A method for preparing titanium-doped iron oxide red and its application

Abstract

This invention, entitled "A Preparation Method and Application of Titanium-Doped Iron Oxide Red," belongs to the field of lithium-ion battery cathode material technology. The preparation method involves: controlling the titanium content of ferrous sulfate, a byproduct of titanium dioxide production; precipitating and removing impurities from it with Fe and Ti elements; adjusting the pH; and adding Fe... 2+ Heating, filtration, washing, and drying yield titanium-doped iron oxide red precursor powder. This invention uses ferrous sulfate, a byproduct of titanium dioxide production, as the iron source and utilizes its titanium impurities for in-situ titanium doping, thus producing high-purity titanium-doped iron oxide red with adjustable titanium content, high purity, and low impurity content. Furthermore, the entire preparation process of titanium-doped iron oxide red is simple, has a short production time, and is low in cost.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically, it relates to a method for preparing titanium-doped iron oxide red and its application. Background Technology

[0002] With the rapid development of the power battery industry, lithium iron phosphate batteries are continuously expanding their market share due to their superior safety and cost advantages. Currently, the main production processes for lithium iron phosphate materials include the iron phosphate process, the ferrous oxalate process, the iron oxide red process, and the hydrothermal process. Faced with increasing market demand, the iron oxide red process, with its lower production cost advantage, has emerged as a leading option.

[0003] Low-cost ferrous sulfate, a byproduct of titanium dioxide production, has become a popular raw material for preparing iron oxide red, a precursor for lithium iron phosphate. However, due to the presence of large amounts of impurities such as titanium, manganese, magnesium, copper, and zinc, directly preparing iron oxide red for use in the synthesis of lithium iron phosphate cathode materials results in reduced performance of the cathode material due to residual manganese and magnesium impurities, while copper and zinc impurities significantly increase battery safety risks. Therefore, ferrous sulfate from titanium dioxide production needs further refining before use. Research has begun to utilize ferrous sulfate from titanium dioxide production by removing impurities such as titanium, manganese, and magnesium through several heating-dissolution-recrystallization processes and preparing low-impurity iron oxide red via hydrothermal treatment. However, this method is currently costly and unsuitable for large-scale industrial manufacturing. Other research has achieved high-purity iron oxide red by repeatedly purifying ferrous sulfate from titanium dioxide production, oxidizing ferrous iron to ferric iron, and then precipitating and calcining it. However, the iron oxide red after high-temperature calcination has a small specific surface area and low reactivity, further leading to poor battery performance.

[0004] Titanium is a commonly used doping element in lithium iron phosphate cathode materials. It can partially replace Fe in the lithium iron phosphate crystal lattice. 2+ Or Li + Titanium doping significantly improves the electronic conductivity and lithium-ion diffusion coefficient of lithium iron phosphate (LFP). Furthermore, titanium doping can significantly suppress excessive grain growth in LFP, thus shortening the lithium-ion insertion / extraction path. Some researchers have proposed preparing titanium-doped LFP using rutile mother liquor as a raw material. This involves removing impurities from the mother liquor and adding metatitanic acid, phosphoric acid, and hydrogen peroxide solution for hydrothermal preparation of titanium-doped LFP, followed by further preparation of titanium-doped LFP via a solid-state method. However, the titanium doping originates from the added metatitanic acid, failing to effectively utilize the titanium in the mother liquor. On the one hand, impurity titanium can serve as a titanium source for doping LFP materials, further reducing production costs. On the other hand, in-situ liquid-phase titanium doping is more likely to achieve atomic-level uniform mixing compared to the solid-phase doping of current iron oxide red processes.

[0005] The preparation of titanium-doped iron oxide red using ferrous sulfate, a byproduct of titanium dioxide production, is a promising research direction. Ferrous sulfate is the main component of titanium dioxide byproducts, and it also contains certain impurities such as titanium, magnesium, manganese, copper, and zinc. Therefore, it is urgent to find a simple and effective method to remove impurities such as magnesium, manganese, copper, and zinc while retaining titanium impurities in order to prepare titanium-doped iron oxide red in situ.

[0006] Relevant patent documents retrieved: This document, published in China (CN113929150A) on January 14, 2022, discloses a hydrothermal process for preparing iron oxide red, a precursor of lithium iron phosphate, from ferrous sulfate, a byproduct of titanium dioxide production. The method involves first adjusting the pH of a titanium dioxide byproduct FeSO4 solution to 2-4 with concentrated sulfuric acid, then adding a small amount of iron scrap. The reaction heat is used to raise the temperature to above 90°C, and the pH is adjusted to allow colloids such as TiO2 to flocculate and precipitate, yielding a FeSO4 supernatant. Then, ammonium sulfide and ferrous sulfide are added to generate chromium sulfide and manganese sulfide precipitates. These precipitates are removed, and the supernatant is retained. Finally, FeSO4 is purified by low-temperature recrystallization. This process is repeated several times with heating, dissolution, and recrystallization to remove impurities such as titanium, manganese, and magnesium, obtaining purified ferrous sulfate heptahydrate crystals. Finally, high-purity iron oxide red is prepared using the ferrous sulfate heptahydrate crystals via a hydrothermal method.

[0007] This document, published in China (CN14156665A) on May 7, 2003, discloses a method for producing iron oxide red pigment from waste ferrous sulfate from titanium dioxide production. The method utilizes the refining, seed crystal preparation, oxidative synthesis, filtration, washing, concentration, and crystallization of waste ferrous sulfate from titanium dioxide production to obtain thoroughly separated Ti... 4+ and Fe 3+ Iron oxide red pigment containing impurities.

[0008] The publication, published in China (CN116692815A) on September 5, 2023, discloses a method for preparing titanium-doped lithium iron phosphate using rutile mother liquor as raw material. The method involves removing impurities from the mother liquor and adding metatitanic acid, phosphoric acid, and hydrogen peroxide solution for hydrothermal preparation of titanium-doped lithium iron phosphate, followed by further preparation of titanium-doped lithium iron phosphate via a solid-state method.

[0009] The prior art represented by the aforementioned documents has at least the following unresolved technical problems or defects: 1. CN113929150A requires the use of hydrothermal equipment for impurity removal, which leads to a sharp increase in manufacturing costs. Furthermore, this patent targets the removal of impurities such as titanium in titanium dioxide by-products to obtain high-purity iron oxide red, but it cannot fully utilize the impurity titanium, resulting in high production costs.

[0010] 2. CN14156665A achieves complete separation of Ti 4+and Fe 3+ Impurities were eliminated, and high-purity iron oxide red pigment was obtained. However, this method is also targeted at Ti in titanium dioxide byproducts. 4+ and Fe 3+ Removing impurities prevents the full utilization of impurity titanium, resulting in higher production costs.

[0011] 3. The titanium doping in CN116692815A is due to the addition of metatitanic acid, and the effective utilization of titanium in the mother liquor is not achieved.

[0012] 4. There are no existing records on how to solve the problem of atomic-level uniform mixing in solid-phase doping of iron oxide red process. Summary of the Invention

[0013] The purpose of this invention is to provide: A method for preparing titanium-doped iron oxide red and its application, and related technologies, to solve the technical problems of complex preparation methods and high production costs, poor doping uniformity, low purity, and uncontrollable titanium doping content of titanium-doped iron oxide red, or a combination thereof.

[0014] Terminology Explanation: Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0015] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0016] The definition of the standard terminology can be found in the reference "Research and Production of Commonly Used Fine Chemical Products" - Shaanxi Science and Technology Press - Lai Shengli - 1st Edition.

[0017] Unless otherwise specified, conventional methods within the scope of the art, such as the test methods in GB / T1863-2008 Iron Oxide Pigments, shall be used.

[0018] Unless specifically defined herein, the use of all commercially available products herein employs standard techniques. For example, it may be carried out using the manufacturer's instructions for use with the kit, or in accordance with methods known in the art or the description of this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0019] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0020] The "ferrous sulfate byproduct of titanium dioxide production" mentioned in this article refers to ferrous sulfate, a byproduct of the sulfuric acid process for titanium dioxide production. Its main component is ferrous sulfate, and it also contains impurities such as titanium, magnesium, manganese, copper, and zinc.

[0021] The term "deionized water" as used in this article refers to water in which almost all ions (cations such as Ca²⁺) have been removed through ion exchange resins. + Mg² + Anions such as SO4²⁻ - Cl - Water with extremely low ion content is commonly used in laboratory analysis (such as HPLC, ICP-MS), electronic industry cleaning, and cosmetic formulation.

[0022] The term "mixing" as used in this article refers to the process of combining two or more different substances (which may be solid, liquid, gas, or a combination of different states) through physical or mechanical means to form a macroscopically homogeneous or relatively homogeneous dispersion system.

[0023] The term "stirring" as used in this article refers to the operation of mixing multiple substances evenly by means of machinery or manual agitation. Specifically, it refers to the process of creating flow in a container with the help of external forces (such as rotating blades, stirring rods, airflow, etc.) to achieve uniform mixing of solids, liquids, or gases.

[0024] The term "titanium in situ doping" as used in this article refers to a doping method in which titanium elements are directly introduced into the matrix lattice sites or defect sites in the form of doped atoms or ions, without introducing additional titanium-containing doped phase precursors during the synthesis or preparation of the target material.

[0025] The term "solid-phase doping" used in this article refers to a doping modification process completed in a solid state, where the dopant and the matrix material are mixed in solid form, and the dopant element enters the crystal structure of the matrix material through solid-phase diffusion via processes such as grinding, high-temperature calcination, and solid-phase sintering, thereby achieving a doping method that controls the material properties.

[0026] In a first aspect, the present invention provides a method for preparing titanium-doped iron oxide red, comprising the following steps: S1. Control of titanium content in titanium dioxide by-products: Dissolve ferrous sulfate, a by-product of titanium dioxide production, and prepare solution A using elemental iron and a flocculant; the molar ratio of elemental iron to iron ions in ferrous sulfate from titanium dioxide production in solution A is 0-0.45:1, and the pH value is 1-2; the weight percentage of flocculant added to solution A is 0-0.5%; When the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, is 0, it indicates that no elemental iron was added during the preparation of solution A. When the weight percentage of flocculant added to solution A is 0%, it means that no flocculant was added during the preparation of solution A. S2. Precipitation and removal of Fe and Ti elements: Add oxidant to solution A, add alkaline solution to adjust pH, stir and react at a constant temperature to obtain powder B; S3. Mix powder B with water, add alkaline solution, then add ferrous sulfate aqueous solution. After the reaction is completed at a constant temperature, the product is obtained.

[0027] Preferably, the specific operation of dissolving in step S1 is to dissolve the ferrous sulfate by-product of titanium dioxide in a solution prepared with 98% concentrated sulfuric acid and deionized water.

[0028] Preferably, the purpose of using elemental iron and flocculant in step S1 is to adjust the pH to hydrolyze titanium and to aggregate the tiny titanium hydrolysis products for removal, respectively.

[0029] Preferably, the elemental iron in step S1 is a zero-valent iron source.

[0030] Preferably, the zero-valent iron source is selected from one or more of iron powder, iron blocks, and iron sheets.

[0031] More preferably, the zero-valent iron source is iron powder.

[0032] Preferably, the molar ratio of elemental iron to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, in step S1 is selected from any value or range between 0 and 0.45, specifically from: 0:1, 0.1:1, 0.2:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, or any two of them.

[0033] More preferably, the molar ratio of elemental iron to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, in step S1 is selected from any value or range between 0 and 0.4, specifically from: 0:1, 0.1:1, 0.2:1, 0.3:1, 0.35:1, 0.4:1, or any two of them.

[0034] More preferably, the molar ratio of elemental iron to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, in step S1 is selected from any value or range between 0 and 0.4, specifically from: 0:1, 0.3:1, 0.35:1, 0.4:1, or any two of them.

[0035] More preferably, the molar ratio of elemental iron in step S1 to the iron ions in the ferrous sulfate byproduct of titanium dioxide is 0.3:1.

[0036] Preferably, the pH value mentioned in step S1 is selected from any value or range between 1 and 2, specifically from: 1, 1.34, 1.52, 1.77, 2 or any two of them.

[0037] More preferably, the pH value mentioned in step S1 is selected from any value or range between 1 and 1.77, specifically from: 1, 1.34, 1.52, 1.77 or any two of them.

[0038] More preferably, the pH value in step S1 is 1.34.

[0039] Preferably, the weight percentage of the flocculant added to solution A in step S1 is selected from any value or range between 0 and 0.5%, specifically from: 0%, 0.07%, 0.1%, 0.15%, 0.2%, 0.26%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or any two of these ranges.

[0040] More preferably, the weight percentage of the flocculant added in solution A in step S1 is selected from any value or range between 0 and 0.45%, specifically from: 0%, 0.07%, 0.1%, 0.15%, 0.2%, 0.26%, 0.3%, 0.35%, 0.4%, 0.45%, or any two of these ranges.

[0041] More preferably, the weight percentage of the flocculant added to solution A in step S1 is selected from any value or range between 0 and 0.45%, specifically from: 0%, 0.07%, 0.26%, 0.45%, or any two of them.

[0042] More preferably, the weight percentage of the flocculant added to solution A in step S1 is 0.07%.

[0043] Preferably, in the preparation of solution A, the reaction temperature when using elemental iron is selected from any value or range between 20-70℃, specifically from: 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃ or any two of these ranges.

[0044] More preferably, in the preparation of solution A, the reaction temperature when using elemental iron is selected from any value or range between 25-65℃, specifically from: 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or any two of them.

[0045] More preferably, in the preparation of solution A, the reaction temperature when using elemental iron is selected from any value or range between 25-65℃, specifically from: 25℃, 45℃, 65℃ or any two of them.

[0046] More preferably, in the preparation of solution A, the reaction temperature is 65°C when elemental iron is used.

[0047] Preferably, in the preparation of solution A, when using elemental iron, the reaction time is selected from any value or range between 1 and 5 hours, specifically from: 1 hour, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours or any two of these ranges.

[0048] More preferably, in the preparation of solution A, when using elemental iron, the reaction time is selected from any value or range between 2 and 5 hours, specifically from 2 hours, 3 hours, 5 hours, or any two of them.

[0049] More preferably, in the preparation of solution A, the reaction time is 2 hours when elemental iron is used.

[0050] Preferably, the preparation of solution A in step S1 also requires stirring.

[0051] Preferably, the stirring speed is selected from any value or range between 100-500 rpm / min.

[0052] More preferably, the stirring speed is selected from any value or range between 100-500 rpm / min, specifically from: 100 rpm / min, 200 rpm / min, 300 rpm / min, 400 rpm / min, 500 rpm / min or any two of them.

[0053] More preferably, the stirring speed is 200 rpm / min.

[0054] Preferably, during the preparation of solution A, the reaction temperature for adding the flocculant is selected from any value or range between 20-70℃, specifically from: 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃ or any two of these ranges.

[0055] More preferably, during the preparation of solution A, the reaction temperature for adding the flocculant is selected from any value or range between 25-65℃, specifically from: 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or any two of them.

[0056] More preferably, during the preparation of solution A, the reaction temperature for adding the flocculant is selected from any value or range between 25-65℃, specifically from: 25℃, 45℃, 65℃ or any two of them.

[0057] More preferably, during the preparation of solution A, the reaction temperature for adding the flocculant is 65°C.

[0058] Preferably, the reaction time for adding the flocculant is 30 minutes.

[0059] Preferably, the flocculant in step S1 is selected from one or more of polyacrylamide, sodium alginate, chitosan, polydimethylammonium chloride, polyaluminum chloride, polyferric sulfate, aluminum sulfate, aluminum chloride, ferric sulfate, and ferric chloride.

[0060] More preferably, the flocculant in step S1 is polyacrylamide.

[0061] Preferably, the pH of solution A described in step S1 needs to be adjusted again.

[0062] Preferably, the specific operation of readjusting the pH is as follows: readjusting the pH to 0.9 with 98% concentrated sulfuric acid.

[0063] Preferably, the oxidant in step S2 is selected from one or more of hydrogen peroxide and ammonium persulfate.

[0064] More preferably, the oxidant in step S2 is hydrogen peroxide.

[0065] Preferably, the alkaline solution in step S2 is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution.

[0066] More preferably, the alkaline solution in step S2 is an aqueous solution of sodium hydroxide.

[0067] Preferably, the molar ratio of the number of transferable electrons in the oxidant in step S2 to the iron ions in solution A is selected from any value or range between 1.0 and 1.5:1, specifically from: 1.0:1, 1.1:1, 1.15:1, 1.2:1, 1.26:1, 1.3:1, 1.4:1, 1.5:1 or any two of them.

[0068] More preferably, the molar ratio of the number of transferable electrons in the oxidant in step S2 to the iron ions in solution A is selected from any value or range between 1.15 and 1.3:1, specifically from: 1.15:1, 1.2:1, 1.26:1, 1.3:1 or any two of them.

[0069] More preferably, the molar ratio of the number of transferable electrons in the oxidant in step S2 to the iron ions in solution A is 1.15:1.

[0070] Preferably, the temperature at which the oxidant is added in step S2 is selected from any value or range between 20 and 70°C, specifically from: 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or any two of these ranges.

[0071] More preferably, the temperature at which the oxidant is added in step S2 is selected from any value or range between 25 and 65°C, specifically from: 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or any two of these ranges.

[0072] More preferably, the temperature at which the oxidant is added in step S2 is selected from any value or range between 25-65°C, specifically from: 25°C, 40°C, 50°C, 65°C or any two of them.

[0073] More preferably, the temperature at which the oxidant is added in step S2 is 50°C.

[0074] Preferably, the specific operation of adding alkaline solution in step S2 is as follows: 30% hydrogen peroxide is added dropwise to solution A at a rate of 2 mL / min for 30 min, and the stirring speed is 200 rpm / min.

[0075] Preferably, the specific operation for preparing the alkaline solution is as follows: preparing a NaOH aqueous solution by mixing 96% NaOH and deionized water.

[0076] Preferably, the OH in the alkaline solution described in step S2 -The molar ratio of iron ions in solution A to iron ions in solution A is selected from any value or range between 2.0 and 2.7:1, specifically from: 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.45:1, 2.5:1, 2.52:1, 2.57:1, 2.7:1 or any two of them.

[0077] More preferably, the OH in the alkaline solution described in step S2 - The molar ratio of iron ions in solution A to iron ions in solution A is selected from any value or range between 2.4 and 2.57:1, specifically from 2.4:1, 2.45:1, 2.52:1, 2.57:1, or any two of them.

[0078] More preferably, the OH in the alkaline solution described in step S2 - The molar ratio of iron ions in solution A to iron ions in solution A is 2.4:1.

[0079] Preferably, the concentration of the alkali solution in step S2 is selected from any value or range between 4 and 15 mol / L, specifically from: 4 mol / L, 4.5 mol / L, 4.9 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12, 13 mol / L, 14 mol / L, 15 mol / L, or any range between two of them.

[0080] More preferably, the concentration of the alkali solution in step S2 is selected from any value or range between 5 and 15 mol / L, specifically from: 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12, 13 mol / L, 14 mol / L, 15 mol / L or any two of them.

[0081] More preferably, the concentration of the alkali solution in step S2 is selected from any value or range between 5 and 15 mol / L, specifically from: 5 mol / L, 9 mol / L, 12 mol / L, 15 mol / L or any two of them.

[0082] More preferably, the concentration of the alkali solution in step S2 is 5 mol / L.

[0083] Preferably, the pH value after adding the alkali solution in step S2 is selected from any value or range between 4 and 6, specifically from: 4, 4.5, 4.7, 5, 5.3, 5.5, 6 or any two of them.

[0084] More preferably, the pH after adding the alkali solution in step S2 is selected from any value or range between 4.5 and 5.3, specifically from: 4.5, 4.7, 5, 5.3 or any two of them.

[0085] More preferably, the pH after adding the alkali solution in step S2 is 4.5.

[0086] Preferably, the temperature of the alkaline solution added in step S2 is selected from any value or range between 20-70°C, specifically from: 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or any two of these ranges.

[0087] More preferably, the temperature of the alkaline solution added in step S2 is selected from any value or range between 25-65℃, specifically from: 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or any two of them.

[0088] More preferably, the temperature of the alkaline solution added in step S2 is selected from any value or range between 25-65°C, specifically from: 25°C, 40°C, 50°C, 65°C or any two of them.

[0089] More preferably, the temperature of the alkaline solution added in step S2 is 50°C.

[0090] Preferably, the dropping rate of the alkali solution in step S2 is selected from any value or range between 5 and 20 mL / min, specifically from: 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 18 mL / min, 20 mL / min, or any range between two of these. (7, 8, 13, 20) More preferably, the dropping rate of the alkaline solution in step S2 is selected from any value or range between 7 and 20 mL / min, specifically from: 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, 18 mL / min, 20 mL / min or any range between two of them.

[0091] More preferably, the dropping rate of the alkaline solution in step S2 is selected from any value or range between 7 and 20 mL / min, specifically from: 7 mL / min, 8 mL / min, 13 mL / min, 20 mL / min or any range between two of them.

[0092] More preferably, the dropping rate of the alkaline solution in step S2 is 20 mL / min.

[0093] Preferably, the specific operation of adding alkaline solution in step S2 is as follows: the alkaline solution prepared by NaOH and deionized water is added dropwise at a rate of 20 mL / min using a peristaltic pump, the addition time is 30 min, and the stirring speed is 350 rpm / min.

[0094] Preferably, the stirring speed in step S2 is 350 rpm / min.

[0095] Preferably, the temperature of the isothermal reaction in step S2 is selected from any value or range between 20-70℃, specifically from: 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃ or any two of them.

[0096] More preferably, the temperature of the isothermal reaction in step S2 is selected from any value or range between 25-65℃, specifically from: 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃ or any two of them.

[0097] More preferably, the temperature of the isothermal reaction in step S2 is selected from any value or range between 25-65°C, specifically from: 25°C, 40°C, 50°C, 65°C or any two of them.

[0098] More preferably, the temperature of the isothermal reaction in step S2 is 50°C.

[0099] Preferably, the isothermal reaction time in step S2 is selected from any value or range between 1 and 3 hours, specifically from: 1 hour, 1.25 hours, 1.5 hours, 1.75 hours, 2 hours, 2.5 hours, 2.75 hours, 3 hours or any two of them.

[0100] More preferably, the isothermal reaction time in step S2 is selected from any value or range between 1 and 3 hours, specifically from: 1 hour, 1.25 hours, 1.5 hours, 1.75 hours, 2 hours, 3 hours or any two of them.

[0101] More preferably, the isothermal reaction time in step S2 is selected from any value or range between 1 and 3 hours, specifically from: 1 hour, 1.5 hours, 2 hours, 3 hours or any two of them.

[0102] More preferably, the isothermal reaction time in step S2 is 1.5 hours.

[0103] Preferably, the powder B described in step S2 further requires filtration, washing, and vacuum filtration.

[0104] Preferably, the specific preparation operations of filtration, washing and vacuum filtration are as follows: after the constant temperature reaction is completed, powder B is filtered, washed and vacuum filtered until the conductivity of the filtrate is <300μS / cm, and the filtered filter cake is placed in a forced-air drying oven at 100℃ and dried for 12h.

[0105] Preferably, the alkaline solution in step S3 is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution.

[0106] More preferably, the alkaline solution in step S3 is an aqueous solution of sodium hydroxide.

[0107] Preferably, the specific operation of preparing the alkaline solution in step S3 is as follows: preparing an aqueous solution of NaOH with a concentration of 96% and deionized water.

[0108] Preferably, the specific operation of adding alkaline solution in step S3 is as follows: the alkaline solution is added dropwise into a 2L three-necked flask containing an aqueous solution of powder B using a peristaltic pump, the addition time is 3min, and the stirring speed is 350rpm / min.

[0109] Preferably, the OH in the alkaline solution described in step S3 - The molar ratio of iron ions in powder B to powder B is selected from any value or range between 0.25 and 0.40:1, specifically from: 0.25:1, 0.28:1, 0.3:1, 0.33:1, 0.37:1, 0.4:1 or any two of them.

[0110] More preferably, the OH in the alkaline solution described in step S3 - The molar ratio of iron ions in powder B to powder B is selected from any value or range between 0.28 and 0.37:1, specifically from: 0.28:1, 0.3:1, 0.33:1, 0.37:1, or any two of them.

[0111] More preferably, the OH in the alkaline solution described in step S3 - The molar ratio of iron ions in powder B to iron ions in powder B is 0.3:1.

[0112] Preferably, the concentration of the alkali solution in step S3 is selected from any value or range between 4 and 15 mol / L, specifically from: 4 mol / L, 4.5 mol / L, 4.9 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L, or any range between two of them.

[0113] More preferably, the concentration of the alkali solution in step S3 is selected from any value or range between 5 and 15 mol / L, specifically from: 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, 15 mol / L or any range between two of them.

[0114] More preferably, the concentration of the alkali solution in step S3 is selected from any value or range between 5 and 15 mol / L, specifically from: 5 mol / L, 9 mol / L, 12 mol / L, 15 mol / L or any range between two of them.

[0115] More preferably, the concentration of the alkali solution in step S3 is 5 mol / L.

[0116] Preferably, the pH of the alkaline solution added in step S3 is selected from any value or range between 12.0 and 14.0, specifically from: 12.0, 12.4, 13.0, 13.4, 13.7, 14.0 or any two of them.

[0117] More preferably, the pH of the alkaline solution added in step S3 is selected from any value or range between 12.4 and 13.7, specifically from: 12.4, 13.0, 13.4, 13.7 or any two of them.

[0118] More preferably, the pH of the alkaline solution added in step S3 is 13.0.

[0119] Preferably, the specific operation of adding ferrous sulfate aqueous solution in step S3 is as follows: the solution is added dropwise to the reaction solution using a peristaltic pump over a period of 3 minutes, and the stirring speed is 350 rpm / min.

[0120] Preferably, the molar ratio of the ferrous sulfate aqueous solution added in step S3 to the iron ions in powder B is selected from any value or range between 0.05 and 0.15:1, specifically from: 0.05:1, 0.06:1, 0.08:1, 0.1:1, 0.12:1, 0.15:1 or any two of them.

[0121] More preferably, the molar ratio of the ferrous sulfate aqueous solution to the iron ions in powder B in step S3 is selected from any value or range between 0.06 and 0.12:1, specifically from: 0.06:1, 0.08:1, 0.1:1, 0.12:1 or any two of them.

[0122] More preferably, the molar ratio of the ferrous sulfate aqueous solution added in step S3 to the iron ions in powder B is 0.08:1.

[0123] Preferably, the purpose of adding the ferrous sulfate aqueous solution is to neutralize the added Fe... 2+ The ferrihydrite phase in the catalytic system transforms into FeOH, which is then converted into iron oxide red. + If the pH of the system is greater than 11.0 at this time, the added Fe 2+ It is consumed by Ferrihydrite in the system and forms a Fe3O4 impurity phase; if the pH value is < 8.5 at this time, FeOH in the system + The proportion is too low, resulting in poor catalytic conversion effect. Preferably, the concentration of the added ferrous sulfate aqueous solution is selected from any value or range between 0.5 and 2.0 mol / L, specifically from: 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2.0 mol / L or any two of them.

[0124] More preferably, the concentration of the added ferrous sulfate aqueous solution is selected from any value or range between 0.5-2.0 mol / L, specifically from: 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L or any two of them.

[0125] More preferably, the concentration of the added ferrous sulfate aqueous solution is 2 mol / L.

[0126] Preferably, in step S3, the ferrous sulfate aqueous solution is added dropwise to adjust the pH. The pH of the system is selected from any value or range between 8.5 and 11.0, specifically from: 8.5, 8.7, 9, 9.5, 10.0, 10.2, 10.5, 11.0 or any two of them.

[0127] More preferably, in step S3, the ferrous sulfate aqueous solution is added dropwise to adjust the pH. The pH of the system is selected from any value or range between 8.7 and 10.5, specifically from 8.7, 9, 10.0, 10.2, 10.5 or any two of them.

[0128] More preferably, in step S3, the ferrous sulfate aqueous solution is added dropwise to adjust the pH, and the pH of the system is 10.2.

[0129] Preferably, the temperature of the isothermal reaction in step S3 is selected from any value or range between 80-120℃, specifically from: 80℃, 90℃, 97℃, 100℃, 110℃, 120℃ or any two of them.

[0130] More preferably, the temperature of the isothermal reaction in step S3 is selected from any value or range between 90-110℃, specifically from: 90℃, 97℃, 100℃, 110℃ or any two of them.

[0131] More preferably, the temperature of the isothermal reaction in step S3 is 100°C.

[0132] Preferably, the isothermal reaction time in step S3 is selected from any value or range between 3 and 8 hours, specifically from 3 hours, 4.5 hours, 5 hours, 6 hours, 7 hours, 8 hours or any two of them.

[0133] More preferably, the isothermal reaction time in step S3 is selected from any value or range between 3 and 6 hours, specifically from: 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours or any two of them.

[0134] More preferably, the isothermal reaction time in step S3 is selected from any value or range between 3 and 8 hours, specifically from 3 hours, 4.5 hours, 6 hours or any two of them.

[0135] More preferably, the isothermal reaction time in step S3 is 3 hours.

[0136] Preferably, the stirring speed in step S3 is 350 rpm / min.

[0137] Preferably, after the isothermal reaction described in step S3 is completed, filtration, washing, vacuum filtration, and drying are also required.

[0138] Preferably, the specific operations of filtration, washing, vacuum filtration and drying are as follows: filtration, washing and vacuum filtration until the conductivity of the filtrate is <300μS / cm; the filtered filter cake is placed in a forced-air drying oven at 100℃ and dried for 12h.

[0139] Based on further solutions to the technical problems of the present invention, or simultaneous solutions to multiple technical problems, the preferred solution in the technical solution provided in the first aspect of the present invention includes: The first preferred solution is a method for preparing titanium-doped iron oxide red. This solution not only solves the technical problem of "complex preparation method and high production cost", but also further solves the technical problem of "poor doping uniformity".

[0140] The second preferred option is a method for preparing titanium-doped iron oxide red. This technical solution, while addressing the technical problems of "complex preparation methods and high production costs and poor doping uniformity," further solves the technical problems of "low purity and uncontrollable titanium doping content."

[0141] Secondly, the present invention provides: a titanium-doped iron oxide red prepared by the above-described preparation method.

[0142] Thirdly, the present invention provides the application of titanium-doped iron oxide red prepared by the above-described preparation method or the above-described titanium-doped iron oxide red in lithium-ion battery cathode materials.

[0143] Examples 1-4 of this invention at least support the protection scope of the molar ratio of elemental iron in solution A to ferrous ions in titanium dioxide byproduct ferrous sulfate as described in the claims.

[0144] Regarding the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, as described in claim 1. The technical feature “the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide is 0-0.4:1” is summarized from the common feature “the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide” in the foregoing explanation and / or Examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature "the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide is 0-0.4:1", the subordinate concept and its essentially equivalent technical means, and the technical means that can replace "the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide is 0-0.4:1" based on existing technology and conventional technical means and common knowledge should all fall within the protection scope of claim 1. For example, if other technical features remain unchanged, replacing "the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide is 0-0.4:1" with a molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate by-product of titanium dioxide, etc., still falls within the protection scope of claim 1 of this invention.

[0145] In this invention, Examples 1-4 at least support the protection range of pH value described in step S1 of the claims.

[0146] Regarding the pH value mentioned in step S1 as described in claim 1 The technical feature "the pH value described in step S1 is 1-1.77" is derived from the pH values ​​of 1, 1.34, 1.52, and 1.77 described in step S1 in the foregoing explanation and / or examples 1-4, summarized by the common feature "the pH of the system after adding elemental iron in step S1". Therefore, those skilled in the art can reasonably infer that the technical feature "the pH value described in step S1 is 1-1.77", its subordinate concepts and their substantially equivalent technical means, and technical means that can replace "the pH value described in step S1 is 1-1.77" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 1. For example, replacing "the pH value described in step S1 is 1-1.77" with the pH value of 1.7 in step S1 while keeping other technical features unchanged still falls within the protection scope of claim 1 of this invention.

[0147] In this invention, Examples 1-4 at least support the protection scope of the weight percentage of flocculant added to solution A in step S1 of the claims.

[0148] Regarding claim 1: the weight percentage of flocculant added to solution A in step S1. The technical feature “the weight percentage of flocculant added to solution A in step S1 is 0-0.45%” is summarized from the common feature “the weight percentage of flocculant added to solution A in step S1”, which is 0%, 0.07%, 0.26%, 0.45% in the foregoing explanation and / or examples 1-4. Therefore, those skilled in the art can reasonably presume that the technical feature "the weight ratio of the flocculant added to solution A in step S1 is 0-0.45%", the subordinate concept and its essentially equivalent technical means, and the technical means that can replace "the weight ratio of the flocculant added to solution A in step S1 is 0-0.45%" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 1. For example, if other technical features remain unchanged, replacing "the weight ratio of the flocculant added to solution A in step S1 is 0-0.45%" with "the weight ratio of the flocculant added to solution A in step S1 is 0.4%", it still falls within the protection scope of claim 1 of this invention.

[0149] In this invention, Examples 1-4 at least support the protection range of the reaction temperature and time when using elemental iron in the preparation process of solution A in the claims.

[0150] Regarding claim 3: the reaction temperature and time when using elemental iron during the preparation of solution A. The technical feature “In the preparation of solution A, the reaction temperature when using elemental iron is 25-65℃” is summarized from the aforementioned explanation and / or the corresponding technical features in Examples 1-4, such as the reaction temperature of 25℃, 45℃, and 65℃ when using elemental iron in the preparation of solution A, through the common feature “In the preparation of solution A, the reaction temperature when using elemental iron”. Therefore, those skilled in the art can reasonably presume that the technical feature "the reaction temperature when using elemental iron in the preparation of solution A is 25-65℃", the subordinate concept and its basically equivalent technical means, and the technical means that can replace "the reaction temperature when using elemental iron in the preparation of solution A is 25-65℃" based on the existing technical level and conventional technical means and common knowledge, should all fall within the protection scope of claim 3. For example, if other technical features remain unchanged, replacing "the reaction temperature when using elemental iron in the preparation of solution A is 25-65℃" with "the reaction temperature when using elemental iron in the preparation of solution A is 30℃" still falls within the protection scope of claim 3 of this invention.

[0151] The technical feature "in the preparation of solution A, the reaction time when using elemental iron is 2-5 hours" is derived from the aforementioned explanation and / or the corresponding technical features in Examples 1-4, such as the reaction time of 2 hours, 3 hours, and 5 hours when using elemental iron in the preparation of solution A, through the common feature "in the preparation of solution A, the reaction time when using elemental iron". Therefore, those skilled in the art can reasonably infer that the technical feature "in the preparation of solution A, the reaction time when using elemental iron is 2-5 hours", its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "in the preparation of solution A, the reaction time when using elemental iron is 2-5 hours" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 3. For example, replacing "in the preparation of solution A, the reaction time when using elemental iron is 2-5 hours" with 3.5 hours when using elemental iron in the preparation of solution A, while keeping other technical features unchanged, still falls within the protection scope of claim 3 of this invention.

[0152] In this invention, Examples 1-4 at least support the molar ratio of the number of transferable electrons in the oxidant described in step S2 of the claim to the iron ions in solution A, and the OH- ions in the alkaline solution. - The protection range of the molar ratio of iron ions in solution A, the concentration of alkali solution, the pH after adding alkali solution as described in step S2, and the temperature and time of the isothermal reaction.

[0153] Regarding claim 6: the molar ratio of the number of transferable electrons in the oxidant to the iron ions in solution A in step S2, the molar ratio of OH- in the alkali solution to the iron ions in solution A, the concentration of the alkali solution, the pH after adding the alkali solution in step S2, and the temperature and time of the isothermal reaction. The technical feature “the molar ratio of the number of transferable electrons in the oxidant in step S2 to the iron ions in solution A is 1.15-1.3:1” is summarized from the common feature “the molar ratio of the number of transferable electrons in the oxidant in step S2 to the iron ions in solution A” in the foregoing explanation and / or Examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature "the molar ratio of the number of transferable electrons in the oxidant described in step S2 to the iron ions in solution A is 1.15-1.3:1", the subordinate concept and its essentially equivalent technical means, and the technical means that can replace "the molar ratio of the number of transferable electrons in the oxidant described in step S2 to the iron ions in solution A is 1.15-1.3:1" based on the existing technical level and conventional technical means and common knowledge, should all fall within the protection scope of claim 6. For example, if other technical features remain unchanged, replacing "the molar ratio of the number of transferable electrons in the oxidant described in step S2 to the iron ions in solution A is 1.15-1.3:1" with a molar ratio of 1.2:1, etc., still falls within the protection scope of claim 6 of this invention.

[0154] Technical feature "OH in the alkaline solution described in step S2" - The molar ratio of iron ions in solution A to 2.4-2.57:1 is described above, as explained in the foregoing and / or in the corresponding technical feature step S2 of Examples 1-4, where the OH- ions in the alkaline solution are... - The molar ratios of iron ions in solution A to those in solution A are 2.4:1, 2.45:1, 2.52:1, and 2.57:1, etc., which share the common characteristic of "OH in the alkaline solution described in step S2". - The molar ratio of iron ions in solution A to the iron ions in solution S2 is summarized as follows. Therefore, those skilled in the art can reasonably infer that the technical feature "OH in the alkaline solution described in step S2" is accurate. - The molar ratio of iron ions in solution A to iron ions in solution A is 2.4-2.57:1. This refers to the lower-level concepts and their essentially equivalent technical means, and, based on existing technology, can replace the OH- ions in the alkaline solution described in step S2 within the scope of conventional technical means and common knowledge. -The technical means of "having a molar ratio of 2.4-2.57:1 of iron ions in solution A" should all fall within the protection scope of claim 6. For example, if other technical features remain unchanged, the "OH in the alkaline solution described in step S2" can be changed to... - The molar ratio of iron ions in solution A to iron ions in solution A is 2.4-2.57:1. This should be replaced with the OH- ions in the alkaline solution described in step S2. - Even with a molar ratio of 2.5:1 to iron ions in solution A, it still falls within the protection scope of claim 6 of this invention.

[0155] The technical feature "the concentration of the alkali solution described in step S2 is 5-15 mol / L" is derived from the common feature "the concentration of the alkali solution described in step S2" in the foregoing explanation and / or examples 1-4, where the concentrations are 5 mol / L, 9 mol / L, 12 mol / L, 15 mol / L, etc. Therefore, those skilled in the art can reasonably infer that the technical feature "the concentration of the alkali solution described in step S2 is 5-15 mol / L", its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "the concentration of the alkali solution described in step S2 is 5-15 mol / L" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 6. For example, replacing "the concentration of the alkali solution described in step S2 is 5-15 mol / L" with 14 mol / L, while keeping other technical features unchanged, still falls within the protection scope of claim 6 of this invention.

[0156] The technical feature “the pH after adding alkali solution in step S2 is 4.5-5.3” is derived from the common feature “pH after adding alkali solution in step S2”, which is 4.5, 4.7, 5, 5.3, etc., as explained above and / or in Examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature “the pH after adding alkali solution in step S2 is 4.5-5.3”, its subordinate concepts and their essentially equivalent technical means, and technical means that can replace “the pH after adding alkali solution in step S2 is 4.5-5.3” based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 6. For example, replacing “the pH after adding alkali solution in step S2 is 4.5-5.3” with “the pH after adding alkali solution in step S2 is 4.8” while other technical features remain unchanged still falls within the protection scope of claim 6 of this invention.

[0157] The technical feature "the temperature of the isothermal reaction in step S2 is 25-65℃" is derived from the common feature "the temperature of the isothermal reaction in step S2" in the foregoing explanation and / or embodiments 1-4, where the temperature is 25℃, 40℃, 50℃, 65℃, etc. Therefore, those skilled in the art can reasonably infer that the technical feature "the temperature of the isothermal reaction in step S2 is 25-65℃", its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "the temperature of the isothermal reaction in step S2 is 25-65℃" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 6. For example, replacing "the temperature of the isothermal reaction in step S2 is 25-65℃" with 30℃ while keeping other technical features unchanged still falls within the protection scope of claim 6 of this invention.

[0158] The technical feature "the isothermal reaction time in step S2 is 1-3 hours" is derived from the common feature "the isothermal reaction time in step S2 is 1 hour, 1.5 hours, 2 hours, 3 hours, etc." in the foregoing explanation and / or embodiments 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature "the isothermal reaction time in step S2 is 1-3 hours", its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "the isothermal reaction time in step S2 is 1-3 hours" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 6. For example, replacing "the isothermal reaction time in step S2 is 1-3 hours" with 2.5 hours while keeping other technical features unchanged still falls within the protection scope of claim 6 of this invention.

[0159] In this invention, Examples 1-4 at least support the presence of OH in the alkaline solution described in step S3 of the claims. - The molar ratio of iron ions in powder B and the concentration of alkali solution.

[0160] Regarding claim 7: the OH in the alkaline solution described in step S3 - The molar ratio of iron ions in powder B and the concentration of alkali solution Technical feature "OH in the alkaline solution described in step S3" - The molar ratio of iron ions in powder B is 0.28-0.37:1, as explained above and / or in the corresponding technical feature step S3 of Examples 1-4, where the OH- ions in the alkaline solution are... -The molar ratio of iron ions in powder B to iron ions in powder B is 0.28:1, 0.3:1, 0.33:1, 0.37:1, etc., which share the common feature "OH in the alkaline solution described in step S3". - The molar ratio of iron ions in powder B is summarized as "the ratio of iron ions in powder B". Therefore, those skilled in the art can reasonably infer that the technical feature "OH in the alkaline solution described in step S3" is correct. - The molar ratio of iron ions in powder B is 0.28-0.37:1; the lower-level concept and its basically equivalent technical means; based on the existing technical level, within the scope of conventional technical means and common knowledge, it can replace "OH in the alkaline solution described in step S3". - The technical means of "having a molar ratio of 0.28-0.37:1 of iron ions in powder B" should all fall within the protection scope of claim 7. For example, if other technical features remain unchanged, the "OH in the alkaline solution described in step S3" can be changed to... - The molar ratio of iron ions in powder B to iron ions in powder B is 0.28-0.37:1. This is replaced with the OH- ions in the alkaline solution described in step S3. - Even if the molar ratio of iron ions in powder B is 0.36:1, it still falls within the protection scope of claim 7 of this invention.

[0161] The technical feature “the concentration of the alkali solution described in step S3 is 5-15 mol / L” is derived from the common feature “the concentration of the alkali solution described in step S3”, which is 5 mol / L, 9 mol / L, 12 mol / L, 15 mol / L, etc., as explained above and / or in Examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature “the concentration of the alkali solution described in step S3 is 5-15 mol / L”, its subordinate concepts and their essentially equivalent technical means, and technical means that can replace “the concentration of the alkali solution described in step S3 is 5-15 mol / L” based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 7. For example, replacing “the concentration of the alkali solution described in step S3 is 5-15 mol / L” with 14 mol / L, etc., while keeping other technical features unchanged, still falls within the protection scope of claim 7 of this invention.

[0162] In this invention, Examples 1-4 at least support the molar ratio of the ferrous sulfate aqueous solution to the iron ions of powder B as described in step S3 of the claims, the concentration of the ferrous sulfate aqueous solution as described in step S3, the pH of the system after the ferrous sulfate aqueous solution is added, and the temperature and time of the isothermal reaction.

[0163] For claims 8 and 9: the molar ratio of the ferrous sulfate aqueous solution added in step S3 to the iron ions in powder B, the concentration of the ferrous sulfate aqueous solution added in step S3, the pH of the system after adding the ferrous sulfate aqueous solution, and the temperature and time of the isothermal reaction.

[0164] The technical feature “the molar ratio of the added ferrous sulfate aqueous solution to the iron ions in powder B in step S3 is 0.06-0.12:1” is summarized from the common feature “the molar ratio of the added ferrous sulfate aqueous solution to the iron ions in powder B in step S3 is 0.06:1, 0.08:1, 0.1:1, 0.12:1, etc.” in the foregoing explanation and / or examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature “the molar ratio of the ferrous sulfate aqueous solution to the iron ions of powder B in step S3 is 0.06-0.12:1”, the subordinate concept and its essentially equivalent technical means, and the technical means that can replace “the molar ratio of the ferrous sulfate aqueous solution to the iron ions of powder B in step S3 is 0.06-0.12:1” based on existing technical levels and conventional technical means and common knowledge, should all fall within the protection scope of claim 8. For example, if “the molar ratio of the ferrous sulfate aqueous solution to the iron ions of powder B in step S3 is 0.06-0.12:1” is replaced with a molar ratio of ferrous sulfate aqueous solution to the iron ions of powder B in step S3 being 0.11:1, etc., while other technical features remain unchanged, it still falls within the protection scope of claim 8 of this invention.

[0165] The technical feature “the concentration of the ferrous sulfate aqueous solution added in step S3 is 0.5-2.0 mol / L” is summarized from the common feature “the concentration of the ferrous sulfate aqueous solution added in step S3” in the foregoing explanation and / or Examples 1-4, where the concentration of the ferrous sulfate aqueous solution added in step S3 is 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, etc. Therefore, those skilled in the art can reasonably infer that the technical feature "the concentration of the ferrous sulfate aqueous solution added in step S3 is 0.5-2.0 mol / L", the subordinate concept and its essentially equivalent technical means, and the technical means that can replace "the concentration of the ferrous sulfate aqueous solution added in step S3 is 0.5-2.0 mol / L" based on the existing technical level and conventional technical means and common knowledge, should all fall within the protection scope of claim 8. For example, if other technical features remain unchanged, replacing "the concentration of the ferrous sulfate aqueous solution added in step S3 is 0.5-2.0 mol / L" with the concentration of the ferrous sulfate aqueous solution added in step S3 being 1.6 mol / L, it still falls within the protection scope of claim 8 of this invention.

[0166] The technical feature “the addition of ferrous sulfate aqueous solution in step S3, with a pH of 8.7-10.5” is summarized from the common feature “the addition of ferrous sulfate aqueous solution in step S3, with a pH of 8.7, 10.0, 10.2, 10.5, etc., as explained above and / or in Examples 1-4, by the aforementioned technical feature “the addition of ferrous sulfate aqueous solution in step S3, adjusting the pH range”. Therefore, those skilled in the art can reasonably presume that the technical feature "the addition of ferrous sulfate aqueous solution in step S3, with a pH of 8.7-10.5", the subordinate concept and its essentially equivalent technical means, and the technical means that can replace "the addition of ferrous sulfate aqueous solution in step S3, with a pH of 8.7-10.5" based on the existing technical level and within conventional technical means and common knowledge, should all fall within the protection scope of claim 8. For example, if other technical features remain unchanged, replacing "the addition of ferrous sulfate aqueous solution in step S3, with a pH of 8.7-10.5" with the addition of ferrous sulfate aqueous solution in step S3, with a pH of 9, still falls within the protection scope of claim 8 of this invention.

[0167] The technical feature "the temperature of the isothermal reaction described in step S3 is 90-110℃" is derived from the common feature "the temperature of the isothermal reaction described in step S3" in the foregoing explanation and / or embodiments 1-4, where the temperature is 90℃, 97℃, 100℃, 110℃, etc. Therefore, those skilled in the art can reasonably infer that the technical feature "the temperature of the isothermal reaction described in step S3 is 90-110℃", its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "the temperature of the isothermal reaction described in step S3 is 90-110℃" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 8. For example, replacing "the temperature of the isothermal reaction described in step S3 is 90-110℃" with 95℃ while keeping other technical features unchanged still falls within the protection scope of claim 8 of this invention.

[0168] The technical feature "the isothermal reaction time in step S3 is 3-6 hours" is derived from the common feature "the isothermal reaction time in step S3 is 3 hours, 4.5 hours, 6 hours, etc." in the foregoing explanation and / or examples 1-4. Therefore, those skilled in the art can reasonably infer that the technical feature "the isothermal reaction time in step S3 is 3-6 hours," its subordinate concepts and their essentially equivalent technical means, and technical means that can replace "the isothermal reaction time in step S3 is 3-6 hours" based on existing technology and conventional technical means and common knowledge, should all fall within the protection scope of claim 8. For example, replacing "the isothermal reaction time in step S3 is 3-6 hours" with "the isothermal reaction time in step S3 is 5.5 hours" while keeping other technical features unchanged still falls within the protection scope of claim 8.

[0169] The beneficial effects of this invention are as follows: The present invention has at least the following beneficial effects: 1. This invention uses ferrous sulfate, a byproduct of titanium dioxide production, as raw material. By adding or not adding iron powder, the Ti doping content can be controlled. Then, by adjusting the pH value of the system, the required Fe, Ti elements and impurity elements such as Mn, Mg, Cu, and Zn can be removed, thus achieving effective utilization of Ti impurities in the ferrous sulfate byproduct of titanium dioxide production. Finally, by adding a ferrous sulfate catalyst and adjusting the pH value of the system, titanium-doped iron oxide red can be obtained, which has adjustable Ti doping amount, high purity, and low impurity content.

[0170] 2. The utilization rate of Ti element in ferrous sulfate, a by-product of titanium dioxide production, can be controllably adjusted within the range of 0-100% according to application requirements. The required yields of Fe and Ti elements are both above 97%, and the utilization rate of Fe powder is above 97%. At the same time, the entire preparation process is simple, has a short reaction time, and is low in cost.

[0171] 3. The titanium-doped iron oxide red prepared by the present invention is formed by the aggregation of primary spherical particles, which is relatively uniform. The titanium element in the iron oxide red can be doped into the iron oxide red phase in the form of co-precipitation. Attached Figure Description

[0172] Figure 1 This is a SEM image of the titanium-doped iron oxide red prepared in Example 1.

[0173] Figure 2 The XRD patterns of titanium-doped iron oxide red prepared in Examples 1, 3, 4, 5, and 6 are shown. Detailed Implementation

[0174] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0175] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0176] Table 1. Reagents and their manufacturers and models

[0177] Example 1: Preparation of Titanium-Doped Iron Oxide Red S1. Titanium content control of titanium dioxide by-products: 278.01g of ferrous sulfate (Fe content 19.11%) from titanium dioxide by-products was dissolved in 1000mL of deionized water and 37.5g of 98% concentrated sulfuric acid. Then, 15.9g of iron powder (99%) was added at 65℃ (wherein the molar ratio of iron powder to iron ions in ferrous sulfate from titanium dioxide by-products = 0.3:1). The reaction was carried out at 65℃ for 2h with a stirring speed of 200rpm / min. After the reaction was completed, the pH of the system was 1.34. Then, 1g of polyacrylamide (0.07% by weight) was added to the system and the reaction was carried out at 65℃ for 30min. After the reaction was completed, the system was filtered and the pH was readjusted to 0.9 with 98% concentrated sulfuric acid to obtain 1223.56g of solution A. S2. Precipitation and removal of Fe and Ti elements: At 50℃, 77.05g of 30% hydrogen peroxide (where the molar ratio of transferable electrons in the oxidant to iron ions in solution A is 1.1:1) was added dropwise at 2mL / min to a 2L three-necked flask containing solution A using a peristaltic pump over 30min with a stirring speed of 200rpm / min; then, at 50℃, 123.04g of NaOH (96%) was added dropwise at 20mL / min using a peristaltic pump. -An alkaline solution (5 mol / L concentration) was prepared by adding 590 mL of deionized water to solution A (iron ion molar ratio = 2.4:1). The addition time was 30 min, the stirring speed was 350 rpm / min, and the pH of the reaction system was 4.5. After the addition was complete, the reaction was carried out at 50℃ for 1.5 h, with the stirring speed at 350 rpm / min during the reaction. After the reaction was completed, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was placed in a forced-air drying oven at 100℃ and dried for 12 h to finally obtain 135.17 g of powder B. S3. Mix the above powder B with 1352g of deionized water, and add 15.01g of NaOH (96%) dropwise using a peristaltic pump. - An alkaline solution (5 mol / L concentration) prepared by adding 72 mL of deionized water and ferrous sulfate (ferrous sulfate:iron ion molar ratio in powder B = 0.30:1) was added dropwise over 3 min with a stirring speed of 350 rpm / min, resulting in a system pH of 13.0. After the alkaline solution was added, a solution (2 mol / L concentration) containing 26.71 g of 99% ferrous sulfate (ferrous sulfate:iron ion molar ratio in powder B = 0.08:1) and 48 mL of deionized water was added. The titanium-doped iron oxide red was added dropwise to the reaction system using a peristaltic pump over a period of 3 minutes, with a stirring speed of 350 rpm / min and a system pH of 10.2. After the addition was complete, the temperature was raised to 100℃ and maintained for 3 hours, with a stirring speed of 350 rpm / min during the reaction. After the reaction was complete, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was then dried in a forced-air drying oven at 100℃ for 12 hours, finally yielding 97.53 g of titanium-doped iron oxide red.

[0178] Analysis revealed that solution A contained 5.62% Fe and 383.3 ppm Ti. Calculations showed that the iron powder utilization rate in step S1 was 98.34%, and the Ti retention rate was 66.56%. Analysis revealed that powder B contained 49.63% Fe, 3422.4 ppm Ti, 301.4 ppm Mn, 170.8 ppm Mg, 21.5 ppm Cu, and 42.3 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.6%, the Ti recovery rate was 98.6%, the Mn removal rate was 92.7%, the Mg removal rate was 97.1%, the Cu removal rate was 97.2%, and the Zn removal rate was 95.4%.

[0179] Analysis revealed that the titanium-doped iron oxide red contained 67.51% Fe, 4723.3 ppm Ti, 2418.3 ppm S, 79.4 ppm Mn, 55.3 ppm Mg, 1.9 ppm Cu, and 17.8 ppm Zn, with a specific surface area of ​​32.4 m². 2 / g; calculated, its overall purity is 97.20%, the Fe yield in step S3 is 98.1%, and the Ti yield is 99.6%.

[0180] Example 2: Preparation of Titanium-Doped Iron Oxide Red S1. Titanium content control of titanium dioxide by-products: 278.01g of ferrous sulfate (Fe content 19.11%), a by-product of titanium dioxide, was dissolved in 1000mL of deionized water and 37.5g of 98% concentrated sulfuric acid to obtain solution A; S2. Precipitation and removal of Fe and Ti elements: At 25℃, 67.99g of 30% hydrogen peroxide (where the molar ratio of transferable electrons in the oxidant to iron ions in solution A is 1.26:1) was added dropwise to a 2L three-necked flask containing solution A at a rate of 2mL / min using a peristaltic pump over a period of 30min, with a stirring speed of 200rpm / min; then, at 25℃, 100.03g of NaOH (96%) was added dropwise at a rate of 7mL / min using a peristaltic pump. - An alkaline solution (12 mol / L) was prepared by adding 200 mL of deionized water to solution A (iron ion molar ratio = 2.52:1) over 30 min with a stirring speed of 350 rpm / min. The pH of the reaction system was 5.0. After the addition was complete, the reaction was carried out at a constant temperature of 25℃ for 3 h with a stirring speed of 350 rpm / min. After the reaction was completed, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was then dried in a forced-air drying oven at 100℃ for 12 h to obtain 102.42 g of powder B. S3. Mix the above powder B with 1024g of deionized water, and add 17.24g of NaOH (96%) dropwise using a peristaltic pump. -An alkaline solution (15 mol / L concentration) was prepared by adding 28 mL of deionized water to powder B (iron ion molar ratio of 0.33:1 in powder B) over 3 min with stirring at 350 rpm / min. The pH of the system was 13.4. After the alkaline solution was added, a solution containing 34.86 g of 99% ferrous sulfate (ferrous sulfate:iron ion molar ratio of 0.1:1 in powder B) and 252 mL of deionized water (ferrous sulfate solution concentration of 0.5 mol / L) was added. L) The titanium-doped iron oxide red was added dropwise to the reaction system using a peristaltic pump over a period of 3 min, with a stirring speed of 350 rpm / min and a system pH of 10.0. After the addition was complete, the temperature was raised to 97℃ and kept constant for 4.5 h, with a stirring speed of 350 rpm / min during the reaction. After the reaction was complete, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered cake was then dried in a forced-air drying oven at 100℃ for 12 h to finally obtain 77.13 g of titanium-doped iron oxide red.

[0181] Analysis revealed that powder C contained 50.85% Fe, 6722.6 ppm Ti, 588.4 ppm Mn, 342.5 ppm Mg, 38.5 ppm Cu, and 49.1 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 98.0%, the Ti recovery rate was 97.7%, the Mn removal rate was 89.2%, the Mg removal rate was 95.6%, the Cu removal rate was 96.3%, and the Zn removal rate was 96.0%.

[0182] Analysis revealed that the titanium-doped iron oxide red contained 67.21% Fe, 8749.5 ppm Ti, 2915.4 ppm S, 87.2 ppm Mn, 59.4 ppm Mg, 3.1 ppm Cu, and 23.4 ppm Zn, with a specific surface area of ​​33.7 m². 2 / g; calculated, its overall purity is 97.35%, the Fe yield in step S3 is 99.5%, and the Ti yield is 98.0%.

[0183] Example 3: Preparation of Titanium-Doped Iron Oxide Red S1. Titanium content control of titanium dioxide by-products: 278.01g of ferrous sulfate (Fe content 19.11%) from titanium dioxide by-products was dissolved in 1000mL of deionized water and 37.5g of 98% concentrated sulfuric acid; then, 18.6g of iron powder (99%) was added at 45℃ (wherein, the molar ratio of iron powder to iron ions in ferrous sulfate from titanium dioxide by-products = 0.35:1), and the reaction was carried out at a constant temperature of 45℃ for 3h, with a stirring speed of 200rpm / min during the reaction; after the reaction was completed, the pH of the system was 1.52, and 3g of polyacrylamide (the weight percentage of flocculant added was 0.26%) was added to the system, and the reaction was carried out at 45℃ for 30min. After the reaction was completed, the system was filtered, and the pH was readjusted to 0.9 with 98% concentrated sulfuric acid to obtain 1243.09g of solution A; S2. Precipitation and removal of Fe and Ti elements: At 40℃, 82.91g of 30% hydrogen peroxide (where the molar ratio of transferable electrons in the oxidant to iron ions in solution A is 1.15:1) was added dropwise at 2mL / min to a 2L three-necked flask containing solution A using a peristaltic pump over 30min with a stirring speed of 200rpm / min; then, at 40℃, 136.72g of NaOH (96%) was added dropwise at 8mL / min using a peristaltic pump. - An alkaline solution (15 mol / L concentration) was prepared by adding 219 mL of deionized water to solution A (iron ion molar ratio = 2.57:1). The addition time was 30 min, the stirring speed was 350 rpm / min, and the pH of the reaction system was 5.3. After the addition was complete, the reaction was carried out at 40℃ for 2 h with the stirring speed at 350 rpm / min. After the reaction was completed, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was placed in a forced-air drying oven at 100℃ and dried for 12 h to finally obtain 138.65 g of powder B. S3. Mix the above powder B with 1386g of deionized water, and add 19.33g of NaOH (96%) dropwise using a peristaltic pump. -An alkaline solution (9 mol / L concentration) was prepared by adding 52 mL of deionized water to powder B (iron ion molar ratio = 0.37:1) over 3 min with stirring at 350 rpm. The pH of the system was 13.7. After the alkaline solution was added, a solution containing 41.83 g of iron ions was added. A solution of 99% ferrous sulfate (ferrous sulfate: iron ions in powder B molar ratio = 0.12:1) and 100 mL of deionized water (ferrous sulfate concentration of 1.5 mol / L) was added dropwise to the reaction system using a peristaltic pump over a period of 3 min. The stirring speed was 350 rpm / min, and the pH of the system was 10.5. After the addition was complete, the temperature was raised to 90 °C and maintained for 6 h. During the reaction, the stirring speed was 350 rpm / min. After the reaction was completed, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was dried in a forced-air drying oven at 100 °C for 12 h to finally obtain 102.21 g of titanium-doped iron oxide red.

[0184] Analysis revealed that solution A contained 5.73% Fe and 130.7 ppm Ti. Calculations showed that the iron powder utilization rate in step S1 was 97.58% and the Ti retention rate was 23.06%.

[0185] Analysis revealed that powder B contained 50.51% Fe, 1146.5 ppm Ti, 587.4 ppm Mn, 335.1 ppm Mg, 36.2 ppm Cu, and 48.5 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 98.3%, the Ti recovery rate was 97.8%, the Mn removal rate was 85.4%, the Mg removal rate was 93.8%, the Cu removal rate was 95.2%, and the Zn removal rate was 94.6%.

[0186] Analysis revealed that the titanium-doped iron oxide red contained 67.73% Fe, 1528.1 ppm Ti, 2711.4 ppm S, 95.1 ppm Mn, 77.3 ppm Mg, 2.6 ppm Cu, and 18.5 ppm Zn, with a specific surface area of ​​35.1 m². 2 / g; calculated, its overall purity is 97.06%, the yield in step S3 is 98.9%, and the Ti yield is 98.3%.

[0187] Example 4: Preparation of Titanium-Doped Iron Oxide Red S1. Titanium content control of titanium dioxide by-products: 278.01g of ferrous sulfate (Fe content 19.11%) from titanium dioxide by-products was dissolved in 1000mL of deionized water and 37.5g of 98% concentrated sulfuric acid; then, 21.2g of iron powder (99%) was added at 25℃ (wherein, the molar ratio of iron powder to iron ions in ferrous sulfate from titanium dioxide by-products = 0.4:1), and the reaction was carried out at a constant temperature of 25℃ for 5h. During the reaction, the stirring speed was 200rpm / min. After the reaction was completed, the pH of the system was 1.77, and 6g of polyacrylamide (the weight percentage of flocculant added was 0.45%) was added to the system. The reaction was carried out at 25℃ for 30min; after the reaction was completed, the system was filtered, and the pH was readjusted to 0.9 with 98% concentrated sulfuric acid to obtain 1261.10g of solution A; S2. Precipitation and removal of Fe and Ti elements: At 65℃, 97.13g of 30% hydrogen peroxide (where the molar ratio of transferable electrons in the oxidant to iron ions in solution A is 1.3:1) was added dropwise to a 2L three-necked flask containing solution A using a peristaltic pump at a rate of 2mL / min for 30min, with a stirring speed of 200rpm / min; then, at 65℃, 134.16g of NaOH (96%) was added dropwise at a rate of 13mL / min using a peristaltic pump. - An alkaline solution (9 mol / L) was prepared by adding 358 mL of deionized water to solution A (iron ion molar ratio = 2.45:1) over 30 min with stirring at 350 rpm / min. The pH of the system was 4.7. After the addition was complete, the reaction was carried out at 65℃ for 1 h with stirring at 350 rpm / min. After the reaction was complete, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was then dried in a 100℃ oven for 12 h to obtain 144.53 g of powder B. S3. Mix the above powder B with 1445g of deionized water, and add 14.95g of NaOH (96%) dropwise using a peristaltic pump. -A 12 mol / L alkaline solution was prepared by adding 30 mL of deionized water to powder B (iron ion molar ratio = 0.28:1). The solution was added dropwise over 3 minutes at a stirring speed of 350 rpm / min. The pH of the reaction system was 12.4. After the alkaline solution was added, a solution containing 21.37 g of iron ions was added. A solution of 99% ferrous sulfate (ferrous sulfate: iron ions in powder B molar ratio = 0.06:1) and 78 mL of deionized water (ferrous sulfate concentration of 1 mol / L) was added dropwise to the reaction system using a peristaltic pump over a period of 3 min. The stirring speed was 350 rpm / min, and the pH of the system was 8.7. After the addition was complete, the temperature was raised to 110 °C and maintained for 3 h. During the reaction, the stirring speed was 350 rpm / min. After the reaction was complete, the product was filtered, washed, and vacuum filtered until the conductivity of the filtrate was <300 μS / cm. The filtered filter cake was then dried in a forced-air drying oven at 100 °C for 12 h to finally obtain 104.04 g of titanium-doped iron oxide red.

[0188] Analysis revealed that the Fe content in solution A was 5.82% and the Ti content was 47.0 ppm. Calculations showed that the iron powder utilization rate in step S1 was 95.61% and the Ti retention rate was 8.41%.

[0189] Analysis revealed that powder B contained 49.51% Fe, 401.4 ppm Ti, 605.2 ppm Mn, 190.5 ppm Mg, 40.7 ppm Cu, and 44.7 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.5%, the Ti recovery rate was 97.9%, the Mn removal rate was 84.3%, the Mg removal rate was 96.5%, the Cu removal rate was 94.4%, and the Zn removal rate was 94.8%.

[0190] Analysis revealed that the titanium-doped iron oxide red contained 68.01% Fe, 534.8 ppm Ti, 2019.2 ppm S, 64.2 ppm Mn, 50.1 ppm Mg, 3.7 ppm Cu, and 24.3 ppm Zn, with a specific surface area of ​​25.6 m². 2 / g; calculated, its overall purity is 97.32%, the Fe yield in step S3 is 98.9%, and the Ti yield is 95.9%.

[0191] Comparative Example 1 Compared with Example 1, the difference is that the amount of iron powder added in step S1 is changed to 26.5g (wherein, the molar ratio of iron powder to iron ions in ferrous sulfate by-product of titanium dioxide is 0.5:1), and the rest of the steps and amounts are the same as in Example 1.

[0192] Analysis revealed that solution A contained 5.60% Fe and 0.5 ppm Ti. Calculations showed that the iron powder utilization rate was 69.96% and the Ti retention rate was 0.09% in this step.

[0193] Analysis revealed that powder B contained 47.53% Fe, 4.1 ppm Ti, 315.7 ppm Mn, 155.3 ppm Mg, 32.1 ppm Cu, and 41.8 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.7%, the Ti recovery rate was 94.4%, the Mn removal rate was 91.7%, the Mg removal rate was 97.1%, the Cu removal rate was 95.5%, and the Zn removal rate was 95.1%.

[0194] Analysis revealed that the titanium-doped iron oxide red contained 68.15% Fe, 5.9 ppm Ti, 2019.5 ppm S, 51.1 ppm Mn, 46.2 ppm Mg, 2.2 ppm Cu, and 18.2 ppm Zn, with a specific surface area of ​​31.1 m². 2 / g; calculated, its overall purity is 97.44%, the Fe yield in step S3 is 97.9%, and the Ti yield is 98.3%.

[0195] Comparative Example 2 Compared with Example 1, the difference lies in changing the amount of NaOH added in step S2, which is modified to 143.80g (OH). - The molar ratio of iron ions in solution A to alkali solution A is 2.8:1 (the concentration of the alkali solution is 5 mol / L), the pH of the reaction system is 7.9, and the remaining steps and amounts are the same as in Example 1.

[0196] Analysis revealed that the Fe content in solution A was 5.61% and the Ti content was 390.1 ppm. Calculations showed that the iron powder utilization rate in step S1 was 97.30% and the Ti retention rate was 67.70%.

[0197] Analysis revealed that powder B contained 49.59% Fe, 3464.1 ppm Ti, 3215.8 ppm Mn, 2764.2 ppm Mg, 385.4 ppm Cu, and 469.3 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.5%, the Ti recovery rate was 98.0%, the Mn removal rate was 22.2%, the Mg removal rate was 53.2%, the Cu removal rate was 50.6%, and the Zn removal rate was 49.3%.

[0198] Analysis revealed that the titanium-doped iron oxide red contained 67.49% Fe, 4703.2 ppm Ti, 2625.1 ppm S, 1827.4 ppm Mn, 1396.2 ppm Mg, 278.3 ppm Cu, and 354.4 ppm Zn, with a specific surface area of ​​32.2 m². 2 / g; calculated, its overall purity is 97.17%, and the Fe yield in step S3 is 98.5% and the Ti yield is 98.3%.

[0199] Comparative Example 3 Compared with Example 1, the difference lies in changing the amount of NaOH added in step S3, which is modified to 22.45g (OH). - The molar ratio of iron ions in solution A to alkali solution A is 0.45:1 (the concentration of the alkali solution is 5 mol / L), the pH of the reaction system is 12.5, and the remaining steps and amounts are the same as in Example 1.

[0200] Analysis revealed that the Fe content in solution A was 5.62% and the Ti content was 382.8 ppm. Calculations showed that the iron powder utilization rate in step S1 was 98.61% and the Ti retention rate was 66.51%.

[0201] Analysis revealed that powder B contained 49.61% Fe, 3419.5 ppm Ti, 356.1 ppm Mn, 164.2 ppm Mg, 33.6 ppm Cu, and 41.5 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.2%, the Ti recovery rate was 98.3%, the Mn removal rate was 91.4%, the Mg removal rate was 97.2%, the Cu removal rate was 95.7%, and the Zn removal rate was 95.5%.

[0202] Analysis revealed that the titanium-doped iron oxide red contained 72.78% Fe, 4987.1 ppm Ti, 671.6 ppm S, 671.5 ppm Mn, 260.7 ppm Mg, 2.5 ppm Cu, and 24.1 ppm Zn, with a specific surface area of ​​20.4 m². 2 / g; Calculations show that the Fe yield in step S3 is 97.7% and the Ti yield is 97.2%.

[0203] Comparative Example 4 Compared with Example 1, the difference lies in changing the amount of NaOH added in step S3, which is modified to 9.93g (OH). - The molar ratio of iron ions in powder B is 0.2:1, the concentration of alkaline solution is 5 mol / L, the pH of the reaction system is 5.0, and the remaining steps and amounts are the same as in Example 1.

[0204] Analysis revealed that the Fe content in solution A was 5.60% and the Ti content was 380.7 ppm. Calculations showed that the iron powder utilization rate in step S1 was 97.35% and the Ti retention rate was 66.19%.

[0205] Analysis revealed that powder B contained 49.59% Fe, 3388.5 ppm Ti, 377.5 ppm Mn, 185.2 ppm Mg, 30.5 ppm Cu, and 43.7 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.0%, the Ti recovery rate was 97.5%, the Mn removal rate was 90.9%, the Mg removal rate was 96.9%, the Cu removal rate was 96.1%, and the Zn removal rate was 95.3%.

[0206] Analysis revealed that the titanium-doped iron oxide red contained 64.58% Fe, 4303.1 ppm Ti, 2716.8 ppm S, 90.2 ppm Mn, 53.5 ppm Mg, 2.9 ppm Cu, and 23.8 ppm Zn, with a specific surface area of ​​87.5 m². 2 / g; calculated, its overall purity is 92.95%, the Fe yield in step S3 is 98.3%, and the Ti yield is 95.9%.

[0207] Comparative Example 5 Compared with Example 1, the difference lies in the modification of the amount of NaOH and FeSO4 added in step S3. The amount of NaOH added is modified to 13.07g (OH-). - The molar ratio of ferrous sulfate to iron ions in powder B is 0.26:1, and the concentration of the alkaline solution is 5 mol / L. To maintain the pH of the reaction system at 8.7, the amount of FeSO4 added is modified to 6.71 g (the molar ratio of ferrous sulfate to iron ions in powder B is 0.02:1, and the concentration of the ferrous sulfate solution is 2 mol / L). The remaining steps and amounts are the same as in Example 1.

[0208] Analysis revealed that the Fe content in solution A was 5.59% and the Ti content was 378.2 ppm. Calculations showed that the iron powder utilization rate in step S1 was 96.94% and the Ti retention rate was 65.81%.

[0209] Analysis revealed that powder B contained 49.58% Fe, 3327.1 ppm Ti, 287.1 ppm Mn, 165.8 ppm Mg, 32.6 ppm Cu, and 39.8 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 98.3%, the Ti recovery rate was 97.5%, the Mn removal rate was 93.0%, the Mg removal rate was 97.2%, the Cu removal rate was 95.8%, and the Zn removal rate was 95.7%.

[0210] Analysis revealed that the titanium-doped iron oxide red contained 66.43% Fe, 4467.1 ppm Ti, 2497.2 ppm S, 85.2 ppm Mn, 57.0 ppm Mg, 1.7 ppm Cu, and 18.9 ppm Zn, with a specific surface area of ​​59.1 m². 2 / g; calculated, its overall purity is 95.62%, the Fe yield in step S3 is 98.4%, and the Ti yield is 98.6%.

[0211] Comparative Example 6 Compared with Example 1, the difference is that the isothermal reaction temperature in step S3 is modified to 60°C, while the other steps and dosages are the same as in Example 1.

[0212] Analysis revealed that the Fe content in solution A was 5.61% and the Ti content was 385.1 ppm. Calculations showed that the iron powder utilization rate in step S1 was 97.78% and the Ti retention rate was 66.91%.

[0213] Analysis revealed that powder B contained 49.65% Fe, 3459.1 ppm Ti, 318.8 ppm Mn, 167.2 ppm Mg, 31.3 ppm Cu, and 44.5 ppm Zn. Calculations showed that in step S2, the Fe recovery rate was 97.4%, the Ti recovery rate was 98.9%, the Mn removal rate was 92.3%, the Mg removal rate was 97.2%, the Cu removal rate was 96.0%, and the Zn removal rate was 95.2%.

[0214] Analysis revealed that the titanium-doped iron oxide red contained 62.05% Fe, 4354.2 ppm Ti, 3019.5 ppm S, 50.2 ppm Mn, 27.4 ppm Mg, 2.1 ppm Cu, and 24.5 ppm Zn, with a specific surface area of ​​102.7 m². 2 / g; calculated, its overall purity is 89.34%, the Fe yield in step S2 is 97.9%, and the Ti yield is 98.6%.

[0215] Example 1: Scanning electron microscopy observation and XRD characterization of titanium-doped iron oxide red. 1. Experimental methods: The titanium-doped iron oxide red prepared in Example 1 was observed by scanning electron microscopy; the titanium-doped iron oxide red prepared in Example 1 and Comparative Examples 3-6 were characterized by XRD.

[0216] from Figure 1 It can be seen that the prepared titanium-doped iron oxide red precursor is composed of aggregated primary spherical particles, and the size of the primary particles is relatively uniform, around 100 nm. The obtained titanium-doped iron oxide red precursor was characterized by XRD, and the results are as follows: Figure 2 .from Figure 2 It can be seen that the XRD pattern of the prepared titanium-doped iron oxide red precursor can well match the standard pattern of Fe2O3 (PDF card number 33-0664), which indicates that the titanium element in the precursor is co-precipitated into the iron oxide red phase.

[0217] The Ti content of titanium-doped iron oxide red in Examples 1-4 of this invention is adjustable, and the purity is high with low impurity content. In Comparative Example 1, changing the amount of iron powder added resulted in the complete removal of Ti element. In Comparative Example 2, changing the amount of alkaline solution added to S2 resulted in unsatisfactory impurity removal effect, and the product had high levels of impurities such as Mn, Mg, Cu, and Zn.

[0218] like Figure 2 As shown, Comparative Examples 3 and 4 changed the amount of alkali added to S3, Comparative Example 5 changed the amount of ferrous sulfate added to S3, and Comparative Example 6 changed the reaction temperature of S3. All of them had a certain amount of impurity phase (FeOOH or Fe3O4) in the product, which led to a decrease in its purity.

[0219] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing titanium-doped iron oxide red, characterized in that, The process includes the following steps: S1. Control of titanium content in titanium dioxide by-products: Dissolve ferrous sulfate, a by-product of titanium dioxide production, and prepare solution A using elemental iron and a flocculant; the molar ratio of elemental iron to iron ions in ferrous sulfate from titanium dioxide production in solution A is 0-0.45:1, and the pH value is 1-2; the weight percentage of flocculant added to solution A is 0-0.5%; When the molar ratio of elemental iron in solution A to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, is 0, it indicates that no elemental iron was added during the preparation of solution A. When the weight percentage of flocculant added to solution A is 0%, it indicates that no flocculant was added during the preparation of solution A. S2. Precipitation and removal of Fe and Ti elements: Add oxidant to solution A, add alkaline solution to adjust pH, stir and react at a constant temperature to obtain powder B; S3. Mix powder B with water, add alkaline solution, then add ferrous sulfate aqueous solution. After the reaction is completed at a constant temperature, the product is obtained. Preferably, the molar ratio of elemental iron in solution A in step S1 to ferrous ions in ferrous sulfate, a byproduct of titanium dioxide production, is 0-0.4:

1. Preferably, the pH value in step S1 is 1-1.77; Preferably, the weight percentage of the flocculant added to solution A in step S1 is 0-0.45%.

2. The preparation method according to claim 1, characterized in that, The iron element is a zero-valent iron source; the zero-valent iron source is selected from one or more of iron powder, iron blocks, and iron sheets.

3. The preparation method according to claim 1, characterized in that, In step S1, during the preparation of solution A, when elemental iron is used, the reaction temperature is 20-70℃ and the reaction time is 1-5h. Preferably, in the preparation of solution A, when using elemental iron, the reaction temperature is 25-65℃ and the reaction time is 2-5h.

4. The preparation method according to claim 1, characterized in that, In step S1, the flocculant is selected from one or more of polyacrylamide, sodium alginate, chitosan, polydimethylammonium chloride, polyaluminum chloride, polyferric sulfate, aluminum sulfate, aluminum chloride, ferric sulfate, and ferric chloride.

5. The preparation method according to claim 1, characterized in that, The oxidant in step S2 is selected from one or more of hydrogen peroxide and ammonium persulfate; the alkaline solution is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution.

6. The preparation method according to claim 1, characterized in that, The molar ratio of transferable electrons in the oxidant to iron ions in solution A in step S2 is 1.0-1.5:1; the OH- in the alkaline solution... - The molar ratio of iron ions in solution A to alkali ions is 2.0-2.7:1; the concentration of the alkali solution is 4-15 mol / L; the pH is 4-6; the temperature of the isothermal reaction is 20-70℃; and the reaction time is 1-3 hours. Preferably, the molar ratio of transferable electrons in the oxidant to iron ions in solution A in step S2 is 1.15-1.3:1; the OH- in the alkaline solution... - The molar ratio of iron ions in solution A to alkali ions is 2.4-2.57:1; the concentration of the alkali solution is 5-15 mol / L; the pH is 4.5-5.3; the temperature of the isothermal reaction is 25-65℃; and the reaction time is 1-3 hours.

7. The preparation method according to claim 1, characterized in that, The alkaline solution mentioned in step S3 is selected from one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and ammonia solution; the OH in the alkaline solution... - The molar ratio of iron ions in powder B to iron ions in powder B is 0.25-0.40:1; the concentration of the alkaline solution is 4-15 mol / L. Preferably, the OH in the alkaline solution described in step S3 is... - The molar ratio of iron ions in powder B to iron ions in powder B is 0.28-0.37:1; the concentration of the alkaline solution is 5-15 mol / L.

8. The preparation method according to claim 1, characterized in that, In step S3, the molar ratio of the added ferrous sulfate aqueous solution to the iron ions in powder B is 0.05-0.15:1; the concentration of the ferrous sulfate aqueous solution is 0.5-2.0 mol / L; the pH is adjusted to 8.5-11.0 during the addition of the ferrous sulfate aqueous solution; the temperature of the isothermal reaction is 80-120℃; and the reaction time is 3-8 hours. Preferably, the molar ratio of the ferrous sulfate aqueous solution to the iron ions in powder B in step S3 is 0.06-0.12:1; the pH of the ferrous sulfate aqueous solution is adjusted to 8.7-10.5; the temperature of the isothermal reaction is 90-110℃; and the reaction time is 3-6 hours.

9. A titanium-doped iron oxide red prepared by the preparation method according to any one of claims 1-8.

10. The application of titanium-doped iron oxide red prepared by the preparation method according to any one of claims 1-8 or the titanium-doped iron oxide red according to claim 9 in the cathode material of lithium-ion batteries.

Images