Preparation method of solid polysilicate aluminum ferric

Abstract

The invention discloses a preparation method of solid polysilicate aluminum ferric, and belongs to the technical field of water treatment. The method comprises the following steps: adding a composite curing agent which is a mixture of polyacrylamide and glycine into cured liquid polyaluminum ferric silicate, uniformly stirring, and drying to obtain solid polyaluminum ferric silicate. The preparation method of the liquid-state polysilicate aluminum ferric comprises the steps that secondary lead smelting slag is sequentially subjected to hydrochloric acid leaching and solid-liquid separation to obtain a leaching solution, the pH value of the leaching solution is adjusted to 2.0-3.0, and then the liquid-state polysilicate aluminum ferric is obtained after polymerization curing. The invention aims to obtain the solid polysilicate aluminum ferric product with good water solubility and flocculation effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of water treatment, and more particularly relates to a preparation method of solid-state polysilicate aluminum iron. BACKGROUND

[0002] Polysilicate aluminum iron is a new type of inorganic polymer flocculant. It combines the excellent performance of polysilicate, polyaluminum and polyiron, and simultaneously plays the synergistic effect of electric neutralization and adsorption bridging, showing broad application prospects in water treatment. Compared with traditional aluminum salt and iron salt flocculants, polysilicate aluminum iron has the advantages of fast flocculation, high density, fast settling speed, wide pH range, low residual aluminum content in treated water, etc.

[0003] Compared with liquid products, solid-state polysilicate aluminum iron is more convenient to store and transport, and has higher stability, and is especially suitable for intermittent, distributed or emergency water treatment scenarios. However, the preparation process of solid-state polysilicate aluminum iron still faces several key technical difficulties, which restricts the improvement of product quality and the expansion of large-scale application.

[0004] At present, the common preparation methods of polysilicate aluminum iron mainly include direct chemical synthesis method and waste resource utilization method. However, no matter which raw material route is adopted, the conversion (solidification) process of liquid polysilicate aluminum iron precursor to stable solid-state product exists the challenge of structure destruction in the drying process. That is, if the temperature control is not proper (for example, too high or too fast heating), the product surface may be crusty, the internal moisture may evaporate rapidly, and the pore collapse or cracking may be caused, which destroys the high molecular network structure, and finally affects the solubility and flocculation activity of the solid-state product.

[0005] For example, the patent application file with the patent application number 202110539163.7 and the application publication date of September 7, 2021 discloses a polysilicate aluminum iron flocculant and its preparation method and application. The preparation method mixes a silicon source solution with sulfuric acid to a pH value of 2-4, activates to obtain a polysilicate solution, sequentially adds aluminum salt and trivalent iron salt to the polysilicate solution to obtain a reaction solution, ages to obtain the polysilicate aluminum iron flocculant, and then performs post-treatment to dry the aged reaction solution to obtain solid-state polysilicate aluminum iron. This method uses low-temperature drying to obtain solid-state product, avoiding the problem of high-temperature rapid gelation. However, because the drying temperature is low, the required time is long, and the problem of gelation in the long-time heating and drying process cannot be avoided.

[0006] For another example, the patent application file with the patent application number 202210800317.8 and the application publication date of July 8, 2022 discloses a polysilicate aluminum iron flocculant for treating indigo wastewater and its preparation method and application. The preparation method includes the following steps: S1: spraying a silicic acid sol to activated Al Silicon was obtained by stirring and bubbling in an aqueous Fe solution. aluminum Iron solution; S2: then to silicon aluminum A sodium carbonate aqueous solution is added to an iron solution to obtain a brown polyaluminum-iron polysilicate sol; S3: The brown polyaluminum-iron polysilicate sol is then freeze-dried under vacuum to obtain the polyaluminum-iron polysilicate flocculant. This method obtains a solid product through vacuum freezing, but it requires sophisticated equipment, is costly, and is economically impractical.

[0007] Therefore, there is an urgent need to develop a method for preparing solid aluminum ferrosilicon. Summary of the Invention

[0008] 1. The problem to be solved The purpose of this invention is to provide a method for preparing solid aluminum ferric silicate, which aims to obtain a solid product with good water solubility and flocculation effect.

[0009] 2. Technical Solution To solve the above problems, the technical solution adopted by the present invention is as follows: According to the purpose of this invention, a method for preparing solid polyaluminum ferrosilicon is provided, comprising the following steps: adding a composite curing agent to the cured liquid polyaluminum ferrosilicon, stirring evenly and then drying to obtain solid polyaluminum ferrosilicon, wherein the composite curing agent is a mixture of polyacrylamide and glycine.

[0010] Under the above technical solution, at room temperature, the silicic acid in liquid aluminum silicate will spontaneously undergo a slow polymerization reaction until it gels and fails. During the drying process of liquid aluminum silicate, heating accelerates the polymerization reaction. Therefore, to inhibit polymerization during the drying process of liquid aluminum silicate, a mixture of polyacrylamide and glycine is added as a composite curing agent to participate in the drying process, producing a synergistic effect to jointly inhibit the polymerization of liquid aluminum silicate. Specifically, polyacrylamide can form a network structure to encapsulate H3SiO4. - The polymerization of glycine is inhibited, while the acid-base fluctuations of the system caused by the polymerization reaction can be slowed down, thereby inhibiting polymerization. The combined effect of these two factors ensures that the product will not prematurely gel and fail during the drying process.

[0011] As one possible implementation, in the composite curing agent, the mass ratio of polyacrylamide to glycine is (1... 3) : 500. Below this range, the solidification effect is poor; above this range, the flocculation effect is affected, and it is not conducive to cost control.

[0012] As one possible implementation, to prevent uneven dissolution of polyacrylamide, the polyacrylamide is pre-dissolved in water, preferably with a mass fraction of 0.2 wt% for the polyacrylamide solution, wherein the mass ratio of the 0.2 wt% polyacrylamide solution to glycine is (1~3):1.

[0013] When using the above technical solution, polyacrylamide is first dissolved into a polyacrylamide solution, glycine is added to the polyacrylamide solution in solid form, and finally added to the liquid polyaluminum iron silicate in solution form.

[0014] As one possible approach, the ratio of the amount of composite curing agent added to liquid aluminum silicate iron is 0.01~0.05 g / mL.

[0015] As one possible implementation, the preferred drying temperature is 50~60℃ and the drying time is 6~10 h.

[0016] As one possible implementation, in the composite curing agent, the mass ratio of 0.2 wt% polyacrylamide solution to glycine is 2:1, the ratio of the amount of composite curing agent added to liquid aluminum ferric silicate is 0.03 g / mL, the drying temperature is 50℃, and the drying time is 8 h.

[0017] As one possible implementation, the molecular weight of polyacrylamide is 10 million to 30 million.

[0018] As one possible implementation, the preparation method of the liquid polyaluminum ferrosilicon is as follows: the recycled lead smelting slag is successively leached with hydrochloric acid and separated into solid and liquid to obtain a leachate. The pH value of the leachate is adjusted to 2.0~3.0, and then polymerized and matured to obtain liquid polyaluminum ferrosilicon.

[0019] As one possible implementation, in the preparation method of liquid polyaluminum ferrosilicon, the recycled lead smelting slag is a waste product discharged during the pyrometallurgical recycling of lead-containing solid waste such as waste lead-acid batteries.

[0020] As one possible implementation, in the preparation method of liquid polyaluminum ferrosilicon, the particle size of the recycled lead smelting slag is at least 100 mesh.

[0021] As one possible implementation, in the preparation method of liquid polyaluminum iron silicate, the molar concentration of hydrochloric acid is 1.5~2.5 mol / L, the solid-liquid ratio in hydrochloric acid leaching is 1:(20~50) g / mL, the leaching temperature is 20~40℃, and the leaching time is 10~180 min.

[0022] As one possible implementation, in the preparation method of liquid polyaluminum iron silicate, the molar concentration of hydrochloric acid is 2 mol / L, the solid-liquid ratio in hydrochloric acid leaching is 1:30 g / mL, the leaching temperature is 20℃, and the leaching time is 30 min.

[0023] As one possible implementation, in the preparation method of liquid aluminum ferrosilicon, the pH value of the leachate is adjusted to 2.5.

[0024] As one possible implementation, in the preparation method of liquid polyaluminum iron silicate, the polymerization and curing process involves a curing temperature of 20-40°C and a curing time of 1-8 h.

[0025] As one possible implementation, in the preparation method of liquid polyaluminum iron silicate, the polymerization and curing process involves a curing temperature of 20°C and a curing time of 2 hours.

[0026] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a method for preparing solid polyaluminum iron silicate. Before drying liquid polyaluminum iron silicate, a composite curing agent is added and dissolved in it. This can effectively prevent silica from gelling prematurely during the long drying process at medium and low temperatures. It eliminates the need for complex curing equipment with strict requirements and high energy consumption, thereby simplifying the production process and reducing product costs. The resulting solid product does not gel at low temperatures, has good stability, and is convenient for storage and transportation.

[0027] (2) The method for preparing solid polyaluminum ferrosilicon of the present invention also provides a new way for the resource utilization of recycled lead smelting slag. The recycled lead smelting slag is water-quenched slag. After adding hydrochloric acid, the main components of the slag, iron, silicon and aluminum, will enter the liquid phase. Adjusting the pH value will make Fe 3+ Al 3+ With H3SiO4 － They undergo a polymerization reaction together, and after maturation, they form liquid polyaluminum iron silicate. Attached Figure Description

[0028] Figure 1 The image shows the infrared spectrum of polyacrylamide. Figure 2 The infrared spectrum of glycine; Figure 3 The infrared spectrum of polyaluminum iron silicate before drying in Comparative Example 1; Figure 4 The infrared spectrum of polyaluminum iron silicate + polyacrylamide after drying in Comparative Example 2; Figure 5 The infrared spectrum of polyaluminum iron silicate + polyacrylamide + glycine after drying in Example 1 is shown. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments.

[0030] In a specific embodiment, liquid polyaluminum ferrosilicon was prepared using recycled lead smelting slag as raw material. The slag originated from a recycling company in Jieshou City, Anhui Province, and its chemical composition and content are shown in Table 1 below. Table 1 Chemical composition of recycled lead smelting slag

[0031] A method for preparing solid aluminum ferrosilicon polysilicate, comprising the following steps: S1. Preparation of liquid aluminum ferrosilicon: Taking recycled lead smelting slag as a raw material as an example, liquid polyaluminum ferrosilicon is prepared. It should be noted that the effective components of liquid polyaluminum ferrosilicon prepared by any method are the same, therefore the method for preparing the solidified polyaluminum ferrosilicon is the same; the specific method is as follows: The recycled lead smelting slag is ground to a particle size of at least 100 mesh, and slowly added to 1.5~2.5 mol / L hydrochloric acid with stirring. After leaching for a period of time, it is placed in a centrifuge for solid-liquid separation to obtain a leachate. In the hydrochloric acid leaching, the solid-liquid ratio is 1:20~1:50 g / mL, the leaching temperature is 20~40℃, and the leaching time is 10~180 min. The leachate is then adjusted to pH 2.0~3.0 by adding 5 mol / L NaOH solution dropwise, and then stirred and polymerized at 20~40℃ for 1~8 h to obtain liquid polyaluminum ferric silicate. S2. Add a composite curing agent (a mixture of 0.2wt% polyacrylamide solution and glycine) to the cured liquid polyaluminum silicate obtained in step S1, stir evenly and then dry to obtain solid polyaluminum silicate product. The mass ratio of 0.2wt% polyacrylamide solution to glycine is (1~3):1, the ratio of the amount of composite curing agent added to liquid aluminum ferric silicate is 0.01~0.05 g / mL, and the drying temperature is 50~60℃ until it is completely converted into a solid state; the molecular weight of polyacrylamide is 10 million~30 million.

[0032] Table 2 shows the preparation method parameters for specific embodiments and comparative examples.

[0033] The properties of the obtained solid aluminum silicate iron were tested according to the methods of the embodiments and comparative examples shown in Table 2. The test methods are as follows: The wastewater used was silty wastewater with a silt content of 1 g / L, a turbidity of 400 NTU, and a pH of 7.2. The ratio of solid polyaluminum silicate ferric sulfate (PAF) to water was 0.05 g / mL. After dissolution, the ratio of PAF to wastewater was 3 mL / L. The wastewater treatment process was as follows: the solid PAF obtained in each example and comparative example was dissolved in water, and wastewater with a turbidity of 400 NTU was added. The mixture was stirred at 800 r / min for 1 min at 20 ℃, allowed to settle for 30 min, and then the supernatant was collected 2 cm above the surface. The turbidity of the supernatant, i.e., the residual turbidity of the wastewater, was measured using a WGZ-3 turbidimeter manufactured by Shanghai Xinrui Instrument Co., Ltd. Specific test results are shown in Table 3. The experimental results show that the solid PAF prepared in this invention has good water solubility and flocculation effect.

[0034] Table 2. Preparation method parameters for each embodiment and comparative example.

[0035] Table 3. Properties of solid aluminum ferrosilicon obtained in each embodiment and comparative example

[0036] As can be seen from Table 3, the solid polyaluminum iron silicate prepared in Examples 1-4 of the present invention has good water solubility. After adding the composite curing agent, the rapid polymerization of Examples 1-4 was inhibited, so there was less insoluble matter.

[0037] Comparative Example 1, without the addition of polyacrylamide and glycine, basically failed to gel during the drying process at 50°C.

[0038] Comparative Examples 2 and 3 were separately mixed with polyacrylamide and glycine and then dried. During the water dissolution process, a large amount of insoluble matter appeared. This insoluble matter was polyaluminum iron silicate that had failed to gel. The cause of this was the rapid polymerization of silicic acid during the drying process. It can be seen that neither the formation of a network structure by the long-chain molecules of polyacrylamide to block the connection of silicic acid molecular chains, nor the control of the pH of the system alone can effectively control the polymerization of silicic acid. Therefore, the turbidity reduction effect of the wastewater in subsequent wastewater treatment was significantly worse than that in Example 1, and the flocculation effect was poor.

[0039] Comparative Example 4, dried at 100℃, still failed to gel even with the addition of polyacrylamide and glycine, indicating that the composite curing agent could not effectively prevent the rapid polymerization of silicic acid at high temperatures.

[0040] To investigate the curing mechanism of this application, five samples were taken for infrared detection. The samples were polyacrylamide, glycine, polyaluminum iron silicate from Comparative Example 1, polyaluminum iron silicate + polyacrylamide from Comparative Example 2, and polyaluminum iron silicate + polyacrylamide + glycine from Example 1. Figures 1-5As shown, it can be seen that: Figure 4 , Figure 5 It is a sample with added curing agent, and Figure 1 , Figure 2 , Figure 3 Comparison with pure substances revealed that no new absorption peaks appeared in the sample after the addition of the curing agent, indicating that polyaluminum iron silicate did not react with the curing agent during the drying process; the long-chain molecules of polyaluminum iron silicate did not copolymerize with silicic acid molecules, but instead formed a network structure encapsulating H3SiO4. - This prevents silicic acid molecules from linking together; glycine also does not react with silicic acid molecules, inhibiting silicic acid polymerization by controlling the pH of the system.

[0041] The above embodiments have described in detail the purpose and effects of the present invention. It should be understood that the above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. All modifications, equivalent substitutions, improvements, etc., made by those skilled in the art or by adopting the technical concept and technical solution of the present invention within the spirit and principles of the present invention and without departing from the design concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing solid aluminum ferrosilicon, characterized in that: The steps are as follows: add a composite curing agent to the cured liquid polyaluminum ferric silicate, stir evenly and then dry to obtain solid polyaluminum ferric silicate. The composite curing agent is a mixture of polyacrylamide and glycine.

2. The method for preparing solid aluminum ferrosilicon according to claim 1, characterized in that: In the composite curing agent, the mass ratio of polyacrylamide to glycine is (1:1). 3) :

500.

3. The method for preparing solid aluminum ferrosilicon according to claim 1, characterized in that: Polyacrylamide is pre-dissolved in water to obtain a polyacrylamide solution with a mass fraction of 0.2 wt%.

4. The method for preparing solid aluminum ferrosilicon according to claim 3, characterized in that: The mass ratio of 0.2 wt% polyacrylamide solution to glycine is (1~3):1; preferably, the mass ratio of 0.2 wt% polyacrylamide solution to glycine is 2:

1.

5. The method for preparing solid polyaluminum ferric silicate according to claim 2, characterized in that: The ratio of the amount of composite curing agent added to liquid aluminum ferric silicate is 0.01~0.05 g / mL; preferably, the ratio of the amount of composite curing agent added to liquid aluminum ferric silicate is 0.03 g / mL.

6. A method for preparing solid aluminum ferrosilicon according to any one of claims 1 to 5, characterized in that: The molecular weight of the polyacrylamide is 10 million to 30 million.

7. A method for preparing solid aluminum ferrosilicon according to claim 6, characterized in that: The drying temperature is 50~60℃ and the drying time is 6~10 h; preferably, the drying temperature is 50℃ and the drying time is 8 h.

8. The method for preparing solid aluminum ferrosilicon according to claim 6, characterized in that: The preparation method of the liquid polyaluminum ferrosilicon is as follows: the recycled lead smelting slag is successively leached with hydrochloric acid and separated into solid and liquid to obtain a leachate. The pH value of the leachate is adjusted to 2.0~3.0, and then polymerized and matured to obtain liquid polyaluminum ferrosilicon.

9. A method for preparing solid polyaluminum ferrosilicon according to claim 8, characterized in that: In the preparation method of liquid polyaluminum iron silicate, the molar concentration of hydrochloric acid is 1.5~2.5 mol / L, the solid-liquid ratio in hydrochloric acid leaching is 1:(20~50) g / mL, the leaching temperature is 20~40℃, and the leaching time is 10~180 min; preferably, the molar concentration of hydrochloric acid is 2 mol / L, the solid-liquid ratio is 1:30 g / mL, the leaching temperature is 20℃, and the leaching time is 30 min.

10. A method for preparing solid polyaluminum ferric silicate according to claim 8, characterized in that: The polymerization curing process involves a curing temperature of 20-40°C and a curing time of 1-8 h; preferably, the curing temperature is 20°C and the curing time is 2 h.

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