A method for determining different forms of aluminum in water

Abstract

The present invention discloses a method for determining different forms of aluminum in water, comprising: adding a complexing reagent to a water sample to be tested containing aluminum to obtain a first mixed solution, and determining the first aluminum content in the water sample to be tested; extracting the first mixed solution by a turbidity point extraction method after a first preset time to obtain a first extraction phase and a first aqueous phase; determining the second aluminum content in the first aqueous phase; determining the content of the first form of aluminum based on the first aluminum content and the second aluminum content; extracting the first mixed solution by a turbidity point extraction method after a second preset time to obtain a second extraction phase and a second aqueous phase; determining the third aluminum content in the second aqueous phase, determining the aluminum content of the second form of aluminum based on the second aluminum content and the third aluminum content; and determining the content of the third form of aluminum based on the third aluminum content.

Description

Technical Field

[0001] The invention belongs to the field of environmental analytical chemistry, and in particular relates to a method for determining different forms of aluminum in water. Background Art

[0002] Aluminum(III) in aqueous solution exhibits different hydrolysis forms due to its inherent hydrolysis characteristics. The distribution of aluminum forms in water is key to understanding the flocculation mechanism of aluminum-based flocculants. It is also crucial in environmental chemistry to fully understand the migration and transformation of aluminum and effectively control aluminum pollution in water. Furthermore, it is crucial in biochemistry to understand aluminum's biological metabolism and effectively prevent aluminum poisoning. Therefore, accurately identifying aluminum forms in aqueous solution is crucial.

[0003] At present, the relevant technologies mainly use Ferron time-by-time complexation colorimetry and nuclear magnetic resonance to characterize the aluminum form of aluminum in aqueous solution. However, both of these methods have certain requirements on the aluminum concentration in the aqueous solution. The time-by-time complexation colorimetry method requires that the aluminum concentration be within 10 -5 to 10 -4 mol / L to comply with the Lambert-Beer law; use 27 Al NMR requires the aluminum concentration to be 10 -4 mol / L or above, when the concentration is lower than 10 -5 mol / L, the above two methods cannot accurately determine the aluminum form of low concentration aluminum. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a method for determining low concentrations of different forms of aluminum in water, comprising:

[0005] A complexing reagent is added to a water sample to be tested containing aluminum to obtain a first mixed solution, and the first aluminum content in the above-mentioned water sample to be tested is measured; after a first preset time, the above-mentioned first mixed solution is extracted by a turbidity point extraction method to obtain a first extraction phase and a first aqueous phase; the second aluminum content in the above-mentioned first aqueous phase is measured; the content of the first form of aluminum is determined based on the above-mentioned first aluminum content and the above-mentioned second aluminum content; after a second preset time, the above-mentioned first mixed solution is extracted by a turbidity point extraction method to obtain a second extraction phase and a second aqueous phase; the third aluminum content in the above-mentioned second aqueous phase is measured, and the content of the second form of aluminum is determined based on the above-mentioned second aluminum content and the above-mentioned third aluminum content; the content of the third form of aluminum is determined based on the above-mentioned third aluminum content.

[0006] According to an embodiment of the present invention, the first form of aluminum includes monomeric form of aluminum, the second form of aluminum includes polymeric form of aluminum, and the third form of aluminum includes inert form of aluminum.

[0007] According to an embodiment of the present invention, determining the content of the first aluminum form according to the first aluminum content and the second aluminum content includes: determining the content of the first aluminum form according to the difference between the first aluminum content and the second aluminum content.

[0008] According to an embodiment of the present invention, determining the content of the second form of aluminum based on the second aluminum content and the third aluminum content includes: determining the content of the second form of aluminum based on a difference between the second aluminum content and the third aluminum content.

[0009] According to an embodiment of the present invention, the first preset duration includes 0 minutes, and the second preset duration includes 120 minutes.

[0010] According to an embodiment of the present invention, the complexing agent includes 7-iodo-8-hydroxyquinoline-5-sulfonic acid.

[0011] According to an embodiment of the present invention, the first mixed solution is extracted by turbidity point extraction to obtain a first extraction phase and a first aqueous phase after a first preset time, comprising: adding a surfactant and a sodium chloride aqueous solution to the first mixed solution after the first preset time, and obtaining the first extraction phase and the first aqueous phase by centrifugal separation.

[0012] According to an embodiment of the present invention, the surfactant includes a nonionic surfactant.

[0013] According to an embodiment of the present invention, the concentration of the sodium chloride aqueous solution ranges from 0 to 500 ug / L.

[0014] According to an embodiment of the present invention, the centrifugal separation speed is 2000-5000 rpm, and the centrifugal separation time is 5-20 min.

[0015] The present invention provides a method for determining different forms of aluminum in water. The aluminum in a water sample to be tested is complexed by a complexing reagent at a first preset time and a second preset time. The complexing reagent and the aluminum complex in a first mixed solution are enriched into a first extraction phase and a second extraction phase by utilizing the phase separation effect of a surfactant in turbidity point extraction. The second aluminum content and the third aluminum content in the first aqueous phase and the second aqueous phase are respectively measured, and the first aluminum content of the water sample to be tested is measured. The content of the first form of aluminum is determined by the difference between the first aluminum content and the second aluminum content; the content of the second form of aluminum is determined by the difference between the second aluminum content and the third aluminum content; and the content of the third form of aluminum is determined by the third aluminum content, thereby realizing the measurement of aluminum state changes in an aqueous solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of a method for determining different forms of aluminum in water according to the present invention is schematically shown.

[0017] Figure 2 The principle diagram of a method for determining different forms of aluminum in water according to the present invention is schematically shown.

[0018] Figure 3 The recovery rate diagram of the present invention in measuring aluminum standard solutions with different concentrations is schematically shown. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings. It is apparent that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention are intended to fall within the scope of protection of the present invention.

[0020] The main methods widely used in related technologies for characterizing aluminum forms in aqueous solutions include: Ferron time-complexation colorimetry and nuclear magnetic resonance. Among them, Ferron time-complexation colorimetry is a relatively rapid and simple method for analyzing aluminum forms. Its main principle is to utilize the difference in the complexation reaction rates between different forms of aluminum in solution and Ferron reagent to achieve the determination of different aluminum forms. Ferron time-complexation colorimetry divides aluminum in water into monomeric form (Ala), which reacts instantaneously with Ferron reagent; polymeric form (Alb), which reacts slowly with Ferron reagent; and inert form (Alc), which does not react with Ferron reagent or reacts very slowly, i.e., aluminum oxide sol or gel.

[0021] Another method widely recognized by researchers to determine the distribution and structure of aluminum in solution is nuclear magnetic resonance. Nuclear magnetic resonance can identify monomeric aluminum, dimerized aluminum and Al 13 For the polymer, the resonance peaks of the three aluminum forms are at 0.0 ppm, 4.5 ppm and 63.0 ± 0.5 ppm, respectively.

[0022] In summary, both methods cannot be used to determine the aluminum form in low-concentration aqueous solutions during water treatment. Therefore, there is an urgent need to develop a method for determining the aluminum form of trace aluminum in aqueous solutions.

[0023] The present invention provides a method for determining different forms of aluminum in water, comprising: adding a complexing reagent to a water sample to be tested containing aluminum to obtain a first mixed solution, and determining the first aluminum content in the water sample to be tested; extracting the first mixed solution by a turbidity point extraction method after a first preset time to obtain a first extraction phase and a first aqueous phase; determining the second aluminum content in the first aqueous phase; determining the content of the first form of aluminum based on the first aluminum content and the second aluminum content; extracting the first mixed solution by a turbidity point extraction method after a second preset time to obtain a second extraction phase and a second aqueous phase; determining the third aluminum content in the second aqueous phase, determining the content of the second form of aluminum based on the second aluminum content and the third aluminum content; and determining the content of the third form of aluminum based on the third aluminum content.

[0024] Figure 1 A flow chart of a method for determining different forms of aluminum in water according to the present invention is schematically shown.

[0025] In an embodiment of the present invention, the aluminum in the water sample to be tested is complexed by a complexing reagent at a first preset time and a second preset time, and the complex of the complexing reagent and the aluminum in the first mixed solution is enriched into the first extraction phase and the second extraction phase by utilizing the phase separation effect of the surfactant of the turbidity point extraction. The second aluminum content and the third aluminum content in the first aqueous phase and the second aqueous phase are respectively measured, and the first aluminum content of the water sample to be tested is measured. The content of the first form of aluminum is determined by the difference between the first aluminum content and the second aluminum content; the content of the second form of aluminum is determined by the difference between the second aluminum content and the third aluminum content; and the content of the third form of aluminum is determined by the third aluminum content, thereby realizing the determination of the change of aluminum state in the aqueous solution.

[0026] According to an embodiment of the present invention, the first form of aluminum includes monomeric form of aluminum, the second form of aluminum includes polymeric form of aluminum, and the third form of aluminum includes inert form of aluminum.

[0027] According to an embodiment of the present invention, determining the content of the first aluminum form according to the first aluminum content and the second aluminum content includes: determining the content of the first aluminum form according to the difference between the first aluminum content and the second aluminum content.

[0028] According to an embodiment of the present invention, determining the aluminum content of the second form of aluminum based on the second aluminum content and the third aluminum content includes: determining the aluminum content of the second form of aluminum based on a difference between the second aluminum content and the third aluminum content.

[0029] According to an embodiment of the present invention, the first preset duration includes 0 minutes, and the second preset duration includes 120 minutes.

[0030] In an embodiment of the present invention, a complexing reagent is added to a water sample to be tested. Within a first preset time period including 0 min, a complexing reaction occurs between the complexing reagent and the first form of aluminum Ala in the water sample. The first form of aluminum Ala is complexed by the complexing reagent and enriched in the first extraction phase under the phase separation action of the surfactant in the turbidity point extraction.

[0031] In an embodiment of the present invention, a complexing reagent is added to the water sample to be tested. Under the second preset time period including 120 minutes, the complexing reagent and the second form of aluminum Alb in the water sample undergo a complex reaction, and are enriched in the second extraction phase under the phase separation action of the surfactant of the turbidity point extraction.

[0032] In the embodiment of the present invention, the third form of aluminum Alc does not react with the complexing agent and is separated into the second aqueous phase.

[0033] According to an embodiment of the present invention, the complexing agent includes 7-iodo-8-hydroxyquinoline-5-sulfonic acid.

[0034] In the embodiment of the present invention, the complexing reagent includes 7-iodo-8-hydroxyquinoline-5-sulfonic acid. In the embodiment of the present invention, the complexing reagent adopts Ferron reagent, the main component of which is 7-iodo-8-hydroxyquinoline-5-sulfonic acid.

[0035] According to an embodiment of the present invention, the first mixed solution is extracted by turbidity point extraction to obtain a first extraction phase and a first aqueous phase after a first preset time, comprising: adding a surfactant and a sodium chloride aqueous solution to the first mixed solution after the first preset time, and obtaining the first extraction phase and the first aqueous phase by centrifugal separation.

[0036] According to an embodiment of the present invention, the surfactant includes a nonionic surfactant.

[0037] In the embodiment of the present invention, the surfactant includes but is not limited to Triton TX-114. The surfactant can separate and enrich the complex of the complexing agent and aluminum: the first form of aluminum Ala and the second form of aluminum Alb in the extraction phase to form micelles.

[0038] According to an embodiment of the present invention, the concentration of the surfactant is 5-10%.

[0039] In the embodiment of the present invention, the concentration of the surfactant is 5-10%, for example, 5%, 7%, 8%, 10%.

[0040] According to an embodiment of the present invention, the concentration of the sodium chloride aqueous solution ranges from 0 to 500 ug / L.

[0041] In an embodiment of the present invention, the concentration of the sodium chloride aqueous solution includes 0 to 500 ug / L, for example, 0 ug / L, 100 ug / L, 300 ug / L, and 500 ug / L.

[0042] In the embodiment of the present invention, the concentration of the sodium chloride aqueous solution is 0ug / L, and the recovery rate of aluminum is 95%. The concentration of the sodium chloride aqueous solution is greater than 0ug / L, which can improve the recovery rate of aluminum.

[0043] According to an embodiment of the present invention, the centrifugal separation speed is 2000-5000 rpm, and the centrifugal separation time is 5-20 min.

[0044] In an embodiment of the present invention, the centrifugal separation rate includes 2000-5000 rpm, for example, 2000 rpm, 3500 rpm, 4000 rpm, 5000 rpm; the centrifugal separation time includes 5-20 min, for example, 5 min, 10 min, 15 min, 20 min.

[0045] In an embodiment of the present invention, the first mixed solution is separated into a first extraction phase and a first aqueous phase under turbidity point extraction at a first preset time, the first form of aluminum Ala is complexed by a complexing reagent and enriched in the first extraction phase, and the second aluminum content in the first aqueous phase is measured; the first mixed solution is separated into a second extraction phase and a second aqueous phase at a second preset time, the second form of aluminum Alb is complexed by a complexing reagent and enriched in the second extraction phase, and the third form of aluminum Alc does not react with the complexing reagent and is separated in the second aqueous phase.

[0046] In an embodiment of the present invention, aluminum in the water sample to be tested is complexed and enriched in the extraction phase by turbidity point extraction combined with time-by-time complexation technology, and the first aluminum content in the water sample to be tested, the second aluminum content in the first aqueous phase, and the third aluminum content in the second aqueous phase are determined by inductively coupled plasma mass spectrometry (ICP-MS). The content of the first form of aluminum Ala is obtained by subtracting the second aluminum content from the first aluminum content, the content of the second form of aluminum Alb is obtained by subtracting the third aluminum content from the second aluminum content, and the content of the third form of aluminum Alc is obtained by the third aluminum content, thereby realizing the determination of the change of aluminum forms in the aqueous solution.

[0047] Figure 2 The principle diagram of a method for determining different forms of aluminum in water according to the present invention is schematically shown.

[0048] from Figure 2It can be seen that the water sample to be tested is placed in a centrifuge tube, Ferron reagent and surfactant TX-114 are added, shaken and centrifuged. Under the action of TX-114, the water sample is separated into an extraction phase and a supernatant. The complex of the complexing reagent and aluminum in the water sample is enriched in the extraction phase. The supernatant is taken and the aluminum content in the supernatant is determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0049] Figure 3 The recovery rate of the present invention in measuring Al standard solutions with different concentrations is schematically shown.

[0050] from Figure 3 It can be seen that under the action of surfactant TX-114, when the concentration of Al standard solution increases from 25μg / L, 50μg / L, 100μg / L, 150μg / L, 200μg / L to 250μg / L, the recovery rate of Al remains at about 95%, indicating that the recovery rate of Al standard solution is good.

[0051] The present invention is described in detail below with reference to specific embodiments.

[0052] The present invention optimizes the turbidity point extraction conditions through experiments, and obtains the following turbidity point extraction conditions: TX-114 concentration is 3% to 7% (m / v), NaCl concentration is 50 to 500 μM, and the optimal turbidity point extraction conditions are as follows: TX-114 concentration is 5% (m / v), NaCl concentration is 100 μM, centrifugal speed is 4500 r / min, and the optimal is 10 min.

[0053] Example 1

[0054] Homemade Al 13 Determination of different forms of aluminum in solution

[0055] Before testing, the homemade Al 13 The solution was diluted to 100 μg / L (in terms of Al). To avoid interference, ultrapure water was used during the experiment.

[0056] (1) Take 5 mL of diluted Al 13 Add 2 mL of Ferron reagent and 2 mL of 5% (m / V) TX-114 to the solution sample and quickly adjust the volume to 10 mL. Immediately centrifuge at 4500 r / min for 10 min and take the supernatant for testing.

[0057] (2) Take 5 mL of diluted Al 13 2 mL of Ferron reagent was added to the solution sample and allowed to react for 120 min. Then 2 mL of 5% (m / V) TX-114 was added and the volume was adjusted to 10 mL. The solution was immediately centrifuged at 4500 r / min for 10 min, and the supernatant was collected for testing.

[0058] (3) The first aluminum content of the tap water sample to be tested was tested by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the second aluminum content and the third aluminum content in the supernatant in steps (1) and (2) were calculated, and the aluminum content and proportion of different forms were obtained, as shown in Table 1 below.

[0059] Table 1 Al after dilution 13 Content and proportion of different forms of aluminum in samples

[0060]

[0061] As can be seen from Table 1, the content of the first form of aluminum Ala is 4.47 μg / L, accounting for 5.06% of the water sample; the content of the second form of aluminum Alb is 66.75 μg / L, accounting for 75.57% of the water sample; the content of the third form of aluminum Alc is 17.11 μg / L, accounting for 19.37% of the water sample.

[0062] Example 2

[0063] Determination of different forms of aluminum in laboratory tap water

[0064] Take 20 mL of tap water sample from the laboratory. To avoid interference, all water used in the experiment was ultrapure water.

[0065] (1) Add 2 mL of Ferron reagent, 2 mL of 5% (m / v) TX-114, and 10 μL of 1 mM sodium chloride aqueous solution to 5 mL of tap water sample and adjust the volume to 10 mL. Immediately centrifuge at 4500 rpm for 10 min and collect the supernatant for analysis.

[0066] (2) Add 2 mL of Ferron reagent to 5 mL of tap water sample, mix well, and let it react for 120 min. Then add 2 mL of 5% (m / V) TX-114 and 10 μL of 1 mM sodium chloride aqueous solution, and adjust the volume to 10 mL. Immediately centrifuge at 4500 r / min for 10 min, and collect the supernatant for analysis.

[0067] (3) The first aluminum content of the tap water sample to be tested was tested by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of the second aluminum content and the third aluminum content in the supernatant in steps (1) and (2) were calculated, and the aluminum content and proportion of different forms were obtained, as shown in Table 2 below.

[0068] Table 2 Content and proportion of different forms of aluminum in tap water samples

[0069]

[0070] As can be seen from Table 2, the content of the first form of aluminum Ala is 28.70 μg / L, accounting for 81.99% of the water sample; the content of the second form of aluminum Alb is 1.54 μg / L, accounting for 4.28% of the water sample; the content of the third form of aluminum Alc is 4.82 μg / L, accounting for 13.73% of the water sample.

[0071] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining different forms of aluminum in water, comprising: Adding a complexing agent to a water sample to be tested containing aluminum to obtain a first mixed solution, and measuring a first aluminum content in the water sample to be tested; After a first preset time, extracting the first mixed solution by turbidity point extraction to obtain a first extraction phase and a first aqueous phase; determining a second aluminum content in the first aqueous phase; determining a content of first aluminum form according to the first aluminum content and the second aluminum content; After a second preset time, extracting the first mixed solution by turbidity point extraction to obtain a second extraction phase and a second aqueous phase; measuring a third aluminum content in the second aqueous phase, and determining a content of the second form of aluminum based on the second aluminum content and the third aluminum content; determining a content of a third form of aluminum based on the third aluminum content; wherein, a surfactant and a sodium chloride aqueous solution are added to the first mixed solution, wherein the concentration of the surfactant is 5-10%, and the concentration of the sodium chloride aqueous solution is 0-500 μg / L; wherein the first aluminum content in the water sample to be tested, the second aluminum content in the first aqueous phase, and the third aluminum content in the second aqueous phase are determined by inductively coupled plasma mass spectrometry; Wherein, the aluminum concentration in the water sample to be tested is less than 10 -5 mol / L.

2. The method according to claim 1, wherein The first form of aluminum includes monomeric form of aluminum, the second form of aluminum includes polymeric form of aluminum, and the third form of aluminum includes inert form of aluminum.

3. The method according to claim 1, wherein Determining the content of the first form of aluminum based on the first aluminum content and the second aluminum content includes: The content of the first aluminum species is determined based on the difference between the first aluminum content and the second aluminum content.

4. The method according to claim 1, wherein Determining the aluminum content of the second form of aluminum based on the second aluminum content and the third aluminum content includes: The content of the second form of aluminum is determined based on the difference between the second aluminum content and the third aluminum content.

5. The method according to claim 1, wherein The first preset duration includes 0 min, and the second preset duration includes 120 min.

6. The method according to claim 1, wherein The complexing agent includes 7-iodo-8-hydroxyquinoline-5-sulfonic acid.

7. The method according to claim 1, wherein The step of extracting the first mixed solution by turbidity point extraction to obtain a first extraction phase and a first aqueous phase after a first preset time period includes: After the first preset time, a surfactant and a sodium chloride aqueous solution are added to the first mixed solution, and the first extraction phase and the first aqueous phase are obtained by centrifugal separation.

8. The method according to claim 7, wherein: The surfactant includes a nonionic surfactant.

9. The method according to claim 7, wherein: The centrifugal separation speed is 2000-5000 rpm, and the centrifugal separation time is 5-20 min.

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