Composite polyaluminum ferric chloride water purifying agent as well as preparation method and application thereof

Abstract

The invention provides a composite polyaluminum ferric chloride water purifying agent as well as a preparation method and application thereof, and belongs to the technical field of waste resource recycling and municipal sewage treatment. The industrial hazardous waste aluminum ash is subjected to innocent treatment and then reacts with the pickling steel waste liquid of the steel mill, and the polyaluminum ferric chloride meeting the industrial standard is prepared. The polyaluminum ferric chloride and a cationic adsorbent are compounded according to a specific proportion to obtain the composite polyaluminum ferric chloride water purifying agent. According to the method provided by the invention, the resource recycling of hazardous wastes is realized, and the composite polyaluminum ferric chloride water purifying agent obtained by the method is used for treating municipal sewage, so that the treated water quality can reach the first-grade discharge standard A.

Description

Technical Field

[0001] The invention belongs to the technical field of waste resource recycling and municipal sewage treatment, and specifically relates to a composite polyaluminium ferric chloride water purifier and a preparation method and application thereof. Background Art

[0002] Polyaluminium ferric chloride (PAFC) is an inorganic polymer flocculant developed on the basis of polyaluminium salt and polyferric salt flocculants. It has the advantages of both polyaluminium salt and polyferric salt flocculants and makes up for their deficiencies, especially for the treatment of low-temperature and low-turbidity water and low-temperature and high-turbidity water. Therefore, it is widely used in the treatment of tap water and sewage.

[0003] At present, the synthesis method of polyaluminium chloride ferric is mainly to add ferric chloride solution to the finished product polyaluminium chloride that has been prepared, and the obtained mixed solution is regarded as polyaluminium chloride ferric. For example, patent application CN115448371A discloses a production process of polyaluminium chloride ferric, comprising the following steps: S1. Prepare 3% ferric chloride solution, and put the ferric chloride liquid into a ton barrel, and wait for the addition during the filter pressing; S2. Put the crystallized aluminum chloride mother liquor wastewater into the pre-finished product pool through a feed pump, the product is precipitated for 10-12 hours, and then put into the plate and frame filter press for filter pressing, and the clear liquid produced after the filter pressing is put into a stirring barrel; S3. Put the ferric chloride solution configured in S1 into the reaction tank, and at the same time put into the clear liquid in the stirring barrel in S2, according to the mass ratio of 1-3:7-10, mix and stir for 30-50 minutes, and the stirring rate is more than 800r / min; S4. Pump the mixed solution after stirring into the finished product pool, and after aging for 15 hours, it is the finished product polyaluminium chloride ferric, and the preparation of polyaluminium chloride ferric is completed. The polymerization degree of the polyaluminium ferric chloride obtained by the method is not high enough, and the effect is greatly reduced when used for sewage treatment; and the production cost of the method is also high.

[0004] Aluminum ash is the scum and skimming floating on the upper layer of aluminum liquid during the metallurgical melting process of electrolytic aluminum, cast aluminum, and recycled aluminum. It also includes the residue left after subsequent treatment processes such as ash frying and ball milling. After aluminum ash was listed as hazardous waste, the disposal of aluminum ash has become a major problem that troubles aluminum processing companies, restricting the further development of the aluminum processing industry. Studies have shown that aluminum ash has obvious hazardous characteristics, especially secondary aluminum ash after aluminum recovery. Secondary aluminum ash has obvious leaching toxicity due to the presence of highly toxic fluorides, chlorides, etc., and the amount of ammonia released by reaction with water is large. Therefore, it is very necessary to harmlessly treat aluminum ash or even recycle it. Summary of the invention

[0005] Based on the above technical problems, the present invention provides a method for preparing a composite polyaluminium ferric chloride water purifier. The method uses industrial hazardous waste aluminium ash as raw material, performs harmless treatment on it, and then reacts it with cold-rolled steel pickling waste liquid generated in steelmaking enterprises to prepare polyaluminium ferric chloride that meets industry standards. The polyaluminium ferric chloride is then compounded with a cationic adsorbent in a specific ratio to obtain a composite polyaluminium ferric chloride water purifier.

[0006] In order to achieve the above object, the present invention specifically adopts the following technical solutions: A method for preparing a composite polyaluminium ferric chloride water purifier comprises the following steps: S1. Soaking aluminum ash in hydrochloric acid, adding water-soluble calcium salt and heavy metal remover to the solution obtained after soaking, and fully reacting; after the reaction is completed, filtering and collecting the filtrate; S2, add cold-rolled steel pickling waste liquid to the filtrate of step S1, then add chlorine-containing oxidant, mix well, heat to 50-90°C for insulation reaction; after the reaction is completed, dilute with water, adjust the pH to 3.5-4.5 with a pH regulator, let stand and precipitate, and the upper clear liquid is a polyaluminium ferric chloride solution; S3. Evenly mix the polyaluminium ferric chloride solution and the cationic adsorbent solution to obtain a composite polyaluminium ferric chloride water purifier; the mass of the polyaluminium ferric chloride is calculated based on the mass of alumina, and the ratio of the mass of the polyaluminium ferric chloride to the mass of the effective ingredient of the cationic adsorbent in the mixed solution is controlled to be (7:1) to (10:1) or 26:1.

[0007] In a preferred embodiment, the mass concentration of hydrochloric acid in step S1 is 10% to 25%, and the mass ratio of hydrochloric acid to aluminum ash is (1.5 to 3.0): 1. The mass concentration of hydrochloric acid is preferably 20%.

[0008] In a preferred embodiment, the mass of the water-soluble calcium salt in step S1 accounts for 3% to 10% of the mass of the aluminum ash.

[0009] In a further preferred embodiment, the mass of the water-soluble calcium salt in step S1 accounts for 5% of the mass of the aluminum ash.

[0010] In a preferred embodiment, the water-soluble calcium salt in step S1 is at least one of calcium nitrate, anhydrous calcium chloride and calcium chloride dihydrate.

[0011] In a further preferred embodiment, the water-soluble calcium salt in step S1 is calcium chloride dihydrate.

[0012] In a preferred embodiment, the heavy metal remover in step S1 is at least one of sodium sulfide, trithiotriazine trisodium salt, and sodium hydrosulfide.

[0013] In a further preferred embodiment, the heavy metal remover in step S1 is trimercaptotriazine trisodium salt.

[0014] In a preferred embodiment, the amount of cold-rolled steel pickling waste liquid added in step S2 is controlled according to the molar ratio of the iron element in the cold-rolled steel pickling waste liquid to the aluminum element in the filtrate of step S1 (1~3.5):1.

[0015] In a preferred embodiment, the chlorine-containing oxidant in step S2 is any one of sodium chlorate, potassium chlorate, sodium perchlorate, and potassium perchlorate, or a combination of several of them.

[0016] In a further preferred embodiment, the chlorine-containing oxidant in step S2 is sodium chlorate.

[0017] In a preferred embodiment, the pH regulator in step S2 is any one or a combination of calcium hydroxide, calcium aluminate, and sodium carbonate. The content of aluminum in the mixed solution diluted with water after the reaction is completed is detected. If the aluminum content is insufficient, calcium aluminate is preferably selected as the pH regulator.

[0018] In a preferred embodiment, the reaction temperature in step S2 is 70°C.

[0019] In a preferred embodiment, the cationic adsorbent in step S3 is at least one of polyacrylamide, dicyandiamide formaldehyde resin, and polydimethyldiallylammonium chloride.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) The present invention uses aluminum ash, a hazardous industrial waste, hydrochloric acid, a by-product of the chemical production industry, and pickling waste liquid from steel mills as raw materials to prepare polyaluminum ferric chloride that meets industry standards, thereby achieving the recycling of waste resources.

[0021] (2) The prepared polyaluminium ferric chloride is compounded with a cationic adsorbent in a specific ratio. When the obtained composite polyaluminium ferric chloride water purifier is used to treat municipal sewage, the treated water quality can reach the first-class standard A specified in GB 18918-2002.

[0022] (3) The preparation method of the present invention is simple, has low equipment requirements and low production cost. DETAILED DESCRIPTION

[0023] The following content is combined with the embodiments to clearly and completely describe the technical solution of the present application so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made to the following implementation modes by those of ordinary skill in the art without creative work belongs to the protection scope of the present application.

[0024] The aluminum ash used in the following examples comes from Hubei Huajin Aluminum Co., Ltd., and its main chemical components are as follows: Al2O3 35.47%, AlN 1.73%, Al 0.76%, F 1.35%, Fe2O3 2.17%, SiO2 9.38%, heavy metal 60ppm, organic matter 2.36%, and water 19.23%.

[0025] The specific embodiment of the present application provides a method for preparing a composite polyaluminium ferric chloride water purifier, comprising the following steps: S1. Harmless treatment of aluminum ash At below 40°C, 1000kg of aluminum ash is put into dilute hydrochloric acid (mass concentration is 10%~25%), a byproduct of the chemical production industry, and soaked for one day and night. The mass ratio of dilute hydrochloric acid to aluminum ash is (1.5~3.0):1. Add 3%~10% of the mass of aluminum ash to the solution obtained after soaking. Water-soluble calcium salt and heavy metal remover are added, and the reaction is stirred for 5~10 hours. After the reaction is completed, filter it with a plate and frame filter press. Blow dry the filter cake with air pressure and outsource it for treatment. Collect the filtrate for later use.

[0026] S2. Preparation of polyaluminium ferric chloride The filtrate in step S1 is pumped into the reactor, and the cold-rolled steel pickling waste liquid is added. The amount of cold-rolled steel pickling waste liquid added is controlled according to the molar ratio of the iron element in the waste liquid to the aluminum element in the filtrate of step S1 (1~3.5):1. Add chlorine-containing oxidant accounting for 1%~5% of the mass of aluminum ash to the reactor, and stir continuously, raise the temperature to 50℃~90℃ and react for 6~12 hours. After the reaction is completed, dilute with water, adjust the pH value to 3.5~4.5 with a pH adjuster, and then precipitate for 10~24 hours to obtain a dark brown supernatant, which is polyaluminum ferric chloride.

[0027] S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is mixed evenly with the cationic adsorbent solution; the mass of the polyaluminium ferric chloride is calculated based on the mass of the converted aluminium oxide, and the mass ratio of the polyaluminium ferric chloride to the effective component of the cationic adsorbent in the mixed solution is controlled to be (7:1) to (10:1) or 26:1, to obtain a composite polyaluminium ferric chloride water purifier.

[0028] As an example, the water-soluble calcium salt in step S1 is any one of calcium nitrate, anhydrous calcium chloride, and calcium chloride dihydrate, or a combination of several of them.

[0029] As an example, the heavy metal remover in step S1 is any one of sodium sulfide, trithiotriazine trisodium salt, and sodium hydrosulfide, or a combination of several of them.

[0030] As an example, the chlorine-containing oxidant in step S2 is any one of sodium chlorate, potassium chlorate, sodium perchlorate, and potassium perchlorate, or a combination of several of them.

[0031] As an example, the pH regulator in step S2 is any one or a combination of calcium hydroxide, calcium aluminate, and sodium carbonate; preferably calcium aluminate. As an example, the cationic adsorbent in step S3 is at least one of polyacrylamide, dicyandiamide formaldehyde resin, and polydimethyldiallyl ammonium chloride. When the cationic adsorbent is polyacrylamide and / or dicyandiamide formaldehyde resin, the mass ratio of polyaluminum ferric chloride to the effective component of the cationic adsorbent in the mixed solution is controlled to be (7:1) to (10:1). When the cationic adsorbent is polydimethyldiallyl ammonium chloride, the mass ratio of polyaluminum ferric chloride to the effective component of the cationic adsorbent in the mixed solution is controlled to be 26:1.

[0032] Example 1 A method for preparing a composite polyaluminium ferric chloride water purifier comprises the following steps: S1. Harmless treatment of aluminum ash At below 40°C, 1000kg of aluminum ash is put into dilute hydrochloric acid (mass concentration is 20%), a byproduct of the chemical production industry, and soaked for one day and night. The mass ratio of dilute hydrochloric acid to aluminum ash is 2.0:1. Add calcium chloride dihydrate and heavy metal remover TMT15 (trimercaptotriazine trisodium salt) accounting for 5% of the mass of aluminum ash to the solution obtained after soaking, and stir to react for 8 hours. After the reaction is completed, filter it with a plate and frame filter press. Blow dry the filter cake with air pressure and outsource it for processing. Collect the filtrate for later use.

[0033] S2. Preparation of polyaluminium ferric chloride The filtrate in step S1 is pumped into the reactor, and the cold-rolled steel pickling waste liquid is added. The amount of cold-rolled steel pickling waste liquid added is controlled according to the molar ratio of the iron element in the waste liquid to the aluminum element in the filtrate of step S1, which is 2:1. Sodium chlorate accounting for 3% of the mass of aluminum ash is added to the reactor, and it is stirred continuously, and the temperature is raised to 70°C for reaction for 10 hours. After the reaction is completed, dilute with water, adjust the pH value to 4.0 with calcium aluminate, and then precipitate for 16 hours to obtain a dark brown supernatant, which is polyaluminum ferric chloride.

[0034] S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is evenly mixed with the polyacrylamide (PAM) solution, and the mass ratio of polyaluminium ferric chloride to PAM converted by alumina content in the mixed solution is controlled to be 8:1, so as to obtain a composite polyaluminium ferric chloride water purifier.

[0035] Example 2 The method for preparing the composite polyaluminium ferric chloride water purifier in this embodiment is basically the same as that in embodiment 1, except that step S3: S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is evenly mixed with the dicyandiamide formaldehyde resin solution, and the mass ratio of polyaluminium ferric chloride to dicyandiamide formaldehyde resin converted by alumina content in the mixed solution is controlled to be 7:1, so as to obtain a composite polyaluminium ferric chloride water purifier.

[0036] Example 3 The method for preparing the composite polyaluminium ferric chloride water purifier in this embodiment is basically the same as that in embodiment 1, except that step S3: S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is evenly mixed with the polydimethyldiallyl ammonium chloride (PDADMAC) solution, and the mass ratio of polyaluminium ferric chloride to polydimethyldiallyl ammonium chloride converted by alumina content in the mixed solution is controlled to be 26:1, so as to obtain a composite polyaluminium ferric chloride water purifier.

[0037] Example 4 A method for preparing a composite polyaluminium ferric chloride water purifier comprises the following steps: S1. Harmless treatment of aluminum ash At a temperature below 40°C, 1000 kg of aluminum ash is put into dilute hydrochloric acid (mass concentration is 10%), a byproduct of the chemical production industry, and soaked for one day and night. The mass ratio of dilute hydrochloric acid to aluminum ash is 1.5:1. Add calcium nitrate accounting for 3% of the mass of aluminum ash and heavy metal remover sodium sulfide to the solution obtained after soaking, and stir for 5 hours. After the reaction is completed, filter it with a plate and frame filter press. Blow dry the filter cake with air pressure and outsource it for processing. Collect the filtrate for later use.

[0038] S2. Preparation of polyaluminium ferric chloride Pump the filtrate in step S1 into the reactor and add the cold-rolled steel pickling waste liquid. The amount of cold-rolled steel pickling waste liquid added is controlled according to the molar ratio of iron element in the waste liquid to aluminum element in the filtrate of step S1, which is 1:1. Add potassium chlorate accounting for 1% of the mass of aluminum ash to the reactor, stir continuously, and heat to 50°C for 12 hours. After the reaction is completed, dilute with water, adjust the pH value to 3.5 with calcium aluminate, and then precipitate for 10 hours to obtain a dark brown supernatant, which is polyaluminum ferric chloride.

[0039] S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is evenly mixed with the polyacrylamide (PAM) solution, and the mass ratio of polyaluminium ferric chloride to PAM converted by alumina content in the mixed solution is controlled to be 9:1, so as to obtain a composite polyaluminium ferric chloride water purifier.

[0040] Example 5 A method for preparing a composite polyaluminium ferric chloride water purifier comprises the following steps: S1. Harmless treatment of aluminum ash At a temperature below 40°C, 1000 kg of aluminum ash is put into dilute hydrochloric acid (mass concentration is 25%), a byproduct of the chemical production industry, and soaked for one day and night. The mass ratio of dilute hydrochloric acid to aluminum ash is 3.0:1. Anhydrous calcium chloride accounting for 10% of the mass of aluminum ash and heavy metal remover sodium hydrosulfide are added to the solution obtained after soaking, and the reaction is stirred for 10 hours. After the reaction is completed, filter it with a plate and frame filter press. Blow dry the filter cake with air pressure and outsource it for processing. Collect the filtrate for later use.

[0041] S2. Preparation of polyaluminium ferric chloride The filtrate in step S1 is pumped into the reactor, and the cold-rolled steel pickling waste liquid is added. The amount of cold-rolled steel pickling waste liquid added is controlled according to the molar ratio of the iron element in the waste liquid to the aluminum element in the filtrate of step S1, which is 3.5:1. A mixture of sodium perchlorate and potassium perchlorate in a mass ratio of 1:1 (the mass of the mixture accounts for 5% of the mass of aluminum ash) is added to the reactor, and stirred continuously, and the temperature is raised to 90°C for 6 hours. After the reaction is completed, dilute with water, adjust the pH value to 4.5 with calcium aluminate, and then precipitate for 24 hours to obtain a dark brown supernatant, which is polyaluminium ferric chloride.

[0042] S3. Preparation of composite polyaluminium ferric chloride water purifier The polyaluminium ferric chloride solution prepared in step S2 is evenly mixed with the polyacrylamide (PAM) solution, and the mass ratio of polyaluminium ferric chloride to PAM converted by alumina content in the mixed solution is controlled to be 10:1, so as to obtain a composite polyaluminium ferric chloride water purifier.

[0043] Comparative Example 1 The method for preparing the composite polyaluminium ferric chloride water purifier in this comparative example is basically the same as that in Example 1, except that the reaction is carried out at 40° C. for 14 hours in step S2.

[0044] Comparative Example 2 The method for preparing the composite polyaluminium ferric chloride water purifier in this comparative example is basically the same as that in Example 1, except that the reaction is carried out at 110° C. for 5 hours in step S2.

[0045] Product performance testing Referring to the method in HG / T 5359-2018 "Water Treatment Agent Polyaluminium Ferric Chloride", the polyaluminium ferric chloride prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was tested, and the test results are shown in Table 1.

[0046] Table 1 Test results of polyaluminium ferric chloride

[0047] As can be seen from Table 1, the test results of the polyaluminium ferric chloride prepared in the embodiment meet the requirements of the industry standard, while after the reaction temperature of step S2 in Comparative Example 1 and Comparative Example 2 is changed, the basicity of the product is very different. When the reaction temperature is too low or too high, the basicity of polyaluminium ferric chloride also meets the requirements of the national standard, but is significantly lower than the basicity in this application. This shows that when polyaluminium ferric chloride is prepared using the scheme in this application, it is necessary to control the appropriate reaction temperature to make the basicity of polyaluminium ferric chloride the highest.

[0048] According to the method specified in Table 7 of GB 18918-2002 "Pollutant Emission Standard for Urban Sewage Treatment Plants", the same amount of the composite polyaluminum ferric chloride water purifier prepared in Examples 1 to 3 and Comparative Examples 1 to 2 was used to treat the same amount of municipal sewage (taken from the Zhuankou Sewage Treatment Plant in Hanyang District, Wuhan City), and the water quality before and after treatment was tested. The test results of the main control indicators are shown in Table 2.

[0049] Table 2 Municipal sewage treatment results

[0050] As can be seen from the data in Table 2, when the composite polyaluminium chloride ferric water purifier prepared in the embodiment and the comparative example is used to treat municipal sewage, the same treatment process can meet the A standard of the first-level standard in GB 18918-2002 "Pollutant Discharge Standard for Urban Sewage Treatment Plants". When the composite polyaluminium chloride ferric water purifier prepared in Comparative Example 1 and Comparative Example 2 is used to treat municipal sewage, the removal rates of total phosphorus, total nitrogen and ammonia nitrogen are significantly low. That is, when the same amount of water purifier is used to treat the same amount of municipal sewage, the treatment effect of the water purifier in this application is significantly better. This is mainly because the basicity of the composite polyaluminium chloride ferric water purifier prepared in the embodiment is significantly higher than the basicity of the composite polyaluminium chloride ferric water purifier prepared in the comparative example. The higher the basicity, the higher the treatment efficiency of the composite polyaluminium chloride ferric water purifier. Therefore, when the water purifier in the comparative example is used to treat municipal sewage, if the treatment effect in this application needs to be achieved, more water purifiers need to be used for a longer time. Compared with the water purifier in the comparative example, the water purifier in this application is more cost-effective.

[0051] The above-described embodiments are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. For any person skilled in the art, the present application may have various changes and modifications. Any simple equivalent changes and modifications made based on the scope of protection of the present application and the contents of the specification should be included in the scope of protection of the present application.

Claims

1. A method for preparing a composite polyaluminium ferric chloride water purifier, characterized in that: The following steps are involved: S1. Soaking aluminum ash in hydrochloric acid, adding water-soluble calcium salt and heavy metal remover to the solution obtained after soaking, and fully reacting; after the reaction is completed, filtering and collecting the filtrate; S2, add cold-rolled steel pickling waste liquid to the filtrate of step S1, then add chlorine-containing oxidant, mix well, heat to 50-90°C for insulation reaction; after the reaction is completed, dilute with water, adjust the pH to 3.5-4.5 with a pH regulator, let stand and precipitate, and the upper clear liquid is a polyaluminium ferric chloride solution; S3. Evenly mix the polyaluminium ferric chloride solution and the cationic adsorbent solution to obtain a composite polyaluminium ferric chloride water purifier; the mass of the polyaluminium ferric chloride is calculated based on the mass of converted alumina, and the ratio of the mass of the polyaluminium ferric chloride to the mass of the effective component of the cationic adsorbent in the mixed solution is controlled to be (7:1) to (10:1) or 26:

1.

2. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: The mass concentration of hydrochloric acid in step S1 is 10%-25%, and the mass ratio of hydrochloric acid to aluminum ash is (1.5-3.0):

1.

3. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: The mass of the water-soluble calcium salt in step S1 accounts for 3% to 10% of the mass of the aluminum ash.

4. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: The water-soluble calcium salt in step S1 is at least one of calcium nitrate, anhydrous calcium chloride, and calcium chloride dihydrate; or / and the heavy metal remover in step S1 is at least one of sodium sulfide, trisodium trithiotriazine, and sodium hydrosulfide.

5. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: In step S3, the cationic adsorbent is at least one of polyacrylamide, dicyandiamide formaldehyde resin, and polydimethyldiallylammonium chloride.

6. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: The amount of the cold-rolled steel pickling waste liquid added in step S2 is controlled according to the molar ratio of the iron element in the cold-rolled steel pickling waste liquid to the aluminum element in the filtrate of step S1 (1-3.5):

1.

7. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: The chlorine-containing oxidant in step S2 is any one of sodium chlorate, potassium chlorate, sodium perchlorate, and potassium perchlorate, or a combination of several of them.

8. The method for preparing the composite polyaluminium ferric chloride water purifier according to claim 1, characterized in that: In step S2, the pH regulator is any one of calcium hydroxide, calcium aluminate, and sodium carbonate, or a combination of several of them.

9. The composite polyaluminium ferric chloride water purifier prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the composite polyaluminium ferric chloride water purifier according to claim 9 in sewage treatment.

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