Sample preparation method for granular silicon in river water

Abstract

The invention is applicable to the technical field of water quality analysis of environmental science and hydrology and water resource science, and provides a preparation method of a sample for granular silicon in river water, which comprises the following steps: 1, sample preparation: accurately weighing 20mg of sediment sample, and putting into a 50mL polypropylene centrifuge tube; step 2, sample digestion: adding 40ml of 0.1 M sodium carbonate (Na2CO3) solution (metal trace level) into the sample centrifuge tube to ensure that the solution completely covers the sample; 3, extracting a sample, namely extracting 1mL of supernate from a 50mL centrifugal tube in a water bath for 2 hours, 3 hours and 5 hours; and step 4, neutralization treatment: adding 0.2 ml of 1M hydrochloric acid (HCl) into a 15ml centrifugal tube filled with the supernatant, and diluting the supernatant by using Milli-Q ultrapure water until the total volume reaches 10mL. And 5, determining the silicon concentration, namely, quantitatively analyzing the silicon concentration in the solution by using a silicon molybdenum blue colorimetric method or a silicon molybdenum blue photometric method and then using a spectrophotometer or a flow analyzer. The treatment mode is favorable for improving the extraction efficiency of the granular silicon and reducing the interference on other silicon forms in the sample at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of water quality analysis in environmental science and hydrology and water resources science. More specifically, it relates to a method for preparing samples of particulate silicon in river water. Background Art

[0002] Particulate silicon (Amorphous Silica, ASi) is an important silicon form in water bodies. It adheres to sediment and consists of multiple components, including diatom remains, silicon particles generated by weathering, clay minerals, secondary minerals, anthropogenic silicon, and amorphous silicon particles, etc. In the laboratory, ASi is usually defined as the silicon particles intercepted when filtering through a 0.2μm or 0.45μm pore size filter membrane. Although the initial bioavailability of ASi is relatively low, under specific environmental conditions, such as the weakly alkaline environment of estuaries, it can dissolve and release dissolved silica (DSi), thereby increasing its bioavailability. As the second most abundant element on Earth, silicon plays a central role in the biogeochemical cycle. It not only regulates the primary productivity of marine ecosystems but also affects the global carbon cycle on geological time scales through the process of silicate weathering. Therefore, accurately determining the content of particulate silicon in river water is of great significance for evaluating water quality, ecosystem health, and understanding the role of silicon in the geochemical cycle.

[0003] However, there are some challenges in traditional river water sample collection and processing methods, such as complex operation, long time consumption, and easy sample contamination. In addition, the differences in methods and requirements adopted by different laboratories lead to poor data comparability. These problems are mainly reflected in sample pretreatment, selection of separation test solutions, setting of water bath temperature, and calculation methods of particulate silicon concentration. To overcome these challenges, it becomes particularly important to develop a new, unified, and efficient sample preparation method for particulate silicon in river water. This method should simplify the operation process, shorten the processing time, reduce the risk of sample contamination, and provide standardized analysis means to ensure the consistency and comparability of data between different laboratories. Through the improvement of this method, we can more accurately evaluate water quality and ecosystem health, providing a scientific basis for the protection and management of aquatic ecosystems. At the same time, this will also help us better understand the role of silicon in the geochemical cycle and its potential impact on the global carbon cycle. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for preparing samples of particulate silicon in river water (beneficial effects) (invention name).

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A sample preparation method for particulate silicon in river water, comprising the following steps:

[0007] Step 1: Sample preparation. Accurately weigh 20 mg of sediment sample and put it into a 50 mL polypropylene centrifuge tube.

[0008] Step 2: Sample digestion. Add 40 ml of 0.1 M carbonate (Na2CO3) solution (metal trace level) to the sample centrifuge tube to ensure that the solution completely covers the sample.

[0009] Step 3: Sample extraction. At 2 hours, 3 hours, and 5 hours of water bath, carefully remove the 50 mL centrifuge tube and extract 50 mL of supernatant from it.

[0010] Step 4: Neutralization treatment. Add 0.2 ml of 1 M hydrochloric acid (HCl) to the 15 ml centrifuge tube containing the supernatant, gently shake, and dilute the supernatant to a total volume of 10 mL with Milli-Q ultrapure water to neutralize the solution to make it roughly neutral.

[0011] Step 5: Silicon concentration determination. First use the silicomolybdate blue colorimetric method or the silicomolybdate blue photometry method, and then apply a spectrophotometer or a flow analyzer to quantitatively analyze the silicon concentration in the solution.

[0012] Step 6: Data analysis. Measure the silicon content at 2 hours, 3 hours, and 5 hours of water bath, draw a relationship graph between concentration and time, and obtain a concentration straight line.

[0013] Preferably, in Step 2: Add the Na2CO3 solution, cover the centrifuge tube lid, gently shake to ensure full contact between the sample and the solution, and place the centrifuge tube in a water bath pre-set to 85 °C to promote the dissolution of amorphous silicon.

[0014] Preferably, in Step 3: Pipette 1 mL of supernatant from the centrifuge tube and transfer it to a 15 mL polypropylene centrifuge tube for subsequent analysis.

[0015] Preferably, in Step 6, extend the straight line to 0 hour, and the intercept of the straight line at 0 hour is the silicon content.

[0016] The advantages of the present invention are:

[0017] 1. In the present invention, by using 0.1 M sodium carbonate (Na2CO3) solution as a weak alkaline medium, this solution can maximize the dissolution of amorphous silicon while minimizing the impact on refractory crystalline silicon. This treatment method helps to improve the extraction efficiency of particulate silicon and reduce the interference with other silicon forms in the sample.

[0018] 2. For the present invention, the method has low requirements for the instruments used in on-machine testing, and only needs to have a channel for detecting silicon. This means that the method can be widely applied to various laboratories without the need for additional investment in expensive dedicated equipment, thereby reducing the experimental cost and improving the accessibility of the experiment. Detailed implementation mode

[0019] The present invention provides the following technical solution: A method for preparing a sample of particulate silicon in river water, the method for preparing a river water particulate silicon sample includes the following steps:

[0020] Step 1: Sample preparation

[0021] Accurately weigh 20 mg of sediment sample and put it into a 50 mL polypropylene centrifuge tube.

[0022] Step 2: Sample digestion

[0023] Add 40 ml of 0.1 M sodium carbonate (Na2CO3) solution (metal trace level) to the sample centrifuge tube to ensure that the solution completely covers the sample.

[0024] Cover the centrifuge tube lid and gently shake to ensure full contact between the sample and the solution.

[0025] Put the centrifuge tube into a water bath pre-set to 85 °C to promote the dissolution of amorphous silicon.

[0026] Step 3: Sample extraction

[0027] At 2 hours, 3 hours, and 5 hours of water bath, extract 1 mL of supernatant from the 50 mL centrifuge tube.

[0028] Transfer 1 mL of supernatant from the centrifuge tube to a 15 mL polypropylene centrifuge tube for subsequent analysis.

[0029] Step 4: Neutralization treatment

[0030] Add 0.2 ml of 1 M hydrochloric acid (HCl) to the 15 ml centrifuge tube containing the supernatant and gently shake.

[0031] Use Milli-Q ultrapure water to dilute the supernatant to a total volume of 10 mL to neutralize the solution to make it approximately neutral.

[0032] Step 5: Silicon concentration determination

[0033] In this step, two colorimetric techniques, namely the silicon molybdenum blue colorimetric method and the silicon molybdenum blue photometric method, are used to quantitatively analyze the silicon concentration in the solution. For samples with a relatively high silicon concentration, the silicon molybdenum yellow method is also an optional method. Although its sensitivity is not high, it has the advantage of simple operation. When conducting the determination, any of the following instruments can be selected:

[0034] Spectrophotometer: Such as the V-1200 visible light spectrophotometer, which can accurately measure the absorbance at specific wavelengths, thereby accurately determining the silicon concentration in the solution.

[0035] Flow analyzer: Such as the Skakar nutrient automatic analyzer and the LaChat QuikChem8500S2 flow injection analyzer. These instruments are suitable for continuous flow analysis, featuring rapidity and automation. In particular, the LaChat QuikChem 8500S2 flow injection analyzer, using the QuikChem method 31-114-27-1-D, has a wide detection range (10 to 2000 mg / L), a low detection limit (0.3 mmol / L), and excellent precision (±0.5%) and accuracy (1.2%), making it very suitable for high-precision determination of silicon concentration.

[0036] Step Six: Data analysis

[0037] Determine the silicon content at 2 hours, 3 hours, and 5 hours in the water bath, plot the relationship between concentration and time, and obtain a concentration straight line.

[0038] Extend the straight line to 0 hour. The intercept of the straight line at 0 hour is the silicon content. (The reason for taking the intercept is to assume that amorphous silicon completely dissolves within the first hour of extraction, and clay / more crystalline silicon releases dissolved silicon at a constant rate within the experimental time range.)

[0039] Chemical information

[0040] Preparation of 0.1M Na2CO3 solution: Dissolve 10.60 g of Na2CO3 (molecular weight 105.99) in 1 L of Milli-Q ultrapure water.

[0041] Preparation of 1M HCl solution: Dissolve 36.46 g of HCl (molecular weight 36.46) in 1 L of Milli-Q ultrapure water.

[0042] Result representation

[0043] ASi is expressed as dry weight (%) and concentration (unit: mM). The calculation of ASi dry weight is based on the sediment weight added in each extraction, the volume of the extraction solution at each water bath time point (2, 3, and 5 hours), and the amount of dissolved silicon in the solution at that time point. The final ASi dry weight is the intercept value of the linear regression as described above. The calculation of ASi concentration is based on the suspended particulate matter concentration (g / L) at the sampling time point and the ASi dry weight. Then, the ASi concentration is converted from mg / L to mM.

[0044] Through the above steps, the present invention provides an accurate and widely applicable method for preparing samples of particulate silicon in river water, which is suitable for the determination of particulate silicon in river water under different environmental conditions, improving the purity of the samples and the accuracy of analysis.

[0045] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing samples of particulate silicon in river water, characterized in that: The following steps are involved: Step 1: Sample preparation: accurately weigh 20 mg of sediment sample and place it in a 50 mL polypropylene centrifuge tube; Step 2: Sample digestion: add 40 ml of 0.1 M sodium carbonate (Na2CO3) solution (metal trace level) to the sample centrifuge tube, ensuring that the solution completely covers the sample; Step 3: Sample extraction: After 2 hours, 3 hours, and 5 hours in the water bath, carefully remove the 50 mL centrifuge tube and extract 1 mL of supernatant from the 50 mL centrifuge tube; Step 4: Neutralization: add 0.2 ml 1M hydrochloric acid (HCl) to the 15 ml centrifuge tube containing the supernatant, shake gently, and dilute the supernatant to a total volume of 10 mL with Milli-Q ultrapure water to neutralize the solution to make it roughly neutral; Step 5: Determination of silicon concentration, first using the silicon molybdenum blue colorimetry or silicon molybdenum blue photometry, and then using a spectrophotometer or flow analyzer to quantitatively analyze the silicon concentration in the solution; Step 6: Data analysis: measure the silicon content after 2 hours, 3 hours, and 5 hours in the water bath, draw a graph of the relationship between concentration and time, and obtain a concentration straight line.

2. A method for preparing samples of particulate silicon in river water according to claim 1, characterized in that: The step 2 is: adding Na2CO3 solution, covering the centrifuge tube with a lid, gently shaking to ensure that the sample is fully in contact with the solution, and placing the centrifuge tube in a water bath pre-set to 85°C to promote the dissolution of amorphous silicon.

3. A method for preparing a sample of particulate silicon in river water according to claim 2, characterized in that: Step 3: 1 mL of supernatant was removed from the centrifuge tube and transferred to a 15 mL polypropylene centrifuge tube for subsequent analysis.

4. A method for preparing a sample of particulate silicon in river water according to claim 3, characterized in that: In step six, the straight line is extended to 0 hours, and the intercept of the straight line at 0 hours is the silicon content.