and aluminum ions in the chromium slag leachate. By controlling the pH of the leaching solution to precipitate iron and aluminum ions, the iron and aluminum ions in the leaching solution and the Cr in the chromium slag are oxidized by potassium permanganate. 3+ The reduction product MnO2 is converted into MnO2 / iron-aluminum (hydroxide) composite nanomaterials and deposited in situ on the surface of the amino carbon material, and finally a composite material of amino carbon / MnO2 / iron-aluminum (hydroxide) is obtained. On the one hand, this method completes the complete removal of chromium from the chromium slag and the efficient leaching and impurity removal and purification process of the acid leaching solution. On the other hand, it uses pyrolysis biochar residue to remove impurities and obtains a composite material of amino carbon / MnO2 / iron-aluminum (hydroxide). The carbon slag uses its special porous structure as a carrier to give it a high specific surface area, and the iron-aluminum (hydroxide) composite nanomaterial contained therein has high specific surface area for Cr. 6+ The composite material has good affinity to Cr 6+ The maximum adsorption capacity reaches 60 mg / g. In summary, the present invention successfully achieves efficient detoxification of chromium slag and purification of acid leaching liquid without the risk of secondary pollution. In addition, a high-performance chromium adsorption material is prepared based on the purification process, which is conducive to the coordinated and comprehensive utilization of solid waste resources and promotes the realization of the unity of resource, economic and environmental benefits.

[0044] According to some embodiments of the present invention, the concentration of the potassium permanganate acid solution is 2 to 5 mol / L.

[0045] According to some embodiments of the present invention, the liquid-to-solid ratio of the leaching is 2-5 mL:1 g.

[0046] According to some embodiments of the present invention, the stirring speed of the leaching is 100 to 500 rpm.

[0047] According to some embodiments of the present invention, the leaching temperature is 60-100°C.

[0048] According to some embodiments of the present invention, the leaching time is 2 to 12 hours.

[0049] The pyrolysis biochar adsorption material of the present invention is added to the acid leaching solution, a precipitation reaction is carried out, and the solid product obtained by filtration is Cr 6+ Adsorption material, the filtrate can meet the discharge standards. DETAILED DESCRIPTION

[0050] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0051] In some embodiments of the present invention, the present invention provides a pyrolyzed biochar adsorption material, comprising a pyrolyzed biochar carrier, on which amino functional groups are distributed.

[0052] As can be understood, the pyrolytic biochar adsorption material of the present invention can achieve complete detoxification and resource utilization of chromium slag, as well as resource utilization of municipal sludge pyrolysis carbon residue. It can completely detoxify chromium slag without the risk of secondary pollution, and the investment cost of this material is low, with good economic benefits.

[0053] It can also be understood that the pyrolyzed biochar adsorption material of the present invention has amino functional groups distributed on the pyrolyzed biochar carrier, which can improve its adsorption and deposition capabilities for metal ions.

[0054] In some embodiments of the present invention, the raw material for preparing the pyrolysis biochar carrier includes municipal sludge.

[0055] In some other embodiments of the present invention, the present invention provides a method for preparing a pyrolyzed biochar adsorption material, comprising the following steps:

[0056] S1: immersing municipal sludge powder in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate to obtain modified municipal sludge powder;

[0057] S2: pyrolyzing the modified municipal sludge powder under a protective atmosphere to obtain sludge-based biochar;

[0058] S3: dispersing the sludge-based biochar into water, adding a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate to carry out an amination reaction to obtain a pyrolysis biochar adsorption material.

[0059] It can be understood that in steps S1 and S2, the dried sludge powder is impregnated with a mixed solution of ammonium bifluoride and ammonium aluminum carbonate and then pyrolyzed. Compared with the general reagent impregnation, the ammonia, carbon dioxide and hydrogen fluoride gas generated during the pyrolysis of the dried sludge after impregnation with the mixed solution of ammonium bifluoride and ammonium aluminum carbonate can not only change the pore size, pore volume and other structures of the pyrolytic carbon, but the presence of fluorine atoms can also increase the affinity of the pyrolytic carbon for heavy metals such as hexavalent chromium, and can deeply remove a variety of heavy metals with a large adsorption capacity.

[0060] The preparation method of the present invention does not require expensive equipment and complicated process control, has undemanding reaction conditions, has readily available raw materials, has low production costs, and is easy to industrialize.

[0061] In some embodiments of the present invention, in step S1, the municipal sludge powder is a dried powder obtained by dehydrating, drying, and crushing the municipal sludge.

[0062] In some embodiments of the present invention, in step S1, the solid-liquid ratio of the municipal sludge powder to the mixed solution is 1:1-20.

[0063] In some embodiments of the present invention, in the mixed solution of ammonium bifluoride and ammonium aluminum carbonate, the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 1:3-1.

[0064] In some embodiments of the present invention, the municipal sludge powder is immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate for 2 to 24 hours.

[0065] In some embodiments of the present invention, after impregnation, the mixture is dried at 105°C to 120°C.

[0066] In some embodiments of the present invention, in step S2, the pyrolysis temperature is 450°C to 650°C.

[0067] In some embodiments of the present invention, the holding time of pyrolysis is 30 to 50 minutes.

[0068] In some embodiments of the present invention, the heating rate of pyrolysis is 10-15° C. / min.

[0069] In some embodiments of the present invention, the protective atmosphere is nitrogen, argon or other inert gases with a mass fraction of more than 99%.

[0070] In some embodiments of the present invention, after pyrolysis, the mixture is naturally cooled to room temperature.

[0071] In some embodiments of the present invention, in step S3, the sludge-based biochar is washed to neutrality before being dispersed into water.

[0072] In some embodiments of the present invention, in step S3, the solid-to-liquid ratio of the mixed solution of sludge-based biochar, hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium sulfate is 1 g:1-5 mL.

[0073] In some embodiments of the present invention, in the mixed solution of cetyltrimethylammonium acetate and cetyltrimethylammonium sulfate, the volume ratio of cetyltrimethylammonium acetate to cetyltrimethylammonium sulfate is 1:3-1.

[0074] It should be noted that cetyltrimethylammonium acetate and cetyltrimethylammonium sulfate can synergistically improve the amination effect of biochar. During impregnation modification, the synergistic effect of the two can be distributed more evenly inside and on the surface of the biochar, and the amination modification of the biochar is more thorough. If only one is used, the biochar modification may not be thorough. If the modification is not thorough, it will affect the subsequent adsorption and deposition effects of metal ions.

[0075] It should also be noted that there are lone pairs of electrons on the N atom of the amino group, which are easy to combine with metal cations. The reaction of the material containing amino functional groups to adsorb metal ions is a chelation reaction. The material rich in amino functional groups can form a chelate structure with heavy metals. 3+ 、Al 3+ 、C r6+ Metal ions can quickly complex and coordinate with these functional groups to form coordination compounds with a specific structure. Increasing the content of amino functional groups on biochar materials can create more coordination sites, thereby improving their ability to adsorb and deposit metal ions.

[0076] In some embodiments of the present invention, the temperature of the amination reaction is 40°C to 60°C.

[0077] In some embodiments of the present invention, the amination reaction time is 3 to 6 hours.

[0078] In some other embodiments of the present invention, the present invention provides a method for removing chromium from chromium slag, comprising the following steps:

[0079] (1): Leaching the chromium slag fine material with potassium permanganate acid solution, separating the solid and liquid, and obtaining acid-leached chromium slag and acid leaching solution;

[0080] (2): The pyrolysis biochar adsorption material of the present invention is added to the acid leaching solution to carry out a precipitation reaction.

[0081] It can be understood that the chromium slag can be directly oxidized and leached by potassium permanganate acid solution. 3+ Oxidized to Cr 6+ The chromium slag leachate also contains a large amount of metal ions such as iron and aluminum ions. The existing technology mainly purifies and removes these metal ions as pollutants. The technical solution of the present invention cleverly uses pyrolysis carbon residue as a carrier. After the surface polarity of the carbon residue is modified, it can be used as a carrier material to efficiently adsorb and precipitate iron and aluminum ions in the chromium slag leachate. By controlling the pH of the leaching solution to precipitate iron and aluminum ions, the iron and aluminum ions in the leaching solution and the Cr in the chromium slag are oxidized by potassium permanganate. 3+The reduction product MnO2 is converted into MnO2 / iron-aluminum (hydroxide) composite nanomaterials and deposited in situ on the surface of the amino carbon material, and finally a composite material of amino carbon / MnO2 / iron-aluminum (hydroxide) is obtained. On the one hand, this method completes the complete removal of chromium from the chromium slag and the efficient leaching and impurity removal and purification process of the acid leaching solution. On the other hand, it uses pyrolysis biochar residue to remove impurities and obtains a composite material of amino carbon / MnO2 / iron-aluminum (hydroxide). The carbon slag uses its special porous structure as a carrier to give it a high specific surface area, and the iron-aluminum (hydroxide) composite nanomaterial contained therein has high specific surface area for Cr. 6+ The composite material has good affinity to Cr 6+ The maximum adsorption capacity reaches 60 mg / g. In summary, the present invention successfully achieves efficient detoxification of chromium slag and purification of acid leaching liquid without the risk of secondary pollution. In addition, a high-performance chromium adsorption material is prepared based on the purification process, which is conducive to the coordinated and comprehensive utilization of solid waste resources and promotes the realization of the unity of resource, economic and environmental benefits.

[0082] In some embodiments of the present invention, the concentration of the potassium permanganate acid solution is 2-5 mol / L.

[0083] In some embodiments of the present invention, the liquid-to-solid ratio of the leaching is 2-5 mL:1 g.

[0084] In some embodiments of the present invention, the stirring speed of the leaching is 100-500 rpm.

[0085] In some embodiments of the present invention, the leaching temperature is 60-100°C.

[0086] In some embodiments of the present invention, the leaching time is 2 to 12 hours.

[0087] The pyrolysis biochar adsorption material of the present invention is added to the acid leaching solution, a precipitation reaction is carried out, and the solid product obtained by filtration is Cr 6+ Adsorption material, the filtrate can meet the discharge standards.

[0088] The technical solution of the present invention will be better understood with reference to specific embodiments below.

[0089] The chromium slag used in the experiment was obtained from a ferroalloy company. The chemical composition is shown in Table 1.

[0090] The mass fractions of total chromium and hexavalent chromium in the chromium slag are 3.12% and 1.21% respectively, of which hexavalent chromium accounts for 38.78% of the total chromium mass. The mass fractions of Fe and Al in the chromium slag are 8.78% and 3.95% respectively.

[0091] Table 1 Chemical composition of chromium slag %

[0092] Element Total chromium <![CDATA[Cr 6+ ]]> Fe Ca Al Mg Si Content / wt% 3.12 1.21 8.78 20.60 3.95 9.60 4.52

[0093] Example 1

[0094] This embodiment prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0095] The following steps are involved:

[0096] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0097] The chromium residue was leached using a 4 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 4 mL:1 g, a stirring speed of 350 rpm, a leaching temperature of 80° C., and a leaching time of 10 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 2) and acid leaching solution and other residues (test results are shown in Table 3);

[0098] The dried powder sample was obtained by dehydrating, drying and crushing the municipal sludge;

[0099] The dried sludge powder was immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution was 1:10, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate was 1:2. After immersion for 12 hours, the powder was filtered and dried at 110° C. to obtain modified municipal sludge powder.

[0100] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept warm for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​256m 2 / g;

[0101] The sludge-based biochar was washed to neutrality and dispersed in water, and then a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate was added for amination reaction to obtain an amination biochar material. The conditions for the amination reaction were: the reaction ratio of sludge pyrolysis carbon residue to hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1 g:4 mL, the reaction temperature was 50°C, the reaction time was 5 h, and the volume ratio of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1:2;

[0102] Amination biochar material was added to the residues such as the obtained acid leaching liquid, precipitation reaction was carried out, and filtration was performed to obtain a solid product which was a Cr(VI) adsorption material. The filtrate (test results are shown in Table 3) met the discharge standards.

[0103] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 2.

[0104] Table 2 Chromium slag leaching toxicity test results before and after detoxification

[0105] Sample name Original chromium slag Detoxified chromium residue Cr(VI) leaching concentration (mg / L) 30.40 2.52 Total chromium leaching concentration (mg / L) 48.45 2.53

[0106] As shown in Table 2, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.52 mg / L and 2.53 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0107] Table 3 Detection results of chromium slag leachate and filtrate

[0108] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.62 47.82 filtrate 0.21 0.23

[0109] The total chromium concentration in the obtained filtrate was 0.23 mg / L and the hexavalent chromium concentration was 0.21 mg / L, which met the standards of Cr(VI) less than 0.5 mg / L and total chromium less than 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0110] Example 2

[0111] This embodiment prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0112] The following steps are involved:

[0113] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0114] The chromium residue was leached using a 3 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 3 mL:1 g, a stirring speed of 400 rpm, a leaching temperature of 70° C., and a leaching time of 8 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 4) and acid leaching solution and other residues (test results are shown in Table 5);

[0115] The municipal sludge is dehydrated, dried, and crushed to obtain a dried powder sample; the dried sludge powder is immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution is 1:15 and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 2:1. After immersion for 16 hours, the sludge powder is filtered and dried at 115° C. to obtain a modified municipal sludge powder.

[0116] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 600°C at a rate of 14°C / min, kept at this temperature for 45 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​243m 2 / g; after washing the sludge-based biochar to neutrality, the biochar was dispersed in water, and then a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate was added to carry out an amination reaction to obtain an aminated biochar material. The conditions for the amination reaction were as follows: the reaction ratio of the sludge pyrolysis carbon residue to the hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1g:3mL, the reaction temperature was 45°C, the reaction time was 4h, and the volume ratio of the hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 3:2;

[0117] Amination biochar material was added to the residues such as the obtained acid leaching liquid, precipitation reaction was carried out, and filtration was performed to obtain a solid product which was a Cr(VI) adsorption material. The filtrate (test results are shown in Table 5) met the discharge standards.

[0118] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 4.

[0119] Table 4 Chromium slag leaching toxicity test results before and after detoxification

[0120] Sample name Original chromium slag Detoxified chromium residue Cr(VI) leaching concentration (mg / L) 30.40 2.15 Total chromium leaching concentration (mg / L) 48.45 2.17

[0121] As shown in Table 4, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.15 mg / L and 2.17 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0122] Table 5 Test results of chromium slag leachate and filtrate

[0123] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 48.13 48.21 filtrate 0.25 0.26

[0124] The total chromium concentration in the obtained filtrate was 0.26 mg / L and the hexavalent chromium concentration was 0.25 mg / L, which met the standards of Cr(VI) less than 0.5 mg / L and total chromium less than 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0125] Example 3

[0126] This embodiment prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0127] The following steps are involved:

[0128] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0129] The chromium residue was leached using a 5 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 3.5 mL:1 g, a stirring speed of 250 rpm, a leaching temperature of 90° C., and a leaching time of 7 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 6) and acid leaching solution and other residues (test results are shown in Table 7);

[0130] The dried powder sample was obtained by dehydrating, drying and crushing the municipal sludge;

[0131] The dried sludge powder was immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution was 1:15, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate was 2:1. After immersion for 16 hours, the mixture was filtered and dried at 115° C. to obtain modified municipal sludge powder.

[0132] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 600°C at a rate of 14°C / min, kept at this temperature for 45 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​239m 2 / g;

[0133] The sludge-based biochar was washed to neutrality and dispersed in water, and then a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate was added for amination reaction to obtain an amination biochar material. The conditions for the amination reaction were: the reaction ratio of sludge pyrolysis carbon residue to hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1 g:3 mL, the reaction temperature was 45°C, the reaction time was 4 h, and the volume ratio of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 3:2;

[0134] Amination biochar material was added to the residues such as the obtained acid leaching liquid, precipitation reaction was carried out, and filtration was performed to obtain a solid product which was a Cr(VI) adsorption material. The filtrate (test results are shown in Table 7) met the discharge standards.

[0135] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 6.

[0136] Table 6 Chromium slag leaching toxicity test results before and after detoxification

[0137] Sample name Original chromium slag Detoxified chromium residue Cr(VI) leaching concentration (mg / L) 30.40 2.15 Total chromium leaching concentration (mg / L) 48.45 2.17

[0138] As shown in Table 6, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.15 mg / L and 2.17 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0139] Table 7 chromium slag leachate and filtrate test results

[0140] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.89 48.12 filtrate 0.25 0.26

[0141] The total chromium concentration in the obtained filtrate was 0.26 mg / L and the hexavalent chromium concentration was 0.25 mg / L, which met the standards of Cr(VI) less than 0.5 mg / L and total chromium less than 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0142] Comparative Example 1

[0143] This comparative example prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0144] The following steps are involved:

[0145] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0146] 4 mol / L sulfuric acid was used, the liquid-solid ratio was 4 mL:1 g, the stirring speed was 350 rpm, the leaching temperature was 80° C., and the leaching time was 10 h to leach the chromium slag. The solid-liquid separation was performed to obtain acid-leached chromium slag (test results are shown in Table 8) and acid leaching liquid and other residues (test results are shown in Table 9);

[0147] The dried powder sample was obtained by dehydrating, drying and crushing the municipal sludge;

[0148] The dried sludge powder was immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution was 1:10, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate was 1:2. After immersion for 12 hours, the powder was filtered and dried at 110° C. to obtain modified municipal sludge powder.

[0149] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept at this temperature for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​256m 2 / g;

[0150] The sludge-based biochar was washed to neutrality and dispersed in water, and then a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate was added for amination reaction to obtain an amination biochar material. The conditions for the amination reaction were: the reaction ratio of sludge pyrolysis carbon residue to hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1 g:4 mL, the reaction temperature was 50°C, the reaction time was 5 h, and the volume ratio of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1:2;

[0151] The aminated biochar material was added to the residue of the obtained acid leaching solution, and a precipitation reaction was carried out. After filtration, a solid product was obtained, which was a Cr(VI) adsorption material and a filtrate (the filtrate test results are shown in Table 9).

[0152] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 8.

[0153] Table 8 Chromium slag leaching toxicity test results before and after detoxification

[0154] Sample name Original chromium slag Detoxified chromium residue Cr(VI) leaching concentration (mg / L) 30.40 3.83 Total chromium leaching concentration (mg / L) 48.45 6.68

[0155] As shown in Table 8, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 3.83 mg / L and 6.86 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," and achieves detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0156] Table 9 chromium slag leachate and filtrate test results

[0157] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 48.22 48.62 filtrate 6.91 11.59

[0158] The total chromium concentration in the obtained filtrate was 11.59 mg / L and the hexavalent chromium concentration was 6.91 mg / L, which did not meet the standards of Cr(VI) below 0.5 mg / L and total chromium below 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0159] Comparative Example 2

[0160] This comparative example prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0161] The following steps are involved:

[0162] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0163] The chromium residue was leached using a 4 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 4 mL:1 g, a stirring speed of 350 rpm, a leaching temperature of 80° C., and a leaching time of 10 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 10) and acid leaching solution and other residues (test results are shown in Table 11);

[0164] The municipal sludge was dehydrated, dried and crushed to obtain a dried powder sample.

[0165] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept warm for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​66m 2 / g; after washing the sludge-based biochar to neutrality, it was dispersed in water, and then a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate was added for amination reaction to obtain an amination biochar material. The conditions for the amination reaction were: the reaction ratio of the sludge pyrolysis carbon residue to the hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1g:4mL, the reaction temperature was 50°C, the reaction time was 5h, and the volume ratio of the hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate solution was 1:2; the amination biochar material was added to the residues such as the obtained acid leaching solution, a precipitation reaction was carried out, and the solid product was filtered to obtain a Cr(VI) adsorption material and a filtrate (the filtrate detection results are shown in Table 11).

[0166] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 10.

[0167] Table 10 Chromium slag leaching toxicity test results before and after detoxification

[0168]

[0169] As shown in Table 10, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.52 mg / L and 2.53 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0170] Table 11 Test results of chromium slag leachate and filtrate

[0171] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.62 47.82 filtrate 5.17 5.72

[0172] The total chromium concentration in the obtained filtrate was 5.72 mg / L and the hexavalent chromium concentration was 5.17 mg / L, which did not meet the standards of Cr(VI) below 0.5 mg / L and total chromium below 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0173] Comparative Example 3

[0174] This comparative example prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0175] The following steps are involved:

[0176] The chromium slag was crushed to a particle size of ≤5 mm to obtain a fine chromium slag; 4 mol / L potassium permanganate acid solution was used, with a liquid-to-solid ratio of 4 mL:1 g, a stirring speed of 350 rpm, a leaching temperature of 80° C., and a leaching time of 10 h to leach the chromium slag, and solid-liquid separation was performed to obtain acid-leached chromium slag (test results are shown in Table 12) and acid leaching solution and other residues (test results are shown in Table 13);

[0177] The dried powder sample was obtained by dehydrating, drying and crushing the municipal sludge;

[0178] The dried sludge powder was immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution was 1:10, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate was 1:2. After immersion for 12 hours, the powder was filtered and dried at 110° C. to obtain modified municipal sludge powder.

[0179] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept at this temperature for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​256m 2 / g; biochar material was added to the residue such as the obtained acid leaching solution, and the mixture was filtered to obtain an adsorption material and a filtrate (the test results of the filtrate are shown in Table 13).

[0180] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 12.

[0181] Table 12 Chromium slag leaching toxicity test results before and after detoxification

[0182] Sample name Original chromium slag Detoxified chromium residue Cr(VI) leaching concentration (mg / L) 30.40 2.52 Total chromium leaching concentration (mg / L) 48.45 2.53

[0183] As shown in Table 12, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.52 mg / L and 2.53 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0184] Table 13 Test results of chromium slag leachate and filtrate

[0185] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.62 47.82 filtrate 8.65 8.76

[0186] The total chromium concentration in the obtained filtrate was 8.76 mg / L and the hexavalent chromium concentration was 8.65 mg / L, which did not meet the standards of Cr(VI) below 0.5 mg / L and total chromium below 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0187] Comparative Example 4

[0188] This comparative example prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0189] The following steps are involved:

[0190] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0191] The chromium residue was leached using a 4 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 4 mL:1 g, a stirring speed of 350 rpm, a leaching temperature of 80° C., and a leaching time of 10 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 2) and acid leaching solution and other residues (test results are shown in Table 3);

[0192] The municipal sludge is dehydrated, dried, and crushed to obtain a dried powder sample; the dried sludge powder is immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution is 1:10, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 1:2. After immersion for 12 hours, the sludge powder is filtered and dried at 110° C. to obtain a modified municipal sludge powder.

[0193] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept warm for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​256m 2 / g;

[0194] The sludge-based biochar was washed to neutrality and then dispersed in water. Cetyltrimethylammonium acetate solution was then added for amination reaction to obtain an amination biochar material. The amination reaction conditions were: the reaction ratio of sludge pyrolysis carbon residue to cetyltrimethylammonium acetate solution was 1g:4mL, the reaction temperature was 50°C, and the reaction time was 5h.

[0195] Amination biochar material was added to the residues such as the obtained acid leaching liquid, precipitation reaction was carried out, and filtration was performed to obtain a solid product which was a Cr(VI) adsorption material. The filtrate (test results are shown in Table 15) met the discharge standards.

[0196] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 14.

[0197] Table 14 Chromium slag leaching toxicity test results before and after detoxification

[0198]

[0199] As shown in Table 14, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.52 mg / L and 2.53 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0200] Table 15 Test results of chromium slag leachate and filtrate

[0201] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.62 47.82 filtrate 5.35 5.65

[0202] The total chromium concentration in the obtained filtrate was 5.65 mg / L and the hexavalent chromium concentration was 5.35 mg / L, which did not meet the standards of Cr(VI) below 0.5 mg / L and total chromium below 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0203] Comparative Example 5

[0204] This comparative example prepares a pyrolysis biochar adsorption material and also provides a method for removing chromium from chromium slag.

[0205] The following steps are involved:

[0206] Crushing the chromium slag to a particle size of ≤5mm to obtain chromium slag fines;

[0207] The chromium residue was leached using a 4 mol / L potassium permanganate acid solution with a liquid-to-solid ratio of 4 mL:1 g, a stirring speed of 350 rpm, a leaching temperature of 80° C., and a leaching time of 10 h. The solid-liquid separation was performed to obtain acid-leached chromium residue (test results are shown in Table 2) and acid leaching solution and other residues (test results are shown in Table 3);

[0208] The municipal sludge is dehydrated, dried, and crushed to obtain a dried powder sample; the dried sludge powder is immersed in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate, wherein the solid-liquid ratio of the sludge powder to the mixed solution is 1:10, and the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 1:2. After immersion for 12 hours, the sludge powder is filtered and dried at 110° C. to obtain a modified municipal sludge powder.

[0209] The obtained municipal sludge powder was placed in a pyrolysis furnace with a nitrogen inert gas content of more than 99% by mass, and the temperature was raised to 550°C at a heating rate of 12°C / min, kept at this temperature for 40 minutes, and then naturally cooled to room temperature to obtain sludge-based biochar with a specific surface area of ​​256m 2 / g; after washing the sludge-based biochar to neutrality, disperse it in water, and then add hexadecyltrimethylammonium sulfate solution to carry out amination reaction to obtain amination biochar material. The conditions of the amination reaction are:

[0210] The reaction ratio of sludge pyrolysis carbon residue and hexadecyltrimethylammonium sulfate solution was 1g:4mL, the reaction temperature was 50℃, and the reaction time was 5h. Aminated biochar material was added to the residues such as the obtained acid leaching solution, and precipitation reaction was carried out. After filtration, the solid product obtained was Cr(VI) adsorption material, and the filtrate (test results are shown in Table 17) met the discharge standards.

[0211] According to the national standard (hazardous waste identification standard leaching toxicity identification GB5085.3-2007) and the industry standard (solid waste leaching toxicity leaching method sulfuric acid and nitric acid method HJ / T299-2007), the leaching toxicity of the chromium slag samples before and after detoxification was analyzed. The analysis results are shown in Table 16.

[0212] Table 16 Chromium slag leaching toxicity test results before and after detoxification

[0213]

[0214] As shown in Table 16, the Cr(VI) and total chromium leaching toxicities of the chromium slag before detoxification were 30.40 mg / L and 48.45 mg / L, respectively. After detoxification, the Cr(VI) and total chromium leaching toxicities were reduced to 2.52 mg / L and 2.53 mg / L, respectively. This meets the hazardous waste identification standards of less than 5 mg / L for Cr(VI) and less than 15 mg / L for total chromium, as stipulated in the national standard "GB5085.3-2007 Hazardous Waste Identification Standard - Leaching Toxicity Identification," achieving detoxification of Cr(VI) in chromium slag, a hazardous industrial solid waste.

[0215] Table 17 Test results of chromium slag leachate and filtrate

[0216] pollutants Hexavalent chromium concentration (mg / L) Total chromium concentration (mg / L) leachate 47.62 47.82 filtrate 4.37 4.64

[0217] The total chromium concentration in the obtained filtrate was 4.64 mg / L and the hexavalent chromium concentration was 4.37 mg / L, which did not meet the standards of Cr(VI) below 0.5 mg / L and total chromium below 1.5 mg / L stipulated in the national standard "Integrated Wastewater Discharge Standard GB8798-1996".

[0218] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. A method for preparing pyrolysis biochar adsorption material, characterized in that: The following steps are involved: S1: immersing municipal sludge powder in a mixed solution of ammonium bifluoride and ammonium aluminum carbonate to obtain modified municipal sludge powder; S2: pyrolyzing the modified municipal sludge powder under a protective atmosphere to obtain sludge-based biochar; S3: dispersing the sludge-based biochar into water, adding a mixed solution of hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate to carry out an amination reaction to obtain the pyrolysis biochar adsorption material.

2. The method according to claim 1, characterized in that In step S1, the solid-liquid ratio of the municipal sludge powder to the mixed solution is 1:1-20.

3. The method according to claim 1, characterized in that In the mixed solution of ammonium bifluoride and ammonium aluminum carbonate, the volume ratio of ammonium bifluoride to ammonium aluminum carbonate is 1:3-1.

4. The method according to claim 1, wherein In step S2, the pyrolysis temperature is 450°C to 650°C.

5. The method according to claim 1, wherein The heat preservation time of the pyrolysis is 30 to 50 minutes.

6. The method according to claim 1, characterized in that The heating rate of the pyrolysis is 10-15°C / min.

7. The method according to claim 1, characterized in that In step S3, the solid-liquid ratio of the mixed solution of the sludge-based biochar, hexadecyltrimethylammonium acetate and hexadecyltrimethylammonium sulfate is 1 g:1-5 mL.

8. The method according to claim 1, characterized in that In the mixed solution of cetyltrimethylammonium acetate and cetyltrimethylammonium sulfate, the volume ratio of cetyltrimethylammonium acetate to cetyltrimethylammonium sulfate is 1:3-1.

9. The method according to claim 1, characterized in that The temperature of the amination reaction is 40°C to 60°C.

10. The method according to claim 1, characterized in that The amination reaction time is 3 to 6 hours.

11. A method for removing chromium from chromium slag, characterized in that: The following steps are involved: (1): Leaching the chromium slag fine material with potassium permanganate acid solution, separating the solid and liquid, and obtaining acid-leached chromium slag and acid leaching solution; (2) The pyrolysis biochar adsorption material prepared by the method according to any one of claims 1 to 10 is added to the acid leaching solution to carry out a precipitation reaction.

12. The chromium slag removal method according to claim 11, characterized in that: The concentration of the potassium permanganate acid solution is 2-5 mol / L.

13. The chromium slag removal method according to claim 11, characterized in that: The liquid-to-solid ratio of the leaching is 2-5 mL:1 g.

14. The method for removing chromium from chromium slag according to claim 11, characterized in that: The stirring speed of the leaching is 100-500 rpm.

15. The method for removing chromium from chromium slag according to claim 11, characterized in that: The leaching temperature is 60-100°C.

16. The method for removing chromium from chromium slag according to claim 11, characterized in that: The leaching time is 2 to 12 hours.

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