Method for preparing auxiliary cementing material from titanium extraction slag and auxiliary cementing material

Abstract

The invention provides a method for preparing an auxiliary cementing material from extracted titanium slag and the auxiliary cementing material.The method comprises the steps that the extracted titanium slag is washed with water till soluble chloride ions in the extracted titanium slag are completely dissolved out, first filter residues and first filtrate are obtained, and the first filtrate mainly comprises calcium chloride and magnesium chloride; drying the first filter residue, and grinding to obtain first powder; continuously washing the first powder with water so that the content of chloride ions in the first powder is reduced to 2 / 10000 or below, and filtering to obtain a second filter residue and a second filtrate; the second filter residues are dried and mechanically activated to obtain second powder, and the second powder can be used as an auxiliary cementing material. The method has the advantages that chloride ions in the titanium extraction slag are removed through water leaching, secondary water leaching is carried out by means of the characteristic that filter residues obtained after water leaching do not absorb moisture, residual chloride ions are fully removed, the super-active superfine slag powder with the high activity reaching up to the S105 level or above is prepared, energy is saved, environment friendliness is achieved, and the added value of products is increased.

Description

[0001] This divisional application of a Chinese patent application has an application date of August 31, 2021, an application number of 202111016564.0, and an invention title of "Method for Preparing Auxiliary Cementitious Material from Titanium-Extracting Slag and an Auxiliary Cementitious Material". Technical Field

[0002] The present invention relates to the technical field of resource disposal and utilization of titanium-extracting slag. Specifically, it relates to a method for preparing an auxiliary cementitious material from titanium-extracting slag and an auxiliary cementitious material. Background Art

[0003] Panzhihua Iron and Steel Group has made important progress and achieved good results in titanium extraction using the high-temperature carbonization-low-temperature selective chlorination process. However, due to the low-temperature chlorination link in the process, a large amount of chlorine-containing titanium-extracting slag is produced (with an annual output of more than 10 wt%). These titanium-extracting slags have a certain chemical reaction activity, but due to the relatively high content of water-soluble chloride ions, usually with a chlorine mass percentage between 2% and 7%, they cannot be directly used as cement and concrete admixtures like ordinary blast furnace slag. Currently, they are mainly stockpiled, which not only occupies a large amount of land resources but also poses potential pollution hazards to the surrounding environment, causing huge economic, environmental, and social pressures on the enterprise. How to treat and utilize these chlorine-containing titanium-extracting slags has become an urgent problem to be solved in aspects such as the sustainable development of this titanium extraction process and environmental protection. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies existing in the prior art. For example, on the one hand, the present invention provides a method for preparing an auxiliary cementitious material from titanium-extracting slag that realizes the resource utilization of titanium-extracting slag, has no three wastes discharge throughout the process, and is energy-saving and environmentally friendly. Another purpose of the present invention is to provide an auxiliary cementitious material with excellent performance, which can improve the early strength of concrete, improve the workability of concrete, and reduce the heat of hydration.

[0005] To achieve the above purpose, the present invention provides a method for preparing an auxiliary cementitious material from titanium-extracting slag, and the method includes the steps:

[0006] Wash the titanium-extracting slag with water until the soluble chloride ions are completely dissolved, obtaining a first filter residue and a first filtrate. The main components in the first filtrate are calcium chloride and magnesium chloride; the chlorine content in the titanium-extracting slag is 2 - 7% wt;

[0007] Dry the first filter residue and then grind it to obtain a first powder;

[0008] Continue to wash the first powder with water until the chloride ion content is reduced to less than two ten-thousandths, and filter to obtain a second filter residue and a second filtrate;

[0009] Dry the second filter residue and mechanically activate it to obtain a second powder, which is the supplementary cementitious material.

[0010] The content of SO in the second powder 3 is less than 0.6%, the loss on ignition is ≤ 2.5%, and the specific surface area is ≥ 500 m 2 / kg.

[0011] In an exemplary embodiment of one aspect of the present invention, the method may further include the steps of:

[0012] Evaporate and concentrate the first filtrate, and add sodium hydroxide or aluminum chloride solution to completely precipitate magnesium ions and aluminum ions therein to form magnesium hydroxide and aluminum hydroxide, wash and filter to obtain a third filter residue and a third filtrate;

[0013] Add sodium carbonate solution to the third filtrate to completely precipitate Ca therein 2+ to form calcium carbonate, and filter to obtain a fourth filtrate and a fourth filter residue;

[0014] Use the waste heat generated by low-temperature chlorination of titanium-containing slag to evaporate and concentrate the fourth filtrate to obtain a concentrated solution of the fourth filtrate;

[0015] Electrolyze the concentrated solution of the fourth filtrate to obtain hydrogen, chlorine and sodium hydroxide solution respectively, and the chlorine is recycled to the low-temperature chlorination stage of titanium-containing slag as a chlorine raw material.

[0016] In an exemplary embodiment of one aspect of the present invention, the temperature for evaporating and concentrating the first filtrate may be 60 - 120 °C.

[0017] In an exemplary embodiment of one aspect of the present invention, washing the titanium extraction slag until the soluble chloride ions therein are completely dissolved may include subjecting the original titanium extraction slag to multiple water immersions, washing and filtering until the chloride ion content in the first filter residue is below 1‰.

[0018] In an exemplary embodiment of one aspect of the present invention, the first filter residue is directly used as a cement or cement concrete admixture after drying, or as an active mineral material, or a building material is prepared using an alkali activator.

[0019] In an exemplary embodiment of one aspect of the present invention, the particle size of the first powder may be 200 - 600 mesh, and the particle size of the second powder may be 1000 - 2500 mesh.

[0020] In an exemplary embodiment of one aspect of the present invention, the chloride ion content in the second powder may be below two ten-thousandths.

[0021] In an exemplary embodiment of one aspect of the present invention, the mechanical activation equipment may be a jet mill or a Raymond mill.

[0022] On the other hand, the present invention provides an auxiliary cementitious material, which can be prepared by the method described in any one of the above.

[0023] In an exemplary embodiment of another aspect of the present invention, the chloride ion content in the auxiliary cementitious material can be less than two ten-thousandths, the SO 3 content can be <0.6%, the loss on ignition can be ≤2.5%, and the specific surface area can be ≥500 m 2 / kg.

[0024] In an exemplary embodiment of another aspect of the present invention, the applications of the auxiliary cementitious material include: being used for prefabricated buildings, pipe piles, high-speed rail track slabs, ultra-high-strength bridges, paint additives, and diatom mud, and being configured into clinker-free cement or alkali-activated cement together with an alkali activator.

[0025] Compared with the prior art, the beneficial effects of the present invention may include at least one of the following:

[0026] (1) The present invention solves the problem of the difficult resource utilization of titanium slag due to its relatively high chlorine content, which restricts the bottleneck of the chlorination process for titanium extraction. By using water leaching and washing to leach out soluble chloride ions, the chlorine content in the slag is greatly reduced, thus contributing to the resource utilization of titanium slag;

[0027] (2) For the chloride ions in the filtrate, chemical reaction-based fractional treatment and recovery are adopted. Each of the obtained products at all levels can be used and sold as chemical raw materials or commodities. There is no three-waste discharge throughout the process, thus achieving the transformation of waste into treasure and the recycling of industrial solid waste resources, greatly improving the economic effect, resource and environmental benefits, and social benefits of titanium slag;

[0028] (3) It effectively alleviates the economic pressure and environmental protection pressure of enterprises, correspondingly saves land, reduces pollution, realizes the recycling of solid waste resources, saves natural materials, and helps the country's infrastructure construction, etc., which has positive and practical significance. Detailed Embodiments

[0029] Hereinafter, the method for preparing an auxiliary cementitious material from titanium slag and an auxiliary cementitious material of the present invention will be described in detail with reference to exemplary embodiments.

[0030] In the first exemplary embodiment of the present invention, a method for preparing an auxiliary cementitious material from titanium slag, the method comprising the steps:

[0031] Wash the titanium-extracted slag until the soluble chloride ions are completely dissolved, obtaining a first filter residue and a first filtrate. The main components in the first filtrate are calcium chloride and magnesium chloride. For example, washing the titanium-extracted slag until the soluble chloride ions are completely dissolved may include subjecting the original titanium-extracted slag to multiple water immersions, washings, and filtrations until the chloride ion content in the first filter residue is below 1‰. Specifically, take the original titanium-extracted slag and use water washing and water immersion to dissolve the soluble chloride ions therein. Depending on the leaching situation of the chloride ions, multiple water immersions, washings, and filtrations can be carried out until the soluble chloride ions in the filter residue are completely dissolved (i.e., the chloride ion content in the first filter residue is lower than 1‰), obtaining a first filter residue and a first filtrate. Among them, the main components in the first filtrate are calcium chloride and magnesium chloride.

[0032] Dry and grind the first filter residue to obtain a first particle size powder. Here, the first filter residue can be directly used as a cement or cement concrete admixture after drying, or as an active mineral material, or building materials can be prepared using an alkali activator. The first filter residue can also be ground using a ball mill to obtain a fine powder. Specifically, dry the filter residue. At this time, the chloride ions in the filter residue have dropped below 1‰ and it no longer deliquesces and absorbs moisture in the air. The obtained first filter residue can be directly sold as a cement and concrete admixture, or it can also be used as an active mineral material to prepare building materials using alkali activation. Or use a ball mill to grind the first filter residue to obtain a fine powder with a fineness of 200 mesh to 600 mesh.

[0033] Continue to wash the first particle size powder to reduce the chloride ion content to below two ten-thousandths, and filter to obtain a second filter residue and a second filtrate. Specifically, continue to immerse and wash the ball-milled filter residue in water and filter to obtain a second filter residue and a second filtrate. Among them, the chloride ion content in the second filtrate generally does not exceed 50 ppm and can be directly discharged; the chloride ion content in the second filter residue can be further reduced to below two ten-thousandths, fully meeting the chloride ion content requirements for reinforced concrete and prestressed concrete.

[0034] Dry and mechanically activate the second filter residue to obtain a second particle size powder, and the second particle size powder can be used as an auxiliary cementitious material. Here, the chloride ion content in the second powder can be below two ten-thousandths, the SO 3 content can be <0.6%, the loss on ignition can be ≤2.5%, and the specific surface area can be ≥500 m 2 / kg. The mechanical activation equipment can be a jet mill or a Raymond mill. Specifically, use the waste heat generated by low-temperature chlorination of titanium-containing slag to dry the second filter residue, and use a jet mill or a Raymond mill to mechanically activate the second filter residue to make the second filter residue reach about 2000 mesh or finer, and slag-like micro-powder with a strength of s105 grade and above can be obtained. Among these slag-like micro-powders, the chloride ion content is below two ten-thousandths, the SO 3 <0.6%, the loss on ignition ≤2.5%, and the specific surface area ≥500 m2 / kg, meeting the requirements as an auxiliary cementitious material, can be used in prefabricated buildings, pipe piles, high-speed rail track slabs, ultra-high-strength bridges, paint additives, diatom mud, etc. It can enhance the early strength of cement and concrete, improve the workability of concrete, increase the early strength, reduce the heat of hydration, and can also be formulated into clinker-free cement or alkali-activated cement together with alkali activators.

[0035] In this exemplary embodiment, the method may further include the steps of:

[0036] Using the waste heat generated in the low-temperature chlorination stage of titanium-bearing blast furnace slag to evaporate and concentrate the first filtrate to obtain a concentrated first filtrate. Here, the temperature for evaporating and concentrating the first filtrate can be 60 - 120°C, and the concentration of the concentrated first filtrate is 80% or more of the saturated concentration of the calcium chloride solution. For example, the concentrated first filtrate can be a saturated calcium chloride solution. Adding sodium hydroxide or aluminum chloride solution to the concentrated first filtrate to completely precipitate magnesium ions and aluminum ions therein to form magnesium hydroxide and aluminum hydroxide, and washing and filtering to obtain a third filter residue and a third filtrate. Here, the concentrations of sodium hydroxide and aluminum hydroxide solution are not limited, and the addition amount (in moles) is 2 times the molar concentration of magnesium ions and 3 times the molar concentration of aluminum ions per liter of the concentrated first filtrate. From the perspective of economy and simplicity of the preparation process, the concentration of sodium hydroxide is preferably 1 - 2 times the chloride ion concentration in the first filtrate. The advantage of this concentration is that while providing a sufficient amount of solvent for the reaction system, it will not make the volume of the solution after the reaction too large, reducing the workload of subsequent filtration and filtrate treatment.

[0037] Adding a sodium carbonate solution to the third filtrate to completely precipitate Ca 2+ to form calcium carbonate, and filtering to obtain a fourth filtrate and a fourth filter residue. Here, the main component of the fourth filter residue is calcium carbonate ultrafine powder close to the nanoscale, and the main component of the fourth filtrate is sodium chloride. Specifically, adding an appropriate amount of sodium carbonate solution to the third filtrate, the concentration of the added sodium carbonate solution is such that Ca 2+ is completely precipitated to form calcium carbonate, and then filtering to obtain a fourth filtrate and a fourth filter residue. At this time, the obtained fourth filter residue is mainly calcium carbonate ultrafine powder close to the nanoscale, which can be used in products such as rubber fillers, and the fourth filtrate is mainly a sodium chloride solution.

[0038] Using the waste heat generated by the low-temperature chlorination of titanium-bearing slag to evaporate and concentrate the fourth filtrate to obtain a concentrated fourth filtrate. Here, the temperature for evaporating and concentrating the fourth filtrate can be 80 - 160°C, and the concentration of the concentrated fourth filtrate is 80% or more of the saturated concentration of the sodium chloride solution. For example, the concentrated fourth filtrate can be a saturated sodium chloride solution.

[0039] The fourth filtrate concentrate is electrolyzed to obtain hydrogen, chlorine, and sodium hydroxide solution respectively. The chlorine is recycled to the low-temperature chlorination stage of titanium-bearing slag as a chlorine raw material. Specifically, the fourth filtrate concentrate (i.e., saturated brine) is electrolyzed by the electrolysis method to obtain pure H 2 , Cl 2 and NaOH solution. These three substances are all industrial commodities and can be sold separately. Chlorine can also be used as a chlorine raw material for the low-temperature chlorination of titanium-bearing slag, thus realizing the recycling of chlorine element. The sodium hydroxide solution can obtain solid sodium hydroxide products after evaporation.

[0040] In this embodiment, the method may further include the steps of:

[0041] Dissolve the third filter residue with sodium hydroxide, filter to obtain the fifth filter residue and the fifth filtrate. The main component of the fifth filter residue is magnesium hydroxide, and the main component of the fifth filtrate is sodium metaaluminate.

[0042] The first filter residue can be directly used as a cement or cement concrete admixture after being dried by using the waste heat generated in the low-temperature chlorination stage of titanium-bearing blast furnace slag, or can be ground and used as a supplementary cementitious material for preparing concrete to improve its economic benefits.

[0043] The main component of the fifth filter residue is magnesium hydroxide, and the main component of the fifth filtrate is sodium metaaluminate solution.

[0044] The fifth filter residue can be calcined at different temperatures to obtain light-burned magnesia or light magnesium oxide products. Here, the fifth filter residue can be directly sold as an industrial product, or can be calcined at different temperatures. According to the calcination temperature and time, light-burned magnesia or light magnesium oxide products can be obtained respectively. For example, the fifth filter residue can be calcined at 400 - 600 °C for 30 - 90 min to obtain light-burned magnesia; the fifth filter residue can be calcined at 700 - 1300 °C for 10 - 60 min to obtain light magnesium oxide.

[0045] In this exemplary embodiment, the particle size of the first powder may be 200 - 600 mesh, and the particle size of the second powder may be 1000 - 2500 mesh.

[0046] In the second exemplary embodiment of the present invention, the supplementary cementitious material can be prepared by the method described in the above first exemplary embodiment. Here, the chloride ion content in the supplementary cementitious material can be less than two ten-thousandths, the SO 3 content can be < 0.6%, the loss on ignition can be ≤ 2.5%, and the specific surface area can be ≥ 500 m 2 / kg, which can be used in prefabricated buildings, pipe piles, high-speed rail track slabs, ultra-high-strength bridges, paint additives, diatom mud, etc. It can improve the early strength of cement and concrete, improve the workability of concrete, increase the early strength, reduce the heat of hydration, and can also be formulated into clinker-free cement or alkali-activated cement together with alkali activators.

[0047] To better understand the present invention, the following further clarifies the content of the present invention in conjunction with specific Examples 1, 2 and 3, but the content of the present invention is not limited to the following examples.

[0048] Example 1

[0049] Take 1 t of the original titanium slag, wash, soak and filter it repeatedly with water until the soluble chloride ions in the filter residue are completely dissolved, and then filter to obtain the first filter residue and the first filtrate. Among them, the chloride ion content in the first filter residue is 0.8‰, and the first filtrate is mainly a solution of calcium chloride and magnesium chloride. Here, the first filtrate can be further heated and concentrated to prepare a soil arsenic removal solution, prepare Friedel's salt, etc.

[0050] Use the large amount of waste heat generated during the low-temperature chlorination of high-titanium slag to dry the first filter residue. The drying standard is that after continuous drying at 105 °C for 2 h, the mass no longer decreases. At this time, the moisture content of the dried second filter residue is 0%, and because the chloride ion content in it is greatly reduced, the dried second filter residue no longer shows obvious moisture absorption and caking phenomena in the air.

[0051] Cool the dried second filter residue and grind it with a ball mill so that the particle size is ≤ 200 mesh, that is, the maximum particle diameter d max ≤ 75 μm, to obtain the first particle size powder.

[0052] Continue to soak, wash and filter the first particle size powder with water to obtain the second filter residue and the second filtrate. The chlorine content in the second filter residue is 0.18‰, which is lower than 0.2‰. In terms of chlorine content, it is no longer restricted when used in any cement and cement concrete. The second filtrate contains a very small amount of calcium chloride and is continuously recycled as the water leaching solution of titanium slag. While achieving zero discharge, it can also save water resources.

[0053] Continue to dry the second filter residue with the waste heat during the chlorination of high-titanium slag. The drying temperature is ≤ 120 °C, and the drying particle size remains unchanged. The maximum particle diameter d max ≤ 75 μm, and 906 kg of dried second filter residue can be obtained. After these dried second filter residues are cooled, they can be directly used as an auxiliary cementitious material for concrete, or can be packaged and stored for later use or sold as products.

[0054] Example 2

[0055] Take 5t of the original titanium-extracting slag, wash, soak in water and filter repeatedly until the soluble chloride ions in the filter residue are completely dissolved. Then filter to obtain the first filter residue and the first filtrate. The chloride ion content in the first filter residue is 0.6‰, and the first filtrate is mainly a solution of calcium chloride and magnesium chloride. The first filtrate can be further heated and concentrated to prepare a soil arsenic removal solution, Friedel's salt, etc.

[0056] Use the large amount of waste heat generated during the low-temperature chlorination of high-titanium slag to dry the first filter residue. The drying standard is that after continuous drying at 105°C for 2 hours, the mass no longer decreases. At this time, the moisture content of the dried second filter residue is 0%, and due to the greatly reduced chloride ion content, the dried second filter residue no longer shows obvious hygroscopic caking in the air.

[0057] Cool the dried second filter residue and grind it with a ball mill so that the particle size is ≤ 200 mesh, that is, the maximum particle size d max ≤ 75μm, to obtain the first particle size powder.

[0058] Continue to soak, wash and filter the first particle size powder to obtain the second filter residue and the second filtrate. The chlorine content in the second filter residue is 0.08‰, which is lower than 0.2‰. In terms of chlorine content, it is no longer restricted when used in any cement and cement concrete. The second filtrate contains a very small amount of calcium chloride and is continuously recycled as the water immersion solution of titanium-extracting slag. While achieving zero emissions, it can also save water resources.

[0059] Continue to dry the second filter residue with the waste heat during the chlorination of high-titanium slag. The drying temperature is ≤ 120°C, and the drying particle size remains unchanged. The maximum particle size d max ≤ 75μm, and about 4530kg of the dried second filter residue can be obtained. Use a jet mill to ultrafinely crush the second filter residue so that the particle size reaches more than 800 mesh, d max ≤ 50μm, d 50 = 20μm, to obtain the second particle size powder. The second particle size powder is an ultrafinely crushed slag with high chemical reactivity, reaching the activity standard of S105 grade slag, and can be directly used as an auxiliary cementitious material for concrete, or can be packaged and stored for later use or sold as a product.

[0060] Example 3

[0061] Take 2t of the original titanium-extracting slag, wash, soak in water and filter repeatedly until the soluble chloride ions in the filter residue are completely dissolved. Then filter to obtain the first filter residue and the first filtrate. The chloride ion content in the first filter residue is 0.9‰, and the first filtrate is mainly a solution of calcium chloride and magnesium chloride. The first filtrate can be further heated and concentrated to prepare a soil arsenic removal solution, Friedel's salt, etc.

[0062] The large amount of waste heat generated during the low-temperature chlorination of high-titanium slag is used to dry the first filter residue. The drying standard is that after continuous drying at 105°C for 2 hours, the mass no longer decreases. At this time, the moisture content of the second filter residue after drying is 0%, and due to the greatly reduced chloride ion content, the second filter residue after drying no longer shows obvious moisture absorption and caking phenomena in the air.

[0063] Cool the second filter residue after drying and grind it with a ball mill to make the particle size ≤ 200 mesh, that is, the maximum particle size d max ≤ 75 μm, to obtain the first particle size powder.

[0064] Continue to soak, wash with water and filter the first particle size powder to obtain the second filter residue and the second filtrate. The chlorine content in the second filter residue is 0.12‰, which is lower than 0.2‰. In terms of chlorine content, it is no longer restricted when used in any cement and cement concrete. The second filtrate contains a very small amount of calcium chloride and is continuously recycled as the water immersion solution for titanium slag extraction. While achieving zero emissions, it can also save water resources.

[0065] Continue to dry the second filter residue with the waste heat during the chlorination of high-titanium slag. The drying temperature ≤ 120°C, and the drying particle size remains unchanged. The maximum particle size d max ≤ 75 μm, and about 1820 kg of the second filter residue after drying can be obtained. The second filter residue is ultrafinely ground with a jet mill to make the particle size reach more than 2000 mesh, d max ≤ 20 μm, d 50 = 10 μm, to obtain the second particle size powder. The second particle size powder is ultrafinely ground slag, and these ultrafinely ground slags have extremely high chemical reaction activity and can be used as high-quality concrete auxiliary cementitious materials for preparing high-strength concrete and low heat of hydration concrete.

[0066] Although the present invention has been described above in conjunction with exemplary embodiments, those of ordinary skill in the art should clearly understand that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing an auxiliary cementitious material from titanium slag Characterized in that The method includes the steps of: Washing the titanium slag with water until the soluble chloride ions are completely dissolved, obtaining a first filter residue and a first filtrate, the main components in the first filtrate being calcium chloride and magnesium chloride; the chlorine content in the titanium slag is 2 - 7% wt; Drying the first filter residue and then grinding it to obtain a first powder; Continuing to wash the first powder with water to reduce the chloride ion content therein to less than two ten-thousandths, and filtering to obtain a second filter residue and a second filtrate; Drying and mechanically activating the second filter residue to obtain a second powder, and the second powder is the auxiliary cementitious material; The SO in the second powder 3 content < 0.6%, loss on ignition ≤ 2.5%, specific surface area ≥ 500 m 2 / kg.

2. The method for preparing an auxiliary cementitious material from titanium slag according to claim 1 Characterized in that The method further includes the steps of: Evaporating and concentrating the first filtrate, and adding sodium hydroxide or aluminum chloride solution to completely precipitate the magnesium ions and aluminum ions therein to form magnesium hydroxide and aluminum hydroxide, washing and filtering to obtain a third filter residue and a third filtrate; Add sodium carbonate solution to the third filtrate to completely precipitate Ca therein 2+ to form calcium carbonate, and filter to obtain a fourth filtrate and a fourth filter residue; Using the waste heat generated by low-temperature chlorination of titanium-containing slag to evaporate and concentrate the fourth filtrate to obtain a concentrated fourth filtrate; Electrolyzing the concentrated fourth filtrate to obtain hydrogen, chlorine and sodium hydroxide solution respectively, and recycling the chlorine to the low-temperature chlorination stage of titanium-containing slag as a chlorine raw material.

3. The method for preparing an auxiliary cementitious material from titanium slag according to claim 2 Characterized in that The evaporation and concentration temperature of the first filtrate is 60 - 120 °C.

4. The method for preparing an auxiliary cementitious material from titanium slag according to claim 1 Characterized in that Washing the titanium slag with water until the soluble chloride ions are completely dissolved includes subjecting the original titanium slag to multiple water immersions, washings and filtrations until the chloride ion content in the first filter residue is less than 1‰.

5. The method for preparing an auxiliary cementitious material from titanium slag according to claim 1 Characterized in that The first filter residue is directly used as a cement or cement concrete admixture after drying, or as an active mineral material, or a building material is prepared using an alkali activator.

6. The method for preparing an auxiliary cementitious material from titanium slag according to claim 1 Characterized in that The particle size of the first powder is 200 - 600 mesh, and the particle size of the second powder is 1000 - 2500 mesh.

7. The method for preparing an auxiliary cementitious material from titanium slag according to claim 1 Characterized in that The chloride ion content in the second powder is less than two ten-thousandths; the mechanical activation equipment is a jet mill or a Raymond mill.

8. An auxiliary cementitious material Characterized in that The auxiliary cementitious material is prepared by the method according to any one of claims 1 - 7.

9. The auxiliary cementitious material according to claim 8 Characterized in that The chloride ion content in the auxiliary cementitious material is less than two ten-thousandths, and the SO 3 content < 0.6%, the loss on ignition ≤ 2.5%, and the specific surface area ≥ 500 m 2 / kg.

10. The application of the auxiliary cementitious material according to claim 8 or 9 Characterized in that Including: For prefabricated buildings, pipe piles, high-speed rail track slabs, ultra-high-strength bridges, paint additives and diatom mud, and for preparing clinker-free cement or alkali-activated cement together with an alkali activator.