Method for preparing geopolymer from electrolytic manganese residues through wet desulphurization

Abstract

The invention discloses a method for preparing a geopolymer from wet desulphurization electrolytic manganese residues, which comprises the following steps: firstly, carrying out drying and mechanical grinding pretreatment on solid wastes such as electrolytic manganese residues, potassium salt wet desulphurization electrolytic manganese residues, fly ash, steel slag and the like, metakaolin and quick lime, and mixing according to a certain proportion to form a dry functional mixture; preparing an alkaline exciting agent solution from liquid sodium silicate and sodium hydroxide according to a certain proportion, uniformly stirring and mixing the alkaline exciting agent solution with the dry-state functional mixture, and adding a proper amount of water to form slurry with flowability; and finally, carrying out pouring molding, curing and demolding, and carrying out pre-curing and standard curing to obtain the high-performance geopolymer product. Compared with the prior art, the method provided by the invention realizes complete recycling and high-value utilization of multiple bulk industrial solid wastes, and has the advantages of simple process flow, low carbon and environmental protection. The prepared geopolymer has the advantages of being excellent in mechanical property, high in solid waste mixing ratio, low in pollutant leaching amount, remarkable in curing effect on components harmful to the environment and the like, and meanwhile the problem of environmental pollution caused by stockpiling of a large amount of industrial solid waste represented by electrolytic manganese residues can be effectively solved. In addition, the method can also be widely applied to the field of green building materials such as building blocks and roadbed materials, and has very important significance for realizing bulk consumption and high-value utilization of the electrolytic manganese residues and promoting sustainable development of the manganese industry.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial solid waste resource utilization and novel cementitious materials, and relates to a method for preparing geopolymers from wet desulfurization electrolytic manganese slag, as well as the products obtained by this method and their applications. Background Technology

[0002] Manganese metal, as a crucial strategic raw material, plays an irreplaceable role in steel metallurgy, battery materials, chemicals, and national defense. my country is the world's largest producer, consumer, and exporter of electrolytic manganese, accounting for over 92% of global manganese production. The manganese metallurgy industry has become a distinctive and advantageous industry in my country. However, while creating enormous economic value, this industry also faces severe environmental challenges. The core issue lies in the large amount of solid waste generated during the electrolytic manganese production process—electrolytic manganese slag. Electrolytic manganese slag is a high-moisture industrial solid waste produced after manganese ore leaching during the electrolytic production of metallic manganese. In my country, the wet electrolytic manganese process generates approximately 10-12 tons of electrolytic manganese slag for every ton of metallic manganese produced. The large-scale discharge of electrolytic manganese slag severely pollutes the local ecological environment. Electrolytic manganese slag has a complex composition, rich in high concentrations of soluble sulfates (such as manganese sulfate and ammonium sulfate), ammonia nitrogen, and various heavy metal ions. Long-term storage not only occupies significant land resources, but the pollutants within it, through leaching and migration by rainwater, pose a continuous threat to surrounding water bodies, soil, and groundwater ecosystems, becoming a major bottleneck restricting the industry's green and sustainable development. Therefore, developing technologies for the large-scale, high-value utilization of electrolytic manganese slag is urgently needed. Geopolymers are three-dimensional network-like inorganic polymer materials formed by the dissolution, gelation, and polymerization solidification of aluminosilicate raw materials under alkaline conditions. They possess the potential for rapid hardening and early strength, high temperature resistance, corrosion resistance, and good sealing of heavy metal ions, and are considered ideal carriers for green building materials and solid waste resource utilization. Currently, many researchers at home and abroad have conducted research on the preparation of geopolymers from electrolytic manganese slag. For example, patent CN118955032A provides a geopolymer cementitious material based on electrolytic manganese slag and barium slag and its preparation method. However, it simply combines electrolytic manganese slag, barium slag, and fly ash without mentioning any pretreatment of the electrolytic manganese slag. It cannot fundamentally eliminate the risk of later expansion and cracking caused by soluble sulfates in the electrolytic manganese slag, as well as the inhibitory effect on gel network formation. The long-term volume stability and durability of the resulting material have fundamental defects. For example, patent CN114772962B provides a method for the efficient and comprehensive treatment of red mud-electrolytic manganese slag. This method uses water washing to pretreat the electrolytic manganese slag, primarily to extract sodium sulfate rather than permanently stable sulfates. It cannot completely remove or transform all forms of sulfate, and residual sulfates may still be activated under subsequent alkaline activation conditions, leading to long-term volume stability risks in geopolymers. Simultaneously, the water washing process generates a large amount of wastewater requiring treatment, increasing process complexity and environmental burden. In fact, electrolytic manganese slag is rich in aluminosilicates, making it a potential raw material for geopolymer preparation. However, traditional electrolytic manganese slag contains a large amount of soluble sulfates, which can cause later-stage cracking and decreased strength in products, while also increasing the risk of heavy metal leaching, making it difficult to meet engineering application requirements. Existing technologies have failed to fundamentally solve the problem of sulfate hazards. Therefore, there is an urgent need to develop a new method that can completely eliminate sulfate interference and synergistically prepare high-performance geopolymers from multiple solid wastes. The purpose of this invention is to overcome the shortcomings of existing technologies by using desulfurized electrolytic manganese slag after efficient sulfate removal via a potassium salt system to conduct research on the preparation and performance of geopolymers based on electrolytic manganese slag, using wet desulfurization pretreatment and synergistic activation by multiple solid wastes. This provides a simple, high-performance, green, low-carbon, and environmentally friendly method for preparing geopolymers from electrolytic manganese slag. This method effectively activates the manganese slag and overcomes the adverse effects of sulfate and ammonia nitrogen, aiming to provide a new approach and technological prototype for the large-scale, high-value-added, and environmentally safe resource utilization of electrolytic manganese slag, possessing significant environmental, social, and potential economic benefits. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing high-performance geopolymers using potassium salt wet desulfurization electrolytic manganese slag as the core raw material, in conjunction with solid wastes such as fly ash and steel slag. This method solves environmental problems such as sulfate pollution and heavy metal migration from electrolytic manganese slag, as well as the large-scale stockpiling of manganese slag. It achieves efficient synergistic and high-value utilization of multi-source solid waste, with a simple process flow, excellent product mechanical properties, and good environmental safety. 1. A method for preparing geopolymers from wet desulfurization electrolytic manganese slag, characterized by comprising the following steps: S100: Solid wastes such as electrolytic manganese slag, potassium salt wet desulfurization electrolytic manganese slag, fly ash, and steel slag are mixed with metakaolin and quicklime at low temperature and then ground. The mixture is then mixed according to a preset ratio to form a dry functional mixture. S200: Preparation of alkaline activator solution: Mix liquid sodium silicate and sodium hydroxide in a certain proportion to prepare an alkaline activator solution for later use. S300: Add the dry functional mixture and water to the reaction tank at a certain mass ratio, and add an alkaline activator solution. Stir mechanically until a uniform slurry with suitable fluidity is formed. S400: The slurry is poured into a mold, pre-cured and then demolded. It is then placed in a standard curing environment and cured to a specified age to obtain a geopolymer product, and its mechanical properties, leaching toxicity and corrosion resistance are tested. 2. The method for preparing geopolymer from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: in step S100, the amounts of solid wastes such as electrolytic manganese slag, potassium salt wet desulfurization electrolytic manganese slag, fly ash, and steel slag, as well as metakaolin and quicklime, are set to 0~100% respectively. 3. The method for preparing geopolymer from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: in step S200, the alkaline activator is formulated according to M=n (SiO2) / n (Na2O) =1.0~2.0 Calculate the amount of sodium hydroxide and liquid sodium silicate to be added. 4. The method for preparing geopolymer from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: in step S300, the mass ratio of dry functional mixture to water is set to 0.25~0.68. 5. The method for preparing geopolymer from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: in step S400, the stirred and mixed slurry is poured into a 40 mm × 40 mm × 40 mm mold, pre-cured and solidified under 0-80℃ for 6-12 h, and then demolded. After demolding, it is placed in a standard curing chamber for 3-28 days, and its mechanical properties, leaching toxicity and corrosion resistance are tested. Compared with the prior art, the present invention has the following advantages: Compared with existing technologies, this invention has significant comprehensive benefits. In terms of resource utilization, it achieves the full and high-value synergistic utilization of various bulk hazardous / industrial solid wastes using electrolytic manganese slag, potassium salt wet desulfurization electrolytic manganese slag, fly ash, steel slag, metakaolin, etc., as cementing raw materials. This overcomes the bottleneck of traditional methods, which suffer from low dosage and poor performance due to interference from harmful components. In terms of technical performance, through the complementary activity of various solid wastes and precise control of multiple parameters such as the ratio of quicklime, alkaline activator, and liquid-solid ratio, a stable, high-performance, and green geopolymer is successfully prepared. In terms of environmental safety, a dual barrier of "pretreatment stabilization + geopolymer solidification" is constructed, ensuring that pollutants such as heavy metals are efficiently fixed, with leaching toxicity far below national standards, completely eliminating long-term environmental risks. In terms of process cost, the process does not require high-temperature calcination, mainly using room temperature or medium-low temperature curing, resulting in extremely low energy consumption and carbon emissions. It is also easily integrated with existing building material production lines, possessing outstanding industrialization prospects and economic competitiveness. Overall, this invention provides a new path for the resource utilization of electrolytic manganese slag that combines disposal capacity, product performance, environmental friendliness, and economic feasibility, resulting in significant social, environmental, and economic benefits. Specific Implementation Cases To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Example 1 18 kg of potassium salt wet desulfurization electrolytic manganese slag, 12 kg of fly ash, and 1.2 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry functional mixture. 1.5 kg of NaOH and 9.6 L of liquid sodium silicate solution were weighed to prepare an alkaline activation solution, and then 1.0 L of water was added. This solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The mixture was then molded and cured at 60℃ for 8 hours before demolding. After demolding, it was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strengths were tested at 3 days and 7 days, and were 12.76 MPa and 11.56 MPa, respectively. The leaching concentrations of Mn, Fe, Cu, and Pb were 0.1520 mg / L, Fe, Cu, and Cd, respectively. It meets the requirements of the "Identification Standard for Leaching Toxicity GB5085.3-2007". Example 2 18 kg of potassium salt wet desulfurization electrolytic manganese slag, 12 kg of fly ash, and 0.6 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry mixture. 1.7 kg of NaOH and 9.6 L of sodium silicate solution were weighed to prepare an alkali activation solution, and then 0.51 L of water was added. This solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The slurry was then molded and cured at 60℃ for 8 hours before being demolded. After demolding, it was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strengths were tested at 3 days and 7 days, respectively, and were 29.75 MPa and 27.22 MPa. The leaching concentrations of Mn, Fe, Cu, As, Ni, Cd, Cr, Zn, and Pb were 0 mg / L. It meets the requirements of the "Identification Standard for Leaching Toxicity GB5085.3-2007". Example 3 6 kg of potassium salt wet desulfurization electrolytic manganese slag, 24 kg of fly ash, and 0.6 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry mixture. 1.7 kg of NaOH and 9.6 L of sodium silicate solution were weighed to prepare an alkali activation solution, and then 0.51 L of water was added. The solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The mixture was then molded and cured at 60℃ for 8 hours before being demolded. After demolding, the mixture was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strengths were tested after 3 days and 7 days and were 34.79 MPa and 41.32 MPa, respectively. The leaching concentrations of Mn, Fe, Cu, and Cr are 0.0270 mg / L, 0.1408 mg / L, 0.0080 mg / L, 0.0062 mg / L, and 0 mg / L for As, Ni, Cd, Zn, and Pb. This meets the requirements of the "Identification Standard for Leaching Toxicity" (GB5085.3-2007). Example 4 12 kg of potassium salt wet desulfurization electrolytic manganese slag, 18 kg of fly ash, and 0.6 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry mixture. 1.7 kg of NaOH and 9.6 L of sodium silicate solution were weighed to prepare an alkali activation solution, and then 0.51 L of water was added. This solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The mixture was then molded and cured at 60℃ for 8 hours before demolding. After demolding, it was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strengths were tested at 3 days and 7 days, respectively, and were 30.98 MPa and 38.66 MPa. The leaching concentrations of Mn, Fe, Cu, As, Ni, Cd, Cr, Zn, and Pb were 0 mg / L. It meets the requirements of the "Identification Standard for Leaching Toxicity GB5085.3-2007". Comparative Example 1 18 kg of electrolytic manganese slag, 12 kg of fly ash, and 1.2 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry mixture. 1.5 kg of NaOH and 9.6 L of sodium silicate solution were weighed to prepare an alkali activation solution, and then 11.0 L of water was added. This solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The mixture was then molded and cured at 60℃ for 8 hours before demolding. After demolding, it was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strength was tested after 3 days and 7 days, and was 4.87 MPa and 6.87 MPa, respectively. The leaching concentrations of Cu, Cr, As, Mn, Fe, Ni, Cd, Zn, and Pb were 0 mg / L. This meets the requirements of the "Identification Standard for Leaching Toxicity" GB5085.3-2007. Comparative Example 2 18 kg of electrolytic manganese slag, 12 kg of fly ash, and 1.2 kg of quicklime were weighed and placed in a reaction tank and stirred evenly to obtain a dry mixture. 1.5 kg of NaOH and 9.6 L of sodium silicate solution were weighed to prepare an alkali activation solution, and then 14.0 L of water was added. This solution was mechanically stirred with the dry mixture for 2-3 minutes to form a fluid slurry. The slurry was then molded and cured at 60℃ for 8 hours before demolding. After demolding, it was cured in a standard curing room at 20±2℃ and relative humidity ≥95% until the desired curing age was reached. The compressive strength was tested at 3 days and 7 days, and was 2.56 MPa and 3.65 MPa, respectively. The Cu leaching concentration was 0.0108 mg / L, and the leaching concentrations of Cr, As, Mn, Fe, Ni, Cd, Zn, and Pb were 0 mg / L. This meets the requirements of the "Identification Standard for Leaching Toxicity" GB5085.3-2007. Comparative analysis of Comparative Example 1 and Example 1 shows that after desulfurizing electrolytic manganese slag using potassium salt wet desulfurization technology, the water consumption for preparing geopolymers decreased from 11 L (electrolytic manganese slag geopolymer) to 1.0 L (potassium salt wet desulfurization electrolytic manganese slag geopolymer). The 3-day compressive strength of the prepared geopolymer specimens increased from 4.87 MPa (electrolytic manganese slag geopolymer) to 12.76 MPa (potassium salt wet desulfurization electrolytic manganese slag geopolymer), and the 7-day compressive strength increased from 6.87 MPa (electrolytic manganese slag geopolymer) to 11.56 MPa (potassium salt wet desulfurization electrolytic manganese slag geopolymer). The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing geopolymers from wet desulfurization electrolytic manganese slag, characterized in that, Includes the following steps: S100: Solid wastes such as electrolytic manganese slag, potassium salt wet desulfurization electrolytic manganese slag, fly ash, and steel slag are mixed with metakaolin and quicklime at low temperature and then ground. The mixture is then mixed according to a preset ratio to form a dry functional mixture. S200: Preparation of alkaline activator solution: Mix liquid sodium silicate and sodium hydroxide in a certain proportion to prepare an alkaline activator solution for later use. S300: Add the dry functional mixture and water to the reaction tank at a certain mass ratio, and add an alkaline activator solution. Stir mechanically until a uniform slurry with suitable fluidity is formed. S400: The slurry is poured into a mold, pre-cured and then demolded. It is then placed in a standard curing environment and cured to a specified age to obtain a geopolymer product, and its mechanical properties, leaching toxicity and corrosion resistance are tested.

2. The method for preparing geopolymers from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: In step S100, the amounts of solid wastes such as electrolytic manganese slag, potassium salt wet desulfurization electrolytic manganese slag, fly ash, and steel slag, along with metakaolin and quicklime, are set to 0-100%, respectively.

3. The method for preparing geopolymers from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: In step S200, the alkaline activator is prepared according to the formula M=n (SiO2) / n (Na2O) =1.0~2.0 Calculate the amount of sodium hydroxide and liquid sodium silicate to be added.

4. The method for preparing geopolymers from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: In step S300, the mass ratio of dry functional mixture to water is set to 0.25~0.

68.

5. The method for preparing geopolymers from wet desulfurization electrolytic manganese slag as described in claim 1, characterized in that: In step S400, the well-mixed slurry is poured into a 40 mm × 40 mm × 40 mm mold, pre-cured and solidified at 0-80℃ for 6-12 hours before demolding, and then placed in a standard curing chamber for 3-28 days after demolding, and its mechanical properties, leaching toxicity and corrosion resistance are tested.