Low-alkali portland cement using cobalt residue as raw material and preparation method thereof

Abstract

The application belongs to the technical field of cement production, and provides low-alkali silicate cement with cobalt residue as raw material and a preparation method thereof, which comprises the following steps: S1, preparing raw materials; S2, preparing an activator; S21, preparing an A solution; S22, preparing a B solution; and S3, preparing low-alkali silicate cement. The application uses industrial solid waste cobalt residue with stable performance and low price as a mixing material of low-alkali silicate cement, and introduces a chelating agent and an activator to improve and enhance the activity, and through the synergistic effect with clinker and gypsum, the low-alkali silicate cement is prepared. The prepared silicate cement has a compact structure and excellent performance, the raw materials selected in the whole preparation process are simple, the silicate cement with excellent performance can be synthesized, and the problems of land occupation and environmental pollution caused by the large accumulation of solid waste cobalt residue are effectively solved, thereby providing a new way and thought for realizing the recycling of industrial solid waste.

Description

Technical Field

[0001] This invention belongs to the field of cement production technology, and specifically relates to a low-alkali silicate cement using cobalt slag as raw material and its preparation method. Background Technology

[0002] General-purpose silicate cement is a hydraulic cementitious material made from silicate cement clinker, appropriate amounts of gypsum, and specified admixtures. The cement industry is a high-resource-consuming sector, making the comprehensive utilization of various tailings for cement production crucial. Cobalt metal is a strategic national resource, but cobalt slag from smelting occupies vast amounts of land, wastes significant funds, and severely pollutes the environment. Cobalt and zinc metals in tailings can be recovered. Cobalt slag, produced during cobalt smelting, is an industrial slag from hydrometallurgical processes. Millions of tons of various types of cobalt slag are generated annually. If this slag is not fully utilized and continues to accumulate, it will not only cause environmental pollution but also represent a huge waste of resources. Cobalt slag contains large amounts of SiO2, CaO, and Al2O3, all essential components for pozzolanic reactions. Under mechanical and composite activation, it can be prepared into a green cementitious material.

[0003] Cobalt slag, which contains cobalt, also has significant recycling value. Currently, most literature focuses on how to recycle and reuse cobalt slag.

[0004] Reference 1 (Ma Feifei, Yang Bin, Dou Qiangmin. Resource Utilization of Purified Cobalt Slag, Nonferrous Metals, 2022(9):96-116) addresses the problems of high zinc content, low cobalt content, and difficult recovery of organic cobalt slag generated by a novel reagent-based cobalt removal process. Through experimental research, a method for recovering valuable metals such as zinc and cobalt using a cobalt slag water washing-conversion-oxidative leaching process was proposed, and the optimal process parameters were obtained. The cobalt content was enriched to over 10%, the cobalt removal reagent was regenerated and reusable, the process operation was simple, and it could be seamlessly integrated with a hydrometallurgical zinc smelting system.

[0005] Reference 2 (Bai Penghui, Zhang Xu, Liu Jin, Xiao Xiang, Liu Mengyu, Zhang Yunpeng. Separation and recovery of cobalt and nickel from cobalt slag produced by hydrometallurgical zinc refining by oxidation precipitation method, Nonferrous Metals Engineering, 2022(12)60-66) addressed the polymetallic cobalt slag produced by hydrometallurgical zinc refining by using a two-stage process of sulfuric acid leaching followed by neutralization of high-cobalt slag. The resulting leachate with high cobalt content was then subjected to a series of treatments: iron removal by hydrogen peroxide oxidation, cadmium removal by zinc powder replacement, nickel removal by nickel removal reagent, manganese removal by selective oxidation with sodium persulfate, and cobalt precipitation by sodium persulfate oxidation. The results showed that under the optimal acid leaching conditions of 150 g / L sulfuric acid, 80 °C, and 120 min leaching time, the cobalt precipitation rate with sodium persulfate reached 99.98%, and the cobalt slag contained 49.75% cobalt. The liquid after cobalt precipitation could be returned to the hydrometallurgical zinc refining system to recover metallic zinc, thus achieving the separation and recovery of metal resources from the slag.

[0006] Reference 3 (Zhang Hongju, Wang Youchen, Du Ning. Experimental study on improvement of cobalt recovery process from nickel-cobalt slag. China Nonferrous Metallurgy. 2020(49)42-45) used approximately 540t of cobalt slag, a byproduct of hydrometallurgical zinc production, to conduct experiments on cobalt precipitation using various oxidants. The results showed that the acid washing-potassium permanganate oxidation precipitation method for cobalt recovery from nickel-cobalt slag alone was superior to other methods. The experimental process, parameters, and key control points of the process were described and analyzed. The experimental results showed that the process was short, efficient, and saved RMB 80,000 in reagent costs per ton of cobalt recovered. Furthermore, the cobalt content of the product cobalt slag was increased by 2 times compared to the cobalt slag recovered by the previous process, making it easier to sell in the market.

[0007] Research and application of cobalt slag in other industries has only begun in recent years. Reference 4 (Jing Qingxiu, You Wei, Huang Xiaodong, Wang Wei, Zhang Zehui, Zhang Chengxi. Water Treatment Technology, 2020(10): 28-32) reported the use of cobalt slag, river sand, Ca(OH)2, NaHCO3 and sawdust as raw materials. After mixing, an appropriate amount of water was added to wet granulation (particle size of 4-9 mm). The mixture was first dried at 105℃ for 2 hours, and then transferred to a sintering furnace to be sintered at 1125℃ for 1 hour. After being slowly cooled in the furnace, ceramsite was obtained. The cobalt slag-based ceramsite was then used as the filter material of aerated biological filter (BAF). The BAF of this filter material was used to treat simulated wastewater containing nitrogen and phosphorus. The BAF of this filter material can effectively treat nitrogen and phosphorus in wastewater. Reference 5 (He Wei. Preparation and Mechanical Properties Study of Cobalt-Containing Slag and Steel Slag Cementitious Materials [D]. Anhui University of Technology, 2019, Master's Thesis) reports the preparation of cementitious materials using modified slag powder and cobalt slag as the main raw materials, and studies the influence of the specific surface area of ​​the raw materials on the mechanical properties of the modified slag-cobalt slag-cement composite cementitious materials. In the preparation and characterization of cobalt slag-containing cementitious material samples, it was found that with fixed mortar-to-cement ratios of 1:1.5 and 0.5, as the amount of cobalt slag added increased, the 3-day compressive and flexural strengths of the samples showed a trend of first increasing and then decreasing, while the 28-day compressive and flexural strengths gradually decreased. With a cobalt slag addition of 30%, the samples exhibited the highest 3-day compressive and flexural strengths, at 23.0 MPa and 5.5 MPa, respectively.

[0008] In current publicly available literature, there is little use of industrial solid waste cobalt slag as an admixture in silicate cement production. The main reason is that it has poor activity, contains a certain amount of metallic impurities, and is difficult to grind finely, resulting in a significant reduction in the strength of cement after admixture. This severely restricts the large-scale industrial application of cobalt slag as an admixture. Therefore, it is necessary to explore the comprehensive utilization scope of cobalt slag to provide the entire cement industry with a reliable and inexpensive solid waste raw material. Summary of the Invention

[0009] To overcome the above deficiencies, the present invention aims to provide a method for preparing cement using chelating agents and activated cobalt slag as cement admixtures. Unlike traditional admixtures, this method involves adding cobalt slag and employing chelating agents and activators to improve its performance, thus preparing ordinary silicate cement. By treating the solid waste cobalt slag, the influence of metallic impurities is shielded. Furthermore, the activator rapidly activates the activity of the siliceous alumina minerals in the cobalt slag, which, together with the hydration products synergistically formed with gypsum, ettringite and CSH / CASH gels, fully utilizing the properties of the materials in the solid waste cobalt slag. The invention also leverages the reinforcing effect of CaSO4·2H2O in gypsum to prepare cementitious materials with cementitious properties, thereby solving the related technical problems mentioned in the background art.

[0010] This invention is implemented as follows:

[0011] A method for preparing low-alkali silicate cement using cobalt slag as raw material includes the following steps:

[0012] S1. Preparation of raw materials,

[0013] Cement clinker and gypsum are dried, ground, and sieved at a certain temperature until the particle specific surface area reaches a specified value. Cobalt slag of a certain fineness is dried and then set aside for use.

[0014] S2, Preparation of activator,

[0015] The activator solution is prepared in two parts, A and B, which need to be prepared separately. After filtering, the two solutions A and B are stored separately. During use, the two solutions A and B are mixed evenly in a certain mass ratio before use.

[0016] S21. Prepare solution A.

[0017] First, sodium sulfate, sodium hexametaphosphate, sodium hydroxide (pH adjuster), and hydroxypropyl methylcellulose were dissolved in deionized water to prepare four solutions, which were then mixed evenly in a certain mass ratio.

[0018] S22. Prepare solution B.

[0019] Prepare a polycarboxylate solution of a certain concentration separately;

[0020] S3. Preparation of low-alkali silicate cement.

[0021] After treating the cobalt slag with a chelating agent, it is then mixed with an activator in a certain proportion and ground finely. The prepared cement clinker and gypsum are then mixed in a certain proportion and then mixed evenly. Finally, all the above materials are mixed evenly to obtain the prepared low-alkali silicate cement.

[0022] Furthermore, in step S1, the cement clinker is dried, ground, and sieved at 105℃~110℃ until the particle specific surface area is greater than 300m². 2 Up to / kg;

[0023] The gypsum was dried, ground, and sieved at 75℃~80℃ until the particle specific surface area was greater than 300m². 2 Up to / kg;

[0024] Cobalt slag with a fineness greater than 200 mesh is dried at 105℃~110℃ before use.

[0025] Furthermore, in step S2, solutions A and B are mixed evenly in a mass ratio of 4:1 before use.

[0026] Furthermore, in step S21, the mass ratio of the four solutions prepared by dissolving sodium sulfate, sodium hexametaphosphate, sodium hydroxide (pH adjuster), and hydroxypropyl methylcellulose in deionized water is 1:1:0.5:0.05.

[0027] Furthermore, in step S22, the 40% polycarboxylate mother liquor is diluted with deionized water to a 25% polycarboxylate solution.

[0028] Furthermore, in step S3, the mass ratio of cement clinker, gypsum, cobalt slag, chelating agent, and activator is 55-90:1-10:5-40:0.5-2:1-10.

[0029] Furthermore, in step S3, in order to reduce the influence of metals in the cobalt slag on the material properties, firstly, ethylenediaminetetramethylene phosphate sodium or aminetrimethylene phosphate is prepared as a chelating agent to form a 20% solution, and a certain amount is added to the cobalt slag. The mixture is stirred thoroughly and evenly for more than eight hours, and then the temperature is maintained at 105°C for twelve hours to dry.

[0030] On the other hand, a low-alkali silicate cement using cobalt slag as raw material is prepared according to a method for preparing low-alkali silicate cement using cobalt slag as raw material.

[0031] The beneficial effects of this invention are:

[0032] This invention utilizes cobalt slag, an industrial solid waste with stable performance and low price, as a blending material for low-alkali silicate cement. By introducing chelating agents and activators, its activity is improved and enhanced. Through synergistic effects with clinker and gypsum, low-alkali silicate cement is prepared. The prepared silicate cement has a dense structure and excellent performance.

[0033] The entire preparation process uses simple raw materials, which can not only synthesize high-performance silicate cement, but also effectively solve the problems of land occupation and environmental pollution caused by the large accumulation of cobalt slag, providing a new approach and idea for realizing the recycling of industrial solid waste.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0036] Figure 1 This is a flowchart of the preparation method of the present invention;

[0037] Figure 2 The image shown is the XRD pattern of the cement sample prepared in Example 1 of this invention.

[0038] Figure 3 The image shows the microstructure of cement after hydration in Example 1 of this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0041] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0042] Example

[0043] Specifically, such as Figure 1-3 As shown, a method for preparing low-alkali silicate cement using cobalt slag as raw material is provided, comprising the following steps:

[0044] S1. Preparation of raw materials,

[0045] Cement clinker and gypsum are dried, ground, and sieved at a certain temperature until the particle specific surface area reaches a specified value. Cobalt slag of a certain fineness is dried and then set aside for use.

[0046] S2, Preparation of activator,

[0047] The activator solution is prepared in two parts, A and B, which need to be prepared separately. After filtering, the two solutions A and B are stored separately. During use, the two solutions A and B are mixed evenly in a certain mass ratio before use.

[0048] S21. Prepare solution A.

[0049] First, sodium sulfate, sodium hexametaphosphate, sodium hydroxide (pH adjuster), and hydroxypropyl methylcellulose were dissolved in deionized water to prepare four solutions, which were then mixed evenly in a certain mass ratio.

[0050] S22. Prepare solution B.

[0051] Prepare a polycarboxylate solution of a certain concentration separately;

[0052] S3. Preparation of low-alkali silicate cement.

[0053] After treating the cobalt slag with a chelating agent, it is then mixed with an activator in a certain proportion and ground finely. The prepared cement clinker and gypsum are then mixed in a certain proportion and then mixed evenly. Finally, all the above materials are mixed evenly to obtain the prepared low-alkali silicate cement.

[0054] In step S1, the cement clinker is dried, ground, and sieved at 105℃~110℃ until the particle specific surface area is greater than 300m². 2 Up to / kg;

[0055] The gypsum was dried, ground, and sieved at 75℃~80℃ until the particle specific surface area was greater than 300m². 2 Up to / kg;

[0056] Cobalt slag with a fineness greater than 200 mesh is dried at 105℃~110℃ before use.

[0057] In step S2, solutions A and B are mixed evenly in a mass ratio of 4:1 before use.

[0058] In step S21, the mass ratio of the four solutions prepared by dissolving sodium sulfate, sodium hexametaphosphate, sodium hydroxide (pH adjuster), and hydroxypropyl methylcellulose in deionized water is 1:1:0.5:0.05.

[0059] In step S22, the 40% polycarboxylate mother liquor is diluted with deionized water to a 25% polycarboxylate solution.

[0060] In step S3, the mass ratio of cement clinker, gypsum, cobalt slag, chelating agent and activator is 55-90:1-10:5-40:0.5-2:1-10.

[0061] In step S3, to reduce the influence of metals in the cobalt slag on the material properties, firstly, ethylenediaminetetramethylidene phosphate sodium or aminetrimethylidene phosphate is prepared as a chelating agent to form a 20% solution, and a certain amount is added to the cobalt slag. The mixture is stirred thoroughly and evenly for more than eight hours, and then the temperature is maintained at 105℃ for twelve hours to dry.

[0062] A low-alkali silicate cement using cobalt slag as raw material can be prepared by a method for preparing low-alkali silicate cement using cobalt slag as raw material.

[0063] The technical solution and effects of the present invention are illustrated below through specific embodiments:

[0064] The raw material ratios and strength parameters from Examples 1-7 are summarized in the table below:

[0065] Example raw material powder by mass ratio Initial setting time Final freezing time 3-day flexural strength 3-day compressive strength 28-day flexural strength 28-day compressive strength Example 1 55：4：34：0.5：7 2 hours and 30 minutes 4 hours and 15 minutes 5.5MPa 28.6MPa 7.9MPa 46.8MPa Example 2 40：10：40：0.8：10 1 hour 50 minutes 3 hours and 50 minutes 4.8MPa 24.7MPa 7.4MPa 42.7MPa Example 3 50：5：35：0.1：10 2 hours and 10 minutes 4 hours and 5 minutes 5.8MPa 27.5MPa 7.2MPa 43.8MPa Example 4 60：8：28：1.2：4 1 hour 45 minutes 3 hours and 40 minutes 5.8MPa 29.5MPa 8.5MPa 48.6MPa Example 5 70：6：22：1.5：2 2 hours and 10 minutes 3 hours and 20 minutes 5.8MPa 29.2MPa 8.3MPa 47.8MPa Example 6 75：5：15：1.8：5 1 hour 55 minutes 3 hours and 30 minutes 6.0MPa 29.0MPa 8.1MPa 47.5MPa Example 7 80：2：10：2：8 1 hour 20 minutes 2 hours and 50 minutes 6.0MPa 30.5MPa 8.8MPa 49.2MPa

[0066] Based on the different proportions and strength parameters of each embodiment, it can be seen that the stability of each embodiment is qualified and can meet the national standard for No. 42.5 cement.

[0067] Figure 2 The XRD pattern of the cement sample prepared in Example 1 of this invention shows that the peaks of the four mineral phases C3S, C2S, C3A and C4AF of the cement can be clearly found. In addition, there is a small amount of quartz phase. The characteristic peak of C4AF phase is found to be high in the spectrum, indicating that its C4AF phase content is high. The main reason is that the cobalt slag contains a high content of iron-containing substances, which promotes the formation of C4AF phase during the clinker burning process, which is more conducive to the increase of its strength.

[0068] Figure 3 The image shows the microstructure of cement after hydration in Example 1 of this invention. The hydration products are fine, and the main crystalline phases, ettringite and CSH gel, have a dense structure. In particular, the production of needle-like ettringite interspersed within the structure greatly improves the mechanical properties of the cement, especially its flexural strength.

[0069] This invention utilizes cobalt slag, an industrial solid waste with stable performance and low price, as a blending material for low-alkali silicate cement. By introducing chelating agents and activators, its activity is improved and enhanced. Through synergistic effects with clinker and gypsum, low-alkali silicate cement is prepared. The prepared silicate cement has a dense structure and excellent performance.

[0070] The entire preparation process uses simple raw materials, which can not only synthesize high-performance silicate cement, but also effectively solve the problems of land occupation and environmental pollution caused by the large accumulation of cobalt slag, providing a new approach and idea for realizing the recycling of industrial solid waste.

[0071] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to a specific order or hierarchy.

[0072] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0073] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A method for preparing low-alkali silicate cement using cobalt slag as raw material, characterized in that, Includes the following steps: S1. Preparation of raw materials, Cement clinker is dried, ground, and sieved at 105℃~110℃ until the particle specific surface area is greater than 300m² / kg; gypsum is dried, ground, and sieved at 75℃~80℃ until the particle specific surface area is greater than 300m² / kg; cobalt slag with a fineness greater than 200 mesh is dried at 105℃~110℃ for later use. S2, Preparation of activator, The activator solution is prepared in two parts, A and B, which need to be prepared separately. After filtering, the two solutions A and B are stored separately. During use, the two solutions A and B are mixed evenly in a mass ratio of 4:

1. S21. Prepare solution A. First, dissolve sodium sulfate, sodium hexametaphosphate, sodium hydroxide (pH adjuster), and hydroxypropyl methylcellulose separately in deionized water to prepare four solutions, which are then mixed uniformly in a mass ratio of 1:1:0.5:0.

05. S22. Prepare solution B. The 40% polycarboxylate mother liquor was diluted with deionized water to a 25% polycarboxylate solution. S3. Preparation of low-alkali silicate cement. The mass ratio of cement clinker, gypsum, cobalt slag, chelating agent and activator is 55-90:1-10:5-40:0.5-2:1-10. After treating the cobalt slag with the chelating agent, it is mixed with the activator in a certain proportion and then ground. The prepared cement clinker and gypsum are then mixed in a certain proportion and then mixed evenly. Finally, the above materials are mixed evenly to obtain the prepared low-alkali silicate cement. In step S3, to reduce the influence of metals in the cobalt slag on the material properties, ethylenediaminetetramethylene phosphate sodium or aminetrimethylene phosphate sodium is first prepared as a chelating agent to form a 20% solution, and a certain amount is added to the cobalt slag. The mixture is stirred thoroughly and evenly for more than eight hours, and then the temperature is maintained at 105℃ for twelve hours to dry.

2. The method for preparing low-alkali silicate cement using cobalt slag as raw material according to claim 1, characterized in that, In step S3, the mass ratio of cement clinker, gypsum, cobalt slag, chelating agent and activator is 55:4:34:0.5:

7.

3. The method for preparing low-alkali silicate cement using cobalt slag as raw material according to claim 1, characterized in that, In step S3, the mass ratio of cement clinker, gypsum, cobalt slag, chelating agent and activator is 80:2:10:2:

8.

4. A low-alkali silicate cement using cobalt slag as raw material, characterized in that, The low-alkali silicate cement is prepared according to any one of claims 1-3 using cobalt slag as raw material.

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