Determination method of alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolysis solution and its application

Abstract

The invention discloses a method for determining alkalinity and sodium aluminate concentration in a secondary aluminum ash hydrolysis solution and its application, and relates to the technical field of chemical analysis. The determination method comprises: (1) taking a secondary aluminum ash hydrolysis solution, adding a first complexing agent, and obtaining a first test solution; (2) adjusting the pH value of the first test solution to 8-8.5 by using an acid solution, and obtaining a first solution; (3) adjusting the pH value of the first solution to below 4.8 by using an acid solution, and heating it at 50-90°C for 5-10 minutes, and obtaining a second test solution; (4) adjusting the pH value of the second test solution to 8-8.5 by using an alkali solution, and obtaining a third solution; (5) adding a second complexing agent to the third solution, and obtaining a third test solution; (6) adjusting the pH value of the third test solution to 8-8.5 by using an acid solution; (7) calculating the concentrations of caustic soda, carbonate and sodium aluminate: based on the above determination method, one-time sampling and continuous measurement can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical analysis, and in particular to a method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolyzate and an application thereof. Background Art

[0002] Secondary aluminum ash is a hazardous solid waste generated by the aluminum industry. Its main components are elemental aluminum, aluminum oxide, aluminum nitride, and also include some salts (fluoride salts and chloride salts, etc.) and silicon dioxide, etc. At present, the most common method of disposing secondary aluminum ash is the alkali solution hydrolysis method, that is, the secondary aluminum ash is hydrolyzed with sodium hydroxide solution at a certain temperature and pressure, thereby decomposing aluminum nitride, aluminum element, etc. into sodium aluminate. Then it is used in the subsequent process. The accurate determination of sodium aluminate and alkalinity (caustic soda, carbonate alkali) in the solution obtained after the hydrolysis reaction is of great significance for subsequent applications.

[0003] On the other hand, the common caustic soda determination methods in the field are the double indicator method or the barium chloride method, and sodium aluminate generally uses the EDTA back titration method. These methods are relatively cumbersome and slow in testing speed; they cannot measure quickly and continuously, which is not conducive to production monitoring and control. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for determining the alkalinity and sodium aluminate concentration in a secondary aluminum ash hydrolyzate, which can quickly and reliably determine the concentrations of caustic soda, alkali carbonate and sodium aluminate in the secondary aluminum ash hydrolyzate, providing a data basis for production control.

[0005] The technical problem that the present invention also aims to solve is to provide a method for determining the alkalinity and sodium aluminate concentration in a secondary aluminum ash hydrolysis solution and apply it to the secondary aluminum ash hydrolysis.

[0006] In order to solve the above technical problems, the present invention provides a method for determining the alkalinity and sodium aluminate concentration in a secondary aluminum ash hydrolyzate, which comprises the following steps:

[0007] (1) taking a secondary aluminum ash hydrolyzate, adding a first complexing agent, and obtaining a first test solution; wherein the first complexing agent is selected from one or more of EDTA-2Na, sodium gluconate, sodium salicylate, sodium oxalate, and acetylacetone;

[0008] (2) adjusting the pH of the first test solution to 8 to 8.5 using a first acid solution to obtain a first solution;

[0009] (3) adjusting the pH of the first solution to below 4.8 using a second acid solution, and heating the solution at 80 to 120° C. for 5 to 10 minutes to obtain a second test solution;

[0010] (4) adjusting the pH of the second test solution to 8 to 8.5 using an alkali solution to obtain a third solution;

[0011] (5) adding a second complexing agent to the third solution to obtain a third test solution; wherein the second complexing agent is selected from one or more of KF and sodium sulfosalicylate;

[0012] (6) adjusting the pH of the third test solution to 8 to 8.5 using a third acid solution;

[0013] (7) The concentrations of caustic soda, alkali carbonate and sodium aluminate in the secondary aluminum ash hydrolyzate are calculated according to the following formula group:

[0014]

[0015]

[0016]

[0017] Wherein, c1, c2, c3 are the molar concentrations of caustic soda, alkali carbonate, and sodium aluminate in the secondary aluminum ash hydrolyzate, respectively; V1 is the volume of the first acid solution consumed in step (2), is the H in the first acid solution + V2 is the volume of the second acid solution consumed in step (3), is H in the second acid solution + V3 is the volume of the alkali solution consumed in step (4), It is OH in the alkali solution - The molar concentration of V s V4 is the volume of the secondary aluminum ash hydrolyzate taken in step (1); V5 is the volume of the third acid solution consumed in step (6), It is H in the third acid solution + The molar concentration of the secondary aluminum ash hydrolyzate; A is the dilution multiple when the first test solution is formed.

[0018] As an improvement of the above technical solution, in step (1), an aqueous solution of a first complexing agent is added to the secondary aluminum ash hydrolyzate, wherein the concentration of the first complexing agent is 20 to 30 wt %;

[0019] The amount of the aqueous solution of the first complexing agent added is more than twice the sampling volume of the secondary aluminum ash hydrolyzate before dilution.

[0020] As an improvement of the above technical solution, the first complexing agent is EDTA-2Na and / or sodium gluconate.

[0021] As an improvement of the above technical solution, in step (5), an aqueous solution of a second complexing agent is added to the third solution, wherein the concentration of the second complexing agent is 20 to 30 wt %;

[0022] The amount of the aqueous solution of the second complexing agent added is at least 1.5 times the sampling volume of the secondary aluminum ash hydrolyzate before dilution.

[0023] As an improvement of the above technical solution, step (1) includes:

[0024] (1.1) Take the secondary aluminum ash hydrolyzate, add 4 to 8 times the volume of the first complexing agent aqueous solution, and dilute it by a preset multiple;

[0025] (1.2) Take a preset amount of the diluted hydrolyzate and add 20 to 30 times the volume of the aqueous solution of the first complexing agent to obtain the first test solution.

[0026] As an improvement of the above technical solution, the first acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution, the second acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution, the alkali solution is selected from sodium hydroxide solution and / or potassium hydroxide solution, and the third acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution.

[0027] As an improvement of the above technical solution, the first acid solution, the second acid solution and the third acid solution are hydrochloric acid solutions with a concentration of 0.5-1 mol / L; the alkali solution is sodium hydroxide solution with a concentration of 0.5-1 mol / L.

[0028] As an improvement of the above technical solution, in step (2), the first test solution is titrated to a pH of 8.2 to 8.3 using a first acid solution to obtain a first solution; in step (3), the first test solution is titrated to a pH of 4.4 to 4.5 using a second acid solution, and heated at 60 to 90° C. for 3 to 5 minutes to obtain a second test solution.

[0029] As an improvement of the above technical solution, in step (4), the pH of the second test solution is titrated to 8.2-8.3 using an alkali solution to obtain a third solution;

[0030] In step (6), the pH of the solution of the third test sample is titrated to 8.2-8.3 using a third acid solution.

[0031] Correspondingly, the present invention also discloses the application of the above-mentioned method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolysis solution in the secondary aluminum ash hydrolysis.

[0032] The implementation of the present invention has the following beneficial effects:

[0033] The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate of the present invention first coordinates with aluminum through a first ligand with a weaker coordination effect with aluminum, and measures the caustic soda and carbonate in the secondary aluminum ash hydrolyzate, and then uses a second ligand with a stronger coordination effect with aluminum to displace the hydroxyl in the stoichiometric relationship, and then determines the concentration of sodium aluminate. Based on the above determination method, one-time sampling and continuous measurement are achieved. And the determination method of the present invention has reliable determination results. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with specific implementation methods.

[0035] The present invention provides a method for determining the alkalinity and sodium aluminate concentration in a secondary aluminum ash hydrolyzate, which comprises the following steps:

[0036] (1) taking a secondary aluminum ash hydrolyzate, adding a first complexing agent, and obtaining a first test solution;

[0037] Specifically, step (1) includes:

[0038] (1.1) Take the secondary aluminum ash hydrolyzate, add 4 to 8 times the volume of the first complexing agent aqueous solution, and dilute it by a preset multiple;

[0039] Specifically, in the aqueous solution of the first complexing agent, the concentration of the first complexing agent is 20-30wt%. The first complexing agent can be selected from disodium EDTA, sodium gluconate, potassium gluconate, calcium gluconate, sodium salicylate, potassium salicylate, sodium oxalate, potassium oxalate, acetylacetone, but is not limited thereto. Preferably, the first complexing agent is selected from one or more of EDTA-2Na, sodium gluconate, sodium salicylate, sodium oxalate, and acetylacetone.

[0040] Specifically, the dilution factor can be 1 to 20 times, exemplarily 5 times, 10 times, 15 times or 20 times, but not limited thereto. Preferably, in one embodiment of the present invention, 5 to 20 mL of the secondary aluminum ash hydrolyzate is taken, 4 to 8 times the volume of the first complexing agent aqueous solution is added, and water is added to dilute it to 10 times.

[0041] (1.2) Take a preset amount of the diluted hydrolyzate and add 20 to 30 times the volume of the aqueous solution of the first complexing agent to obtain the first test solution.

[0042] Illustratively, in one embodiment of the present invention, 5 to 10 mL of the diluted hydrolyzate is taken, and an aqueous solution of the first complexing agent in an amount of 20 to 30 times its volume is added to obtain a first test solution.

[0043] (2) adjusting the pH of the first test solution to 8 to 8.5 using a first acid solution to obtain a first solution;

[0044] Specifically, the first acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution, but not limited thereto. Preferably, it is hydrochloric acid solution, and its concentration is 0.5 to 1 mol / L. Specifically, the pH can be indicated by a pH meter or a pH reagent (such as phenolphthalein), but not limited thereto.

[0045] Preferably, in one embodiment of the present invention, the first test solution is titrated to a pH of 8.2 to 8.3 using a first acid solution to obtain a first solution.

[0046] (3) adjusting the pH of the first solution to below 4.8 using a second acid solution, and heating the solution at 50 to 90° C. for 5 to 10 minutes to obtain a second test solution;

[0047] Specifically, the second acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution, but not limited thereto. Preferably, hydrochloric acid solution has a concentration of 0.3 to 0.8 mol / L. Specifically, pH can be indicated by a pH meter or a pH reagent (such as methyl orange), but not limited thereto. In addition, by heating, a small amount of carbonic acid in the solution can be decomposed to avoid affecting the measurement results.

[0048] Preferably, in one embodiment of the present invention, the first supply solution is titrated to a pH of 4.4-4.5 using a second acid solution, and heated at 80-120° C. for 3-5 min to obtain a second test solution.

[0049] (4) adjusting the pH of the second test solution to 8 to 8.5 using an alkali solution to obtain a third solution;

[0050] Specifically, the alkali liquid is selected from sodium hydroxide solution and / or potassium hydroxide solution, but not limited thereto. Preferably, the alkali liquid is selected from sodium hydroxide solution, and its concentration is 0.5 to 1 mol / L. Specifically, the pH can be indicated by a pH meter or a pH reagent (such as phenolphthalein), but not limited thereto.

[0051] (5) adding a second complexing agent to the third solution to obtain a second test solution;

[0052] Specifically, an aqueous solution of a second coordinating agent is added to the third solution, and the mixture is uniformly mixed to obtain a second test solution. The second coordinating agent may be KF, sulfosalicylic acid or its salt (sodium sulfosalicylate), but is not limited thereto. The concentration of the second coordinating agent in the aqueous solution of the second coordinating agent is 20 to 30 wt%. Preferably, sodium sulfosalicylate is selected as the second coordinating agent. Specifically, the amount of the aqueous solution of the second coordinating agent added is more than 1.5 times the sample volume of the secondary aluminum ash hydrolyzate before dilution.

[0053] (6) adjusting the pH of the third test solution to 8 to 8.5 using a third acid solution;

[0054] Specifically, the third acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution, but not limited thereto. Preferably, it is hydrochloric acid solution, and its concentration is 0.5-1 mol / L. Specifically, the pH can be indicated by a pH meter or a pH reagent (such as phenolphthalein), but not limited thereto.

[0055] Preferably, in one embodiment of the present invention, the pH of the solution of the third test sample is titrated to 8.2-8.3 using a third acid solution.

[0056] (7) The concentrations of caustic soda, alkali carbonate and sodium aluminate in the secondary aluminum ash hydrolyzate are calculated according to the following formula group:

[0057]

[0058]

[0059]

[0060] Wherein, c1, c2, c3 are respectively the molar concentrations of caustic soda (in terms of Na2O), alkali carbonate (in terms of Na2O), and sodium aluminate (in terms of Al2O3) in the secondary aluminum ash hydrolyzate; V1 is the volume of the first acid solution consumed in step (2), is the H in the first acid solution + V2 is the volume of the second acid solution consumed in step (3), is H in the second acid solution + V3 is the volume of the alkali solution consumed in step (4), It is OH in the alkali solution - The molar concentration of V s V4 is the volume of the secondary aluminum ash hydrolyzate taken in step (1); V5 is the volume of the third acid solution consumed in step (6), It is H in the third acid solution + The molar concentration of the secondary aluminum ash hydrolyzate; A is the dilution multiple when the first test solution is formed.

[0061] The present invention will be further described below with reference to specific embodiments.

[0062] Example 1

[0063] 1. Instrument

[0064] (1) pH meter, (2) two 25 mL dual-sensor burettes, (3) 100 mL volumetric flask, (4) 10 mL pipette, (5) 100 mL measuring cylinder, (6) 500 mL polytetrafluoroethylene beaker, (7) magnetic stirrer, (8) electric furnace;

[0065] 2. Chemical reagents

[0066] (1) 0.5 mol / L hydrochloric acid standard solution, (2) 0.5 mol / L sodium hydroxide standard solution, (3) 20% sodium gluconate solution, (4) 30% potassium fluoride solution;

[0067] 3 Operation steps

[0068] (1) Quantitatively transfer 10 mL of the sample solution into a 100 mL volumetric flask, add 40 mL of 20% sodium gluconate solution, dilute to 100 mL, shake well and set aside;

[0069] (2) Quantitatively pipette 10 mL of solution (1), add 50 mL of 20% sodium gluconate solution, add an appropriate amount of distilled water to remove carbon dioxide, and titrate with 0.5 mol / L hydrochloric acid standard solution to a pH value of 8.2, and record the volume V1;

[0070] (3) Add a certain volume V2 of 0.5 mol / L hydrochloric acid standard solution to solution (2) to a pH value of 4.2, and heat to decompose to produce carbonic acid;

[0071] (4) Titrate solution (3) with 0.5 mol / L sodium hydroxide standard solution to a pH value of 8.2 and record the volume V3;

[0072] (5) Add 50 mL of 30% potassium fluoride solution to solution (4), titrate the solution to pH 8.2 with 0.5 mol / L hydrochloric acid standard solution, and record the volume V4.

[0073] 4 Calculation results

[0074] Titrate three times respectively, and the calculation results are as follows:

[0075]

[0076]

[0077] In the table, the concentration of hydrochloric acid is 0.4994 mol / L, the concentration of sodium hydroxide used is 0.4930 mol / L, and 10 ml of the sample is taken.

[0078] In addition, the same volume of solution was taken and the concentrations of caustic soda, alkali carbonate and sodium aluminate were measured respectively according to the mixed alkali method and EDTA back titration method known in the art. The results are as follows:

[0079]

[0080] It can be seen that the data obtained by the method adopted in the present invention and the existing mature method have small errors and high accuracy.

[0081] Example 2

[0082] 1. Instrument

[0083] (1) Acidic precision pH test paper, (2) 2 25 mL dual-element burettes, (3) 100 mL volumetric flask, (4) 10 mL pipette, (5) 100 mL measuring cylinder, (6) 500 mL polytetrafluoroethylene beaker, (7) magnetic stirrer, (8) electric furnace;

[0084] 2. Chemical reagents

[0085] (1) 0.5 mol / L hydrochloric acid standard solution, (2) 0.5 mol / L sodium hydroxide standard solution, (3) 20% sodium salicylate solution, (4) 30% sodium sulfosalicylate solution, (5) phenolphthalein indicator;

[0086] 3 Operation steps

[0087] (1) Quantitatively transfer 10 mL of the sample solution into a 100 mL volumetric flask, add 40 mL of 20% sodium salicylate solution, dilute to 100 mL, shake well and set aside;

[0088] (2) Quantitatively pipette 10 mL of solution (1), add 50 mL of 20% sodium salicylate solution, add an appropriate amount of distilled water to remove carbon dioxide, add two drops of phenolphthalein indicator, and titrate with 0.5 mol / L hydrochloric acid standard solution until it turns slightly red, and record the volume V1;

[0089] (3) Add a quantitative volume V2 of 0.5 mol / L hydrochloric acid standard solution to solution (2) until the acid precision pH test paper shows below 4.5, and heat to decompose to produce carbonic acid;

[0090] (4) Titrate solution (3) with 0.5 mol / L sodium hydroxide standard solution until the solution turns slightly red and record the volume V3;

[0091] (5) Add 50 mL of 30% sodium sulfosalicylate solution to solution (4), and titrate the solution with 0.5 mol / L hydrochloric acid standard solution until it turns slightly red. Record the volume V4.

[0092] 4 Calculation results

[0093] Titrate three times respectively, and the calculation results are as follows:

[0094] <![CDATA[V1 / mL]]> <![CDATA[V2 / mL]]> <![CDATA[V3 / mL]]> <![CDATA[V4 / mL]]> <![CDATA[c1(mol / L)]]> <![CDATA[c2(mol / L)]]> <![CDATA[c3(mol / L)]]> 1 3.62 7.52 6.78 3.33 0.697 0.826 0.277 2 3.63 7.51 6.77 3.34 0.700 0.826 0.278 3 3.64 7.53 6.75 3.35 0.693 0.865 0.279 Standard Deviation 0.004 0.023 0.001

[0095] In the table, the concentration of hydrochloric acid is 0.4994 mol / L, the concentration of sodium hydroxide used is 0.4930 mol / L, and 10 ml of the sample is taken.

[0096] In addition, the same volume of solution was taken and the concentrations of caustic soda, alkali carbonate and sodium aluminate were measured respectively according to the mixed alkali method and EDTA back titration method known in the art. The results are as follows:

[0097]

[0098] It can be seen that the data obtained by the method adopted in the present invention and the existing mature method have small errors and high accuracy.

[0099] The above is a preferred embodiment of the invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the invention. These improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolyzate, characterized in that: The following steps are involved: (1) taking a secondary aluminum ash hydrolyzate, adding a first complexing agent, and obtaining a first test solution; wherein the first complexing agent is selected from one or more of EDTA-2Na, sodium gluconate, sodium salicylate, sodium oxalate, and acetylacetone; (2) adjusting the pH of the first test solution to 8 to 8.5 using a first acid solution to obtain a first solution; (3) adjusting the pH of the first solution to below 4.8 using a second acid solution, and heating the solution at 80 to 120° C. for 5 to 10 minutes to obtain a second test solution; (4) adjusting the pH of the second test solution to 8 to 8.5 using an alkali solution to obtain a third solution; (5) adding a second complexing agent to the third solution to obtain a third test solution; wherein the second complexing agent is selected from one or more of KF and sodium sulfosalicylate; (6) adjusting the pH of the third test solution to 8 to 8.5 using a third acid solution; (7) The concentrations of caustic soda, alkali carbonate and sodium aluminate in the secondary aluminum ash hydrolyzate are calculated according to the following formula group: Wherein, c1, c2, c3 are the molar concentrations of caustic soda, alkali carbonate, and sodium aluminate in the secondary aluminum ash hydrolyzate, respectively; V1 is the volume of the first acid solution consumed in step (2), is the H in the first acid solution + V2 is the volume of the second acid solution consumed in step (3), is H in the second acid solution + V3 is the volume of the alkali solution consumed in step (4), It is OH in the alkali solution - The molar concentration of V s V4 is the volume of the secondary aluminum ash hydrolyzate taken in step (1); V5 is the volume of the third acid solution consumed in step (6), It is H in the third acid solution + The molar concentration of the secondary aluminum ash hydrolyzate; A is the dilution multiple when the first test solution is formed.

2. The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate according to claim 1, characterized in that: In step (1), an aqueous solution of a first complexing agent is added to the secondary aluminum ash hydrolyzate, wherein the concentration of the first complexing agent is 20 to 30 wt %; The amount of the aqueous solution of the first complexing agent added is more than twice the sampling volume of the secondary aluminum ash hydrolyzate before dilution.

3. The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate according to claim 2, characterized in that: The first complexing agent is EDTA-2Na and / or sodium gluconate.

4. The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate according to claim 1, characterized in that: In step (5), an aqueous solution of a second complexing agent is added to the third solution, wherein the concentration of the second complexing agent is 20 to 30 wt %; The amount of the aqueous solution of the second complexing agent added is at least 1.5 times the sampling volume of the secondary aluminum ash hydrolyzate before dilution.

5. The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate according to claim 4, characterized in that: Step (1) comprises: (1.1) Take the secondary aluminum ash hydrolyzate, add 4 to 8 times the volume of the first complexing agent aqueous solution, and dilute it by a preset multiple; (1.2) Take a preset amount of the diluted hydrolyzate and add 20 to 30 times the volume of the aqueous solution of the first complexing agent to obtain the first test solution.

6. The method for determining the alkalinity and sodium aluminate concentration in the secondary aluminum ash hydrolyzate according to claim 4, characterized in that: The first acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution; the second acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution; the alkali solution is selected from sodium hydroxide solution and / or potassium hydroxide solution; and the third acid solution is selected from one or more of nitric acid solution, hydrochloric acid solution, and sulfuric acid solution.

7. The method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolyzate according to claim 1, characterized in that: The first acid solution, the second acid solution and the third acid solution are hydrochloric acid solutions with a concentration of 0.5-1 mol / L; the alkali solution is sodium hydroxide solution with a concentration of 0.5-1 mol / L.

8. The method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolyzate according to claim 1, characterized in that: In step (2), the first test solution is titrated to a pH of 8.2 to 8.3 using a first acid solution to obtain a first solution; in step (3), the first test solution is titrated to a pH of 4.4 to 4.5 using a second acid solution, and heated at 60 to 90° C. for 3 to 5 minutes to obtain a second test solution.

9. The method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolyzate according to claim 1, characterized in that: In step (4), the pH of the second test solution is titrated to 8.2-8.3 using an alkali solution to obtain a third solution; In step (6), the pH of the solution of the third test sample is titrated to 8.2-8.3 using a third acid solution.

10. Use of the method for determining alkalinity and sodium aluminate concentration in secondary aluminum ash hydrolysis solution according to any one of claims 1 to 9 in secondary aluminum ash hydrolysis.

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