Industrial solid waste treatment methods, cementitious materials, and manufactured products

Abstract

The present application relates to the field of resource and environmental technology, and in particular to industrial solid waste treatment methods, cementitious materials, and manufactured products. The industrial solid waste treatment method includes the following steps: providing nitrogen-doped biochar, which has nitrogen-containing groups bound to at least the surface; providing industrial solid waste, which contains heavy metal ions; subjecting the nitrogen-doped biochar and the industrial solid waste to a first mixing treatment to obtain a cementitious material precursor, which can be further used to prepare a cementitious material and a manufactured product. Heavy metal ions will be adsorbed and fixed by the nitrogen-doped biochar, making them less likely to dissolve and harm the environment. After adsorption, the mechanical properties of the manufactured products made from the cementitious material are also improved, while giving the cementitious material a carbon fixation effect. The treatment method of the present application can recycle industrial solid waste containing heavy metal ions, the treatment method is process-controllable, and the obtained cementitious material has excellent performance.

Description

Technical Field

[0001] The present application relates to the field of resource and environmental technology, and in particular to industrial solid waste treatment methods, gelling materials, and manufactured parts. Background Art

[0002] Industrial solid waste, such as waste concrete, phosphogypsum, and steel slag, often contains heavy metal elements in the form of ions. Depending on the content of heavy metal ions, they can be divided into heavy metal-free, low heavy metal content, and high heavy metal content. When recycling and using them for building materials, it is necessary to select industrial solid waste that is heavy metal-free or has a low heavy metal content. However, the proportion of industrial solid waste that meets the requirements is very small. Most industrial solid waste contains high levels of heavy metal ions, such as mercury, lead, cadmium, chromium, and other heavy metal ions. These heavy metal ions are easily dissolved after recycling, which not only easily pollutes the environment and is harmful to the human body, but also affects the strength of the resulting building materials. In addition, it is often difficult to remove these heavy metal ions in industrial solid waste using existing technologies. Summary of the Invention

[0003] The purpose of this application is to provide an industrial solid waste treatment method, a gelling material, and a manufactured product, aiming to solve the technical problem in the prior art that industrial solid waste containing heavy metal ions is difficult to recycle.

[0004] To achieve the above application objectives, the technical solutions adopted in this application are as follows:

[0005] In a first aspect, the present application provides a method for treating industrial solid waste, comprising the following steps:

[0006] providing nitrogen-doped biochar, wherein the nitrogen-doped biochar has nitrogen-containing groups bound to at least the surface;

[0007] Provide industrial solid waste, which contains heavy metal ions;

[0008] The nitrogen-doped biochar is first mixed with industrial solid waste to obtain a cementitious material precursor.

[0009] The treatment method of the present application first provides nitrogen-doped biochar. The nitrogen-doped atoms form an electroactive state in the biochar, which is beneficial to the adsorption performance of the nitrogen-doped biochar for heavy metal ions. The nitrogen-doped biochar can also chelate heavy metal ions to further improve the adsorption performance. The nitrogen-containing groups further fix the heavy metal ions on the surface of the nitrogen-doped biochar through a variety of chemical pathways. The nitrogen-doped biochar also has strong carbon dioxide adsorption performance. Therefore, after mixing the nitrogen-doped biochar with industrial solid waste, a cementitious material precursor can be obtained, which can be further used to prepare cementitious materials. The heavy metal ions will be adsorbed and fixed by the nitrogen-doped biochar, and are not easily dissolved and harm the environment. At the same time, the nitrogen-doped biochar gives the cementitious material a carbon fixation effect. In summary, the treatment method of the present application can recycle industrial solid waste containing heavy metal ions, the treatment method process is controllable, and the obtained cementitious material has excellent performance.

[0010] In a second aspect, the present application provides a gelling material, which is prepared from a gelling material precursor prepared by the industrial solid waste treatment method of the above-mentioned application.

[0011] The present cementitious material is produced from a cementitious material precursor prepared using the aforementioned treatment method. Therefore, industrial solid waste containing heavy metal ions can be fully recycled and utilized. Furthermore, the heavy metal ions are adsorbed and fixed by nitrogen-doped biochar, making them less likely to dissolve and harm the environment. This also helps improve the mechanical strength of the cementitious material produced from the precursor for use in building components and imparts carbon sequestration properties through carbon dioxide adsorption. Therefore, the present cementitious material exhibits the beneficial effects of high resource utilization, green and low emissions, and high strength.

[0012] In a third aspect, the present application provides a product, which is made by hydrating the gelling material of the above application.

[0013] Because the present cementitious material exothermally solidifies during hydration, the nitrogen-doped biochar, which adsorbs and fixes heavy metal ions, improves the mechanical strength of the product while reducing the dissolution of heavy metal ions. The nitrogen-doped biochar also imparts carbon sequestration to the cementitious material by adsorbing carbon dioxide. Consequently, the product exhibits high mechanical strength and is environmentally friendly and low-emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] Figure 1 is a SEM image of nitrogen-doped biochar in the treatment method of Example 1 of the present application;

[0016] Figure 2 This is a SEM image of ordinary biochar in the treatment method of Comparative Example 1 of this application;

[0017] Figure 3 This is a comparison chart of the compressive strength of the cementitious materials obtained by the treatment methods of Examples 1 to 8 and Comparative Examples 1 to 5 of the present application after hydration curing for 28 days;

[0018] Figure 4 This is a comparison chart of the flexural strength of cementitious materials obtained by the treatment methods of Examples 1 to 8 and Comparative Examples 1 to 5 of the present application after hydration and curing for 28 days. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0020] In this application, the term "and / or" describes the relationship between associated objects, indicating that three possible relationships exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0021] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0022] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0023] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0024] The weights of the relevant components mentioned in the examples of this application may not only refer to the specific content of each component, but also represent the weight ratio between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the examples of this application, it is within the scope disclosed in the examples of this application. Specifically, the mass in the examples of this application may be μg, mg, g, kg, etc., which are mass units known in the chemical industry.

[0025] The terms "first" and "second" are used solely for descriptive purposes to distinguish objects, such as substances, from one another and should not be understood to indicate or imply relative importance or to implicitly specify the quantity of the technical features being referred to. For example, without departing from the scope of the embodiments of this application, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX. Thus, features defined as "first" or "second" may explicitly or implicitly include one or more of such features.

[0026] A first aspect of the present invention provides a method for treating industrial solid waste, comprising the following steps:

[0027] S10. Providing nitrogen-doped biochar, wherein the nitrogen-doped biochar has nitrogen-containing groups bound to at least the surface;

[0028] S20. Provide industrial solid waste containing heavy metal ions;

[0029] S30. Performing a first mixing treatment on the nitrogen-doped biochar and industrial solid waste to obtain a cementitious material precursor.

[0030] The processing method of the embodiment of the present application first provides nitrogen-doped biochar, and introduces nitrogen-doped atoms into the biochar. Due to the difference in electronegativity between carbon and nitrogen, the charge distribution of the π electron network in the biochar is changed, so that a local unbalanced charged area is generated in the carbon structure of the biochar, forming an electroactive state, which is beneficial to the adsorption performance of the nitrogen-doped biochar for heavy metal ions; the nitrogen-doped biochar can also complex heavy metal ions, and can share electrons in the complexation process, further improving the adsorption performance; the nitrogen-containing groups on the surface of the nitrogen-doped biochar further fix the heavy metal ions on the surface of the nitrogen-doped biochar through a variety of chemical pathways; the nitrogen-doped biochar also has a strong carbon dioxide adsorption performance and has a carbon fixation effect. Therefore, after mixing the nitrogen-doped biochar with industrial solid waste, a cementitious material precursor can be obtained, which can be further used to prepare cementitious materials. The heavy metal ions in the cementitious material will be adsorbed and fixed by the nitrogen-doped biochar, and are not easy to dissolve and harm the environment. At the same time, the nitrogen-doped biochar gives the cementitious material a carbon fixation effect, which can be used as a green and low-carbon building material. In summary, the treatment method of the embodiment of the present application can be used to recycle industrial solid waste containing heavy metal ions, the treatment method is process-controllable, and the obtained gelling material has excellent performance.

[0031] [Step S10]

[0032] Step S10 is a step of providing nitrogen-doped biochar. The existing biochar itself has the carbon fixation effect of adsorbing carbon dioxide and is an ideal carbon fixation material. After being modified, the existing biochar can also be used to adsorb heavy metal ions in wastewater to reduce the harmfulness of the wastewater. However, in the prior art, this modified biochar is a consumable material. After adsorbing heavy metal ions to saturation, it cannot be reused and can only be discarded. Moreover, it is difficult to adsorb non-free heavy metal ions in the solid and can often only be used to treat wastewater. The nitrogen-doped biochar provided in step S10 also has the ability to adsorb carbon dioxide, and the nitrogen doping and the nitrogen-containing groups on the surface give the nitrogen-doped biochar the above-mentioned electroactive state, complexing properties, chemical fixation and other effects. Compared with the existing ordinary biochar, this nitrogen-doped biochar can adsorb and fix heavy metal ions. The treatment method of the embodiment of the present application prepares a cementitious material precursor from nitrogen-doped biochar and industrial solid waste, and in the process of preparing the cementitious material from the precursor, the heavy metal ions become free and are adsorbed and fixed by the nitrogen-doped biochar, ensuring the effect of industrial solid waste treatment. After adsorbing heavy metal ions, nitrogen-doped biochar is modified and used in building materials to improve their mechanical strength. Furthermore, the adsorbed heavy metal ions are fully retained in the cementitious material, allowing for full utilization without waste. This broadens the application of existing modified biochar, which can only be used to adsorb heavy metal ions from wastewater and must be discarded after saturation.

[0033] The nitrogen-doped biochar in the embodiments of this application has nitrogen-containing groups bound to at least one surface. In some embodiments, the nitrogen-containing groups include basic nitrogen groups, which include at least one of amine, pyridinic nitrogen, pyrrolic nitrogen, graphitic nitrogen, and quaternary ammonium groups. These basic nitrogen groups provide a certain alkalinity to the surface of the nitrogen-doped biochar, further improving its adsorption performance for heavy metal ions and immobilizing the heavy metal ions on the adsorbent surface through various chemical pathways.

[0034] Among them, amine group (-NH2): amine group is one of the most common nitrogen-containing basic groups, which can react with acidic substances and has strong adsorption capacity.

[0035] Pyridinic nitrogen: Pyridinic nitrogen is a nitrogen atom with sp 2 The hybrid orbital participates in the six-membered ring of carbon, similar to the nitrogen atom in the pyridine molecule. This nitrogen atom has basic properties and can participate in acid-base reactions.

[0036] Pyrrolic N: Pyrrolic N is a nitrogen atom that forms a five-membered ring with a carbon atom in the form of sp 2 The hybrid orbitals are conjugated and the basicity is weak.

[0037] Graphitic N: Graphitic N refers to nitrogen atoms in a graphene-like layer structure in the form of sp 2 The hybrid orbital replaces the carbon atom and has certain alkalinity and conductivity.

[0038] Quaternary ammonium group: A quaternary ammonium group is a basic group formed by four hydrocarbon groups connected to a nitrogen atom, which can combine with anions.

[0039] In some embodiments, in step S10 above, the method for preparing nitrogen-doped biochar includes the following steps:

[0040] S11. performing a second mixing process on the alkaline source, the nitrogen source and the biomass to obtain a nitrogen-doped biochar precursor;

[0041] S12. In a protective atmosphere, sinter the nitrogen-doped biochar precursor to obtain nitrogen-doped biochar.

[0042] The nitrogen-doped biochar prepared by the above preparation method can not only be doped with nitrogen elements in the biochar, but also form a variety of nitrogen-containing groups on at least the surface of the biochar, so that the prepared nitrogen-doped biochar can adsorb and fix heavy metal ions in multiple dimensions through charge adsorption, chemical complexation reaction, etc.

[0043] The biomass in step S11 may be agricultural and forestry waste, and in an exemplary embodiment, may include straw, rice husks, wood scraps, firewood, peanut shells, etc., and the particle size of the biomass particles may be controlled to be less than 1 mm by a crusher. Alternatively, the biomass may be first subjected to an acidic impurity removal liquid, such as hydrochloric acid or citric acid, to remove impurities therein, and then filtered, the filter residue retained and dried in a protective atmosphere, optionally at 90°C for 15 hours, to obtain the dried and impurity-removed biomass.

[0044] The alkali source, nitrogen source, and biomass are then subjected to a second mixing process to produce a nitrogen-doped biochar precursor. The alkali source may include at least one of sodium bicarbonate, sodium hydroxide, sodium carbonate, potassium hydroxide, and potassium carbonate, and the nitrogen source may include at least one of urea, aqueous ammonia, nitrogen gas, and ammonia gas. The mass ratio of the alkali source, nitrogen source, and biomass may be (0.5-4):(0.5-4):1. This raw material and ratio is conducive to producing nitrogen-doped biochar, and the incorporation of nitrogen-containing groups enhances the adsorption and fixation of heavy metal ions.

[0045] In the embodiment, in order to improve the effect of the preparation method, the mass ratio of different nitrogen sources to biomass can be as follows: ① The mass ratio of urea to biomass can be: 1: 1 to 3: 1. Urea decomposes into ammonia at high temperature, which can effectively introduce nitrogen elements. A higher urea ratio helps to increase the degree of nitrogen doping, but may also lead to the generation of more by-products. ② The mass ratio of ammonia water to biomass can be: 0.5: 1 to 2: 1 (calculated based on the nitrogen content of ammonia water). Ammonia water provides ammonia molecules and reacts with biomass during the pyrolysis process. A higher ammonia water ratio can increase the nitrogen doping amount, but care should be taken to control the reaction conditions to avoid excessive corrosion of the biochar structure.

[0046] In the embodiment, in order to improve the effect of the preparation method, the mass ratio of different alkali sources to biomass can be referred to as follows: ① The mass ratio of sodium hydroxide to biomass can be 1: 1 to 4: 1. NaOH is commonly used in the activation process of biochar. A higher ratio can increase the specific surface area and porosity of biochar, while promoting nitrogen doping. ② The mass ratio of potassium hydroxide to biomass can be 1: 1 to 3: 1. KOH is also a commonly used activating agent. An appropriate ratio can effectively improve the pore structure of biochar and help introduce more nitrogen-containing groups. ③ The mass ratio of sodium carbonate to biomass can be 0.5: 1 to 2: 1. Sodium carbonate is a mild alkali source. A lower ratio is suitable for maintaining the structure of biochar while providing a moderate activation effect at higher temperatures. ④ The mass ratio of potassium carbonate to biomass can be 1: 1 to 3: 1. When potassium carbonate is used to activate biochar, a higher ratio can increase the surface area and porosity, which is conducive to nitrogen doping.

[0047] In an exemplary embodiment, a second mixing process can be performed in a solution. An alkali source, a nitrogen source, and water are first prepared into a solution, and then the biomass is added thereto. The mass ratio of the alkali source, nitrogen source, water, and biomass can be 2:2:20:1. In an exemplary embodiment, the mixture can be performed in a mass ratio of sodium bicarbonate: urea: water: biomass of 2:2:20:1. The raw materials can be stirred for 3 hours to fully mix, and then filtered to remove the liquid and retain the filter residue.

[0048] Step S12 further sintering the nitrogen-doped biochar precursor in step S11 to produce nitrogen-doped biochar. The sintering process needs to be carried out in a protective atmosphere, which can be nitrogen and / or an inert gas. In some embodiments, the sintering temperature can be 600-1000°C. In exemplary embodiments, it can include but is not limited to any value of 600°C, 700°C, 800°C, 900°C, 1000°C, or a range between any two values. The sintering temperature can be adjusted according to the nitrogen source to improve the sintering effect. When the nitrogen source is urea, the sintering temperature is more suitable at 600°C-900°C. When the nitrogen source is ammonia water, the sintering temperature is 500°C-800°C. When the nitrogen source is a nitrogen or ammonia environment, the sintering temperature is 700°C-1000°C. The temperature can be increased to the sintering temperature at a heating rate of 10°C / h and maintained at this temperature for 1 hour. The temperature of the sintering treatment causes the nitrogen-doped biochar precursor to be carbonized, and the nitrogen element therein is also doped and combined in the sintered carbon, and forms nitrogen-containing groups at least on the surface to obtain nitrogen-doped biochar.

[0049] [Step S20]

[0050] Step S20 is a step of providing industrial solid waste, wherein the industrial solid waste contains heavy metal ions; the industrial solid waste may include at least one of waste concrete, phosphogypsum, and steel slag.

[0051] Among them, the main components of waste concrete are: silicates (CaSiO3, Ca3SiO5, Ca2SiO4): These are the main hydration products of concrete and constitute the matrix of concrete. Calcium hydroxide (Ca(OH)2): Produced by cement hydration reaction, it forms an alkaline environment in concrete. Calcium carbonate (CaCO3): Due to carbonization, concrete often contains a certain amount of calcium carbonate. Iron oxide (Fe2O3): It exists in small amounts and mainly comes from the raw materials of cement. It often contains the following heavy metal ions: lead (Pb), cadmium (Cd), nickel (Ni), zinc (Zn), and copper (Cu). These heavy metals may come from the pollution of concrete during use, such as from industrial wastewater, air pollution, etc.

[0052] The main components of phosphogypsum are: Calcium sulfate dihydrate (CaSO4·2H2O): The main component of phosphogypsum. Free acid (H3PO4): Some phosphogypsum may contain small amounts of free phosphoric acid. Silicates and aluminosilicates: These are present in small quantities and originate from ore impurities. Phosphogypsum often contains the following heavy metal ions: lead (Pb), arsenic (As), cadmium (Cd), and chromium (Cr). These heavy metals may originate from impurities in phosphate rock and contaminants introduced during the wet-process phosphoric acid production process.

[0053] The main components of steel slag are: Calcium oxide (CaO): It is the main component of steel slag and is used to neutralize acidic substances in the steel production process. Silicon oxide (SiO2): It is present in high content in steel slag and combines with CaO to form calcium silicate. Ferrous oxide and ferric oxide (FeO, Fe2O3): They exist in large quantities and come from iron ore in the steelmaking process. Magnesium oxide (MgO): It is used to adjust the properties of slag. Aluminum oxide (Al2O3): It comes from impurities in the ore. It often contains the following heavy metal ions: lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), nickel (Ni), and copper (Cu).

[0054] Heavy metals in steel slag usually come from impurities in iron ore or foreign contaminants during the steelmaking process.

[0055] These industrial solid wastes often contain large amounts of heavy metal ions, making them difficult to recycle. In one example, these industrial solid wastes can be crushed to produce particles with a particle size of less than 1 mm. Alternatively, the industrial solid wastes can be filtered through an acidic impurity removal solution, such as hydrochloric acid or citric acid, to remove impurities. The residue is then filtered and dried in a protective atmosphere, optionally at 90°C for 15 hours, to obtain the dried, impurity-free industrial solid waste.

[0056] It should be understood that the sequence numbers of step S10 and step S20 do not imply a specific order of execution; some or all of the steps may be executed in parallel or sequentially, and do not constitute any limitation on the implementation process of the embodiments of the present application.

[0057] [Step S30]

[0058] Step S30 is the step of preparing a cementitious material precursor. In some embodiments, the mass ratio of industrial solid waste to nitrogen-doped biochar can be (10-25):1. In exemplary embodiments, the mass ratio can include, but is not limited to, any ratio of 10:1, 15:1, 20:1, and 25:1, or a range between any two ratios, with 20:1 being an option. The first mixing treatment can be performed by stirring the two to obtain a cementitious material precursor. In exemplary embodiments, the dried, impurity-removed, and powdered particles can be thoroughly mixed. These cementitious material precursors can be used to prepare cementitious materials, thereby fully recycling industrial solid waste.

[0059] After obtaining the gelling material precursor, it can be further processed according to the following steps:

[0060] S40. Activate the gelling material precursor with an alkali activator to obtain an alkali-activated gelling material.

[0061] The cementitious material precursor itself does not chemically react with water and is chemically inert. Therefore, it can be activated by an alkaline activator to activate the precursor's gelling properties and produce an alkali-activated cementitious material. Furthermore, during the alkaline activation process, heavy metal ions contained in the industrial solid waste in the cementitious material precursor will also become free and are then absorbed and fixed by the nitrogen-doped biochar. They are firmly bound to the nitrogen-doped biochar and are not easily dissolved, greatly reducing the harmfulness of these heavy metal ions. At the same time, after the nitrogen-doped biochar adsorbs and fixes heavy metal ions through physical adsorption and chemical reactions, the porosity on the surface of the nitrogen-doped biochar decreases, the specific surface area decreases, and the density increases, which is beneficial for improving the mechanical strength of the alkali-activated cementitious material used in construction components.

[0062] In some embodiments, during the activation process, the mass ratio of the gelling material precursor to the alkaline activator is 20:(1-3). In exemplary embodiments, the mass ratio may include, but is not limited to, any ratio of 20:3, 20:2, or 20:1, or a range between any two ratios. These ratios are beneficial for enhancing the activation of the gelling material precursor by the alkaline activator, improving gelling properties, and promoting the adsorption and fixation of heavy metal ions by the nitrogen-doped biochar.

[0063] In some embodiments, the alkaline activator may include an alkali metal hydroxide and / or an alkali metal silicate. In exemplary embodiments, the alkaline activator may include at least one of sodium hydroxide, potassium hydroxide, sodium silicate, and potassium silicate. The alkaline activator may be a single material or a combination of two or more of these materials. In exemplary embodiments, an alkaline activator solution may be prepared first, and then the cementitious material precursor is activated. The alkaline activator solution may be a mixture of sodium hydroxide: sodium silicate: water in a mass ratio of 1:2:4. The cementitious material precursor and the alkaline activator solution are then placed in a container and thoroughly immersed and stirred to ensure a uniform mixture, thereby fully activating the activity of the cementitious material precursor and causing the heavy metal ions contained therein to be adsorbed and fixed by the nitrogen-doped biochar.

[0064] After obtaining the alkali-activated gelling material, it can be further processed according to the following steps:

[0065] S50. In a protective atmosphere, the alkali-activated cementitious material is calcined to obtain a cementitious material. In some embodiments, the calcination temperature is 1300-1450°C. In exemplary embodiments, the calcination temperature may include, but is not limited to, any value or a range between any two values ​​of 1300°C, 1350°C, 1400°C, and 1450°C. The calcination time may be 2 hours. The calcination process decomposes the components in the alkali-activated cementitious material and generates a clinker rich in various cementitious minerals, such as dicalcium silicate and tricalcium silicate, through calcination, i.e., the cementitious material. The cementitious material can react with water to form a gelling agent. The nitrogen-doped biochar contained in the cementitious material adsorbs and fixes heavy metal ions, making them less likely to dissolve and cause harm. The nitrogen-doped biochar adsorbing heavy metal ions can also improve the strength of the cementitious material and give the cementitious material the ability to adsorb carbon dioxide and fix carbon.

[0066] In some embodiments, an alkali-activated cementitious material can be mixed with a cement material and then calcined to obtain a cementitious material. The cement material can be cement raw material. Adding cement raw material to the calcination process can improve the gelling properties of the obtained cementitious material, that is, improve the cohesive properties, and further improve the mechanical properties of the parts made of the cementitious material. Moreover, only a small amount of cement material needs to be added during mixing to obtain a high-strength cementitious material. In some embodiments, the mass ratio of the alkali-activated cementitious material to the cement material is (1-9):1. In exemplary embodiments, it can include but is not limited to any ratio of 1:1, 3:1, 6:1, 9:1, or a range between any two ratios. In the prior art, the production of cement materials consumes a lot of energy and has high carbon emissions. Therefore, compared with the traditional method of using a large amount of cement as a cementitious material, the treatment method of the embodiment of the present application can replace a large amount of high-energy cement materials with the above-mentioned alkali-activated cementitious material, greatly reducing the carbon emissions during the production process of the cementitious material. At the same time, the nitrogen-doped biochar can also absorb carbon dioxide from the atmosphere during the hydration process of the cementitious material, thus achieving a low-carbon life cycle from production to use. In summary, the prepared cementitious material is green and low-carbon, heavy metal ions are not easily dissolved, and the mechanical strength of the prepared parts is high.

[0067] A second aspect of the embodiments of the present application provides a gelling material, which is prepared from a gelling material precursor prepared by the industrial solid waste treatment method of the embodiments of the present application.

[0068] The preparation method of the cementitious material in the embodiment of the present application can refer to the further processing method of the cementitious material precursor in the embodiment of the previous application. Specifically, the cementitious material precursor can be subjected to alkali excitation treatment and then calcined to obtain the cementitious material. The calcination treatment can be carried out together with a small amount of cement raw material.

[0069] The cementitious material of the embodiment of the present application is made from the cementitious material precursor obtained by the treatment method of the embodiment of the present application above, so that industrial solid waste containing heavy metal ions can be fully recycled and utilized, and the heavy metal ions are adsorbed and fixed by nitrogen-doped biochar, and are not easily dissolved and harm the environment. In addition, after the nitrogen-doped biochar adsorbs and fixes the heavy metal ions, the pores on the surface are reduced, the specific surface area is reduced, and the density is increased, which is conducive to improving the mechanical strength of the cementitious material made from the precursor for use in building components. It also gives the cementitious material the carbon fixation property of adsorbing carbon dioxide. Therefore, the cementitious material of the embodiment of the present application has the beneficial effects of high resource utilization, green and low emissions, and high strength.

[0070] A third aspect of the embodiments of the present application provides a product, which is obtained by hydrating the gelling material of the embodiments of the present application.

[0071] The parts of the embodiment of the present application are prepared by hydrating the cementitious material of the embodiment of the present application. When preparing the parts, water and cementitious material are mixed and cast into shape. The water-cement ratio can be 0.4 to 0.5. Aggregates, auxiliary cementitious materials, water reducers and other components can also be added. The curing time of the hydration treatment can be 7 days to 28 days to obtain the parts.

[0072] Because the cementitious material of the present application exothermically solidifies during hydration, the nitrogen-doped biochar, which adsorbs and fixes heavy metal ions, improves the mechanical strength of the product while reducing the dissolution of heavy metal ions. The nitrogen-doped biochar also imparts carbon sequestration to the cementitious material by adsorbing carbon dioxide. Therefore, the product of the present application embodiment has high mechanical strength and is environmentally friendly and low-emission.

[0073] The following describes the details in conjunction with specific embodiments.

[0074] Example 1

[0075] This embodiment provides a method for treating industrial solid waste.

[0076] The processing method includes the following steps:

[0077] S1. Preparation of nitrogen-doped biochar:

[0078] The straw is added into a crusher and crushed to a particle size of less than 1 mm to obtain wood powder;

[0079] The wood powder was added to an acidic impurity removal liquid, hydrochloric acid, to remove impurities therein, and then filtered, and the filter residue was taken and dried at 90° C. for 15 h in a nitrogen atmosphere to obtain dry wood powder;

[0080] Add sodium bicarbonate: urea: water in a mass ratio of 2:2:20 to the soaking reactor, further fully mix the solution, and then pass the dry wood powder into the soaking reactor and soak and stir for 3 hours. The mass ratio of sodium bicarbonate to wood powder is 2:1;

[0081] After filtration, the filter residue was placed in an incinerator, heated to 900°C at a rate of 10°C / h under a nitrogen atmosphere, and incinerated for 1 hour to obtain nitrogen-doped biochar.

[0082] S2. Provide dry industrial solid waste powder:

[0083] Industrial solid waste is solid waste, including waste concrete, phosphogypsum, and steel slag in a mass ratio of 1:1:1. The industrial solid waste is added to the crusher and crushed to a particle size of less than 1 mm to obtain solid waste powder;

[0084] The solid waste powder was added to an acidic impurity removal liquid, hydrochloric acid, to remove impurities therein, and the filter residue was taken after filtration and dried at 90° C. for 15 h in a nitrogen atmosphere to obtain a dry industrial solid waste powder.

[0085] S3. Providing gelling material precursor:

[0086] The industrial solid waste powder dried in step S2 and the nitrogen-doped biochar in step S1 are mixed and stirred in a mass ratio of 10:1 to obtain a cementitious material precursor.

[0087] S4. Further prepare gelling materials and products:

[0088] The gelling material precursor in step S3 is activated by introducing sodium hydroxide: sodium silicate: water in a mass ratio of 1:2:4 into an excitation reactor to prepare an alkaline activator solution. The gelling material precursor in step S3 is added to the excitation reactor and immersed and stirred. The mass ratio of the total mass of sodium hydroxide and sodium silicate to the gelling material precursor is 1:20 to activate the activity of the gelling material precursor. After filtering, the filter residue is removed and dried at 90° C. in a nitrogen atmosphere for 15 hours to obtain an alkaline activated gelling material.

[0089] Alkali-activated cementitious material: cement raw material are added into the cement kiln in a mass ratio of 9:1, and calcined at 1400°C for 2 hours to obtain agglomerated cementitious material, which is then introduced into a crusher to be crushed into powder to obtain powdered cementitious material;

[0090] Example 2

[0091] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that the mass ratio of industrial solid waste powder to nitrogen-doped biochar in step S3 is changed from 10:1 to 15:1, and all other aspects are the same.

[0092] Example 3

[0093] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that the mass ratio of industrial solid waste powder to nitrogen-doped biochar in step S3 is changed from 10:1 to 20:1, and all other aspects are the same.

[0094] Example 4

[0095] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that the mass ratio of industrial solid waste powder to nitrogen-doped biochar in step S3 is changed from 10:1 to 25:1, and all other aspects are the same.

[0096] Example 5

[0097] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that the mass ratio of alkali-activated cementitious material to cement raw material in step S4 is changed from 9:1 to 5:1, and all other aspects are the same.

[0098] Example 6

[0099] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that no cement raw meal is added in step S4, and only the alkali-activated cementitious material is calcined, and all other aspects are the same.

[0100] Example 7

[0101] This embodiment provides a method for treating industrial solid waste, which differs from Embodiment 1 only in that the industrial solid waste in step S2 is replaced by only waste concrete, and all other aspects are the same.

[0102] Example 8

[0103] This embodiment provides a method for treating industrial solid waste, which differs from Example 1 only in that the industrial solid waste in step S2 is changed to only phosphogypsum, and all other aspects are the same.

[0104] Comparative Example 1

[0105] This comparative example provides a method for treating industrial solid waste, which differs from Example 1 only in that sodium bicarbonate and urea are not added to the soaking reactor in step S1, and ordinary biochar is produced, and the ordinary biochar is used instead of nitrogen-doped biochar in the subsequent step S3, and all other aspects are the same.

[0106] Comparative Example 2

[0107] This comparative example provides a method for treating industrial solid waste, which differs from Example 2 only in that sodium bicarbonate and urea are not added to the soaking reactor in step S1, and ordinary biochar is produced, and the ordinary biochar is used instead of nitrogen-doped biochar in the subsequent step S3, and all other aspects are the same.

[0108] Comparative Example 3

[0109] This comparative example provides a method for treating industrial solid waste, which differs from Example 3 only in that sodium bicarbonate and urea are not added to the soaking reactor in step S1, and ordinary biochar is produced, and the ordinary biochar is used instead of nitrogen-doped biochar in the subsequent step S3, and all other aspects are the same.

[0110] Comparative Example 4

[0111] This comparative example provides a method for treating industrial solid waste, which differs from Example 4 only in that sodium bicarbonate and urea are not added to the soaking reactor in step S1, and ordinary biochar is produced, and the ordinary biochar is used instead of nitrogen-doped biochar in the subsequent step S3, and all other aspects are the same.

[0112] Comparative Example 5

[0113] This comparative example provides a method for treating industrial solid waste, which differs from Example 1 only in that no nitrogen-doped biochar is added in step S3, that is, the industrial solid waste is directly used as a cementitious material precursor, and all other aspects are the same.

[0114] The differences between Examples 1 to 8 and Comparative Examples 1 to 5 are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] Electron microscopy test:

[0119] The nitrogen-doped biochar prepared in step S1 of Example 1 and the biochar prepared in step S1 of Comparative Example 1 were tested by scanning electron microscopy, and the SEM images were as follows: Figure 1 、 Figure 2 shown.

[0120] from Figure 1 、 Figure 2 It can be seen from the comparison that Figure 1 Nitrogen-doped biochar and Figure 2 Compared with the ordinary biochar, it is obvious that there are fewer defects and a denser structure. According to the BET data report in Table 2, it can be seen that the total pore volume of the nitrogen-doped biochar in Example 1 (0.042483 cm 3 / g) is higher than the ordinary biochar in Comparative Example 1 (0.025898 cm 3 / g), reflecting its higher porosity. Furthermore, the average pore size of nitrogen-doped biochar (7.3711 nm) is smaller than that of conventional biochar (20.0455 nm). Nitrogen-doped biochar exhibits a more pronounced microporous structure within the small pore size range, while conventional biochar exhibits a more pronounced pore structure within the large pore size range. The superior micropore structure of nitrogen-doped biochar is beneficial for the hydration process of cement-based materials and the adsorption of heavy metal ions.

[0121] Table 2

[0122]

[0123] Performance testing:

[0124] The cementitious materials of Examples 1 to 8 and Comparative Examples 1 to 5 were made into articles, specifically proportioned according to a cementitious material: water mass ratio of 5:2, a water-cement ratio of 0.4, cast and formed, and cured for 28 days to obtain articles after complete solidification. Three article samples were prepared for each cementitious material.

[0125] Freshly mixed cementitious composite materials were poured into a mold with a diameter of 40 mm and a height of 160 mm. The mixture was vibrated thoroughly for approximately one minute to reduce voids in the slurry. After vibration, the upper end of the mold was sealed with a polytetrafluoroethylene film. The cement mortar specimens were pre-cured with the mold at a temperature of (20 ± 3)°C and a relative humidity of (60 ± 5)% for 6 hours, followed by a 24-hour curing period after the mold was removed. Following pre-curing, the specimens were cured at a temperature of (20 ± 1)°C and a relative humidity of (70 ± 2)% until the date of testing.

[0126] 1. Compression performance test

[0127] The products provided in Examples 1 to 8 and Comparative Examples 1 to 5 were subjected to compression resistance tests according to the following steps:

[0128] Among them, three parts made of the cementitious material of each embodiment or comparative example are tested, and the average value of the three parts is taken as the final compressive performance value to reduce errors. The compressive strength and flexural strength tests are carried out in accordance with the GB / T17671-2021 standard. The loading rates are 2400N / s and 50N / s, respectively. In addition, in order to observe the compressive properties of the cementitious material at different ages during the hydration process, the compressive performance tests are carried out according to the above steps on the 3rd, 7th and 28th days of the curing treatment, and the results of 7d and 28d are recorded in Table 3 below. Since the 3d and 7d strengths only reflect the changes in the hydration process, Table 3 mainly looks at the 28d strength.

[0129] Table 3

[0130]

[0131]

[0132] Comparing the average values ​​of the products of each embodiment and comparative example, the 28-day compressive strength graph is shown in FIG. Figure 3 Those skilled in the art can also know the embodiments or comparative examples corresponding to the symbols in the figures.

[0133] From Table 3, Figure 3 It can be seen that in Examples 1 to 8, after preparing cementitious material precursors using industrial solid waste and nitrogen-doped biochar, and then further preparing cementitious materials, the compressive strength of the prepared parts is significantly higher than that of the cementitious material of Comparative Example 5 without adding any biochar, and Examples 1 to 4 are also higher than Comparative Examples 1 to 4 respectively, indicating that the performance of the cementitious material finally prepared by treating industrial solid waste with nitrogen-doped biochar is higher than that of ordinary biochar.

[0134] As shown in Examples 1 to 6, a small amount of raw cement can be added during the calcination of alkali-activated cementitious materials to improve performance, but it can also be omitted. Substantially replacing cement with these cementitious materials can significantly reduce the amount of cement-based cementitious materials used and reduce energy consumption. As shown in Examples 1 to 8, this treatment method is applicable to the treatment of a variety of industrial solid wastes, provides reliable treatment results, and enhances resource recovery and utilization.

[0135] 2. Bending performance test

[0136] The products provided in Examples 1 to 8 and Comparative Examples 1 to 5 were subjected to a flexural performance test according to the following steps:

[0137] Three articles made from the cementitious materials of each example or comparative example were tested, and the average of these three articles was taken as the final flexural performance value to reduce error. Furthermore, to observe the flexural performance of the cementitious materials at different ages during the hydration process, flexural performance tests were conducted according to the above steps on the 3rd, 7th, and 28th days of curing. The results at 7 days and 28 days are recorded in Table 4 below. Since the 3d and 7d strengths only reflect changes during the hydration process, the 28d strength is primarily reported in Table 4.

[0138] Table 4

[0139]

[0140]

[0141] Comparing the average values ​​of the products of each embodiment and comparative example, the 28-day flexural strength graph is shown in FIG. Figure 4 As shown in Table 4, Figure 4As can be seen from the data, Examples 1 to 8, after preparing cementitious material precursors using industrial solid waste and nitrogen-doped biochar, and then further preparing cementitious materials, exhibit significantly higher flexural strength than the cementitious material obtained in Comparative Example 5, which does not contain any biochar. Furthermore, it is noted that the mass ratio of industrial solid waste to nitrogen-doped biochar (biochar), that is, the amount of nitrogen-doped biochar added, significantly affects flexural properties. Furthermore, when Examples 1 to 4 are compared with Comparative Examples 1 to 4, the strengths of Examples 1 to 4 are, respectively, higher than those of Comparative Examples 1 to 4, as determined by a single factor. This indicates that the performance of the cementitious material ultimately produced by treating industrial solid waste with nitrogen-doped biochar is superior to that of ordinary biochar.

[0142] As shown in Examples 1 to 6, a small amount of raw cement can be added during the calcination of alkali-activated cementitious materials to improve performance, but it can also be omitted. Substantially replacing cement with these cementitious materials can significantly reduce the amount of cement-based cementitious materials used and reduce energy consumption. As shown in Examples 1 to 8, this treatment method is applicable to the treatment of a variety of industrial solid wastes, provides reliable treatment results, and enhances resource recovery and utilization.

[0143] 3. Heavy metal ion dissolution test

[0144] The 28-day-cured articles from Examples 1 to 8 and Comparative Examples 1 to 5 were tested for heavy metal ion dissolution using the toxicity characteristic leaching method. The tests were conducted in accordance with the Chinese standard "HJ / T 300-2007," using a heavy metal analyzer to determine the type of heavy metal ions. The pH of the glacial acetic acid extract was adjusted to 2.64±0.05 using a 0.1 mol / L NaOH solution. The 28-day-cured sample was ground in a mortar and sieved through a 200-mesh sieve. The ground powder and extract were placed in a centrifuge tube at a ratio of 1:20. The centrifuge tube was shaken in an oscillator at 32 rpm and 23±2°C for 20 hours. The supernatant was then filtered and analyzed for heavy metal concentration using an electronic titrator. The results for each case are reported in Table 5. The "Identification Criteria" in Table 5 follows the "Identification of Hazardous Wastes: Leaching Toxicity" (GB5085.3).

[0145] Table 5

[0146]

[0147] As can be seen from Table 5, after preparing cementitious material precursors using industrial solid waste and nitrogen-doped biochar, and then further preparing cementitious materials in Examples 1 to 8, the heavy metal ion leaching rate of the resulting articles was significantly lower than that of the cementitious material without any biochar added in Comparative Example 5. Furthermore, Examples 1 to 4 were also lower than Comparative Examples 1 to 4, respectively. This indicates that the heavy metal ion leaching rate of the cementitious materials ultimately produced by treating industrial solid waste with nitrogen-doped biochar was lower than that of ordinary biochar. Clearly, the treatment methods of the present application fully recycle industrial solid waste, and the nitrogen-doped biochar can fully adsorb and fix heavy metal ions. Together, these two methods can significantly reduce the dissolution of heavy metal ions in the cementitious materials and the resulting articles, alleviating related hazards and achieving green treatment.

[0148] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for treating industrial solid waste, characterized in that: The steps include: performing a second mixing process of the alkali source, the nitrogen source and the biomass to obtain a nitrogen-doped biochar precursor; Sintering the nitrogen-doped biochar precursor in a protective atmosphere to obtain nitrogen-doped biochar, wherein the nitrogen-doped biochar has nitrogen-containing groups bound to at least the surface; Providing industrial solid waste, wherein the industrial solid waste contains heavy metal ions; performing a first mixing process on the nitrogen-doped biochar and industrial solid waste to obtain a cementitious material precursor; activating the gelling material precursor with an alkali activator to obtain an alkali-activated gelling material; In a protective atmosphere, the alkali-activated cementitious material is mixed with cement raw material and then calcined to obtain the cementitious material; Wherein, the industrial solid waste includes at least one of waste concrete, phosphogypsum and steel slag; the temperature of the calcination treatment is 1300-1450°C.

2. The industrial solid waste treatment method according to claim 1, characterized in that: The mass ratio of the industrial solid waste to the nitrogen-doped biochar is (10-25):1; And / or, the nitrogen-containing group includes a basic nitrogen group, and the basic nitrogen group includes at least one of an amino group, a pyridinic nitrogen, a pyrrolic nitrogen, a graphitic nitrogen, and a quaternary ammonium group.

3. The industrial solid waste treatment method according to claim 1, characterized in that: The mass ratio of the alkaline source, the nitrogen source and the biomass is (0.5-4): (0.5-4): 1; And / or, the sintering temperature is 600-1000°C.

4. The method for treating industrial solid waste according to claim 1, wherein: During the activation process, the mass ratio of the gelling material precursor to the alkaline activator is 20:(1-3); And / or, the alkali activator includes alkali metal hydroxide and / or alkali metal silicate.

5. The industrial solid waste treatment method according to claim 1, characterized in that: The mass ratio of the alkali-activated cementitious material to the cement raw material is (1-9):

1.

6. A gelling material, characterized in that: The gelling material is obtained by the industrial solid waste treatment method according to any one of claims 1 to 5.

7. A manufactured article, characterized in that: The article is made by hydrating the gelling material according to claim 6.

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