CN112897594A - Method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge - Google Patents
Method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge Download PDFInfo
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- CN112897594A CN112897594A CN202110355096.3A CN202110355096A CN112897594A CN 112897594 A CN112897594 A CN 112897594A CN 202110355096 A CN202110355096 A CN 202110355096A CN 112897594 A CN112897594 A CN 112897594A
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide (Fe2O3)
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/20—Silicates
- C01B33/32—Alkali metal silicates
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- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
Abstract
The invention discloses a method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge, belonging to the technical field of waste recycling and environment protection. Firstly, calcining the water-containing desiliconized sludge at high temperature for dechlorination and grinding, then adding a sodium hydroxide solution for hydrothermal reaction, dehydrating to obtain a sodium disilicate solution and an iron oxide red precipitate, washing and drying an iron oxide red filter cake for multiple times to obtain iron oxide red powder, adding an auxiliary agent into the sodium disilicate solution, and evaporating, drying and calcining to obtain sodium disilicate crystals. The invention adopts a one-step method for mold adjustment to directly synthesize the sodium disilicate mother liquor, realizes the dissolution and separation of silicon in iron oxide red and the synchronous synthesis of the sodium disilicate, simultaneously utilizes aluminum impurities contained in desiliconized sludge to dissolve out silicon while alkali dissolves out the silicon and enters the sodium disilicate mother liquor, and improves the performance of the synthesized layered sodium disilicate.
Description
Technical Field
The invention relates to a method for synchronously synthesizing layered sodium disilicate by preparing iron oxide red from industrial wastes, belonging to the technical field of waste recycling and high-efficiency utilization and environmental protection.
Background
Before the hot rolled steel strip is subjected to the cold rolling process, the iron and steel enterprises usually go through an acid pickling process to remove iron oxide scales, oil stains and dirt on the surface of the steel. Hydrochloric acid pickling has become a mainstream technology in steel strip pickling because of its characteristics of high speed, easy acid regeneration, low cost and the like. The pickling waste liquid can be regenerated: after the reaction in iron dissolving tank, adding 20% ammonia water to regulate pH value to raise pH value of waste acid to 2.5-4, at the same time introducing compressed air to oxidize ferrous iron into ferric iron and produce Fe (OH)3Floc of SiO in solution2And (2) coating, adding polyacrylamide, separating in a sedimentation tank to remove silicon impurities in the waste acid, and dehydrating the generated sediment to obtain desiliconized sludge which mainly comprises iron, silicon, chlorine and the like, possibly contains heavy metals based on the properties of steel, has strong acidity and belongs to dangerous waste. Nearly ten thousand tons of desiliconized sludge are discharged every year from a large cold rolling mill, and the desiliconized sludge is usually subjected to landfill treatment.
For example, chinese patent application No. 201210359797.5, published as 2013, 1, 9, discloses a method for preparing ultra-fine iron oxide red from acid-regenerated desilicated mud cake. According to the patent, the desiliconized mud cake is subjected to pulping, drying, calcining, grinding and sieving to prepare the iron oxide red with uniform granularity, good quality and low cost, but the silicon removal process is not adopted in the preparation process, so that the obtained iron oxide red has high silicon content and low quality.
For another example, chinese patent application No. 201410083054.9, published as 2014, 3, 7 discloses a post-desiliconization method of iron oxide powder as a byproduct of regeneration of pickling waste liquid in steel plant. According to the method, the water glass in the suction filtration waste liquid is recovered while the iron oxide red product is prepared through roasting, alkaline leaching, washing and suction filtration, silicon in the desiliconized sludge is utilized to reduce the content of impurity silicon in iron oxide powder to obtain high-purity iron oxide powder, the silicon content of the iron oxide powder can be reduced to 0.005-0.008%, the method is used for desiliconizing the regenerated iron oxide red powder, although the purity of the iron oxide powder is improved, the silicon content in the iron oxide powder is originally low, the concentration of the produced water glass is low, and the re-concentration cost is high.
In 2019, 01, 15 days, 55-57 pages in 2019, 01 th period of 2019, Zhu Cheng et al disclose an article named as a research on a desiliconized sludge treatment method, the article is prepared by adding a solvent to desiliconized sludge for dissolution, heating for aeration and oxidation, then adjusting the pH value to 8 to precipitate iron ions which are not precipitated, adding a flocculating agent, and passing the precipitated iron ions through a solid-liquid separation device to prepare light yellow powdered iron oxide. However, because the iron hydroxide gel generated by hydrolysis is easy to wrap a large amount of water, the chloride ions in the iron hydroxide gel can meet the requirements after being washed for many times, and a large amount of wastewater needing secondary treatment is generated in the washing process; the method described in this paper still contains 0.9% of chloride ions after multiple washing, and cannot meet the requirements for iron making.
In 2016, 11 months, volume 48, 11 th stage, pages 41-43 of inorganic salt industry, Van Jiali et al disclose an article named 'synthetic research on high-performance layered sodium disilicate', explore the process rule of preparing high-calcium magnesium ion exchange capacity layered sodium disilicate by adding an auxiliary agent (KCl), and characterize the product by means of an X-ray diffractometer (XRD), infrared (FT-IR) and the like. The research result shows that: addition of KCl [ n (K): (Si) ═ 0.015] and calcination at 680 ℃ for 0.5h gave layered sodium disilicate having high calcium-magnesium exchange capacity (360 mg/g and 430mg/g, respectively). However, in this reaction, sodium disilicate is obtained by adding silica gel to sodium silicate and adjusting the mold, and if silica gel is replaced by siliceous sludge, sodium disilicate is difficult to separate.
Therefore, how to fully extract effective resources in the desiliconized sludge requires a method for synchronously preparing iron oxide red and sodium disilicate by utilizing the desiliconized sludge.
Disclosure of Invention
1. Problems to be solved
In order to fully utilize the resources of the desiliconized sludge, the invention provides a method for synchronously preparing iron oxide red and sodium disilicate by utilizing the desiliconized sludge, which utilizes the characteristic that the desiliconized sludge contains iron and silicon at the same time, utilizes aluminum impurities in the desiliconized sludge, directly prepares sodium disilicate liquid by adding alkali, simultaneously removes the silicon in the desiliconized sludge to obtain high-purity iron oxide red, and obtains amorphous sodium disilicate crystals by adding an auxiliary agent to the obtained sodium disilicate liquid for crystallization.
The invention can synthesize two products simultaneously by utilizing desiliconized sludge, the concentration of the synthesized sodium disilicate is high, the layered crystal sodium disilicate is obtained by calcining and crystallizing amorphous sodium disilicate, and the cost of the prepared layered sodium disilicate crystal is low.
2. Technical scheme
In order to solve the problems, the technical scheme adopted by the invention is as follows:
a method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge comprises the following steps: calcining the desiliconized sludge containing water for dechlorination, adding NaOH solution for hydrothermal reaction, dehydrating, washing filter cakes with hot water to obtain iron oxide red, adding KCl into filtrate for reaction, then evaporating to dryness, and drying to obtain amorphous sodium disilicate, wherein the water content in the desiliconized sludge is a necessary condition for decomposing to form hydrogen chloride in the calcining process, and is generally controlled to be more than 15% so as to ensure that HCl can be generated.
Further, the desiliconized sludge calcination dechlorination step comprises the following steps: and extruding and molding the desiliconized sludge, and calcining, wherein the shape of the extrusion molding is not limited, and can be spherical, columnar and the like, the calcining temperature is 600-750 ℃, and the calcining time is 0.5-2 h.
Further, the desiliconized sludge after calcination and dechlorination is ground to a powder with a screen residue not more than 10% when passing through a square-hole screen with the thickness of 0.08 mm; the ball mill, the vibration mill and the like can be used for grinding; after grinding, more than 90 percent of the calcined desiliconized sludge can pass through a 0.08mm square-hole sieve, so that the contact area of the calcined desiliconized sludge is increased by grinding, and the hydrothermal reaction of the subsequent NaOH and the calcined desiliconized sludge is facilitated.
Further, in the hydrothermal reaction, SiO in the desiliconized sludge participating in the reaction2The molar ratio of the NaOH to the NaOH is 1 (1-1.05); this is done in stoichiometric proportions of sodium and silicon in sodium disilicate of the formula Na2O·2SiO2The modulus is 2, most of the components are synthesized according to NaOH and SiO2The chemical equation of the hydrothermal reaction is shown as follows:
2NaOH+nSiO2＝Na2O·nSiO2+H2O
the sodium disilicate refers to sodium silicate (or called water glass) with the modulus n being 2 or close to 2, namely the value of n is 2-2.1; meanwhile, aluminum impurities contained in the desiliconized sludge are dissolved out while silicon is dissolved out by alkali and enter sodium disilicate mother liquor to form Al-Na2Si2O5The water stability of the layered sodium disilicate can be improved.
Further, in the hydrothermal reaction, the temperature of the hydrothermal reaction is 150-200 ℃, the reaction time is 60-120 min, water is added to make the solid-liquid ratio reach 1 (3-10), the solid-liquid ratio is higher than 1:3, the concentration of solid matters is too high, and the separation after the reaction is difficult; less than 1:10, resulting in low concentration of the synthesized sodium disilicate mother liquor, and increased subsequent drying cost.
Further, the dehydration after the hydrothermal reaction may be performed by a centrifugal dehydrator, a plate-and-frame filter press, or a vacuum dehydrator.
Further, after dehydration, washing the filter cake with hot water at 50-75 ℃ for 4-6 times to obtain iron oxide red; and drying and grinding to obtain iron oxide red powder, washing with hot water is favorable for washing off sodium disilicate solution mixed in the dehydrated filter cake, and the hot water washing accelerates the washing speed and improves the washing effect.
Furthermore, KCl is added into the filtrate generated in the dehydration process, and can induce the crystal phase to be changed from alpha type to delta type, so that the purity of the delta phase is increased, and the calcium-magnesium exchange capacity is improved; the molar ratio of K element in the added KCl to Si element in the filtrate is n (K) and n (Si) is 0.015-0.020, and then the mixture reacts for 1.5-3 h at the temperature of 40-55 ℃ while stirring, wherein the stirring speed is 150-250 rpm; then the sodium disilicate is evaporated to be viscous and is sent into drying equipment to be dried at the temperature of 120-150 ℃ to obtain the amorphous sodium disilicate.
Further, calcining and crystallizing the amorphous sodium disilicate at high temperature to obtain the layered crystalline sodium disilicate.
Further, the calcination temperature of the amorphous sodium disilicate is 600-800 ℃, and the calcination time is 25-45 min; the calcined massive material is layered crystal sodium disilicate, and the calcined sodium disilicate is ground into 80-micron square-hole sieve with the screen residue of less than 10 percent and can be ground into different particle sizes according to the use requirement.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the method for synchronously preparing the iron oxide red and the sodium disilicate by utilizing the desiliconized sludge, the adopted method for directly calcining the desiliconized sludge is used for dechlorinating, so that the efficiency is high, the content of residual chlorine is very low, and the desiliconized sludge can be directly used as an iron-making raw material to be mixed into sinter; compared with the washing aeration process for dechlorination, the method has better calcination dechlorination effect, the hydrogen chloride gas generated by high-temperature calcination can be recycled by a recovery device to generate hydrochloric acid for returning to be used for cleaning, the content of chloride ions in the iron oxide red can be reduced to be below 0.01% by calcination dechlorination, and the washing cannot be generally reduced; meanwhile, in the calcining process, ferric hydroxide in the sludge can be decomposed to form ferric oxide, ferric chloride or ferrous chloride can be decomposed to form ferric oxide and hydrogen chloride gas under the action of water, and the hydrogen chloride gas can be recycled;
(2) according to the invention, the one-step method is adopted for mold adjustment, the sodium disilicate mother liquor is directly synthesized, the dissolving separation of silicon in iron oxide red and the synchronous synthesis of sodium disilicate are realized, and meanwhile, aluminum impurities contained in desiliconized sludge are utilized to dissolve out silicon while alkali is dissolved out and enter the sodium disilicate mother liquor, so that the performance of the synthesized layered sodium disilicate is improved;
(3) the invention utilizes high-temperature calcination to generate iron oxide red, and simultaneously chlorine in the desiliconized sludge generates hydrogen chloride gas under the action of moisture, and the hydrogen chloride gas can be prepared by further recycling; after high-temperature calcination, the iron oxide red and the silicon dioxide are adhered together and cannot be directly separated, and the directly separated iron oxide red has high impurity content and poor quality; the iron oxide red enters the subsequent hydrothermal reaction along with other substances, so that the purity of the iron oxide red can be improved to a certain extent in the hydrothermal reaction, and the iron oxide red after the hydrothermal reaction is more bright in color; the silicon in the iron oxide red is decomposed by alkali dissolution, the silicon content in the iron oxide red can be reduced to be below 0.1 percent, the grade of the iron oxide red is improved, impurities in the iron oxide red are removed, and the iron oxide red is beneficial to utilization of the iron oxide red;
(4) according to the method for synchronously preparing the iron oxide red and the sodium disilicate by utilizing the desiliconized sludge, the sodium disilicate is directly synthesized by utilizing the solution formed by alkali dissolution while the alkali dissolution is carried out, and meanwhile, the performance of the formed sodium disilicate is improved by utilizing the aluminum impurities of the desiliconized sludge and the added auxiliary agent, so that the water softening capacity of the sodium disilicate is stronger;
(5) according to the method for synchronously preparing the iron oxide red and the sodium disilicate by utilizing the desiliconized sludge, the sodium disilicate is directly synthesized while silicon in the desiliconized sludge is separated, and the high-purity iron oxide red powder is obtained, so that the synthesis process is reduced, the environmental pollution is avoided, and the full utilization of the desiliconized sludge is realized.
Drawings
FIG. 1 is an XRD pattern of iron oxide red prepared in example 1;
FIG. 2 is a schematic electron microscope of sodium disilicate prepared in example 1.
Detailed Description
The invention is further described with reference to specific examples.
Example 1
The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge comprises the following steps:
1. the desiliconized sludge in the steel plant is extruded into balls and then is put into a muffle furnace for roasting, wherein the roasting temperature is 600 ℃, and the heat preservation time is 2 hours. Then the desiliconized sludge after calcination and dechlorination is ground, and the granularity of the ground powder requires 5.2 percent of the residue of a square-hole sieve with the granularity of 0.08 mm.
2. The milled desiliconized sludge contains SiO2Taking 100g of the mixture with the mass content of 25.48 percent, putting the mixture into a high-pressure reaction kettle, and adding 40 percent of sodium hydroxide into the high-pressure reaction kettle40.5ml of solution with a molar ratio of n (Na)2O):n(SiO2) Adding water until the solid-to-liquid ratio is 1:2.1, carrying out hydrothermal reaction in a high-pressure reaction kettle at 200 ℃ for 60min, and fully reacting and leaching silicon dioxide in the iron oxide powder with alkali liquor.
3. And (3) dehydrating the alkaline leaching solution after the hydrothermal reaction, wherein the dehydration equipment can be a centrifugal dehydrator, and washing the dehydrated filter cake with hot water at 50 ℃ for 6 times, drying and drying to obtain the iron oxide red. The silicon content of the iron oxide powder after the silicon removal is 0.06%, and XRD analysis of the solid after the silicon removal is shown in figure 1, which shows that the iron oxide powder is red iron oxide and has very high purity.
4. Adding 0.4746g of potassium chloride auxiliary agent into the dehydrated filtrate, wherein the molar ratio of K element in KCl to Si in the filtrate is n (K) to n (Si) is 0.015, reacting the filtrate at 40 ℃ for 3h, stirring at the same time at the speed of 150rpm, evaporating to be viscous, sending into a drying box, drying at the temperature of 120 ℃, evaporating to dryness, and drying to obtain amorphous sodium disilicate.
5. Calcining the amorphous sodium disilicate obtained after drying at the high temperature of 600 ℃ for 45min, and cooling to obtain layered crystalline sodium disilicate; fig. 2 is a schematic electron microscope showing sodium disilicate, and it can be seen that the synthesized sodium disilicate is layered.
The exchange capacity of the obtained layered crystal calcium magnesium disilicate is 385mg/g and 410mg/g respectively, which are larger than 300mg/g and 370mg/g specified by the national standard GB/T20214-2006.
Example 2
The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge comprises the following steps:
1. the desiliconized sludge in the steel plant is extruded into balls and then is put into a muffle furnace for roasting, wherein the roasting temperature is 650 ℃, and the heat preservation time is 1.5 h. Then the desiliconized sludge after calcination and dechlorination is ground, and the granularity of the ground powder requires 7.3 percent of the residue of a square-hole sieve with the granularity of 0.08 mm.
2. The milled desiliconized sludge contains SiO275g of the mixture with the mass content of 27.72 percent is put into a high-pressure reaction kettle, and 45.1ml of 30 percent sodium hydroxide solution with the molar ratio of n (Na) is added into the high-pressure reaction kettle2O):n(SiO2)＝1:2.05，Then adding water until the solid-to-liquid ratio is 1:10, and carrying out hydrothermal reaction in a high-pressure reaction kettle at 180 ℃ for 100min to ensure that the silicon dioxide in the iron oxide powder is fully reacted and leached with alkali liquor.
3. And (3) dehydrating the alkaline leaching solution after the hydrothermal reaction, wherein the dehydration equipment can be a plate-and-frame dehydrator, and washing the dehydrated filter cake with hot water at 75 ℃ for 6 times, drying and drying to obtain the iron oxide red. The silicon content in the iron oxide powder after silicon removal is 0.052%.
4. 0.4130g of potassium chloride assistant is added into the dehydrated filtrate, the amount of the KCl assistant is n (K) which is the molar ratio of K element in KCl to Si in the filtrate, n (Si) is 0.016, the filtrate reacts for 2h at 45 ℃, the stirring speed is 200rpm, the filtrate is evaporated to be viscous and is sent into a drying box, the drying temperature is 150 ℃, the filtrate is evaporated to dryness, and amorphous sodium disilicate is obtained after drying.
5. Calcining the amorphous sodium disilicate obtained after drying at the high temperature of 700 ℃ for 30min, and cooling to obtain the layered crystalline sodium disilicate.
6. The obtained layered crystal calcium magnesium silicate sodium has the exchange capacity of 386mg/g and 404mg/g respectively, which is more than 300mg/g and 370mg/g specified in the national standard GB/T20214-2006.
Example 3
The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge comprises the following steps:
1. the desiliconized sludge in the steel plant is extruded into a rod shape and is put into a muffle furnace for roasting, wherein the roasting temperature is 700 ℃, and the heat preservation time is 1 h. Then the desiliconized sludge after calcination and dechlorination is ground, and the granularity of the ground powder is required to be 4.9 percent of the residue of a square-hole sieve with the granularity of 0.08 mm.
2. The ground desiliconized sludge contains SiO2Taking 100g of the powder with the mass content of 26.13 percent, putting the powder into a high-pressure reaction kettle, and adding 87.1ml of 20 percent sodium hydroxide solution with the molar ratio of n (Na)2O):n(SiO2) Adding water to the mixture until the solid-to-liquid ratio is 1:2, and carrying out hydrothermal reaction in a high-pressure reaction kettle at 170 ℃ for 100min to ensure that the silicon dioxide in the iron oxide powder is fully reacted and leached with alkali liquor.
3. And (3) dehydrating the alkaline leaching solution after the hydrothermal reaction, wherein the dehydration equipment can be a plate-and-frame dehydrator, and washing a filter cake after dehydration by hot water at 60 ℃ for 5 times, drying and drying to obtain the iron oxide red. The silicon content in the iron oxide powder after silicon removal is 0.07%.
4. Adding 0.5516g of potassium chloride auxiliary agent into the dehydrated filtrate, wherein the molar ratio of K element in KCl to Si in the filtrate is n (K) to n (Si) 0.017, reacting the filtrate at 55 ℃ for 1.5h, stirring at the same time at the stirring speed of 200rpm, evaporating to be viscous, sending into a drying box, drying at the temperature of 130 ℃, evaporating to dryness, and drying to obtain the amorphous sodium disilicate.
5. Calcining the amorphous sodium disilicate obtained after drying at the high temperature of 700 ℃ for 30min, and cooling to obtain the layered crystalline sodium disilicate.
6. The obtained layered crystal calcium magnesium disilicate has the exchange capacity of 396mg/g and 415mg/g respectively, which is more than 300mg/g and 370mg/g specified in the national standard GB/T20214-2006.
Example 4
The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge comprises the following steps:
1. the desiliconized sludge in the steel plant is extruded into balls and then is put into a muffle furnace for roasting, wherein the roasting temperature is 750 ℃, and the heat preservation time is 0.5 h. Then the desiliconized sludge after calcination and dechlorination is ground, and the granularity of the ground powder requires 8.7 percent of the residue of a square-hole sieve with the granularity of 0.08 mm.
2. The ground desiliconized sludge contains SiO2Taking 50g of the mixture with the mass content of 27.72 percent, putting the mixture into a high-pressure reaction kettle, and adding 22.6ml of 40 percent sodium hydroxide solution into the high-pressure reaction kettle according to the mol ratio of n (Na)2O):n(SiO2) Adding water until the solid-to-liquid ratio is 1:2.05, carrying out hydrothermal reaction in a high-pressure reaction kettle at 150 ℃ for 120min to ensure that the silicon dioxide in the iron oxide powder is fully reacted and leached with alkali liquor.
3. And (3) dehydrating the alkaline leaching solution after the hydrothermal reaction, wherein the dehydration equipment can be a vacuum frame dehydrator, and washing the dehydrated filter cake with hot water at 75 ℃ for 4 times, drying and drying to obtain the iron oxide red. The silicon content in the iron oxide powder after silicon removal is 0.092%.
4. Adding 0.3442g of potassium chloride auxiliary agent into the dehydrated filtrate, wherein the molar ratio of K element in KCl to Si in the filtrate is n (K) to n (Si) 0.020, reacting the filtrate at 50 ℃ for 1.5h, stirring at the same time at the speed of 250rpm, evaporating to be viscous, sending into a drying box, drying at the temperature of 130 ℃, evaporating to dryness, and drying to obtain the amorphous sodium disilicate.
5. Calcining the amorphous sodium disilicate obtained after drying at the high temperature of 800 ℃ for 25min, and cooling to obtain the layered crystalline sodium disilicate.
6. The obtained layered crystal calcium magnesium disilicate has the exchange capacity of 387mg/g and 425mg/g respectively, which is more than 300mg/g and 370mg/g specified by the national standard GB/T20214-2006.
Comparative example
Taking a 40% sodium silicate aqueous solution with the modulus of 3.1, and adding sodium hydroxide to adjust the modulus to 2.0-2.1. Adding an auxiliary agent KCl for reaction, wherein the molar ratio of K element in KCl to Si in filtrate is n (K) to n (Si) 0.015, reacting at 50 ℃ for 2 hours, drying in a drying oven at 140-200 ℃ to obtain amorphous sodium disilicate, transferring into a muffle furnace, and calcining and crystallizing at 700 ℃ for a certain time to obtain the product. The calcium magnesium silicate of the lamellar crystal is measured to have the exchange capacity of 357mg/g and 397mg/g respectively. It can be seen that the performance of the layered crystalline sodium disilicate prepared by the method is better.
The present invention and the embodiments thereof have been described in an illustrative manner, and the description is not intended to be limiting, so that those skilled in the art should be able to devise technical solutions and embodiments similar to the technical solutions without departing from the spirit of the present invention.
Claims (9)
1. A method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge is characterized by comprising the following steps: the method comprises the following steps: calcining the desiliconized sludge containing water for dechlorination, adding NaOH solution for hydrothermal reaction, dehydrating, washing a filter cake with hot water to obtain iron oxide red, adding KCl into filtrate for reaction, evaporating to dryness, and drying to obtain amorphous sodium disilicate.
2. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: the desiliconized sludge calcination dechlorination method comprises the following steps: and extruding and molding the desiliconized sludge, and calcining at the temperature of 600-750 ℃ for 0.5-2 h.
3. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: the residue of the calcined and dechlorinated desiliconized sludge is not more than 10 percent when the calcined and dechlorinated desiliconized sludge is ground to pass through a square-hole sieve with the diameter of 0.08 mm.
4. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: in the hydrothermal reaction, SiO in desiliconized sludge participating in the reaction2The molar ratio of the NaOH to the NaOH is 1 (1-1.05).
5. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: in the hydrothermal reaction, water is added to enable the solid-liquid ratio to reach 1 (3-10), the temperature of the hydrothermal reaction is 150-200 ℃, and the reaction time is 60-120 min.
6. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: washing the filter cake with hot water at 50-75 deg.c for 4-6 times to obtain iron oxide red.
7. The method for synchronously preparing iron oxide red and sodium disilicate by utilizing desiliconized sludge according to claim 1, characterized in that: in the filtrate, the molar ratio of KCl to Si in the filtrate is n (K) and n (Si) is 0.015-0.020, and then the filtrate is reacted for 1.5-3 h at the temperature of 40-55 ℃ while stirring, wherein the stirring speed is 150-250 rpm; and then the sodium disilicate is evaporated to be viscous and is sent into drying equipment to be dried at 120-150 ℃ to obtain the amorphous sodium disilicate.
8. The method for synchronously preparing iron oxide red and sodium disilicate by using desiliconized sludge according to any one of claims 1 to 7, characterized in that: and calcining and crystallizing the amorphous sodium disilicate at high temperature to obtain the layered crystalline sodium disilicate.
9. The method for synchronously preparing iron oxide red and sodium disilicate by using desiliconized sludge according to claim 8, characterized in that: the calcination temperature of the amorphous sodium disilicate is 600-800 ℃, and the calcination time is 25-45 min.
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