A method for preparing polyaluminum chloride based on directional activation of fly ash secondary aluminum ash acid leaching residue

Abstract

The application discloses a method for preparing polyaluminum chloride based on directional activation of fly ash secondary aluminum ash acid leaching residue, relates to the technical field of solid waste resource utilization, and aims at the technical problems of low aluminum leaching rate of direct acid leaching of water-washed secondary aluminum ash acid leaching residue and difficulty in high-value utilization of inert aluminum phase in the residue, so that the method realizes the transformation of the insoluble aluminum phase in the acid leaching residue into activated clinker which can be leached in a hydrochloric acid system through sintering activation of water-washed fly ash / calcium oxide composite calcium source, and significantly improves the release efficiency of aluminum in the secondary aluminum ash acid leaching residue. The water-washed fly ash is converted from a simple calcium source substitute into a composite phase regulation component. By controlling 45% to 55% of the total amount of additional calcium provided by the water-washed fly ash, the method avoids the introduction of excessive silicon in the water-washed fly ash to induce the generation of a large amount of stable silicate aluminate phases such as Ca2Al2SiO7, and simultaneously utilizes the sulfur component in the water-washed fly ash to participate in the formation of calcium aluminate sulfate phases such as Ca4Al6O 12 SO4, so that the activated clinker is more conducive to the leaching of aluminum under the appropriate calcium amount correction window.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, specifically to a method for preparing polyaluminum chloride based on fly ash-directed activation of secondary aluminum ash acid leaching residue. Background Technology

[0002] Secondary aluminum ash is a typical hazardous solid waste generated during the smelting and processing of recycled aluminum. Its composition is complex, typically containing alumina, metallic aluminum, aluminum nitride, magnesium aluminum spinel, chlorides, fluorides, and aluminosilicates. Current disposal methods mostly employ processes such as water washing, acid leaching, desalination, and deammoniation to reduce its environmental risks and recover some soluble aluminum components. However, the acid leaching residue of secondary aluminum ash still retains a large amount of insoluble aluminum phases, especially alumina, magnesium aluminum spinel, and silica-alumina mineral phases. Direct acid leaching results in a low aluminum leaching rate, making it difficult to reuse it as an aluminum source for the preparation of polyaluminum chloride (PAC) for high-value utilization. PAC is an inorganic polymeric coagulant widely used in the treatment of drinking water, industrial wastewater, and municipal sewage. Its preparation process requires a stable, inexpensive, and easily acid-soluble aluminum source. If the inert aluminum phase in the acid leaching residue of secondary aluminum ash can be converted into active aluminum clinker that can be efficiently leached in hydrochloric acid system, it will not only improve the resource utilization level of the entire process of secondary aluminum ash, but also reduce the dependence of the polyaluminum chloride production process on traditional aluminum source minerals or industrial aluminum salts, which has significant environmental benefits and economic value.

[0003] Currently, existing patents and literature mostly involve mixing aluminum ash, aluminum ash slag, or aluminum ash treatment residue with calcium-based raw materials such as limestone, calcium oxide, carbide slag, and waste incineration fly ash, followed by high-temperature calcination to prepare calcium aluminate, high-alumina cement, steelmaking refining agents, or other building materials. Chinese patent CN113816410B discloses a method for preparing calcium aluminate from aluminum ash slag and waste incineration fly ash, involving mixing aluminum ash slag, waste incineration fly ash, a fluoride-fixing agent, and a denitrifying agent, followed by denitrification, melting, and casting to prepare calcium aluminate products. Chinese patent CN114182103A discloses a method for the co-processing and resource utilization of aluminum ash and municipal solid waste incineration fly ash, involving mixing aluminum ash treatment residue with washed fly ash and then calcining at high temperatures to prepare high-alumina cement. Chinese patent CN110194474A discloses the production of polyaluminum chloride and... The process for producing calcium aluminate involves reacting the filter residue from secondary aluminum ash treatment with calcium-based auxiliary materials such as limestone or carbide slag at high temperatures. Chinese patent CN114455617B discloses a method for producing calcium aluminate from aluminum ash, which involves calcining aluminum ash, calcium-containing raw materials, iron powder, and minerals. Chinese patent CN114195177A discloses a method for preparing polyaluminum chloride and co-producing magnesium aluminum spinel from aluminum ash, which involves sintering aluminum ash acid hydrolysis residue with calcium carbonate to obtain calcium aluminate, and further coupling this with the polyaluminum chloride preparation process. While these methods can achieve resource utilization of aluminum ash or fly ash to some extent, their target products are mostly metallurgical materials, building material clinker, ordinary calcium aluminate products, or polyaluminum chloride co-production systems. They do not specifically design for the high-acid-soluble aluminum source clinker required for the polyaluminum chloride preparation process, nor do they use the aluminum leaching rate in the hydrochloric acid system as a core evaluation indicator.

[0004] Waste incineration fly ash contains a large amount of calcium-based components, such as calcium oxide, calcium hydroxide, calcium carbonate, and calcium sulfate, and is therefore often regarded as a low-cost calcium source to replace calcium oxide. However, fly ash is not a single calcium source; it also contains multiple components such as silicon, sulfur, magnesium, chlorine, fluorine, and heavy metals. During the high-temperature sintering and activation process of secondary aluminum ash acid leaching residue, the silicon components in the fly ash readily react with calcium and aluminum in the system to form stable aluminosilicate phases such as calcium aluminum feldspar, which locks aluminum in a poorly acid-soluble lattice, limiting the efficiency of subsequent hydrochloric acid leaching. At the same time, the sulfur components in the fly ash may participate in the formation of calcium sulfoaluminate phase, which, under suitable conditions, is conducive to the formation of an aluminum-containing activated phase with better acid solubility. Therefore, simply equating water-washed fly ash with calcium oxide and replacing it entirely makes it difficult to stably obtain highly acid-soluble aluminum clinker.

[0005] In summary, there is an urgent need to develop a process that can simultaneously activate inert aluminum in acid leaching residue of secondary aluminum ash, co-utilize water-washed fly ash, and prepare polyaluminum chloride source solution, in order to solve the current problems of insufficient high-value utilization of secondary aluminum ash acid leaching residue and low utilization efficiency of calcium-based components in water-washed fly ash. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing polyaluminum chloride based on fly ash-directed activation of secondary aluminum ash acid leaching residue.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A method for preparing polyaluminum chloride based on fly ash directionally activated secondary aluminum ash acid leaching residue is provided, comprising the following steps: S1: The secondary aluminum ash acid leaching residue is sequentially washed with water, separated from solids and liquids and dried to obtain water-washed secondary aluminum ash acid leaching residue; S2: After washing and dechlorinating the fly ash from municipal solid waste incineration, solid-liquid separation and drying are performed to obtain washed fly ash; S3: Determine the contents of Al, Mg, Si, and Ca in the acid leaching residue and fly ash from the secondary aluminum ash to be treated, and calculate the molar amount of calcium oxide that needs to be added: ; in, The total molar amount of aluminum in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of magnesium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of silicon in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of calcium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. This is the calcium compatibility coefficient, and The value is 0.8~1.2; S4: Determine the amount of calcium oxide doping based on the molar amount of calcium oxide to be added, and ball mill the acid leaching residue of the secondary aluminum ash to be treated, the water-washed fly ash and the calcium oxide for doping together to obtain the composite calcium source material. S5: Sinter the composite calcium source material at 1250~1350℃ for 60~180min to obtain activated clinker; S6: After cooling the activated clinker, place it in a hydrochloric acid system for acid leaching reaction. After solid-liquid separation, aluminum enrichment is completed to obtain aluminum-rich leachate. S7: Use aluminum-rich leachate as aluminum source solution to prepare polyaluminum chloride.

[0008] Furthermore, the specific steps for washing the secondary aluminum ash acid leaching residue are as follows: mix the secondary aluminum ash acid leaching residue with hot water at 80~90℃ at a ratio of 1kg:8~12L, and stir at 80~90℃ for 100~140min.

[0009] Furthermore, in step S3, the amount of water-washed fly ash used is determined by its molar amount of Ca. occupy The percentage is recorded as follows: =45~55%.

[0010] Furthermore, It is version 1.0. Furthermore, in step S4, the ball milling process uses a ball-to-material mass ratio of 5~10:1, a rotation speed of 300~600 r / min, a milling time of 10~60 min, and the material passes through an 80~120 mesh sieve after milling.

[0011] Furthermore, the ball mill uses a ball-to-material mass ratio of 7.5:1, a rotation speed of 450 r / min, a milling time of 30 min, and the material is then passed through a 100-mesh sieve after milling.

[0012] Furthermore, in step S6, the acid leaching specifically involves placing the activated clinker in a hydrochloric acid aqueous solution and soaking it at 85°C for 120 minutes.

[0013] Furthermore, the concentration of the hydrochloric acid aqueous solution is 6 mol / L, and the ratio of activated clinker to hydrochloric acid aqueous solution is 1 kg: 10 L.

[0014] The present invention also provides the application of the aluminum-rich leachate prepared by the above method in the preparation of polyaluminum chloride, wherein the aluminum-rich leachate obtained by enriching aluminum based on the secondary aluminum ash acid leaching residue after directional activation of fly ash is used as the aluminum source solution to prepare polyaluminum chloride.

[0015] The beneficial effects of this invention are as follows: This invention addresses the technical problems of low aluminum leaching rate in direct acid leaching of secondary aluminum ash residue and the difficulty in further utilizing the inert aluminum phase in the residue at high value. By sintering and activating a composite calcium source of washed fly ash / calcium oxide, the insoluble aluminum phase in the acid leaching residue is transformed into an activated clinker that can be leached in a hydrochloric acid system, significantly improving the aluminum release efficiency in secondary aluminum ash acid leaching residue. This is achieved by converting the washed fly ash from a simple calcium source substitute into a composite phase control component. By controlling the amount of added calcium provided by the washed fly ash to 45%~55%, excessive silicon is avoided from being introduced by the full volume of washed fly ash, which would induce the large-scale formation of stable aluminosilicate phases such as Ca2Al2SiO7. Simultaneously, the sulfur component in the washed fly ash participates in the formation of Ca4Al6O7. 12 (SO4) and other calcium sulfoaluminate phases are used to obtain activated clinker that is more conducive to acid leaching and aluminum extraction under a suitable calcium content correction window.

[0016] This invention employs a calcium compatibility coefficient to control the amount of added calcium in the system, incorporating magnesium-locked aluminum and silicon-consumed calcium factors into the compatibility design. Simultaneously, it utilizes the sulfur components in water-washed fly ash to participate in the formation of the calcium sulfoaluminate phase, avoiding uncontrolled phase composition caused by simply increasing the calcium source. Experimental results show that in the water-washed fly ash / calcium oxide composite calcium source system, further increasing the amount of added calcium does not necessarily increase the aluminum leaching rate; only within a suitable compatibility window can higher acid solubility be achieved.

[0017] This invention enables the synergistic resource utilization of two types of solid waste: acid leaching residue from water-washed secondary aluminum ash and fly ash from municipal solid waste incineration. On the one hand, it improves the utilization efficiency of the refractory aluminum phase in the acid leaching residue from secondary aluminum ash, and on the other hand, it utilizes the calcium-based and sulfur-based components in the water-washed fly ash, avoiding the environmental risks and resource waste caused by separate disposal.

[0018] The process of this invention is simple and mainly includes steps such as raw material washing, composition determination, compound calcium source compatibility, grinding or ball milling homogenization, high-temperature sintering activation and hydrochloric acid leaching. The required equipment mainly includes a water washing device, a mixing device, a high-temperature sintering device and an acid leaching reaction device. It is easy to connect with existing solid waste resource utilization and polyaluminum chloride preparation processes and has further industrial application value. Detailed Implementation

[0019] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0020] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available industrial-grade raw materials.

[0021] Example 1 The following steps were used to prepare the aluminum-rich leaching solution for polyaluminum chloride: S1: Mix the secondary aluminum ash acid leaching residue with 80℃ hot deionized water at a liquid-solid ratio of 8L:1kg, stir and wash for 100min, then separate the solid and liquid and dry to obtain the water-washed secondary aluminum ash acid leaching residue.

[0022] S2: The fly ash from municipal solid waste incineration is washed and dechlorinated, and after solid-liquid separation and drying, washed fly ash is obtained.

[0023] S3: XRF analysis was performed on the obtained acid leaching residue of secondary aluminum ash and the washed fly ash. The results are shown in Table 1 below. Table 1

[0024] Based on the proportions of each component in the acid leaching residue of the secondary aluminum ash and the water-washed fly ash in Table 1, the calcium compatibility coefficient K is set to 0.8, and the total amount of added calcium provided by the water-washed fly ash is 45.1% for compatibility. S4: According to the compatibility parameters in S3, weigh 10.0 kg of water-washed secondary aluminum ash acid leaching residue, 3.7 kg of water-washed fly ash and 2.4 kg of calcium oxide and place them in a ball mill for dry ball milling and homogenization. The ball-to-material mass ratio is 5:1, the rotation speed is 300 r / min, the ball milling time is 10 min, and after ball milling, pass through an 80-mesh sieve to obtain the composite calcium source compatibility material.

[0025] S5: Place the composite calcium source material in a high-temperature sintering furnace, sinter at 1250℃ and hold for 60 minutes, and then cool naturally after sintering to obtain activated clinker.

[0026] XRD analysis of the activated clinker showed that the main phases of the activated clinker included Ca. 12 Al 14 O 33 Ca4Al6O 12 (SO4), calcium silicate phase, MgAl2O4 and a small amount of Ca2Al2SiO7; S6: Take activated clinker and 6 mol / L hydrochloric acid aqueous solution and mix them at a liquid-solid ratio of 10 L: 1 kg. Mix them in an acid leaching reactor at 85℃ with mechanical stirring for 120 min. After the reaction is completed, perform solid-liquid separation to obtain aluminum-rich leachate.

[0027] ICP analysis was performed on the aluminum-rich leaching solution, and the aluminum leaching rate was calculated. The aluminum leaching rate was calculated as the percentage of the mass of aluminum in the liquid phase relative to the mass of aluminum in the activated clinker used for acid leaching. The mass of aluminum in the liquid phase was determined by the aluminum concentration measured by ICP. Volume of aluminum-rich leachate The product calculation; the aluminum mass in the activated clinker used for acid leaching is based on the total aluminum mass in the original blended materials. Total mass of activated clinker after sintering and the quality of raw materials before sintering and activation The calculated result (assuming the mass of aluminum remains constant during sintering and activation) is as follows:

[0028] The aluminum leaching rate in this embodiment was calculated to be 58%.

[0029] In summary, under the conditions of 45.1% total added calcium from water-washed fly ash and K=0.8, the system has formed acid-soluble aluminate phase and calcium sulfoaluminate phase, but a small amount of calcium aluminum feldspar aluminum-locking phase still exists.

[0030] Example 2 The following steps were used to prepare the aluminum-rich leaching solution for polyaluminum chloride: S1: Mix the secondary aluminum ash acid leaching residue with 85℃ hot water at a liquid-solid ratio of 10L:1kg, stir and wash for 120min, then separate the solid and liquid and dry to obtain the water-washed secondary aluminum ash acid leaching residue.

[0031] S2: The fly ash from municipal solid waste incineration is washed and dechlorinated, and after solid-liquid separation and drying, washed fly ash is obtained.

[0032] S3: XRF testing was performed on the obtained acid leaching residue of secondary aluminum ash and the washed fly ash. Based on the test results, the calcium compatibility coefficient K was set to 1.0, and the total amount of added calcium provided by the washed fly ash was 50.2% for compatibility. The formula for calculating the required molar amount of calcium oxide to be added is as follows: ; in, The total molar amount of aluminum in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of magnesium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of silicon in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of calcium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. S4: According to the compatibility parameters in S3, weigh 10.0 kg of water-washed secondary aluminum ash acid leaching residue, 5.1 kg of water-washed fly ash and 2.7 kg of calcium oxide and place them in a ball mill for dry ball milling and homogenization. The ball-to-material mass ratio is 7.5:1, the rotation speed is 450 r / min, the ball milling time is 30 min, and after ball milling, pass through a 100-mesh sieve to obtain the composite calcium source compatibility material.

[0033] S5: Place the composite calcium source material in a high-temperature sintering furnace, sinter at 1300℃ and hold for 120 minutes, and air cool after sintering to obtain activated clinker.

[0034] S6: Take activated clinker and 6 mol / L hydrochloric acid aqueous solution and mix them at a liquid-solid ratio of 10 L: 1 kg. Mix them in an acid leaching reactor at 85℃ with mechanical stirring for 120 min. After the reaction is completed, perform solid-liquid separation to obtain aluminum-rich leachate.

[0035] Using the method described in Example 1, XRD analysis was performed on the activated clinker, and ICP analysis was performed on the aluminum-rich leachate to calculate the aluminum leaching rate. The results showed that the main phases of the activated clinker included Ca. 12 Al 14 O 33 Ca4Al6O 12 The aluminum-locking phases (SO4), calcium silicate, MgAl2O4, and Ca2Al2SiO7 were significantly weakened; ICP analysis showed that the aluminum leaching rate was 67%.

[0036] In summary, under the conditions of 50.2% total added calcium from water-washed fly ash and K=1.0, the sulfate component in water-washed fly ash is conducive to the formation of calcium sulfoaluminate phase, and the addition of calcium oxide can inhibit the aluminum-locking effect induced by silicon components.

[0037] Example 3 The following steps were used to prepare the aluminum-rich leaching solution for polyaluminum chloride: S1: Mix the secondary aluminum ash acid leaching residue with 90℃ hot water at a liquid-solid ratio of 12L:1kg, stir and wash for 140min, then separate the solid and liquid and dry to obtain the water-washed secondary aluminum ash acid leaching residue.

[0038] S2: The fly ash from municipal solid waste incineration is washed and dechlorinated, and after solid-liquid separation and drying, washed fly ash is obtained.

[0039] S3: XRF testing was performed on the obtained acid leaching residue of secondary aluminum ash obtained by water washing and the fly ash obtained by water washing. Based on the test results, the calcium content compatibility coefficient K=1.2 and the total amount of added calcium provided by the fly ash was set to 54.4% for compatibility. S4: According to the compatibility parameters in S3, weigh 10.0 kg of water-washed secondary aluminum ash acid leaching residue, 6.7 kg of water-washed fly ash and 3.0 kg of calcium oxide and place them in a ball mill for dry ball milling and homogenization. The ball-to-material mass ratio is 10:1, the rotation speed is 600 r / min, the ball milling time is 60 min, and the ball milling is passed through a 120 mesh sieve to obtain the composite calcium source compatibility material.

[0040] S5: Place the composite calcium source material in a high-temperature sintering furnace, sinter at 1350℃ and hold for 180 minutes, and air cool after sintering to obtain activated clinker.

[0041] S6: Take activated clinker and 6 mol / L hydrochloric acid aqueous solution and mix them at a liquid-solid ratio of 10 L: 1 kg. Mix them in an acid leaching reactor at 85℃ with mechanical stirring for 120 min. After the reaction is completed, perform solid-liquid separation to obtain aluminum-rich leachate.

[0042] Using the method described in Example 1, XRD analysis was performed on the activated clinker, and ICP analysis was performed on the aluminum-rich leachate to calculate the aluminum leaching rate. The results showed that the main phases of the activated clinker included Ca. 12 Al 14 O 33 Ca4Al6O 12 The aluminum-locking phases (SO4), calcium silicate, MgAl2O4, and Ca2Al2SiO7 were not obvious; the aluminum leaching rate was 71% according to ICP analysis.

[0043] In summary, under the conditions of 54.4% total calcium added by water-washed fly ash and K=1.2, the system can still maintain a high level of aluminum acid dissolution conversion. However, due to the increase in the amount of water-washed fly ash and calcium oxide added, the aluminum mass concentration in the unit acid leaching solution is relatively reduced.

[0044] Comparative Example 1 The difference between this embodiment and embodiment 2 is that the acid leaching residue of the water-washed secondary aluminum ash is directly subjected to S6 for acid leaching reaction. Specifically, 10.0 kg of water-washed secondary aluminum ash acid leaching residue is taken and mixed with a 6 mol / L hydrochloric acid aqueous solution at a liquid-to-solid ratio of 10 L: 1 kg. The mixture is mechanically stirred in an acid leaching reactor at 85 °C for 120 min. After the reaction is completed, solid-liquid separation is performed, and the aluminum mass concentration is measured by taking the liquid phase.

[0045] ICP analysis showed that the aluminum leaching rate was 4%. This result indicates that a large amount of aluminum in the acid leaching residue of the water-washed secondary aluminum ash that has not been sintered and activated is in a poorly soluble state, making it difficult to obtain a high aluminum leaching rate through direct acid leaching.

[0046] Comparative Example 2 The difference between this embodiment and Embodiment 2 is that no water-washed fly ash is added; instead, calcium oxide is used entirely as the external calcium source. Specifically: Weigh 10.0 kg of water-washed secondary aluminum ash acid leaching residue, and mix it with K=1.0, using calcium oxide as the external calcium source. Weigh 5.2 kg of calcium oxide. The remaining water washing, ball milling homogenization, sintering and acid leaching conditions are the same as in Example 2.

[0047] XRD analysis revealed that the main crystalline phases of the sintered product included Ca2Al2SiO7 and Ca... 12 Al 14 O 33 And MgAl2O4; according to ICP analysis, the aluminum leaching rate was 79%.

[0048] The results indicate that pure calcium oxide can activate the insoluble aluminum phase in the acid leaching residue of secondary aluminum ash from water washing, but it does not achieve the synergistic resource utilization of water-washed fly ash, nor can it demonstrate the promoting effect of sulfate components in water-washed fly ash on the formation of sulfur-containing calcium aluminate phase.

[0049] Comparative Example 3 The difference between this embodiment and Embodiment 2 is that: all instances use water-washed fly ash as the external calcium source, without adding calcium oxide. Specifically: Weigh 10.0 kg of water-washed secondary aluminum ash acid leaching residue, and mix it with K=1.0, using water-washed fly ash as the external calcium source. Weigh 10.6 kg of water-washed fly ash. The remaining water washing, ball milling homogenization, sintering and acid leaching conditions are the same as in Example 2.

[0050] XRD analysis revealed that the main crystalline phases of the sintered product included Ca2Al2SiO7 and MgAl2O4; ICP analysis showed that the aluminum leaching rate was 57%.

[0051] The results indicate that water-washed fly ash cannot be simply replaced by calcium oxide; in the full-volume water-washed fly ash system, the silicon components introduced by the fly ash promote the formation of aluminosilicate phases such as Ca2Al2SiO7, which locks in aluminum and reduces the acid leaching release efficiency.

[0052] In summary, Examples 1-3 correspond to the lower, middle, and upper limits of the washing conditions, calcium supply ratio of washed fly ash, K value, ball milling conditions, and sintering conditions in the technical solution, respectively, demonstrating that the present invention can prepare aluminum source clinker for polyaluminum chloride within the specified parameter range. Comparative Examples 1-3 further show that the aluminum leaching rate is extremely low when the unactivated washed secondary aluminum ash acid leaching residue is directly acid-leached; although the pure calcium oxide system can improve the aluminum leaching rate, it cannot achieve synergistic resource utilization of washed fly ash; the full-volume washed fly ash system easily generates a stable aluminosilicate phase and reduces the aluminum leaching rate. In contrast, the present invention, through a composite calcium source of washed fly ash / calcium oxide and a K-value calcium content correction model, achieves the activation of the sparingly soluble aluminum phase in the secondary aluminum ash acid leaching residue and the synergistic resource utilization of washed fly ash.

[0053] Example 4 The aluminum-rich leachate obtained in Example 2 was used to prepare polyaluminum chloride, specifically: The aluminum-rich leaching solution obtained in Example 2 was filtered and subjected to solid-liquid separation to remove insoluble residues, yielding an aluminum stock solution. This aluminum stock solution was placed in a reactor and heated to 85°C under stirring. A 20% (w / w) sodium carbonate solution was slowly added as an alkalizing agent. The addition was stopped when the system basicity reached 55%, and the solution was kept at this temperature for 2 hours. Subsequently, it was allowed to mature at room temperature for 24 hours and then filtered to obtain a polyaluminum chloride solution. The product was tested according to the testing methods specified in GB / T 22627-2022. The basicity, Al2O3 content, and impurity content of the obtained polyaluminum chloride solution all met the standards.

Claims

1. A method for preparing polyaluminum chloride based on fly ash-directed activation of secondary aluminum ash acid leaching residue, characterized in that, Includes the following steps: S1: The secondary aluminum ash acid leaching residue is sequentially washed with water, separated from solids and liquids and dried to obtain water-washed secondary aluminum ash acid leaching residue; S2: After washing and dechlorinating the fly ash from municipal solid waste incineration, solid-liquid separation and drying are performed to obtain washed fly ash; S3: Determine the contents of Al, Mg, Si, and Ca in the acid leaching residue and fly ash from the secondary aluminum ash to be treated, and calculate the molar amount of calcium oxide that needs to be added: ； in, The total molar amount of aluminum in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of magnesium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of silicon in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. The total molar amount of calcium in the acid leaching residue of secondary aluminum ash and the fly ash from water washing. This is the calcium compatibility coefficient, and The value is 0.8~1.2; S4: Determine the amount of calcium oxide doping based on the molar amount of calcium oxide to be added, and ball mill the acid leaching residue of the secondary aluminum ash to be treated, the water-washed fly ash and the calcium oxide for doping together to obtain the composite calcium source material. S5: Sinter the composite calcium source material at 1250~1350℃ for 60~180min to obtain activated clinker; S6: After cooling the activated clinker, place it in a hydrochloric acid system for acid leaching reaction. After solid-liquid separation, aluminum enrichment is completed to obtain aluminum-rich leachate. S7: Use aluminum-rich leachate as aluminum source solution to prepare polyaluminum chloride.

2. The method according to claim 1, characterized in that, The specific steps for washing the secondary aluminum ash acid leaching residue are as follows: mix the secondary aluminum ash acid leaching residue with hot water at 80~90℃ at a ratio of 1kg:8~12L, and stir at 80~90℃ for 100~140min.

3. The method according to claim 1, characterized in that, In step S3, the amount of water used for washing fly ash is determined by the molar amount of Ca. occupy The percentage is recorded as follows: =45~55%.

4. The method according to claim 1, characterized in that, The It is 1.

0.

5. The method according to claim 1, characterized in that, In step S4, the ball milling process uses a ball-to-material mass ratio of 5~10:1, a rotation speed of 300~600 r / min, a milling time of 10~60 min, and the material passes through an 80~120 mesh sieve after milling.

6. The method according to claim 5, characterized in that, The ball mill uses a ball-to-material mass ratio of 7.5:1, a rotation speed of 450 r / min, a milling time of 30 min, and the material is then passed through a 100-mesh sieve after milling.

7. The method according to claim 1, characterized in that, In step S6, acid leaching specifically involves placing the activated clinker in a hydrochloric acid aqueous solution and soaking it at 85°C for 120 minutes.

8. The method according to claim 7, characterized in that, The concentration of the hydrochloric acid aqueous solution is 6 mol / L, and the ratio of activated clinker to hydrochloric acid aqueous solution is 1 kg: 10 L.

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