A method for achieving low-carbon and harmless titanium gypsum and producing porous matrix

Abstract

This invention belongs to the field of titanium gypsum utilization technology, specifically relating to a method for achieving low-carbon and harmless treatment of titanium gypsum and producing a porous matrix. The method involves flash drying titanium gypsum with added ethanol. The treated titanium gypsum crystals break down and disintegrate, forming a porous matrix of varying sizes. The environmentally harmful active substances in the original titanium gypsum are significantly reduced within the matrix, transforming the original alkaline conditions to near-neutral pH conditions. The resulting porous matrix provides a rich habitat for microorganisms, allowing them to maintain activity for extended periods. Over time, the number of beneficial microorganisms in the matrix gradually increases, while the number of harmful microorganisms decreases. This invention achieves low-carbon, harmless, and stable treatment of titanium gypsum using a one-step method. The entire process is low-carbon and pollution-free, expanding the application areas of titanium gypsum.

Description

Technical Field

[0001] This invention belongs to the field of titanium gypsum treatment and utilization technology, specifically relating to a method for achieving low-carbon and harmless titanium gypsum and producing porous matrix. Background Technology

[0002] Titanium gypsum is a waste residue mainly composed of dihydrate gypsum, produced during the sulfuric acid process for titanium dioxide production. This waste is generated by adding lime (or carbide slag) to neutralize the acidic wastewater. In recent years, titanium dioxide, as a raw material for coatings, has been widely used, and the production of titanium gypsum has increased rapidly. With the rapid growth of the titanium dioxide industry, the construction of titanium dioxide production lines in my country has also experienced rapid development. However, more than 90% of titanium dioxide production in China still uses the sulfuric acid process. Currently, the national stock of titanium gypsum exceeds 60 million tons, and the production of titanium gypsum is showing a year-on-year increasing trend. It is expected that the production of titanium gypsum in my country will remain high.

[0003] Titanium gypsum, primarily composed of calcium gypsum dihydrate, has Fe2O3 as its main impurity. Classified as Class I general industrial solid waste, its disposal has become a major headache for titanium dioxide plants. Resource utilization would significantly alleviate environmental pressure and solve the problem of substantial land occupation. Increasingly, countries are paying close attention to this issue, strengthening regulations and penalties for solid waste discharge and treatment, forcing manufacturers to actively seek new waste disposal methods. However, due to the lack of ideal utilization solutions and treatment technologies, titanium gypsum is currently only temporarily stockpiled, and suitable large-scale disposal technologies for titanium gypsum urgently need development.

[0004] For many years, numerous universities and enterprises have conducted extensive experimental work on the utilization of titanium gypsum, such as: producing gypsum building materials (paper-faced gypsum board, plaster, gypsum blocks, gypsum putty, lightweight aggregates, etc.); using it as a roadbed material in highway construction projects; and making it into a cementitious material as a cement retarder. However, due to policy, technology, and market issues, the comprehensive utilization rate of titanium gypsum in China is less than 10%. Essentially, this is mainly because the resource utilization of titanium gypsum is difficult and lacks technological innovation.

[0005] The researchers of this invention conducted a component analysis of titanium gypsum. Under a scanning electron microscope (SEM), the titanium gypsum crystals appeared as radially elongated and platy crystals similar to those found in calcite and iron oxide matrices. X-ray diffraction (XRD) of the iron concentrate showed the presence of goethite and hematite. The calcium content of titanium gypsum was 18.9%, and the concentrations of trace elements (As, B, Cd, Or, Cu, Ni, and Pb) measured in the study were all low. Based on the characteristics of titanium gypsum and its application in soil improvement, some studies suggest that titanium gypsum can be used as a soil conditioner. This is because titanium gypsum contains sufficient calcium and sulfur, as well as some iron and silicon, which can provide essential nutrients for crop growth. Calcium sulfate compound fertilizer produced from titanium gypsum, when applied to the soil, can fully exert its fertilizing effect, completely meeting the soil's requirements for calcium and sulfur. Appropriate amounts of titanium gypsum can improve rapeseed growth, increasing plant height and yield by more than 10% at harvest. Furthermore, titanium gypsum flocculates rapidly in the soil, which can prevent soil erosion to a certain extent.

[0006] However, the high water content, low strength, high viscosity, and numerous impurities of titanium gypsum severely restrict its direct application. The first challenge is addressing the stability of the active substances in titanium gypsum. Titanium gypsum contains unstable substances such as ferric iron, calcium oxide, and magnesium oxide. These substances react with air and water to create alkalinity in the environment, exacerbating soil alkalinity. Furthermore, under the national "dual-carbon" strategy, research on greening, low-carbon, and harmless treatment technologies for titanium gypsum and other bulk industrial solid wastes—which are generated in large quantities, underutilized, and pose significant land resource occupation, soil and groundwater pollution risks—is scarce. Conventional harmless treatment methods typically involve calcination at temperatures exceeding 300°C or even 500°C, or the production of porous matrices by doping with other expensive pore-forming materials. Research on directly utilizing titanium gypsum for low-carbon, harmless treatment without other dopants, and simultaneously obtaining a porous matrix from the stable state of the active substances, is limited.

[0007] Therefore, this invention, for the first time, avoids conventional high-temperature calcination and achieves low-carbon and harmless production while simultaneously obtaining a porous matrix without other impurities. This not only improves the physical morphology of titanium gypsum, but also meets the national "dual-carbon" strategic requirements. Furthermore, the obtained porous matrix expands the application range of titanium gypsum. Summary of the Invention

[0008] This experiment innovatively employs a one-step flash evaporation technique to stabilize titanium gypsum with low-carbon active substances and form a functionalized porous matrix for microbial adsorption, laying the foundation for expanding the application of titanium gypsum in the field of green and healthy living.

[0009] The objective of this invention is achieved through the following technical solution:

[0010] A method for achieving low-carbon and harmless titanium gypsum and producing a porous matrix involves flash drying the titanium gypsum to obtain the porous matrix.

[0011] Furthermore, the flash drying process includes the following steps:

[0012] S1. Add ethanol to the titanium gypsum, and simultaneously perform pre-pulverization and stir thoroughly to obtain pre-pulverized wet material;

[0013] S2. The wet material is conveyed to a flash dryer for crushing and drying.

[0014] Furthermore, in step S1, the mass of the ethanol added is 5%-8% of the mass of the titanium plaster.

[0015] Furthermore, in step S1, the particle size of the wet material is 0.355mm-5mm.

[0016] Furthermore, in step S2, the gas used for the pulverization and drying process is a mixture of carbon dioxide and oxygen.

[0017] Furthermore, in the mixed gas, the concentrations of carbon dioxide and oxygen are 70% and 30%, respectively.

[0018] Furthermore, before performing the pulverization and drying process described in step S2, the mixed gas is first heated to 50-60°C and kept in a flash dryer for 1.5-2.5 hours, preferably 2 hours, for pre-drying.

[0019] Furthermore, after the pre-drying is completed, the subsequent mixed gas is heated to 110-115°C and subjected to the pulverization and drying process described in step S2.

[0020] Furthermore, in step S2, the pulverization and drying process takes 3.5-4.5 hours, preferably 4 hours.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention uses flash drying technology to process titanium gypsum, causing the titanium gypsum crystals to break down and disintegrate, forming porous materials of varying sizes. This provides a rich habitat for microorganisms during the further development and utilization of titanium gypsum, and allows the inhabiting microorganisms to remain active for a long time. After inoculation, over time, the number of beneficial microorganisms in the substrate gradually increases, while the number of harmful microorganisms decreases.

[0023] 2. The porous matrix produced by this invention greatly reduces the harmful active substances in the original titanium gypsum and increases the content of stable carbonate compounds, thus changing the original alkaline conditions of titanium gypsum to near-neutral conditions and expanding the application range of titanium gypsum.

[0024] 3. Before flash drying, the present invention adds ethanol to titanium gypsum, which has the function of dissolving harmful substances and helps the liquid substances to escape rapidly during flash drying, thereby further reducing energy consumption in the process.

[0025] 4. This invention utilizes the flash dryer in the existing technology to achieve low-carbon, harmless, and stable titanium gypsum in one step. The entire process is free of secondary pollution, making an outstanding contribution to solving the pollution problem of titanium gypsum and providing valuable reference for the green and healthy comprehensive utilization technology of titanium gypsum. Attached Figure Description

[0026] Figure 1 EMS electron microscope scans of the products of Example 1 and Comparative Example 1 of this invention;

[0027] Figure 2 The reduction rate of active substances and the increase rate of stable compounds generated in the products of this invention embodiment;

[0028] Figure 3 Example 1: Test results of the fertilizer retention capacity of the product;

[0029] Figure 4 Fluorescence effects of the products in Example 1 and Comparative Example 1 after one month of microbial adsorption;

[0030] Figure 5 There were no changes in beneficial bacteria in the products of Example 1 and Comparative Example 1 after one month of microbial loading.

[0031] Figure 6 Example 1: Changes in beneficial bacteria over time after product inoculation with microorganisms. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0033] The flash dryer used in this invention is a novel continuous drying equipment integrating drying, crushing, and screening, based on existing flash dryer technology. It consists of a heater, feeder, mixing and crushing system, classifier, main drying pipe, cyclone separator, bag filter, and fan. The working principle is as follows: material enters the main drying pipe through the screw feeder, while hot gas enters tangentially from the cyclone separator at the bottom of the dryer. Driven by the agitator, a powerful, high-speed rotating upward airflow is formed. Under the combined action of the airflow and the mixing and crushing system, the material is dispersed by impact, friction, and shearing forces, rapidly crushing lumps and ensuring full contact with the hot air for heating and drying. The dried material is carried by the airflow into the dust collection system for collection and treatment, meeting environmental protection requirements. The exhaust gas is discharged by an induced draft fan, completing the entire drying process.

[0034] Example 1

[0035] In this embodiment, 10 kg of titanium gypsum was randomly selected from the accumulation of titanium dioxide in a titanium dioxide plant, and the following steps were performed:

[0036] S1. Add 0.7 kg of ethanol to the titanium gypsum, pre-crush it to a particle size of 0.355 mm to 0.850 mm using a mechanical impact pulverizer, and stir it thoroughly to obtain pre-crushed wet material;

[0037] S2. The wet material is conveyed to a flash dryer for pulverization and drying. The gas used for the process is a mixture of carbon dioxide and oxygen with concentrations of 70% and 30%, respectively. Before drying, the mixture is heated to 50°C and kept in the flash dryer for 2 hours for pre-drying. After the pre-drying is completed, the mixture is heated to 110°C for pulverization and drying for 4 hours to obtain a porous matrix.

[0038] Comparative Example 1

[0039] In this embodiment, 10 kg of titanium gypsum was randomly selected from the accumulation of titanium dioxide in a titanium dioxide plant, and the following steps were performed:

[0040] S1. Pre-crush it to a particle size of 0.355mm to 0.850mm using a mechanical impact crusher;

[0041] S2. The pre-crushed titanium gypsum is dried using conventional drying methods.

[0042] EMS electron microscopy: After the experiment, the porous matrix obtained in Example 1 and the product obtained in Comparative Example 1 were subjected to EMS electron microscopy. The scanning results are shown in the attached figure. Figure 1 As shown, b, d, and f are crystal electron microscope images of Example 1, and a, c, and e are crystal electron microscope images of Comparative Example 1.

[0043] As can be seen, after the titanium gypsum of Example 1 was flash-dried, the crystalline particles were damaged to varying degrees, and the crystal surface was rougher than that of the product of Comparative Example 1 (comparison between a and b). These rough surfaces provided more surface area, providing more habitat for microorganisms for further utilization.

[0044] Meanwhile, the flash drying process also has a certain degree of "disintegration" effect on the titanium gypsum crystals (comparison between c and d). It can be seen that the titanium gypsum crystals in Comparative Example 1 are solid, while the solid state of Example 1 after flash drying is loosened, which provides more aggregate structure for subsequent modification of the porous titanium gypsum matrix.

[0045] Furthermore, compared with Comparative Example 1 (e and f comparison), Example 1 formed more fragmented particles after flash drying. Magnification showed that these fragmented particles had different pore sizes, indicating that flash drying technology can transform titanium gypsum into a porous material. This greatly enhances the water and fertilizer retention capacity of the porous matrix and expands the application range of titanium gypsum.

[0046] Active ingredient detection: Further, the porous matrix obtained in Example 1 and the product obtained in Comparative Example 1 were subjected to component detection.

[0047] The results showed that, after treatment with the technical solution of this invention, the active substances in titanium gypsum were significantly converted into corresponding stable substances. Specifically, see attached... Figure 2 Compared with the titanium gypsum treated in Comparative Example 1, the porous matrix obtained in Example 1 showed the following reduction rates of active substances CaO, Fe2O3, Al2O3, MgO, Na2O, and K2O (86%, 63%, 72%, 62%, 82%, and 79%, respectively) and the corresponding increases in stable products CaCO3, Fe2(CO3)3, Al2(CO3)3, MgCO3, Na2CO3, and K2CO3 (76%, 69%, 72%, 64%, 79%, and 68%, respectively).

[0048] After converting these active compounds into stable compounds, the amount of alkaline compounds slowly released upon contact with water was greatly reduced, lowering the pH value of titanium gypsum from the original 7.5-8.3 to 7.2-7.6. According to my country's soil pH classification standards (strong acidity is pH < 5.0, acidity is pH 5.0-6.5, neutrality is 6.5-7.5, alkalinity is pH 7.5-8.5, and strong alkalinity is pH > 8.5), the results show that the pH value of titanium gypsum treated by the present invention is close to neutral. This will greatly expand the application range of porous titanium gypsum matrix, and at the same time, it will prevent the porous titanium gypsum matrix from causing secondary alkalinization pollution to the environment.

[0049] Determination of fertilizer retention capacity: The fertilizer retention capacity of the titanium gypsum porous matrix produced in Example 1 was also tested. The test method was the 2 mol / L KCl extraction-indophenol blue colorimetric method.

[0050] The blank group (CK) was titanium gypsum treated with Comparative Example 1, and the experimental group was the porous titanium gypsum matrix produced in Example 1. The experimental group consisted of three groups: treatment 1, treatment 2, and treatment 3. The porosity of the soil column in treatment 1 was the same as that in CK, and the porosity of treatments 2 and 3 increased sequentially compared to treatment 1.

[0051] The ammonium nitrogen content in the leachate from the soil columns in the above four groups of experiments was determined, and the total ammonium nitrogen content in the leachate from each soil column was calculated. The results are shown in the appendix. Figure 3 As shown in the figure, the total amount of ammonium nitrogen in the leachate of the CK soil column was the highest, while that in treatment 3 was the lowest. The total amount of ammonium nitrogen in the leachate of the CK soil column was 1.9 times that in treatment 3. Compared with CK, the total amount of ammonium nitrogen in the leachate of treatments 1, 2, and 3 decreased by 33.5%, 40.1%, and 47.5%, respectively. That is, the CK soil column had the lowest amount of ammonium nitrogen, while the treatment 3 soil column had the highest amount of ammonium nitrogen.

[0052] Furthermore, the test results for available phosphorus in the soil column leachate showed the same pattern: the CK soil column leachate had the highest total available phosphorus content, while treatment 3 had the lowest. This indicates that the treated titanium gypsum can significantly improve water and fertilizer retention capacity.

[0053] Adsorption microbial population: The porous matrix obtained in Example 1 and the product of Comparative Example 1 were loaded with Bacillus thuringiensis, Bacillus subtilis, Enterococcus faecalis, Bacillus licheniformis, denitrifying bacteria, yeast, lactobacillus, bifidobacteria, nitrifying bacteria, actinomycetes, photosynthetic bacteria, Bacillus mucilaginosus, Bacillus laterosporus, phosphate-solubilizing bacteria, potassium-solubilizing bacteria, and Azotobacter chrysozoans, etc. After being placed in a natural environment for one month, fluorescence microscopy and population analysis were performed.

[0054] The results of the fluorescence microscopy analysis are attached. Figure 4 As shown, the porous matrix obtained in Example 1 yielded more live bacteria, and the microorganisms maintained a high level of activity without significant mortality. Figure 4 a). In the product of Comparative Example 1, a large number of microorganisms died ( Figure 4 b). This demonstrates that the titanium gypsum porous matrix treated with flash evaporation technology has the effect of adsorbing microorganisms and enabling them to maintain their activity for a long time.

[0055] In addition, high-throughput sequencing analysis was performed on their population changes. (See attached image.) Figure 5As shown, the results also indicate that after one month, the product of Comparative Example 1 contained more microbial populations C2 and B2 that were potentially detrimental to plant growth than the product of Example 1, which contained more microbial populations C1 and B1, such as Blastodiomycota and Glomeromycota.

[0056] Furthermore, attached Figure 6 The results show that the beneficial microbial community for plant growth in the product of Example 1 changes with the inoculation time after inoculation with microorganisms. The results indicate that as the inoculation time is extended, the number of beneficial microbial communities in the product increases, indicating that after flash evaporation treatment, the substrate product can effectively maintain the genetic diversity of beneficial microbial communities and can be further developed and utilized.

[0057] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A method for achieving low-carbon and harmless titanium gypsum and producing porous matrix, characterized in that: The porous matrix is ​​obtained by flash drying the titanium gypsum. The flash drying process includes the following steps: S1. Add ethanol to the titanium gypsum, and simultaneously perform pre-pulverization and stir thoroughly to obtain pre-pulverized wet material; S2. The wet material is conveyed to a flash dryer for pulverization and drying. In step S2, the gas used in the pulverizing and drying process is a mixture of carbon dioxide and oxygen; Before performing the pulverization and drying process described in step S2, the mixed gas is first heated to 50~60℃ and kept in a flash dryer for 1.5~2.5 h for pre-drying; after the pre-drying is completed, the mixed gas is then heated to 110~115℃ for the pulverization and drying process described in step S2. The flash drying process of the titanium gypsum causes the titanium gypsum crystals to break down and disintegrate, forming porous materials of varying sizes.

2. The method for achieving low-carbon and harmless titanium gypsum and producing porous matrix according to claim 1, characterized in that, In step S1, the mass of the added ethanol is 5% to 8% of the mass of the titanium plaster.

3. The method for achieving low-carbon and harmless titanium gypsum and producing porous matrix according to claim 1, characterized in that, In step S1, the particle size of the wet material is 0.355 mm-5 mm.

4. The method for achieving low-carbon and harmless titanium gypsum and producing porous matrix according to claim 1, characterized in that, In the mixed gas, the concentrations of carbon dioxide and oxygen are 70% and 30%, respectively.

5. The method for achieving low-carbon and harmless titanium gypsum and producing porous matrix according to claim 1, characterized in that, In step S2, the crushing and drying process takes 3.5-4.5 hours.

6. The application of the porous matrix obtained by any of the methods for achieving low-carbon and harmless treatment of titanium gypsum and producing porous matrix according to claims 1-5.

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