Carbon-based composite filler based on lime water sulfur ion conversion and preparation method thereof

Abstract

The application relates to the technical field of fillers for wastewater treatment, and particularly discloses a carbon-based composite filler based on lime water sulfur ion conversion and a preparation method thereof. The carbon-based composite filler comprises the following raw materials in parts by weight: 100 parts of expanded graphite, 100-400 parts of modified gasification slag, 50-150 parts of calcium carbonate and 1-3 parts of lithium carbonate; the modified gasification slag is prepared by treating gasification slag through processes including pickling, carbonization and hydrogenation. The carbon-based composite filler can be used for removing sulfur and nitrogen in lime water, and has the effect of simultaneously and efficiently treating sulfur and nitrogen in wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fillers for wastewater treatment, and relates to a carbon-based composite filler based on lime-soaking water sulfur ion conversion and a preparation method thereof. BACKGROUND

[0002] In the leather industry production in China, the depilation operation mostly adopts sulfide alkali technology, and the main reagent used is Na2S and lime, so there are a large amount of sulfides, ammonia nitrogen and nitrate nitrogen in the lime-soaking wastewater. In addition, the wastewater is alkaline, and is the most seriously polluted wastewater in the leather industry. In particular, sulfides have great harmfulness to various types of organisms and cannot be directly discharged into a sewage treatment plant.

[0003] At present, the main methods for treating lime-soaking wastewater are catalytic oxidation, iron salt precipitation and acid absorption. Catalytic oxidation and acid absorption have low application rates in actual projects due to harsh control conditions and complicated operation. The iron salt precipitation method has good treatment effect, simple operation and wide engineering application, but the amount of physicochemical sludge generated accounts for more than 50% of the total sludge amount, and the treatment process is accompanied by serious odor, which is the main source of odor in leather sewage treatment plants. Various types of pollutants exist in wastewater at the same time, and traditional processes emphasize separate treatment, but the above three methods cannot remove sulfides and total nitrogen in wastewater at the same time.

[0004] The lime-soaking water contains a large amount of nitrogen elements, and in order to protect natural water bodies and avoid deterioration of water quality, the lime-soaking water must be subjected to denitrification treatment. The biochemical treatment method for wastewater denitrification is to use autotrophic denitrification or heterotrophic denitrification. For autotrophic denitrification, the most commonly used is sulfur autotrophic denitrification; the reaction is a 0-level reaction; under the action of microorganisms, the reaction rate is only positively correlated with the specific surface area of the filler; the greater the specific surface area of the filler, the higher the sulfur autotrophic denitrification denitrification rate.

[0005] At present, there is no filler or process developed for treating various types of pollutants in lime-soaking water on the market. Only the process for separately treating sulfides in lime-soaking water is available, and then part of the wastewater containing converted sulfides is discharged into a sewage treatment plant as general chemical wastewater, which greatly increases the burden of daily wastewater treatment in the sewage treatment plant.

[0006] In addition, in some related technologies, gasified slag is used to fix microorganisms for wastewater treatment; this method is difficult to achieve the treatment goals of denitrification and desulfurization.

[0007] There is also a related art that mixes expanded graphite and ceramic waste, bentonite, organic carbon source, tetradecyl sulfobetaine, silicon iron copolymer, ferrite / expanded graphite composite, ferrous sulfate, sodium silicate, magnesium sulfate and Fenton reagent to prepare a treatment agent for treating wastewater. The raw materials in this method are complex and the preparation process of the raw materials is complex, and the ferrite / expanded graphite composite and the silicon iron copolymer involved need to be prepared through complicated steps.

[0008] Therefore, it is necessary to provide a water treatment agent for simultaneously treating sulfur and nitrogen in pickling water. SUMMARY

[0009] In order to improve the simultaneous and efficient treatment of sulfur and nitrogen in pickling water, the present application provides a carbon-based composite filler based on the conversion of sulfur ions in pickling water and a preparation method thereof.

[0010] In a first aspect, the present application provides a carbon-based composite filler based on the conversion of sulfur ions in pickling water, which adopts the following technical solution:

[0011] A carbon-based composite filler based on the conversion of sulfur ions in pickling water, the carbon-based composite filler comprises the following raw materials by weight: expanded graphite 100 parts, modified gasification slag 100-400 parts, calcium carbonate 50-150 parts, lithium carbonate 1-3 parts;

[0012] The modified gasification slag is prepared by treating the gasification slag through pickling, carbonization and hydrogenation.

[0013] The present application modifies the gasification slag, and the pickling treatment removes the aluminum-silicon-based impurities and heavy metal oxide impurities inside the original gasification slag, and forms a skeleton of activated carbon-like material with large pores after pickling; the pickling gasification slag is further carbonized at high temperature, which produces a graphite coating structure on its surface, increasing the surface area; further hydrogenation reaction with hydrogen introduces active functional groups such as hydroxyl and aldehyde groups, which are beneficial to the attachment of microorganisms. Therefore, the modified gasification slag has a certain COD adsorption capacity and can also provide a large number of attachment points for sulfur autotrophic denitrifying bacteria, significantly improving the water treatment effect.

[0014] Expanded graphite has a certain COD adsorption capacity and microbial attachment capacity, while modified gasification slag has the ability to attach sulfur autotrophic denitrifying bacteria, and the two work together to convert sulfides in water into non-toxic sulfates, and in this process, the chemical energy of sulfides is used to convert nitrate nitrogen in water into nitrogen gas.

[0015] The added calcium carbonate and lithium carbonate are mainly used as sintering aids. The above raw materials are mixed and sintered to prepare the carbon-based composite filler of the present application. The addition of lithium carbonate is necessary because the addition of lithium carbonate sintering aid can significantly reduce the melting point of calcium carbonate, making the filler combination more uniform and compact.

[0016] In summary, by using the above technical scheme, the carbon-based composite filler prepared by using the above raw material mixture has excellent effect of removing sulfur and nitrogen in wastewater.

[0017] Optionally, the preparation method of the modified gasification slag comprises the following steps:

[0018] After the gasification slag is crushed and mixed with acid solution, it is heated and modified, then washed with water, and solid-liquid separation, drying, to obtain acidified gasification slag;

[0019] The acidified gasification slag is carbonized at a high temperature of 750-900℃ in a hydrogen atmosphere to obtain carbonized gasification slag;

[0020] The carbonized gasification slag is hydrogenated at a high temperature of 500-650℃ in a hydrogen atmosphere to obtain modified gasification slag.

[0021] It should be noted in this scheme that hydrogen is introduced during the carbonization stage, and hydrogen is directly used as the protective gas; and hydrogen is continuously introduced during the later hydrogenation stage to avoid multiple changes of protective gas; the operation is more simple and convenient. During the carbonization stage, the gas discharged is a mixture of hydrogen, water vapor, carbon monoxide and carbon dioxide; and during the hydrogenation stage, methane and hydrogen are discharged. In the above scheme, carbonization and hydrogenation are carried out at appropriate temperatures to load active functional groups such as hydroxyl and aldehyde groups on the gasification slag, thereby improving the adhesion of microorganisms, and achieving the purpose of improving the removal of sulfur and nitrogen in wastewater.

[0022] Optionally, when the crushed gasification slag is mixed with acid solution and heated for modification, the heating temperature is 100-120℃, and the heating and modification time is 100-140min.

[0023] By using the above technical scheme, acid modification under heating conditions can improve the efficiency of washing out aluminum-silicon-based impurities and heavy metal oxide impurities in the gasification slag, and more completely wash out the aluminum-silicon-based impurities and heavy metal oxide impurities in the gasification slag, to form a carbon-like material skeleton with larger pores.

[0024] Optionally, the high-temperature carbonization time is 1-2h.

[0025] Optionally, the high-temperature hydrogenation time is 1.5-2.5h.

[0026] Optionally, the acid in the acid solution at least includes hydrofluoric acid;

[0027] Preferably, the acid in the acid solution further includes hydrochloric acid.

[0028] Hydrofluoric acid has good treatment effect on aluminum-silicon-based impurities, so the addition of hydrofluoric acid is necessary. In addition, other acids such as hydrochloric acid can be added to further improve the acid washing effect.

[0029] Further optionally, the mixing ratio of the gasification slag and hydrofluoric acid is 5-10 g of gasification slag / mL of hydrofluoric acid; the mixing ratio of the gasification slag and dilute hydrochloric acid is 1-4 g of gasification slag / mL of dilute hydrochloric acid.

[0030] Further optionally, the mass percentage of hydrochloric acid in the dilute hydrochloric acid is 3-8 wt%.

[0031] Optionally, the preparation method of the expanded graphite comprises the following steps:

[0032] After the flake graphite and concentrated sulfuric acid are uniformly mixed, potassium permanganate is added, and then reacted at a low temperature of not higher than 25℃, followed by reaction at a medium temperature of 28-45℃, and then dried after washing to neutral, to obtain the oxidized graphite;

[0033] The oxidized graphite is expanded at a high temperature of 900-1200℃, and then cooled to obtain the expanded graphite.

[0034] Optionally, the low-temperature reaction time is 20-40 min, and the medium-temperature reaction time is 20-40 min.

[0035] Optionally, the high-temperature expansion time is 20-40 s.

[0036] Optionally, before the flake graphite and concentrated sulfuric acid are mixed, the method further comprises plasma pretreatment.

[0037] The plasma pretreatment comprises the following steps:

[0038] The flake graphite is dispersed in a solvent to obtain a dispersion liquid;

[0039] The dispersion liquid is placed in a plasma environment, and plasma discharge treatment is performed on the dispersion liquid in a power of 900-1100 W and a protective gas environment for 10-15 min, and then the pretreated graphite is obtained after cooling and washing, and is ready for use;

[0040] The pretreated graphite is used to continue mixing with concentrated sulfuric acid.

[0041] The flake graphite is treated by plasma to increase the defect points and functional groups between the layers of the flake graphite, and to destroy the layered structure of the graphite to a certain extent, so as to increase the surface area of the graphite and provide more attachment points for microorganisms; then the pretreated flake graphite is intercalated by potassium permanganate and sulfuric acid, and expanded at a high temperature, so as to introduce a large number of defect points and functional groups between the layers of the graphite, and a large number of functional groups such as carboxyl and hydroxyl are generated in the interlayer of the expanded graphite, which further increases the attachment points of microorganisms, thereby improving the water treatment effect.

[0042] Optionally, the mixing ratio of the flake graphite or pretreated graphite and concentrated sulfuric acid is 1 g:4-7 mL; and the mixing ratio of the flake graphite or pretreated graphite and potassium permanganate is 1 g:0.2-0.8 mL.

[0043] In a second aspect, the application provides a preparation method of the carbon-based composite filler based on lime water sulfur ion conversion, which adopts the following technical scheme:

[0044] The preparation method of the carbon-based composite filler based on lime water sulfur ion conversion comprises the following steps: mixing expanded graphite, modified gasification slag, calcium carbonate and lithium carbonate according to the proportion, sintering at 600-700 DEG C for 100-150 min in a protective atmosphere, then sintering at 750-900 DEG C for 5-15 min, and washing and drying after cooling.

[0045] The composite filler is prepared by the above method. In the preparation method, low-temperature sintering is performed first, and the main reason is that the volume of lithium carbonate reduces the melting point of calcium carbonate, so that it melts below the decomposition temperature and plays the role of a sintering aid. After sintering, further high-temperature sintering is performed, which has the effect of: at a sintering temperature of about 800 DEG C or higher than 800 DEG C, calcium carbonate will be decomposed to form calcium oxide and carbon dioxide, and the carbon dioxide will overflow with the gas. The calcium oxide forms micropores after being washed with distilled water. Therefore, the calcium carbonate not only provides additional inorganic carbon sources for sulfur autotrophic denitrifying bacteria to promote bacterial growth, but also provides additional cavities for microbial attachment. Through this method, the effect of the composite material on removing nitrogen and sulfur in wastewater is further improved.

[0046] Optionally, the mixing of expanded graphite, modified gasification slag, calcium carbonate and lithium carbonate according to the proportion specifically comprises the following steps: first, mixing expanded graphite, modified gasification slag and calcium carbonate according to the proportion and grinding to 200-400 mesh, and then adding lithium carbonate according to the proportion.

[0047] In summary, the application has the following beneficial effects:

[0048] 1. The gasification slag is originally a waste of coal chemical industry, and its internal structure is similar to that of activated carbon, but its utilization value is low due to the presence of a large amount of aluminosilicate and heavy metal oxides. The gasification slag is modified by hydrofluoric acid and hydrochloric acid. After acidification, the aluminosilicate and heavy metal oxide impurities in the internal pores of the gasification slag are washed out, so that they become the skeleton of the filler and are more suitable for microbial (mainly sulfur autotrophic denitrifying bacteria) attachment, reducing the toxicity of heavy metals to microorganisms. Subsequently, the acidified gasification slag is subjected to carbonization reaction and hydrogenation reaction, which carbonizes organic carbon into inorganic carbon and introduces biophilic functional groups to improve the degree of microbial attachment. Moreover, the pore size in the gasification slag is relatively large, and there is no microbial inhibition caused by micropore adsorption in activated carbon. Therefore, the carbon-based composite filler of the application has excellent effect on removing sulfur ions and total nitrogen.

[0049] 2、The expanded graphite of the present application is prepared by using flake graphite as raw material, pre-treating it by plasma, then oxidizing it by potassium permanganate and intercalating it by concentrated sulfuric acid. The surface layer of the expanded graphite is treated by plasma, increasing the surface area and introducing a large number of defect points and functional groups between the graphite layers, so that a large number of functional groups such as carboxyl and hydroxyl groups are generated in the interlayer of the expanded graphite, further increasing the microbial attachment points. Therefore, under the cooperation of the expanded graphite and the modified gasification slag, the water treatment effect of the carbon-based composite filler is significantly improved.

[0050] 3、The concentration of sulfide in the lime-soaking water is generally 200-4000 mg / L, and most microorganisms cannot grow under this concentration due to inhibition. However, sulfur autotrophic denitrifying bacteria can utilize sulfide for chemotrophic growth; it can utilize low-valence sulfur ions and oxidize them to high-valence nontoxic sulfate ions. Therefore, the carbon-based composite filler of the present application is used for water treatment after loading sulfur autotrophic denitrifying bacteria. The sulfur autotrophic denitrifying bacteria convert sulfide to sulfate, and the nitrate as an electron acceptor is reduced to nitrogen. Sulfur autotrophic denitrifying bacteria often occur in biochemical anaerobic tanks, and are low in cost. In addition, calcium carbonate is added as a binder to the filler, but it is also an inorganic carbon source. The addition of this substance further promotes the growth of sulfur autotrophic denitrifying bacteria and denitrification. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is an electron micrograph of the raw gasification slag and the modified gasification slag prepared in Preparation Example 2; wherein, Figure 1 a is an electron micrograph of the raw gasification slag, Figure 1 b is an electron micrograph of the modified gasification slag obtained in Preparation Example 2;

[0052] Figure 2 is an electron micrograph of the raw flake graphite, the pre-treated graphite obtained in Preparation Example 4, and the expanded graphite prepared in Preparation Example 4; wherein, Figure 2 a is an electron micrograph of the raw flake graphite, Figure 2 b is an electron micrograph of the pre-treated graphite obtained in Preparation Example 4, Figure 2 c is an electron micrograph of the expanded graphite prepared in Preparation Example 4;

[0053] Figure 3 is an electron micrograph of the carbon-based composite filler prepared in Example 2;

[0054] Figure 4 is the concentration of sulfur ions in the sewage and the sulfur ion removal rate during the water treatment experiment using the carbon-based composite filler of Example 2;

[0055] Figure 5 is the concentration of ammonia nitrogen, the concentration of total nitrogen, and the total nitrogen removal rate in the sewage during the water treatment experiment using the carbon-based composite filler of Example 2. DETAILED DESCRIPTION

[0056] The application is further described in detail below in conjunction with the accompanying drawings and examples, and it is particularly pointed out that the following examples, where no specific conditions are noted, were carried out under conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following examples, unless otherwise specified, can be sourced from ordinary commercial markets.

[0057] Preparation example of modified gasification slag

[0058] The gasification slag was purchased from a coal chemical plant in Yulin, Shaanxi, and after screening, the part that could pass through a 50-mesh screen was selected for the preparation of modified gasification slag. Hydrofluoric acid refers to an aqueous solution of hydrogen fluoride, and the mass fraction of hydrogen fluoride is 35-45wt%.

[0059] Preparation example 1

[0060] The preparation method of the modified gasification slag is:

[0061] Step 1, 50g of gasification slag was crushed and mixed with 10mL of hydrofluoric acid (mass fraction of hydrogen fluoride is 35wt%) and 50mL of 3wt% dilute hydrochloric acid on a polytetrafluoroethylene crucible, and heated to 100℃ on an electric furnace, and acid washing modification was carried out, and the heating time was 140min; After heating, it was cooled to room temperature, then filtered, and the solid was washed with water and dried to obtain acidified gasification slag.

[0062] Step 2, the obtained acidified gasification slag was placed in a tube furnace, and hydrogen was used as the protective gas, and carbonized at a high temperature of 750℃ for 2h, and the exhaust gas was a mixture of hydrogen and water vapor, carbon monoxide and carbon dioxide, and then cooled to obtain carbonized gasification slag.

[0063] Step 3, the obtained carbonized gasification slag was placed in a tube furnace, and hydrogen was used as the protective gas, and hydrogenated at a high temperature of 500℃ for 2.5h, and the exhaust gas was a mixture of methane and hydrogen, and then naturally cooled to obtain modified gasification slag.

[0064] Preparation example 2

[0065] The preparation method of the modified gasification slag is:

[0066] Step 1, 50g of gasification slag was crushed and mixed with 10mL of hydrofluoric acid (mass fraction of hydrogen fluoride is 35wt%) and 50mL of 3wt% dilute hydrochloric acid on a polytetrafluoroethylene crucible, and heated to 100℃ on an electric furnace, and acid washing modification was carried out, and the heating time was 140min; After heating, it was cooled to room temperature, then filtered, and the solid was washed with water and dried to obtain acidified gasification slag.

[0067] Step 2, the obtained acidified gasification slag is placed in a tube furnace, and carbonized at a high temperature of 800℃ for 1.5h under the protection of hydrogen, the exhaust gas is a mixed gas of hydrogen, water vapor, carbon monoxide and carbon dioxide, and then the temperature is lowered to obtain carbonized gasification slag.

[0068] Step 3, the obtained carbonized gasification slag is placed in a tube furnace, and hydrogenated at a high temperature of 600℃ for 2h under the protection of hydrogen, the exhaust gas is a mixed gas of methane and hydrogen, and then the temperature is lowered naturally to obtain modified gasification slag.

[0069] The gasification slag and the modified gasification slag prepared in the present preparation example are respectively subjected to electron microscope test, and a Zeiss Gemini 300 electron scanning microscope is used, the magnification is 5000 times, and the obtained electron microscope images are shown in Figure 1 .

[0070] From the results in Figure 1 , compared with the gasification slag, the surface metal oxide particles of the modified gasification slag are washed out, the surface is smooth, the internal macropores are exposed, and the surface pore size is large.

[0071] Preparation Example 3

[0072] The preparation method of the modified gasification slag is as follows:

[0073] Step 1, 50g of gasification slag is crushed and mixed with 5mL of hydrofluoric acid (the mass fraction of hydrogen fluoride is 45wt%) and 200mL of 8wt% dilute hydrochloric acid on a polytetrafluoroethylene crucible, and heated to 120℃ on an electric furnace to perform acid washing modification, the heating time is 100min; after the heating is completed, the temperature is lowered to room temperature, and then filtered, the solid is washed with water and dried to obtain acidified gasification slag.

[0074] Step 2, the obtained acidified gasification slag is placed in a tube furnace, and carbonized at a high temperature of 900℃ for 1h under the protection of hydrogen, the exhaust gas is a mixed gas of hydrogen, water vapor, carbon monoxide and carbon dioxide, and then the temperature is lowered to obtain carbonized gasification slag.

[0075] Step 3, the obtained carbonized gasification slag is placed in a tube furnace, and hydrogenated at a high temperature of 650℃ for 1.5h under the protection of hydrogen, the exhaust gas is a mixed gas of methane and hydrogen, and then the temperature is lowered naturally to obtain modified gasification slag.

[0076] Preparation Example 4

[0077] The preparation method of the modified gasification slag is as follows: 50 g of gasification slag is crushed and mixed with 10 mL of hydrofluoric acid (mass fraction of hydrogen fluoride is 40 wt%) and 200 mL of 5 wt% dilute hydrochloric acid on a polytetrafluoroethylene crucible, and heated to 110°C on an electric heating furnace for acid washing modification, and the heating time is 120 min; after heating, the temperature is lowered to room temperature, then filtered, and the solid is washed with water and dried to obtain the modified gasification slag.

[0078] Preparation Example 5

[0079] The difference between the following preparation example and Preparation Example 2 is that the hydrogenation time is different when preparing the modified gasification slag, which is as follows: in Preparation Example 5, the hydrogenation time is 1 h.

[0080] Preparation of expanded graphite

[0081] The flake graphite is purchased from a graphite ore company in Jiangsu Donghai, and the graphite size is 200 mesh. The mass fraction of sulfuric acid in concentrated sulfuric acid is 98 wt%.

[0082] Preparation Example 1

[0083] The preparation method of the expanded graphite is as follows:

[0084] Step I, 50 g of natural flake graphite is slowly added to 200 mL of concentrated sulfuric acid and stirred uniformly; then 10 g of potassium permanganate is slowly stirred, the reaction temperature is controlled at 10°C and the reaction is carried out for 40 min, then the reaction temperature is heated to 30°C in a water bath and the reaction is carried out for 40 min, after the reaction is completed, the reaction mixture is washed with distilled water until it is neutral, and then placed in a 65°C oven for drying to obtain the oxidized graphite.

[0085] Step II, the oxidized expanded graphite is placed in a muffle furnace at 900°C for high-temperature expansion for 40 s, and then naturally cooled to obtain the expanded graphite.

[0086] Preparation Example 2

[0087] The preparation method of the expanded graphite is as follows:

[0088] Step I, 50 g of natural flake graphite is slowly added to 250 mL of concentrated sulfuric acid and stirred uniformly; then 20 g of potassium permanganate is slowly stirred, the reaction temperature is controlled at 15°C and the reaction is carried out for 30 min, then the reaction temperature is heated to 35°C in a water bath and the reaction is carried out for 30 min, after the reaction is completed, the reaction mixture is washed with distilled water until it is neutral, and then placed in a 65°C oven for drying to obtain the oxidized graphite.

[0089] Step II, the oxidized expanded graphite is placed in a muffle furnace at 1000°C for high-temperature expansion for 30 s, and then naturally cooled to obtain the expanded graphite.

[0090] Preparation Example 3

[0091] The preparation method of the expanded graphite is as follows:

[0092] Step I, 50 g of natural flake graphite was slowly added into 350 mL of concentrated sulfuric acid and stirred evenly; then 40 g of potassium permanganate was slowly added and stirred, the reaction temperature was controlled at 20°C and reacted for 20 min, then the reaction temperature was heated to 45°C in a water bath and reacted for 20 min, after the reaction was completed, it was washed to neutral with distilled water, and then placed in a 65°C oven to dry, to obtain the oxidized graphite.

[0093] Step II, the oxidized expanded graphite was placed in a muffle furnace at 1200°C for high-temperature expansion for 20 s, and then naturally cooled to obtain the expanded graphite.

[0094] Preparation Example 4

[0095] The preparation method of the expanded graphite is as follows:

[0096] Step I, the specific steps are as follows:

[0097] Step I-I, 50 g of natural flake graphite was dispersed in 1000 mL of deionized water, and stirred for 10 min by magnetic stirring to obtain a uniform dispersion.

[0098] Step I-II, the dispersion was transferred to a plasma reaction tank (equipment model Europlasma-CD1200, purchased from Belgium), the power was adjusted to 1000 W, argon was introduced, and the gas pressure was kept at 0.05 MPa; the plasma discharge was started, and the treatment time was 15 min.

[0099] Step I-III, the discharge was turned off, and the temperature was naturally cooled to room temperature, then washed with distilled water and ethanol, and dried to obtain the pretreated graphite.

[0100] Step I-IV, 50 g of pretreated graphite was slowly added into 250 mL of concentrated sulfuric acid and stirred evenly; then 20 g of potassium permanganate was slowly added and stirred, the reaction temperature was controlled at 15°C and reacted for 30 min, then the reaction temperature was heated to 35°C in a water bath and reacted for 30 min, after the reaction was completed, it was washed to neutral with distilled water, and then placed in a 65°C oven to dry, to obtain the oxidized graphite.

[0101] Step II, the oxidized graphite was placed in a muffle furnace at 1000°C for high-temperature expansion for 30 s, and then naturally cooled to obtain the expanded graphite.

[0102] The flake graphite, the pretreated graphite and the expanded graphite prepared by the preparation example were used as raw materials, and electron microscopy tests were carried out, a FEI-Q45 electron scanning microscope was used, the magnification was 5000 times, and the electron microscopy images obtained are shown in Figure 2 From the electron microscopy images, it can be seen that the pretreated graphite prepared by the preparation example has a more uniform particle size and a more uniform particle size distribution than the flake graphite. Figure 2As can be seen from the results, the flake graphite is tightly bonded between layers when untreated; after plasma treatment, numerous gaps appear between the pretreated graphite layers, facilitating the insertion of more functional groups during the preparation of expanded graphite; after the prepared expanded graphite is expanded at high temperature, the distance between the layers increases, forming an accordion-like structure, and the surface area increases.

[0103] Example

[0104] Example 1

[0105] The preparation method of the carbon-based composite filler is as follows: 50 g of the expanded graphite prepared in Preparation Example 1, 50 g of the modified gasification slag prepared in Preparation Example 1, and 25 g of calcium carbonate are uniformly mixed and ground to 200 mesh, and then 0.5 g of lithium carbonate is added and uniformly mixed. The mixture is poured into a ceramic spherical mold, heated and sintered at 600°C for 150 min under a continuous nitrogen atmosphere; then the temperature is continuously increased to 750°C and maintained for 15 min; after natural cooling, washing is performed using distilled water, and then drying is performed.

[0106] Example 2

[0107] The preparation method of the carbon-based composite filler is as follows: 50 g of the expanded graphite prepared in Preparation Example 2, 100 g of the modified gasification slag prepared in Preparation Example 2, and 50 g of calcium carbonate are uniformly mixed and ground to 300 mesh, and then 1 g of lithium carbonate is added and uniformly mixed. The mixture is poured into a ceramic spherical mold, heated and sintered at 650°C for 120 min under a continuous nitrogen atmosphere; then the temperature is continuously increased to 800°C and maintained for 10 min; after natural cooling, washing is performed using distilled water, and then drying is performed.

[0108] The carbon-based composite filler prepared in this example is subjected to electron microscope testing, using a Cess Gemini 300 electron scanning microscope with a magnification of 5000 times, and the electron microscope image obtained is shown in Figure 3 As can be seen from the results, the filler has a pore structure similar to that of activated carbon, and part of the pores are filled with calcium carbonate crystals, and the surface is relatively rough. Figure 3

[0109] Example 3

[0110] The preparation method of the carbon-based composite filler is as follows: 50 g of the expanded graphite prepared in Preparation Example 3, 150 g of the modified gasification slag prepared in Preparation Example 3, and 75 g of calcium carbonate are uniformly mixed and ground to 400 mesh, and then 1.5 g of lithium carbonate is added and uniformly mixed. The mixture is poured into a ceramic spherical mold, heated and sintered at 700°C for 100 min under a continuous nitrogen atmosphere; then the temperature is continuously increased to 900°C and maintained for 5 min; after natural cooling, washing is performed using distilled water, and then drying is performed.

[0111] Example 4 ​

[0112] The difference between this example and Example 2 is that the amount of raw materials used to prepare the carbon-based composite filler is different, specifically as follows: 50 g of the expanded graphite prepared in Preparation Example 2, 50 g of the modified gasification slag prepared in Preparation Example 2, and 100 g of calcium carbonate are mixed uniformly and ground to 300 mesh, and then 1 g of lithium carbonate is added and mixed uniformly. The other steps are the same as in Example 2.

[0113] Example 5

[0114] The difference between this example and Example 2 is that the modified gasification slag is prepared by the method of Preparation Example 5, and the others are the same as in Example 2.

[0115] Example 6

[0116] The difference between this example and Example 2 is that the expanded graphite is prepared by the method of Preparation Example 4, and the others are the same as in Example 2.

[0117] Comparative Example

[0118] Comparative Example 1

[0119] The difference between this comparative example and Example 2 is that the modified gasification slag is prepared by the method of Preparation Example 4, and the others are the same as in Example 2.

[0120] Comparative Example 2

[0121] The difference between this comparative example and Example 2 is that the amount of modified gasification slag added is different, specifically as follows:

[0122] In Comparative Example 2, when preparing the carbon-based composite filler, 50 g of the expanded graphite prepared in Preparation Example 2, 10 g of the modified gasification slag prepared in Preparation Example 2, and 50 g of calcium carbonate are mixed uniformly and ground to 300 mesh, and then 1 g of lithium carbonate is added and mixed uniformly.

[0123] Comparative Example 3

[0124] The difference between this example and Example 2 is that the amount of raw materials used to prepare the carbon-based composite filler is different, specifically as follows: 50 g of the expanded graphite prepared in Preparation Example 2, 25 g of the modified gasification slag prepared in Preparation Example 2, and 25 g of calcium carbonate are mixed uniformly and ground to 300 mesh, and then 1 g of lithium carbonate is added and mixed uniformly. The other steps are the same as in Example 2.

[0125] Comparative Example 4

[0126] The difference between this comparative example and Example 2 is that the modified gasification slag is replaced with an equal amount of gasification slag, and the others are the same as in Example 2.

[0127] 1. Determination of the effect of removing sulfur and nitrogen

[0128] The prepared filler was put into a biofilter with a volume of 3L, and the filler occupied 2L of the filter volume. The wastewater used in the experiment was obtained from a leather factory in Fujian Province after filtering hair and sand, and the average concentration of sulfide in the influent was 840 mg / L, the concentration of ammonia nitrogen was 81 mg / L, and the concentration of total nitrogen was 276 mg / L. In each experiment, 25g of the carbon-based composite filler prepared was used, the dissolved oxygen was controlled below 0.5mg / L, and no additional alkalinity was added.

[0129] The anaerobic sludge from a municipal wastewater treatment plant in Shaanxi Province was acclimated, and sodium thiosulfate solution was used to start the reactor. After the start-up was completed, the addition of sodium thiosulfate was stopped. Through microbiological analysis, the main sulfur autotrophic denitrifying microorganisms in the sludge were Sulfomonas and Sulfobacillus. Subsequently, a continuous influent experiment was conducted, and the total sulfur ion concentration and total nitrogen concentration were detected daily.

[0130] The anaerobic sludge contains sulfur autotrophic denitrifying bacteria, and under the action of these microorganisms, the main biochemical reactions are as follows:

[0131] 1.1S 0 +NO3 - +0.76H2O+0.4CO2+0.08NH4 + →0.5N2+1.10SO4 2- +1.28H + +0.08C5H7O2N;

[0132] Reaction 2:

[0133] 0.421S 2- +0.421HS - +NO3 - +0.086HCO3 - +0.346CO2+0.086NH4 + →0.5N2+0.842SO4 2- +0.262H + +0.086C5H7O2N+0.434H2O.

[0134] 1.1, the effect of the carbon-based composite filler of Example 2 on the removal of sulfur and nitrogen was determined

[0135] Referring to the above method, the carbon-based composite filler of Example 2 was used for water treatment experiment; wherein the sulfide concentration in the wastewater and the sulfide removal rate are shown in Figure 4 , the ammonia nitrogen concentration, total nitrogen concentration and total nitrogen removal rate in the wastewater are shown in Figure 5 . From the results of Figure 4 , the final effluent sulfide content was 366mg / L, and the average removal rate was 56.4%. From the results of Figure 5As can be seen from the results, in this experiment, the ammonia nitrogen effluent concentration is 75 mg / L, and the ammonia nitrogen content does not change significantly; the total nitrogen effluent concentration is 131 mg / L, and the total nitrogen removal rate is 52.5%.

[0136] 1.2. Determination of the effects of sulfur and nitrogen removal of the carbon-based composite filler in different embodiments

[0137] The water treatment experiments of the carbon-based composite filler in different embodiments were carried out according to the above method, the concentration of sulfide and total nitrogen in water was determined, and the removal rates of sulfide and total nitrogen were calculated. The specific results are shown in Table 1.

[0138] Table 1. Effects of sulfur and nitrogen removal of the carbon-based composite filler in different embodiments

[0139]

[0140]

[0141] As can be seen from the data results in Table 1, when sewage is treated by the method of the present application, it has a significantly excellent effect of removing sulfur ions and total nitrogen in sewage.

[0142] As can be seen by comparing the results of Example 2 and Comparative Example 4, if the gasification slag is not modified by the method of the present application, and the carbon-based composite filler is directly prepared from the gasification slag and used for the treatment of sulfur-containing sewage, the total nitrogen removal rate and the sulfur ion removal rate of the effluent will be significantly reduced, which will directly affect the treatment effect. Therefore, it is necessary to modify the gasification slag according to the method of the present application. Further combined with the results of Comparative Example 1, it is found that when preparing the modified gasification slag, only the acid treatment is performed on the gasification slag raw material, and the subsequent carbonization and hydrogenation steps are not performed, and the modified gasification slag obtained is used to prepare the carbon-based composite filler, and the filler is further used for the treatment of sulfur-containing sewage, the total nitrogen removal rate and the sulfur ion removal rate will be improved to some extent compared with Comparative Example 4, but the degree of improvement is not large. Therefore, to obtain a significantly improved total nitrogen removal rate and sulfur ion removal rate of the sulfur-containing sewage, the gasification slag is acidified, carbonized and hydrogenated according to the method of the present application, and the carbon-based composite filler with excellent water treatment effect can be obtained.

[0143] Further combined with Example 5, it is found that when preparing the modified gasification slag, sufficient hydrogenation time is necessary, which determines the content of active functional groups such as hydroxyl groups and aldehyde groups on the surface of the modified gasification slag, which will directly affect the ability of the modified gasification slag to load microorganisms, and further affect the water treatment effect.

[0144] In addition, the results of Example 6 and Example 2 show that when preparing the expanded graphite, the plasma treatment of the flake graphite in advance is beneficial to improve the activity of the expanded graphite, so as to improve the water treatment effect of the carbon-based composite filler.

[0145] And, the comparative example 2 and the comparative example 3 show that the relative amount of the expanded graphite and the modified gasification slag has a great influence on the water treatment ability of the carbon-based composite filler. The amount of the expanded graphite is not recommended to be more than the modified gasification slag, otherwise it is difficult to achieve a high sulfur ion removal rate and a total nitrogen removal rate.

[0146] 2. Rockwell hardness HRR test

[0147] The obtained carbon-based composite filler is subjected to a Rockwell hardness test by using an HRR scale, and the specific results are shown in Table 2.

[0148] Table 2 Rockwell hardness HRC of the carbon-based composite filler obtained in different embodiments

[0149] Embodiment Example 2 Example 4 Example 5 Rockwell hardness HRC 79 61 87

[0150] As can be seen from the data results in Table 2, the carbon-based composite filler prepared in the present application has good hardness.

[0151] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and the modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A carbon-based composite packing material based on sulfur ion conversion in impregnation water, characterized in that, The carbon-based composite filler comprises the following raw materials in parts by weight: 100 parts expanded graphite, 100-400 parts modified gasification slag, 50-150 parts calcium carbonate, and 1-3 parts lithium carbonate; The modified gasification slag is prepared by treating gasification slag through processes including acid washing, carbonization, and hydrogenation. The method for preparing the modified gasification slag includes the following steps: The gasification slag is crushed and mixed with acid solution, heated and modified, washed with water, separated into solid and liquid, and dried to obtain acidified gasification slag. The acid solution contains at least hydrofluoric acid. The acidified gasification slag is carbonized at a high temperature of 750-900℃ in a hydrogen atmosphere to obtain carbonized gasification slag. The carbonized gasification slag is hydrogenated at a high temperature of 500-650℃ in a hydrogen atmosphere to obtain modified gasification slag. When the gasification slag is crushed and mixed with acid solution and then heated for modification, the heating temperature is 100-120℃ and the heating modification time is 100-140min. The method for preparing the expanded graphite includes the following steps: After mixing flake graphite and concentrated sulfuric acid evenly, potassium permanganate was added and the mixture was reacted at a low temperature not exceeding 25°C, followed by a reaction at a medium temperature not lower than 45°C. The mixture was then washed with water until neutral and dried to obtain graphite oxide. Expanded graphite is obtained by expanding graphite at a high temperature of 900-1200℃ and then cooling it. The reaction time at low temperature is 20-40 min, and the reaction time at medium temperature is 20-40 min. Before mixing flake graphite and concentrated sulfuric acid, plasma pretreatment is also included.

2. The carbon-based composite filler based on sulfur ion conversion in impregnation water according to claim 1, characterized in that, The high-temperature carbonization time is 1-2 hours.

3. The carbon-based composite filler based on sulfur ion conversion in impregnation water according to claim 1, characterized in that, The high-temperature hydrogenation time is 1.5-2.5 hours.

4. The carbon-based composite filler based on sulfur ion conversion in impregnation water according to claim 1, characterized in that, The plasma pretreatment includes the following steps: Flake graphite is dispersed in a solvent to obtain a dispersion; The dispersion was placed in a plasma environment and subjected to plasma discharge treatment for 10-15 minutes in a protective gas environment with a power of 900-1100W. After cooling and washing, pretreated graphite was obtained for later use. The pretreated graphite is used for further mixing with concentrated sulfuric acid.

5. A method for preparing a carbon-based composite filler based on sulfur ion conversion in ash impregnation water as described in any one of claims 1-4, characterized in that, The preparation method includes the following steps: Expanded graphite, modified gasification slag, calcium carbonate and lithium carbonate are mixed according to the formula and sintered at 600-700℃ for 100-150 min in a protective atmosphere, and then sintered at 750-900℃ for 5-15 min. After cooling, the mixture is washed and dried to obtain the final product.

6. The method for preparing carbon-based composite filler based on sulfur ion conversion in impregnation water according to claim 5, characterized in that, The specific steps of mixing expanded graphite, modified gasification slag, calcium carbonate and lithium carbonate according to the formula are as follows: First, mix expanded graphite, modified gasification slag and calcium carbonate according to the formula and grind them to 200-400 mesh, and then add lithium carbonate according to the formula.

Images