A separation process for insoluble substances during the preparation of polyaluminum chloride

Abstract

The present invention belongs to the field of new materials for water treatment, and specifically discloses a separation process for insoluble substances during the preparation of polyaluminum chloride; the process includes the following steps: S1. Add 3 - 6 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly, and then add 2 - 4 parts of thickening agent; S2. Add 5 - 10 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, perform solid-liquid separation after sufficient sedimentation to obtain polyaluminum chloride mother liquor with insoluble substances removed. By adding polymeric ferric sulfate and thickening agent (such as guar gum), and in combination with the use of sedimentation agent, the present invention can significantly improve the sedimentation efficiency of insoluble substances, make the solid-liquid separation more thorough, and facilitate the preparation of polyaluminum chloride products with higher purity.

Description

Technical Field

[0001] The present invention belongs to the field of new water treatment materials, and specifically discloses a separation process for insolubles during the preparation of polyaluminum chloride. Background Art

[0002] During the preparation of polyaluminum chloride (PAC), the removal of insolubles is a crucial step. This not only concerns the final quality of the product but also directly affects its market application effect and environmental friendliness. The production of polyaluminum chloride usually adopts the process of acid dissolution of bauxite + adjustment with calcium aluminate. During this process, most of the aluminum oxide in the ore is converted into a liquid polyaluminum chloride form, but other impurities such as SiO2 are insoluble in acid and thus remain as solid-phase substances, forming hydrates and being insoluble; in addition, some aluminum oxide that fails to be completely dissolved will also increase the content of insolubles; these insolubles will not only affect the appearance of polyaluminum chloride, reducing its transparency, but may also affect its flocculation effect and stability, thereby affecting the overall performance and market competitiveness of the product. At the same time, too high an insolubles content may also cause problems such as pipeline blockage during use.

[0003] Currently, there are mainly two methods for removing water-insolubles in polyaluminum chloride: 1. Natural sedimentation method: This method is simple to operate and requires no additional equipment investment, but has disadvantages such as a long production cycle and a large floor area. For some products with a high basicity, due to high viscosity, it is difficult to effectively separate the insolubles, and it is difficult to meet the national standard requirements even after long-term precipitation. 2. Plate and frame filtration method: Compared with the natural sedimentation method, the plate and frame filtration method can remove insolubles more quickly and improve production efficiency. However, this method requires a large equipment investment and power consumption, and has certain limitations on the product basicity (generally below 80%), restricting its scope of application. In addition, the operation process is relatively complex, and washing the filter cloth is cumbersome, which also increases the production cost and time cost.

[0004] In summary, the removal of insolubles during the preparation of polyaluminum chloride is a challenging task. Only by continuously exploring and innovating technical means can existing problems be overcome to improve product quality and market competitiveness, and make greater contributions to environmental protection and resource conservation. Summary of the Invention

[0005] Based on the deficiencies of the existing technology, the present invention discloses a separation process for insolubles during the preparation of polyaluminum chloride.

[0006] The present invention includes the following technical solutions:

[0007] A separation process for insolubles during the preparation of polyaluminum chloride, comprising the following steps:

[0008] 1) Add 3 - 6 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor. After stirring evenly, add 2 - 4 parts of thickening agent.

[0009] 2) Add 5 - 10 parts of sedimentation agent to the polyaluminum chloride system obtained in S1. After sufficient sedimentation, perform solid - liquid separation to obtain the polyaluminum chloride mother liquor with insoluble substances removed.

[0010] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the thickening agent is selected from one or more of guar gum, lauryl alcohol, and methyl cellulose.

[0011] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the thickening agent is guar gum.

[0012] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the guar gum is modified guar gum, which is prepared by the following modification steps:

[0013] S1: Add 1 part of guar gum and 10 - 20 parts of water to a reaction vessel, heat to 65 - 75 °C, and under nitrogen protection, add 0.1 - 0.5 part of strong acid, and stir and react for 45 - 75 min;

[0014] S2: Under nitrogen protection, add 0.5 - 1.5 parts of quaternary ammonium salt 3 - chloro - 2 - hydroxypropyl ammonium chloride, and react for 2 - 4 h;

[0015] S3: After the reaction is completed, add washing water for washing, perform centrifugation at 10000 - 20000 g, and filter to obtain modified guar gum;

[0016] The above parts are parts by mass.

[0017] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the strong acid in step S1 is sulfuric acid or hydrochloric acid.

[0018] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the sedimentation agent in step 2) is a composition including chitosan and synthetic polymer.

[0019] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the synthetic polymer is polyvinyl alcohol.

[0020] Further, in the separation process of insoluble substances during the preparation of the above - mentioned polyaluminum chloride, the mass ratio of chitosan to polyvinyl alcohol is 1:2 - 1:4.

[0021] Further, in the above process for separating insoluble substances in the preparation of polyaluminum chloride, the solid-liquid separation method in step 2) is filtration. The filtration is first carried out through a 50-100 mesh sieve for the first time, and then through a 300-400 mesh sieve for the second time to obtain the polyaluminum chloride mother liquor with insoluble substances removed.

[0022] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0023] 1. High-efficiency removal of insoluble substances: By adding polyferric sulfate and thickeners (such as guar gum), and then cooperating with the use of a settling agent, the sedimentation efficiency of insoluble substances can be significantly improved, making the solid-liquid separation more thorough. This combination not only enhances the stability of the system, but also promotes the rapid aggregation and sedimentation of insoluble substances, thereby improving the purity of the product.

[0024] 2. Optimization of thickener selection: Using guar gum as a thickener, especially the modified guar gum, after the hydroxyl groups and other functional groups in its molecular structure are acidified and quaternized, it can better interact with ions in the solution to form a stable network structure, further promoting the aggregation and sedimentation of insoluble substances. In addition, guar gum is widely sourced, low-cost and environmentally friendly, meeting the requirements of industrial production.

[0025] 3. Innovative settling agent formulation: Combining chitosan with synthetic polymers (such as polyvinyl alcohol) as a settling agent, and utilizing their complementary advantages, efficient capture and sedimentation of insoluble substances are achieved. Chitosan has good biocompatibility and adsorption properties, while polyvinyl alcohol has excellent film-forming properties and stability. The synergistic effect of the two significantly improves the sedimentation effect.

[0026] 4. Fine filtration technology: The processed solution is subjected to solid-liquid screening by means of multi-stage sieve filtration. First, a coarse separation is carried out through a first filtration to remove most of the solid particles, and then a second filtration is carried out through a fine sieve to ensure the purity of the solution. This fine filtration technology can effectively avoid the residue of fine particles and improve the quality of the product.

[0027] 5. Simple and easy to operate: The entire process flow is reasonably designed, the steps are clear and definite, and the required raw materials and equipment are relatively common and easy to obtain. At the same time, the connection between each step is tight and orderly, facilitating industrial production and popularization and application.

[0028] 6. Environmentally friendly and energy-saving: This process pays attention to environmental protection and resource conservation during operation. Most of the raw materials used are renewable or biodegradable materials, and less waste is generated. In addition, by optimizing process parameters and improving production efficiency and other measures, energy consumption and emission levels can be effectively reduced.

[0029] In summary, this technical solution has significant advantages and application prospects in improving the quality of polyaluminum chloride products, reducing production costs, and achieving environmentally friendly production, etc. Description of the Drawings

[0030] Figure 1 Content of insoluble matter wt%. Detailed Implementation Modes

[0031] A separation process for insoluble matter during the preparation of polyaluminum chloride, characterized by comprising the following steps:

[0032] 1) Add 3 - 6 parts of polyferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly, and then add 2 - 4 parts of thickener;

[0033] 2) Add 5 - 10 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment, and then perform solid-liquid separation to obtain the polyaluminum chloride mother liquor with insoluble matter removed.

[0034] The thickener is guar gum.

[0035] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:2 - 1:4.

[0036] The solid-liquid separation method in step 2) is filtration. The filtration is to first filter once with a 50 - 100 mesh sieve, and then filter twice with a 300 - 400 mesh sieve to obtain the polyaluminum chloride mother liquor with insoluble matter removed.

[0037] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0038] Example 1

[0039] A separation process for insoluble matter during the preparation of polyaluminum chloride, comprising the following steps:

[0040] 1) Add 3 parts of polyferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly, and then add 2 parts of thickener;

[0041] 2) Add 5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment, and then perform solid-liquid separation to obtain the polyaluminum chloride mother liquor with insoluble matter removed;

[0042] The thickener is guar gum;

[0043] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:2.

[0044] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for primary filtration, and then with a 300-400 mesh sieve for secondary filtration to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0045] Example 2

[0046] A separation process for insoluble substances in the preparation of polyaluminum chloride includes the following steps:

[0047] 1) Add 4.5 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly and then add 3 parts of thickening agent;

[0048] 2) Add 7.5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment and then carry out solid-liquid separation to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0049] The thickening agent is guar gum.

[0050] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:3.

[0051] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for primary filtration, and then with a 300-400 mesh sieve for secondary filtration to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0052] Example 3

[0053] A separation process for insoluble substances in the preparation of polyaluminum chloride includes the following steps:

[0054] 1) Add 6 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly and then add 4 parts of thickening agent;

[0055] 2) Add 10 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment and then carry out solid-liquid separation to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0056] The thickening agent is guar gum.

[0057] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:4.

[0058] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for primary filtration, and then with a 300-400 mesh sieve for secondary filtration to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0059] Example 4

[0060] A separation process for insoluble substances in the preparation process of polyaluminum chloride, comprising the following steps:

[0061] 1) Add 4.5 parts of polyferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly and then add 3 parts of thickener;

[0062] 2) Add 7.5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment and then carry out solid-liquid separation to obtain polyaluminum chloride mother liquor with insoluble substances removed.

[0063] The thickener is guar gum;

[0064] The guar gum is modified guar gum, which is prepared by the following modification steps:

[0065] S1: Add 1 part of guar gum and 15 parts of water to the reaction vessel, heat to 70 °C, under nitrogen protection, add 0.25 part of sulfuric acid, and stir and react for 60 min;

[0066] S2: Under nitrogen protection, add 1 part of quaternary ammonium salt 3-chloro-2-hydroxypropyl ammonium chloride and react for 3 h;

[0067] S3: After the reaction is completed, add washing water for washing, carry out centrifugation at 15000 g, and filter to obtain modified guar gum;

[0068] The above parts are parts by mass.

[0069] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:3.

[0070] The solid-liquid separation method in step 2) is filtration. The filtration is to first filter once with a 50-100 mesh sieve and then filter twice with a 300-400 mesh sieve to obtain polyaluminum chloride mother liquor with insoluble substances removed.

[0071] Comparative Example 1

[0072] A separation process for insoluble substances in the preparation process of polyaluminum chloride, comprising the following steps:

[0073] 1) Add 4.5 parts of sodium phosphate to 100 parts of polyaluminum chloride mother liquor, stir evenly and then add 3 parts of thickener;

[0074] 2) Add 7.5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment and then carry out solid-liquid separation to obtain polyaluminum chloride mother liquor with insoluble substances removed.

[0075] The thickener is guar gum.

[0076] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:3.

[0077] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for primary filtration, and then with a 300-400 mesh sieve for secondary filtration to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0078] The difference between Comparative Example 1 and Example 2 is that sodium phosphate is used instead of polymeric ferric sulfate, and the rest is the same.

[0079] Comparative Example 2

[0080] A separation process for insoluble substances in the preparation of polyaluminum chloride includes the following steps:

[0081] 1) Add 4.5 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly, and then add 3 parts of thickening agent;

[0082] 2) Add 7.5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment, and then carry out solid-liquid separation to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0083] The thickening agent is emulsifying silicone oil.

[0084] The sedimentation agent in step 2) is composed of chitosan and polyvinyl alcohol in a mass ratio of 1:3.

[0085] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for primary filtration, and then with a 300-400 mesh sieve for secondary filtration to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0086] The difference between Comparative Example 2 and Example 2 is that emulsifying silicone oil is used instead of guar gum, and the rest is the same.

[0087] Comparative Example 3

[0088] A separation process for insoluble substances in the preparation of polyaluminum chloride includes the following steps:

[0089] 1) Add 4.5 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor, stir evenly, and then add 3 parts of thickening agent;

[0090] 2) Add 7.5 parts of sedimentation agent to the polyaluminum chloride system obtained in S1, fully sediment, and then carry out solid-liquid separation to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0091] The thickening agent is guar gum.

[0092] The sedimentation agent in step 2) is polyvinyl alcohol.

[0093] The solid-liquid separation method in step 2) is filtration. The filtration is first carried out with a 50-100 mesh sieve for the first time, and then with a 300-400 mesh sieve for the second time to obtain a polyaluminum chloride mother liquor free of insoluble substances.

[0094] The difference between Comparative Example 3 and Example 2 is that the settling agent is polyvinyl alcohol, and the rest is the same.

[0095] Test Example

[0096] The insoluble matter content of the polyaluminum chloride product was detected by the insoluble matter determination method of GBT22627-2022, and the polyaluminum chloride mother liquors prepared in Examples 1-4 and Comparative Examples 1-3 were detected. The results are shown in Table 1 and Figure 1 as shown. The insoluble matter content in the treated polyaluminum chloride mother liquor is 2.14 wt%.

[0097] Table 1 Insoluble matter content of polyaluminum chloride products

[0098] Insoluble matter content wt% Example 1 0.13 Example 2 0.11 Example 3 0.15 Example 4 0.07 Comparative Example 1 0.19 Comparative Example 2 0.24 Comparative Example 3 0.21

[0099] As can be seen from the above Examples 1-4, the present invention discloses a separation process, which can reduce the insoluble matter content in the polyaluminum chloride mother liquor to less than 0.15 wt%. In particular, in Example 4 where modified guar gum is used as a thickener, the insoluble matter content can be reduced to less than 0.1 wt%, proving that the process described in the present invention has very good effects. Compared with Comparative Examples 1-3, it can be seen that after using sodium phosphate instead of polyferric sulfate, the insoluble matter content will increase by nearly 1 time. After using emulsified silicone oil instead of guar gum, the effect of reducing insoluble matter will also decrease significantly. And after using a single settling agent of polyvinyl alcohol to replace the composite settling agent of chitosan and polyvinyl alcohol, the insoluble matter content will also increase significantly, reflecting that the present invention has great progress compared with the prior art.

[0100] The above are only several limited preferred embodiments of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made, and these all belong to the protection scope of the present invention.

Claims

1. A separation process for insoluble substances during the preparation of polyaluminum chloride, characterized in that, It includes the following steps: 1) Add 3 - 6 parts of polymeric ferric sulfate to 100 parts of polyaluminum chloride mother liquor. After stirring evenly, add 2 - 4 parts of thickener; 2) Add 5 - 10 parts of sedimentation agent to the polyaluminum chloride system obtained in step 1). After sufficient sedimentation, carry out solid - liquid separation to obtain the polyaluminum chloride mother liquor with insoluble substances removed; The thickener is modified guar gum, which is prepared by the following modification steps: S1: Add 1 part of guar gum and 10 - 20 parts of water to the reaction vessel, heat to 65 - 75 °C. Under nitrogen protection, add 0.1 - 0.5 part of strong acid, and stir and react for 45 - 75 min; S2: Under nitrogen protection, add 0.5 - 1.5 parts of quaternary ammonium salt 3 - chloro - 2 - hydroxypropyl ammonium chloride, and react for 2 - 4 h; S3: After the reaction is completed, add washing water for washing, carry out centrifugation at 10000 - 20000 g, and filter to obtain modified guar gum; The above parts are parts by mass.

2. The separation process of insoluble substances during the preparation of polyaluminum chloride according to claim 1, characterized in that, The strong acid in step S1 is sulfuric acid or hydrochloric acid.

3. The separation process of insoluble substances during the preparation of polyaluminum chloride according to claim 1, characterized in that, The sedimentation agent in step 2) is a composition including chitosan and synthetic polymer.

4. The separation process of insoluble substances during the preparation of polyaluminum chloride according to claim 3, characterized in that, The synthetic polymer is polyvinyl alcohol.

5. The separation process of insoluble substances in the preparation process of polyaluminum chloride according to claim 4, characterized in that, The mass ratio of chitosan to polyvinyl alcohol is 1:2 - 1:

4.

6. The separation process of insoluble substances during the preparation of polyaluminum chloride according to claim 1, characterized in that, The solid - liquid separation method in step 2) is filtration. The filtration is to first filter once with a 50 - 100 - mesh sieve, and then filter twice with a 300 - 400 - mesh sieve to obtain the polyaluminum chloride mother liquor with insoluble substances removed.

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