Method for preparing polyaluminum ferric chloride from aluminum-containing waste acid, prepared polyaluminum ferric chloride and application of polyaluminum ferric chloride

Abstract

The invention discloses a method for preparing polyaluminum ferric chloride from aluminum-containing waste acid, the prepared polyaluminum ferric chloride and application, and relates to the technical field of wastewater treatment. According to the method disclosed by the invention, aluminum-containing waste acid and ferric chloride waste liquid are used as raw materials, the polyaluminum ferric chloride flocculant is prepared by utilizing an electrodialysis process, and the mass ratio of aluminum chloride to ferric chloride in a mixed solution in a reaction chamber and the reaction time are controlled; aluminum ions in aluminum-containing waste acid and iron ions in ferric chloride are effectively migrated and polymerized for preparation, the basicity of a polyaluminum ferric chloride flocculant product is improved synergistically, and a good flocculation effect is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and more specifically, to a method for preparing polyaluminium ferric chloride from waste acid containing aluminium, and the prepared polyaluminium ferric chloride and application thereof. Background Art

[0002] In recent years, with the increasing awareness of environmental protection and the increasing shortage of resources, the treatment and resource utilization of aluminum-containing waste acid has become a hot topic of research. Aluminum-containing waste acid mainly comes from industries such as aluminum processing and aluminum oxidation. Direct discharge will cause serious pollution to the environment and is also a waste of resources. At the same time, with the rapid development of industry, wastewater treatment has become an important environmental issue. Flocculants play a key role in wastewater treatment because of their simple operation, low cost and high efficiency in removing suspended colloidal particles and natural organic matter (NOM). Polyaluminum salt flocculants have some limitations, such as low sedimentation efficiency, large sludge volume, poor decolorization effect and possible toxicity of residual aluminum. The flocs formed by polyferric salt flocculants and their hydrolysis products have high strength, good sedimentation and dehydration ability, and have significant water purification effects, strong adaptability to water quality changes, a wide applicable pH range, and low cost. However, the strong corrosiveness of iron salts and the yellow color that may appear in the treated water are its shortcomings. Polyaluminium ferric chloride (PAFC) is an inorganic polymer flocculant developed on the basis of aluminium salt and iron salt flocculants. It has attracted wide attention due to its good flocculation effect, wide adaptability, low dosage, and low sludge production. In summary, there is an urgent need for a new method for preparing polyaluminium ferric chloride flocculant that can utilize aluminium-containing waste acid and ferric chloride waste liquid, reduce costs, reduce environmental pollution, and achieve effective utilization of resources.

[0003] Electrochemical electrodialysis technology is a method of separating and purifying substances by utilizing the phenomenon of ion migration under the action of an electric field, and provides a new idea for the recovery of waste acid and the preparation of flocculants. The prior art discloses a synthesis process of a polyferric sulfate flocculant, which uses potassium chlorate and ferrous sulfate as raw materials, combines electrodialysis with bipolar membrane electrodialysis to prepare a polyferric sulfate flocculant. First, the concentration effect of electrodialysis is used to prepare a high-concentration ClO 3- with Fe 3+ The mixed solution is then split into H by a bipolar membrane under the action of an electric field. + and OH - Participate in the oxidation reaction and hydrolysis reaction of ferrous ions. However, the polyferric sulfate flocculant prepared by this method has a low alkalinity and poor flocculation effect. Summary of the invention

[0004] The purpose of the invention is to overcome the defects and shortcomings of the existing flocculants prepared by using aluminum-containing waste acid, especially polyaluminum ferric chloride (PAFC) products with low basicity and poor water treatment effect of the flocculants, and provide a method for preparing polyaluminum ferric chloride with aluminum-containing waste acid and the application of the prepared polyaluminum ferric chloride. The polyaluminum ferric chloride flocculant is prepared by using an electrodialysis process, and the basicity of the polyaluminum chloride flocculant is significantly increased by controlling specific process conditions, and has a good flocculation effect.

[0005] Another object of the present invention is to provide a polyaluminium ferric chloride.

[0006] Another object of the present invention is to provide an application of polyaluminium ferric chloride in water treatment.

[0007] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0009] S1. The aluminum-containing waste acid solution and the iron-containing waste liquid are pretreated to remove impurities to obtain a pretreated aluminum chloride solution and a ferric chloride solution;

[0010] S2. A three-chamber electrodialysis device is used, and a homogeneous anion exchange membrane is set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The aluminum chloride solution and the ferric chloride solution obtained in S1 are mixed to obtain a mixed solution, which is injected into the reaction chamber for reaction to obtain a polyaluminum ferric chloride flocculant.

[0011] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution in S2 is 1 to 10:1, and the reaction time is 30 to 180 minutes.

[0012] Among them, it should be noted that:

[0013] The impurity removal pretreatment of the present invention may adopt conventional impurity removal treatment in the art, and may specifically preferably remove suspended matter and larger particles first, and then further remove COD in the waste liquid through activated carbon adsorption.

[0014] The three-chamber electrodialysis device used in step S2 of the present invention is a three-chamber electrodialysis device conventionally used in the art, which includes an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane added between the anode chamber and the reaction chamber.

[0015] In the method for preparing polyaluminum ferric chloride by using aluminum-containing waste acid of the present invention, aluminum-containing chloride solution and ferric chloride solution are used as raw materials. On the one hand, aluminum-containing waste acid and ferric chloride waste liquid can be used as raw materials to reduce costs, reduce environmental pollution, and realize effective utilization of resources. On the other hand, an electrodialysis process is used to prepare a polyaluminum ferric chloride flocculant. By controlling the mass ratio of aluminum chloride and ferric chloride in a mixed solution in a reaction chamber and the reaction time, aluminum ions in the aluminum-containing waste acid and iron ions in the ferric chloride are effectively migrated and polymerized for preparation, and the basicity of the polyaluminum ferric chloride flocculant product is synergistically improved. The method has a good flocculation effect, can effectively treat suspended matter and pollutants in water, and improves water quality.

[0016] The method for preparing polyaluminium ferric chloride by using waste acid containing aluminium of the present invention has simple preparation process, low cost and is easy for industrial production.

[0017] Preferably, the mass ratio of aluminum chloride to ferric chloride in the mixed solution in S2 is 3 to 5:1.

[0018] In a specific embodiment, the mass content of aluminum chloride in the mixed solution in S2 of the present invention is preferably 6-8%, and the mass content of ferric chloride is 1-2%.

[0019] In a specific embodiment, in order to better achieve the migration polymerization effect of aluminum ions in aluminum-containing waste acid and iron ions in ferric chloride, the preferred reaction time is 60 to 120 minutes.

[0020] The anolyte and the catholyte of the present invention may also be conventional electrolytes for electrodialysis chemical reactions, for example, the anolyte may be sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte can be a sodium chloride solution, etc. Wherein, the concentration of the anolyte can be 0.1-0.5 mol / L, the concentration of the cathode electrolyte can be 0.1-0.5 mol / L, and the temperature is room temperature (25°C).

[0021] In the electrodialysis chemical reaction, anions will move toward the anode under the action of the electric field, and cations will move toward the cathode under the action of the electric field, and react in the reaction chamber through the homogeneous anion exchange membrane. The conductivity and stability of the electrolyte and the concentration of the electrolyte directly affect the migration effect of the ions. The present invention can further effectively migrate and polymerize the aluminum ions in the aluminum-containing waste acid and the iron ions in the ferric chloride to prepare the polyaluminum ferric chloride flocculant through the selection of the above-mentioned anode electrolyte and cathode electrolyte, and at the same time improve the basicity of the polyaluminum ferric chloride flocculant.

[0022] The three-chamber electrodialysis device of the present invention can use carbon rods as electrodes, and an external DC power supply. The constant current can refer to the conventional settings in the art, for example, setting the constant current to 0.02A.

[0023] The present invention also specifically protects polyaluminium ferric chloride prepared by the above method for preparing polyaluminium ferric chloride using aluminium-containing waste acid, especially polyaluminium ferric chloride having a basicity of 30 to 90%, and more preferably polyaluminium ferric chloride having a basicity of 45 to 90%.

[0024] The present invention also specifically protects the use of polyaluminium ferric chloride in water treatment.

[0025] The polyaluminium ferric chloride prepared by the invention can be used as a flocculant in water treatment.

[0026] In specific water treatment applications, the polyaluminium ferric chloride flocculant of the present invention can be used to treat a variety of high COD wastewaters, for example, papermaking wastewater with a chemical oxygen demand (COD) content ranging from 100 to 1000 mg / L, printing and dyeing wastewater with a chemical oxygen demand (COD) content ranging from 400 to 1000 mg / L, and other organic matter in wastewaters.

[0027] In order to achieve better application effects, preferably, the pH value of the water treatment system is 6-8.

[0028] In specific water treatment applications, the dosage of the polyaluminium ferric chloride flocculant of the present invention can be adjusted according to actual needs. In order to achieve better treatment effects, preferably, the dosage of the polyaluminium ferric chloride in the water treatment application is 0.05-0.1 wt%.

[0029] In specific water treatment applications, the dosage of the polyaluminium ferric chloride flocculant of the present invention can be adjusted according to actual needs. In order to achieve a better comprehensive treatment effect, preferably, the treatment time of the water treatment application is 1 to 5 minutes. In specific applications, the water treatment operation can also be carried out under stirring conditions, wherein the stirring speed is preferably 50 to 200 r / min.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The method for preparing polyaluminum ferric chloride by using aluminum-containing waste acid of the present invention uses aluminum-containing waste acid and ferric chloride waste liquid as raw materials, utilizes an electrodialysis process to prepare a polyaluminum ferric chloride flocculant, and effectively migrates and polymerizes aluminum ions in the aluminum-containing waste acid and iron ions in the ferric chloride by controlling the mass ratio of aluminum chloride and iron chloride in a mixed solution in a reaction chamber and the reaction time, thereby synergistically achieving the improvement of the basicity of the polyaluminum ferric chloride flocculant product, having a good flocculation effect, being able to effectively treat suspended matter and pollutants in water, improving water quality, and at the same time being conducive to reducing costs, reducing environmental pollution, and realizing effective utilization of resources. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0033] Example 1

[0034] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0035] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0036] S2. A three-chamber electrodialysis device was used, which included an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane was set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte was 0.3 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.3 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0037] The 7% aluminum chloride solution and 1.5% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into the reaction chamber for 90 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0038] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 3:1.

[0039] The basicity (alkalinity) of the polyaluminium ferric chloride flocculant (PAFC) was determined to be 85% by sodium hydroxide titration.

[0040] Example 2

[0041] The invention discloses an application of polyaluminium ferric chloride in water treatment.

[0042] The polyaluminium ferric chloride flocculant prepared in Example 1 was applied to industrial sewage to conduct a flocculant coagulation effect experiment.

[0043] Among them, the main properties of industrial wastewater before treatment are as follows Table 1:

[0044] Table 1

[0045] Wastewater color pH COD(mg / L) Papermaking wastewater tan 6.92 852.3

[0046] Add an appropriate amount of alkali or acid to adjust the pH value of the water sample to 7, add 0.1% by mass fraction of the polyaluminum ferric chloride flocculant of Example 1, put it on a six-in-one stirrer with a stirring speed of 150r / min, maintain the stirring time for 3min and then let it stand for 15min, observe the experimental phenomena, and measure the COD of the water sample after the final treatment to be 143mg / L, and the COD removal rate is 83.2%.

[0047] Example 3

[0048] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0049] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0050] S2. A three-chamber electrodialysis device was used, which included an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane was set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte was 0.3 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.3 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0051] The 6% aluminum chloride solution and the 1% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into the reaction chamber for 90 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0052] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 5:1.

[0053] The basicity (alkalinity) of polyaluminium ferric chloride flocculant (PAFC) was determined to be 68%.

[0054] Example 4

[0055] The invention discloses an application of polyaluminium ferric chloride in water treatment.

[0056] The polyaluminium ferric chloride flocculant prepared in Example 3 was applied to industrial wastewater to conduct a flocculant coagulation effect experiment.

[0057] Among them, the main properties of industrial sewage before treatment are as shown in Example 2.

[0058] Add an appropriate amount of alkali or acid to adjust the pH value of the water sample to 7, add 0.1% by mass fraction of the polyaluminum ferric chloride flocculant of Example 3, put it on a six-in-one stirrer with a stirring speed of 100 r / min, maintain the stirring time for 5 min and then let it stand for 15 min to observe the experimental phenomena. The COD of the original papermaking wastewater is 852.3 mg / L, and the COD removal rate is 69.4%.

[0059] Example 5

[0060] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0061] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0062] S2. A three-chamber electrodialysis device was used, which included an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane was set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte was 0.1 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0063] The 8% aluminum chloride solution and the 2% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into the reaction chamber for 90 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0064] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 8:1.

[0065] The basicity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 58.9%.

[0066] Example 6

[0067] The invention discloses an application of polyaluminium ferric chloride in water treatment.

[0068] The polyaluminium ferric chloride flocculant prepared in Example 5 was applied to industrial wastewater to conduct a flocculant coagulation effect experiment.

[0069] Among them, the main properties of industrial sewage before treatment are as shown in Example 2.

[0070] Add an appropriate amount of alkali or acid to adjust the pH value of the water sample to 7, add 0.1% by mass fraction of the polyaluminum ferric chloride flocculant of Example 5, put it on a six-in-one stirrer with a stirring speed of 200 r / min, maintain the stirring time for 2 min and then let it stand for 15 min to observe the experimental phenomena. The COD of the original papermaking wastewater is 852.3 mg / L, and the COD removal rate is 45.7%.

[0071] Example 7

[0072] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0073] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0074] S2. A three-chamber electrodialysis device was used, which included an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane was set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte was 0.1 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0075] The 7% aluminum chloride solution and 1.5% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into the reaction chamber for 120 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0076] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 3:1.

[0077] The alkalinity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 87.1%.

[0078] Example 8

[0079] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0080] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0081] S2. A three-chamber electrodialysis device was used, which included an anode chamber and a cathode chamber distributed on both sides of the pool, a reaction pool in the middle, and a homogeneous anion exchange membrane was set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte was 0.1 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0082] The 7% aluminum chloride solution and 1.5% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into the reaction chamber for 180 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0083] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 3:1.

[0084] The alkalinity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 46.1%.

[0085] Referring to Example 2, the polyaluminium ferric chloride flocculant prepared in Example 8 was applied to industrial wastewater to conduct a flocculant coagulation effect experiment.

[0086] The COD of the original papermaking wastewater is 852.3 mg / L, and the COD removal rate is 30.6%.

[0087] Comparative Example 1

[0088] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0089] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0090] S2. It includes an anode chamber and a cathode chamber distributed on both sides of the pool, and a reaction pool in the middle. A homogeneous anion exchange membrane is set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte is 0.1 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0091] The 7% aluminum chloride solution and the 1.5% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into a reaction chamber for 200 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0092] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 3:1.

[0093] The alkalinity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 38.5%.

[0094] Comparative Example 2

[0095] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0096] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0097] S2. It includes an anode chamber and a cathode chamber distributed on both sides of the pool, and a reaction pool in the middle. A homogeneous anion exchange membrane is set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte is 0.1 mol / L sodium sulfate (Na 2 SO 4 ) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0098] The 7% aluminum chloride solution and the 1.5% ferric chloride solution obtained in S1 were mixed to obtain a mixed solution, which was injected into a reaction chamber for reaction for 90 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC), wherein the mass ratio of aluminum chloride to ferric chloride in the mixed solution was 12:1.

[0099] The basicity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 25.4%.

[0100] Comparative Example 3

[0101] A method for preparing polyaluminium ferric chloride from waste aluminium acid and application of the prepared polyaluminium ferric chloride comprises the following steps:

[0102] S1. The waste acid solution containing aluminum chloride and the waste ferric chloride solution are first subjected to physical filtration by sedimentation to remove suspended matter and larger particulate matter, and then further removed by activated carbon adsorption to obtain pretreated aluminum chloride solution and ferric chloride solution;

[0103] S2. It includes an anode chamber and a cathode chamber distributed on both sides of the pool, and a reaction pool in the middle. A homogeneous anion exchange membrane is set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The anolyte is 0.1 mol / L sodium sulfate (Na 2 SO 4) solution, the cathode electrolyte is 0.1 mol / L sodium chloride solution, the carbon rod is used as the electrode, and a DC power supply is applied, and the constant current is set to 0.02A;

[0104] The 7% aluminum chloride solution obtained in S1 and the 1.5% ferric chloride solution were mixed to obtain a mixed solution, which was injected into the reaction chamber for 90 minutes to obtain a polyaluminum ferric chloride flocculant (PAFC).

[0105] Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution is 0.1:1.

[0106] The basicity of polyaluminium ferric chloride flocculant (PAFC) was determined to be 10.1%.

[0107] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing polyaluminium ferric chloride from waste acid containing aluminium, characterized in that: The steps include: S1. The aluminum-containing waste acid solution and the iron-containing waste liquid are pretreated to remove impurities to obtain a pretreated aluminum chloride solution and a ferric chloride solution; S2. A three-chamber electrodialysis device is used, and a homogeneous anion exchange membrane is set between the anode chamber and the reaction chamber and between the cathode chamber and the reaction chamber. The aluminum chloride solution and the ferric chloride solution obtained in S1 are mixed to obtain a mixed solution, which is injected into the reaction chamber for reaction to obtain a polyaluminum ferric chloride flocculant. Wherein, the mass ratio of aluminum chloride to ferric chloride in the mixed solution in S2 is 1 to 10:1, and the reaction time is 30 to 180 minutes.

2. The method for preparing polyaluminium ferric chloride using waste acid containing aluminium as claimed in claim 1, characterized in that: The mass ratio of aluminum chloride to ferric chloride in the mixed solution in S2 is 3 to 5:

1.

3. The method for preparing polyaluminium ferric chloride from aluminium-containing waste acid as claimed in claim 1, characterized in that: The mass content of aluminum chloride in the mixed solution in S2 is 6-8%, and the mass content of ferric chloride is 1-2%.

4. The method for preparing polyaluminium ferric chloride from aluminium-containing waste acid as claimed in claim 1, characterized in that: The reaction time is 60 to 120 minutes.

5. The method for preparing polyaluminium ferric chloride from waste acid containing aluminium as claimed in claim 1, characterized in that: The electrolyte in the anode chamber is a sodium sulfate solution, and the electrolyte in the cathode chamber is a sodium chloride solution, and the electrolyte concentration is 0.1-0.5 mol / L.

6. A polyaluminium ferric chloride prepared by the method for preparing polyaluminium ferric chloride with aluminium-containing waste acid according to any one of claims 1 to 5, characterized in that: The basicity of the polyaluminium ferric chloride is 45-90%.

7. Use of the polyaluminium ferric chloride according to claim 6 in wastewater treatment.

8. The use according to claim 7, characterized in that The COD value of the wastewater is 100-1000 mg / L.

9. The use according to claim 7, characterized in that: The pH value of the system used for water treatment is 6-8.

10. The use according to claim 7, characterized in that: The dosage of polyaluminium ferric chloride in the application is 0.05-0.1 wt %.