Method for preparing polymeric ferric sulfate from solid waste yellow ferrous sulfate in titanium dioxide plant

Abstract

The present invention provides a method for preparing polyferric sulfate from solid waste yellow ferrous sulfate in a titanium dioxide factory, comprising the following steps: dissolving the yellow ferrous sulfate raw material in water, adding iron oxide red under heating conditions, stirring until the reaction is complete, and then filtering to remove insoluble impurities; adding an oxidant to the filtrate, heating and stirring to carry out oxidation, hydrolysis, and polymerization reactions to obtain a liquid product; concentrating and drying the liquid product to prepare solid polyferric sulfate. The method neutralizes the free acid in the raw material yellow ferrous sulfate by adding iron oxide red, increases the content of effective component iron in the system, and the prepared product has a relatively high basicity and good polymerization effect, and no external acid or alkali is required during the preparation process. The present invention eliminates the environmental protection hidden danger caused by the stacking of solid waste, enables the comprehensive utilization of industrial waste by-products, reduces the production cost of polyferric sulfate, and improves the economic benefit of titanium dioxide production.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of industrial solid waste resources. Specifically, it relates to a method for preparing polyferric sulfate from solid waste yellow ferrous sulfate in a titanium dioxide plant. Background Technique

[0002] The production methods of titanium dioxide mainly include the chloride process and the sulfuric acid process. In China, the production of titanium dioxide mainly uses the sulfuric acid process. Compared with the chloride process, the raw materials used in this method are cheap and easily available, generally ilmenite, and the technology is relatively mature and the equipment operation is simple. However, there are more waste by-products, such as yellow ferrous sulfate and iron oxide red.

[0003] Among them, yellow ferrous sulfate is a solid waste precipitated after the concentration of titanium white waste acid, and its main component is FeSO4·H2O. A large amount of waste acid containing ferrous sulfate will be generated during the production of titanium white by the sulfuric acid process, such as the remaining acid after acid decomposing ilmenite and the residual acid in the filtration and washing liquid. These waste acids are mainly comprehensively utilized through concentration and acid mixing processes, that is, the waste acid with a concentration of about 25% is mixed with sulfuric acid with a concentration of 98% to form sulfuric acid with a concentration of 55%. During the concentration process, as the concentration of sulfuric acid increases, the common ion effect enhances, and ferrous sulfate in the waste acid precipitates in the form of yellow ferrous sulfate. The precipitated yellow ferrous sulfate contains more free acid and impurity elements, so it cannot be directly utilized. At present, it is mainly treated by mixing and burning to produce sulfuric acid and lime neutralization and discharge. Among them, due to the limitation of equipment production capacity, the amount of yellow ferrous sulfate consumed each year is limited. The remaining yellow ferrous sulfate is then treated by lime neutralization and stacked in the form of solid slag.

[0004] Iron oxide red is produced after yellow ferrous sulfate and sulfur are mixed and burned to produce industrial sulfuric acid. Mixing and burning to produce acid can make full use of the sulfur and iron resources in yellow ferrous sulfate. Among them, sulfur elements enter the downstream process in the form of SO2, while iron elements are discharged in the form of slag (i.e., iron oxide red), and its main component is Fe2O3, with a purity of about 55%. Since sulfur belongs to a clean acid-making raw material, the impurity elements contained in the obtained iron oxide red are the same as those in yellow ferrous sulfate. These titanium white waste by-products not only have a high treatment cost, but also cause certain resource waste and environmental protection hazards after simple stacking or landfill.

[0005] Polyferric sulfate is an inorganic polymer flocculant, which is prepared by oxidation, hydrolysis, and polymerization reactions under acidic conditions with FeSO4 as the raw material. Compared with traditional iron-based and aluminum-based flocculants, polyferric sulfate has stronger flocculation and adsorption capabilities and is widely used in the treatment of drinking water, industrial wastewater, and domestic sewage.

[0006] In existing research and actual engineering, ferrous sulfate pure substance or titanium white by-product ferrous sulfate heptahydrate with relatively high purity is mostly used as raw materials. By adding sulfuric acid, oxidants or catalysts externally, polyferric sulfate is prepared, resulting in relatively high production costs. However, there is less research on using yellow ferrous sulfate as a raw material. If a technology can be developed to solve the problem that the content of free acid in yellow ferrous sulfate is too high to be directly utilized, and the iron resources of iron oxide red, a waste by-product of titanium white, can be fully utilized, promoting the coupled development of the industrial chain of the titanium dioxide industry, using the waste by-products of a certain process as raw materials for another process to form a complete production chain, the competitiveness of enterprises can be greatly enhanced, and the economic benefits of titanium dioxide plants can be improved. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art, aiming to solve the problem that the content of free acid in yellow ferrous sulfate is too high to be directly utilized, and provide a method for preparing polyferric sulfate from solid waste yellow ferrous sulfate in a titanium dioxide plant. Using yellow ferrous sulfate as a raw material, by adding iron oxide red to neutralize the free acid in the raw material yellow ferrous sulfate, polyferric sulfate is prepared after oxidation, hydrolysis, and polymerization reactions. The present invention relates to the resource utilization of titanium white by-product yellow ferrous sulfate and iron oxide red, eliminates the environmental protection hidden dangers brought by the stacking of solid waste, enables the comprehensive utilization of industrial waste by-products, reduces the production cost of polyferric sulfate, and improves the economic benefits of titanium dioxide plants.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A method for preparing polyferric sulfate from solid waste yellow ferrous sulfate in a titanium dioxide plant, the method comprising the following steps:

[0010] (1) Dissolve the yellow ferrous sulfate raw material in water, adjust the acid concentration of the solution, add iron oxide red under heating conditions, stir until the reaction is complete, and then filter to remove insoluble impurities;

[0011] (2) Add an oxidant to the filtrate obtained in step (1), heat and stir, and carry out oxidation, hydrolysis, and polymerization reactions to obtain a liquid product;

[0012] (3) Concentrate and dry the liquid product obtained in step (2) to prepare solid polyferric sulfate.

[0013] The present invention is further set as follows: In step (1), the mass ratio of yellow ferrous sulfate to iron oxide red is 1:(0.04 - 0.10), and the added iron oxide red is used to neutralize the excessive free acid in the raw material yellow ferrous sulfate.

[0014] The present invention is further configured such that, in step (1), the mass fraction of free acid in the ferrous yellow solution is regulated to be 8% to 12% by the amount of water added. Since red iron oxide is slag produced after high-temperature calcination of ferrous yellow mixed with acid, its reaction activity is relatively weak. When the acid concentration of the solution is too low, it is difficult for the red iron oxide to react with the free acid in the ferrous yellow solution. By reducing the amount of water added to increase the acid concentration of the solution, it is necessary to avoid the solution being too viscous to ensure sufficient contact between the red iron oxide and the free sulfuric acid.

[0015] The present invention is further configured such that when red iron oxide is added in step (1), the heating temperature is 100-120° C. and the reaction time is 180-300 min. The activation temperature of red iron oxide is relatively high, and the reaction is slow under low temperature conditions, requiring a certain reaction activation energy.

[0016] The present invention is further configured such that the ferrous yellow and red iron oxide in step (1) are waste by-products of titanium dioxide, which contain relatively large amounts of impurities. The insoluble impurities can be removed by filtration, thereby purifying the raw material liquid and improving the quality of the product polyferric sulfate.

[0017] The present invention is further configured such that in step (2), the oxidant is selected from one or more of hydrogen peroxide, sodium chlorate, potassium chlorate, sodium nitrite, nitric acid, and sodium hypochlorite, preferably hydrogen peroxide and sodium chlorate. Furthermore, when hydrogen peroxide is added as the oxidant, the mass ratio of ferrous yellow to hydrogen peroxide is 1:(0.4-1.2), wherein the hydrogen peroxide is calculated as a 30% by mass hydrogen peroxide solution; and when sodium chlorate is added as the oxidant, the mass ratio of ferrous yellow to sodium chlorate is 1:(0.05-0.08).

[0018] The present invention is further configured such that the oxidant in step (2) needs to be added slowly or in batches; when adding the oxidant hydrogen peroxide, it needs to be added slowly dropwise, specifically, the mass of hydrogen peroxide added every 5 to 10 minutes does not exceed 15% of the total mass, and the system temperature is controlled below 60° C. to prevent high temperature from exacerbating the decomposition of hydrogen peroxide and reducing the oxidizing ability; when adding the oxidant sodium chlorate, it needs to be added in batches, with 20% to 25% of the total mass of the oxidant added to the reaction system at intervals of 3 to 5 minutes each time, to prevent a sudden increase in the system temperature caused by a one-time addition.

[0019] The present invention is further configured such that the heating temperature in step (2) is 40-60°C.

[0020] The present invention is further configured such that the reaction time in step (2) is 60 to 120 minutes, and the reaction time is counted from the start of addition of the oxidant.

[0021] The present invention is further configured such that the concentration and drying temperature in step (3) is 60 to 80° C., and the drying time is 24 to 48 hours.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The present invention realizes the resource utilization of the waste by-products yellow ferrous sulfate and iron oxide red in a titanium dioxide factory. The addition of iron oxide red can neutralize the excessive free sulfuric acid in yellow ferrous sulfate. By adjusting the acid concentration of the yellow ferrous sulfate aqueous solution and the reaction temperature when adding iron oxide red, a polyferric sulfate product is prepared. And the filtration treatment before oxidation can remove the insoluble impurities in the raw material liquid, improving the product quality. The present invention effectively utilizes iron oxide red, solves the problem of high treatment cost of solid wastes such as yellow ferrous sulfate and iron oxide red, realizes the resource utilization of waste by-products in the titanium dioxide production process, improves the economic benefits of the titanium dioxide factory, and achieves the purpose of clean production.

[0024] (2) Different from the traditional preparation process, the present invention does not need to add external acids and alkalis during the preparation of polyferric sulfate. Since the raw material yellow ferrous sulfate used contains excessive free sulfuric acid, the present invention does not need to add external sulfuric acid during the preparation of polyferric sulfate. By adding iron oxide red to neutralize the excessive free acid therein, ferric sulfate is generated by reaction and participates in the subsequent reaction as a raw material for preparing polyferric sulfate, increasing the content of the effective component iron in the system. The prepared product has a relatively high degree of polymerization, does not need to add additional alkali to increase the basicity of the product, and the product has a good treatment effect on the actual water sample and has higher economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is the process flow chart for preparing polyferric sulfate from the solid waste yellow ferrous sulfate in a titanium dioxide factory;

[0026] Figure 2 is the XRD pattern of the polyferric sulfate prepared under the conditions of Example 1, Comparative Example 1 and Comparative Example 4;

[0027] Figure 3 is the XRD pattern of the polyferric sulfate prepared under the conditions of Example 2, Comparative Example 5 and Comparative Example 8. DETAILED DESCRIPTION OF THE INVENTION

[0028] The technical idea of the present invention is: using yellow ferrous sulfate as the raw material, neutralizing the free acid therein by adding iron oxide red, and preparing polyferric sulfate through oxidation, hydrolysis and polymerization reactions. The method comprises the following steps:

[0029] (1) Dissolve the yellow ferrous sulfate raw material in a small amount of water, adjust the acid concentration of the solution, add iron oxide red under heating conditions, stir until the reaction is complete, and then filter to remove insoluble impurities;

[0030] (2) Add an oxidant to the filtrate obtained in step (1), heat and stir, and carry out oxidation, hydrolysis and polymerization reactions to obtain a liquid product;

[0031] (3) Concentrate and dry the liquid product obtained in step (2) to prepare solid polymeric ferric sulfate.

[0032] The raw material yellow ferrous used in the present invention is the concentrated solid waste of titanium white waste acid, and its main component is FeSO4·H2O, which contains excessive free sulfuric acid. Excessive content of free acid will affect the hydrolysis step in the preparation of polymeric ferric sulfate (as shown in Equation 2). When the SO4 2- in the system is insufficient, the oxidized Fe 3+ will undergo hydrolysis to generate high-valent hydroxyl iron complex ions, while excessive H2SO4 will cause incomplete hydrolysis of Fe 3+ , thus reducing the polymerization degree of the product and deteriorating the flocculation effect. By adding iron oxide red, the excessive free sulfuric acid can be effectively neutralized to avoid incomplete hydrolysis.

[0033] Equation 1 Oxidation:

[0034] Equation 2 Hydrolysis:

[0035] Equation 3 Polymerization: mFe2(OH) n (SO4) 3-n / 2 =[Fe2(OH) n (SO4) 3-n / 2 m

[0036] The yellow ferrous and iron oxide red added in step (1) are industrial waste by-products, which contain more impurities. Among them, iron oxide red is produced after mixing yellow ferrous and sulfur to produce sulfuric acid, and its purity is about 55%. The impurity elements contained in it are the same as those in yellow ferrous, and no other additional impurities will be introduced. Some impurities such as SiO2 are insoluble in dilute acid, and their existence will affect the appearance of the product, making the prepared liquid product turbid and the insoluble matter content increase. Such impurities can be removed by filtration to purify the raw material liquid and improve the product quality. Some impurities are soluble and cannot be removed by filtration, making the total iron content of the prepared product slightly lower than that of the product prepared from pure substances, but its value still meets the requirements of first-class products in GB / T 14591-2016, and the product has a higher basicity and better polymerization effect.

[0037] The technical solutions of the present invention will be clearly and completely described below with specific examples. It should be understood that the described examples are only part of the examples of the present invention, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples of the present invention without creative efforts shall fall within the scope of the present invention.

[0038] Example 1

[0039] ​Ferrous sulfate (with 61% FeSO4·H2O content, the same below) and iron oxide red were added into the reaction kettle at a mass ratio of 1:0.06. The mass fraction of free acid in the solution was adjusted to 8% according to the water addition amount, and the mixture was stirred and reacted at 110 °C for 240 min. Hydrogen peroxide solution with a mass fraction of 30% was added dropwise to the system at a mass ratio of 1:0.4, and the mixture was stirred and reacted at 50 °C for 90 min. The obtained liquid product was concentrated and dried at 60 °C for 48 h to obtain solid polyferric sulfate.

[0040] Refer to the method specified in GB / T 14591-2016 to analyze the various indexes of the obtained solid product. Among them, the mass fraction of reducing substances (calculated as Fe 2+ is 0.013%, the mass fraction of total iron is 19.52%, and the basicity is 14.88%.

[0041] For the first-class solid polyferric sulfate specified in GB / T 14591-2016, the mass fraction of reducing substances (calculated as Fe 2+ should be ≤0.15%, the mass fraction of total iron should be ≥19.5%, and the basicity should be in the range of 8.0% - 16.0%.

[0042] Comparative Example 1

[0043] Ferrous sulfate was dissolved in a small amount of water, the mass fraction of free acid in the solution was adjusted to 8% according to the water addition amount, iron oxide red was not added additionally, hydrogen peroxide solution with a mass fraction of 30% was added dropwise to the system at a mass ratio of 1:0.4, and the mixture was stirred and reacted at 50 °C for 90 min. The obtained liquid product was concentrated and dried at 60 °C for 48 h to obtain solid polyferric sulfate.

[0044] Refer to the method specified in GB / T 14591-2016 to analyze the various indexes of the obtained solid product. Among them, the mass fraction of reducing substances (calculated as Fe 2+ is 0.011%, the mass fraction of total iron is 14.86%, and the basicity is -1.09%.

[0045] [[ID=2***4]]As Figure 2 shown, the solid polyferric sulfate obtained in Example 1 and Comparative Example 1 are both amorphous structures. By comparing the performance indexes of the two, it can be seen that the product obtained without adding iron oxide red does not meet the standards, and the total iron content and basicity of the product obtained after adding iron oxide red are significantly improved.

[0046] Comparative Example 2

[0047] Ferrous sulfate and iron oxide red were added to the reaction kettle at a mass ratio of 1:0.06. The mass fraction of free acid in the solution was adjusted to 8% according to the water addition amount, and the mixture was stirred and reacted at 90 °C for 240 min. A 30% (mass fraction) hydrogen peroxide solution was added dropwise to the system at a mass ratio of 1:0.4, and the mixture was stirred and reacted at 50 °C for 90 min. The obtained liquid product was concentrated and dried at 60 °C for 48 h to obtain solid polyferric sulfate.

[0048] The indicators of the obtained solid product were analyzed according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ was 0.016%, the mass fraction of total iron was 19.14%, and the basicity was 12.19%.

[0049] By comparing the performance indicators of the solid polyferric sulfate products obtained in Example 1 and Comparative Example 2, it can be seen that when the reaction temperature after adding iron oxide red is lower than the regulated range, the iron oxide red reacts incompletely, and the total iron content and basicity of the obtained product both decrease.

[0050] Comparative Example 3

[0051] Ferrous sulfate and iron oxide red were added to the reaction kettle at a mass ratio of 1:0.06. The mass fraction of free acid in the solution was adjusted to 6% according to the water addition amount, and the mixture was stirred and reacted at 110 °C for 240 min. A 30% (mass fraction) hydrogen peroxide solution was added dropwise to the system at a mass ratio of 1:0.4, and the mixture was stirred and reacted at 50 °C for 90 min. The obtained liquid product was concentrated and dried at 60 °C for 48 h to obtain solid polyferric sulfate.

[0052] The indicators of the obtained solid product were analyzed according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ was 0.014%, the mass fraction of total iron was 18.38%, and the basicity was 10.44%.

[0053] By comparing the performance indicators of the solid polyferric sulfate products obtained in Example 1 and Comparative Example 3, it can be seen that when the acid concentration of the ferrous sulfate aqueous solution is lower than the regulated range, the iron oxide red reacts incompletely, and the total iron content and basicity of the obtained product both decrease.

[0054] Comparative Example 4

[0055] 90% (mass fraction) FeSO4·H2O was added to a small amount of water to dissolve it. 98% (mass fraction) sulfuric acid was added to the system at a mass ratio of 1:0.16. A 30% (mass fraction) hydrogen peroxide solution was added dropwise to the system at a mass ratio of 1:0.4, and the mixture was stirred and reacted at 50 °C for 90 min. The obtained liquid product was concentrated and dried at 60 °C for 48 h to obtain solid polyferric sulfate.

[0056] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ is 0.010%, the mass fraction of total iron is 21.58%, and the basicity is 9.80%.

[0057] As Figure 2 shown, the obtained solid products of polyferric sulfate in Example 1 and Comparative Example 4 are both amorphous structures. By comparing the performance indicators of the two, it can be seen that the total iron content of the product prepared from ferrous yellow as the raw material decreases slightly, while the basicity increases significantly.

[0058] Example 2

[0059] Add ferrous yellow and iron oxide red into the reaction kettle according to the mass ratio of 1:0.08. Adjust the mass fraction of free acid in the solution to 10% according to the water addition amount, and stir and react at 120 °C for 300 min. Add sodium chlorate to the system according to the mass ratio of 1:0.07, stir and react at 40 °C for 60 min, and concentrate and dry the obtained liquid product at 70 °C for 36 h to obtain solid polyferric sulfate.

[0060] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ is 0.022%, the mass fraction of total iron is 19.82%, and the basicity is 15.38%.

[0061] Comparative Example 5

[0062] Dissolve ferrous yellow in a small amount of water, adjust the mass fraction of free acid in the solution to 10% according to the water addition amount, do not add iron oxide red additionally, add sodium chlorate to the system according to the mass ratio of 1:0.07, stir and react at 40 °C for 60 min, and concentrate and dry the obtained liquid product at 70 °C for 36 h to obtain solid polyferric sulfate.

[0063] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ is 0.013%, the mass fraction of total iron is 15.07%, and the basicity is 0.48%.

[0064] As Figure 3 shown, the obtained solid products of polyferric sulfate in Example 2 and Comparative Example 5 are both amorphous structures. By comparing the performance indicators of the two, it can be seen that the product obtained without adding iron oxide red does not meet the standards, and the total iron content and basicity of the product obtained after adding iron oxide red both increase significantly.

[0065] Comparative Example 6

[0066] Ferrous yellow and iron oxide red were added to the reaction kettle at a mass ratio of 1:0.08. The mass fraction of free acid in the solution was adjusted to 10% according to the water addition amount, and the mixture was stirred and reacted at 130 °C for 300 min. Sodium chlorate was added to the system at a mass ratio of 1:0.07, and the mixture was stirred and reacted at 40 °C for 60 min. The obtained liquid product was concentrated and dried at 70 °C for 36 h to obtain solid polyferric sulfate.

[0067] The indexes of the obtained solid product were analyzed according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ ) was 0.025%, the mass fraction of total iron was 19.40%, and the basicity was 12.45%.

[0068] By comparing the performance indexes of the solid product polyferric sulfate obtained in Example 2 and Comparative Example 6, it can be seen that when the reaction temperature after adding iron oxide red is higher than the regulated range, due to a large amount of water evaporation, the solution becomes too viscous, the iron oxide red reacts incompletely, and the total iron content and basicity of the obtained product both decrease.

[0069] Comparative Example 7

[0070] Ferrous yellow and iron oxide red were added to the reaction kettle at a mass ratio of 1:0.08. The mass fraction of free acid in the solution was adjusted to 14% according to the water addition amount, and the mixture was stirred and reacted at 120 °C for 300 min. Sodium chlorate was added to the system at a mass ratio of 1:0.07, and the mixture was stirred and reacted at 40 °C for 60 min. The obtained liquid product was concentrated and dried at 70 °C for 36 h to obtain solid polyferric sulfate.

[0071] The indexes of the obtained solid product were analyzed according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe 2+ ) was 0.023%, the mass fraction of total iron was 18.67%, and the basicity was 11.09%.

[0072] By comparing the performance indexes of the solid product polyferric sulfate obtained in Example 2 and Comparative Example 7, it can be seen that when the acid concentration of the ferrous yellow aqueous solution is higher than the regulated range, due to the decrease in the water addition amount, the solution becomes too viscous, the iron oxide red reacts incompletely, and the total iron content and basicity of the obtained product both decrease.

[0073] Comparative Example 8

[0074] Dissolve 90% (mass fraction) of FeSO4·H2O in a small amount of water, add 98% (mass fraction) sulfuric acid to the system according to a mass ratio of 1:0.16, add sodium chlorate to the system according to a mass ratio of 1:0.07, stir and react at 40 °C for 60 min, and concentrate and dry the obtained liquid product at 70 °C for 36 h to obtain solid polyferric sulfate.

[0075] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe) in the solid product is 0.012%, the mass fraction of total iron is 21.69%, and the basicity is 10.89%. 2+ The mass fraction of reducing substances (calculated as Fe) in the solid product is 0.012%, the mass fraction of total iron is 21.69%, and the basicity is 10.89%.

[0076] As Figure 3 shown, the solid polyferric sulfate products obtained in Example 2 and Comparative Example 8 are both amorphous structures. By comparing the performance indicators of the two, it can be seen that the total iron content of the product prepared from yellow ferrous sulfate as the raw material decreases slightly, while the basicity increases significantly.

[0077] Example 3

[0078] Add yellow ferrous sulfate and iron oxide red to the reaction kettle according to a mass ratio of 1:0.04, adjust the mass fraction of free acid in the solution to 12% according to the amount of water added, and stir and react at 100 °C for 180 min. Dropwise add 30% (mass fraction) hydrogen peroxide solution to the system according to a mass ratio of 1:0.8, stir and react at 60 °C for 100 min, and concentrate and dry the obtained liquid product at 80 °C for 24 h to obtain solid polyferric sulfate.

[0079] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe) in the solid product is 0.006%, the mass fraction of total iron is 19.66%, and the basicity is 14.76%. 2+ The mass fraction of reducing substances (calculated as Fe) in the solid product is 0.006%, the mass fraction of total iron is 19.66%, and the basicity is 14.76%.

[0080] Example 4

[0081] Add yellow ferrous sulfate and iron oxide red to the reaction kettle according to a mass ratio of 1:0.10, adjust the mass fraction of free acid in the solution to 9% according to the amount of water added, and stir and react at 115 °C for 210 min. Add potassium chlorate to the system according to a mass ratio of 1:0.05, stir and react at 40 °C for 80 min, and concentrate and dry the obtained liquid product at 60 °C for 48 h to obtain solid polyferric sulfate.

[0082] Analyze the various indicators of the obtained solid product according to the method specified in GB / T 14591-2016. Among them, the mass fraction of reducing substances (calculated as Fe) in the solid product is 0.006%, the mass fraction of total iron is 19.66%, and the basicity is 14.76%. 2+The mass fraction of total iron is 19.93%, and the basicity is 15.56%.

[0083] Example 5

[0084] Ferrous yellow and red iron oxide were added to a reactor at a mass ratio of 1:0.07. The free acid mass fraction in the solution was adjusted to 11% by the amount of water added, and the reaction was stirred at 105°C for 270 minutes. Sodium nitrite was added to the system at a mass ratio of 1:0.06, and the reaction was stirred at 60°C for 110 minutes. The resulting liquid product was concentrated and dried at 70°C for 36 hours to obtain solid polyferric sulfate.

[0085] The various indicators of the solid product obtained were analyzed according to the method specified in GB / T 14591-2016, among which the reducing substances of the solid product (Fe 2+ The mass fraction of total iron is 19.76%, and the basicity is 15.48%.

[0086] Example 6

[0087] Ferrous yellow and red iron oxide were added to a reactor at a mass ratio of 1:0.05. The free acid mass fraction in the solution was adjusted to 8% by the amount of water added, and the reaction was stirred at 110°C for 300 minutes. A 30% (mass fraction) hydrogen peroxide solution was added dropwise at a mass ratio of 1:0.5, and nitric acid was added dropwise at a mass ratio of 1:0.2. The reaction was stirred at 50°C for 100 minutes. The resulting liquid product was concentrated and dried at 60°C for 48 hours to obtain solid polyferric sulfate.

[0088] The various indicators of the solid product obtained were analyzed according to the method specified in GB / T 14591-2016, among which the reducing substances of the solid product (Fe 2+ The mass fraction of total iron is 19.62%, and the basicity is 14.98%.

[0089] Example 7

[0090] Ferrous yellow and red iron oxide were added to a reactor at a mass ratio of 1:0.09. The free acid mass fraction in the solution was adjusted to 10% by the amount of water added, and the reaction was stirred at 120°C for 180 minutes. Sodium chlorate and sodium hypochlorite were added to the system at a mass ratio of 1:0.06 and 1:0.02, respectively. The reaction was stirred at 60°C for 90 minutes. The resulting liquid product was concentrated and dried at 80°C for 24 hours to obtain solid polyferric sulfate.

[0091] The various indicators of the solid product obtained were analyzed according to the method specified in GB / T 14591-2016, among which the reducing substances of the solid product (Fe2+ The mass fraction of total iron is 19.89%, and the basicity is 15.45%.

[0092] The performance index data of the solid products obtained in the above examples and comparative examples are shown in the following table.

[0093]

[0094]

[0095] This application is described in detail for the purpose of enabling those skilled in the art to understand the contents of this application and implement them. This does not limit the scope of protection of this application. Any equivalent changes or modifications made according to the spirit of this application should be included in the scope of protection of this application.

Claims

1. A method for preparing polymeric ferric sulfate from solid waste yellow ferrous sulfate in a titanium dioxide plant, characterized in that, The method comprises the following steps: (1) Dissolve the raw material of yellow ferrous sulfate in water, add iron oxide red under heating conditions, stir until the reaction is complete, and then filter to remove insoluble impurities; (2) Add an oxidant to the filtrate obtained in step (1), heat and stir to carry out oxidation, hydrolysis and polymerization reactions to obtain a liquid product; (3) Concentrate and dry the liquid product obtained in step (2) to prepare solid polyferric sulfate; Wherein: in step (1), the mass fraction of free acid in the yellow ferrous sulfate solution is adjusted to 8% - 12%, the heating temperature is 100 - 120 °C, and the reaction time is 180 - 300 min; in step (2), the oxidant is selected from one or more of hydrogen peroxide, sodium chlorate, potassium chlorate, sodium nitrite, nitric acid, sodium hypochlorite; in step (2), the heating temperature is 40 - 60 °C, and the reaction time is 60 - 120 min.

2. The method for preparing polymeric ferric sulfate according to claim 1, wherein In step (1), the mass ratio of yellow ferrous sulfate to iron oxide red is 1:(0.04 - 0.10).

3. The method for preparing polymeric ferric sulfate according to claim 1, wherein When adding the oxidant hydrogen peroxide, the mass ratio of yellow ferrous sulfate to hydrogen peroxide is 1:(0.4 - 1.2); when adding the oxidant sodium chlorate, the mass ratio of yellow ferrous sulfate to sodium chlorate is 1:(0.05 - 0.08).

4. The method for preparing polymeric ferric sulfate according to claim 1, wherein When adding the oxidant hydrogen peroxide, the mass of hydrogen peroxide added per 5 - 10 min does not exceed 15% of the total mass; when adding the oxidant sodium chlorate, it is added in batches, and 20% - 25% of the total mass of the oxidant is added to the reaction system at intervals of 3 - 5 min.

5. The method for preparing polymeric ferric sulfate according to claim 1, wherein In step (3), the concentration and drying temperature is 60 - 80 °C, and the time is 24 - 48 h.

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