A LIBS water quality detection method

Abstract

The present application relates to the technical field of LIBS water quality detection, and specifically discloses a LIBS water quality detection method, comprising the following steps: a. soaking wood-derived carbon substrate with secondary pore channel structure in a water sample to be detected to obtain wood-derived carbon substrate adsorbing heavy metal elements in the water sample; b. taking out the substrate material adsorbing heavy metal elements in the water sample and drying to obtain wood-derived carbon substrate to-be-detected sample; and c. detecting the wood-derived carbon substrate to-be-detected sample by using a laser-induced breakdown spectroscopy (LIBS) device, and quantitatively analyzing the heavy metal elements by analyzing plasma emission spectrum. The present application improves the detection sensitivity and reliability of LIBS on heavy metal elements in water, adopts a substrate structure of wood board, has high strength and is not easy to break, and is low in cost.

Description

Technical Field

[0001] This invention relates to the field of LIBS water quality testing technology, and in particular to a LIBS water quality testing method. Background Technology

[0002] Laser-induced breakdown spectroscopy (LIBS) is an elemental analysis technique based on atomic emission spectroscopy. Its principle involves using a high-energy pulsed laser to ablate the sample, generating a transient plasma. By analyzing the wavelength and intensity of the radiation emitted during the plasma's cooling process, the elemental composition and concentration information of the sample can be obtained. After decades of development, LIBS technology has demonstrated unique advantages such as speed, comprehensive elemental analysis, and long-range operation, showing broad application prospects in environmental monitoring, industrial process analysis, geological exploration, and deep-sea and deep-space exploration.

[0003] However, LIBS technology still faces a series of technical challenges when directly detecting liquid samples (especially aqueous solutions), which severely restrict its detection sensitivity and accuracy: First, when the laser directly acts on the liquid surface, scattering and other phenomena occur, dispersing the laser energy; second, the shock wave generated by the plasma can cause liquid splashing and plasma quenching, etc. The above factors together result in the LIBS detection limit for trace metal elements in aqueous solutions being usually high, making it difficult to meet the monitoring needs of ultra-low concentration pollutants (such as Pb, Cr, As, etc.) in environmental water bodies.

[0004] To improve the performance of liquid-phase LIBS, researchers have proposed several improvement strategies, mainly including: liquid jet method, which avoids container wall interference by forming a stable liquid flow, but the system is complex and still cannot completely overcome plasma quenching; substrate enrichment (SE-LIBS), which pre-enriches the analyte on a solid substrate, transforming liquid-phase detection into solid-phase detection, with commonly used substrates such as metal foil and filter paper. For example, using filter paper sampling combined with discharge-assisted LIBS can extend the plasma lifetime to nearly 100 microseconds and improve the spectral signal intensity by 1 to 2 orders of magnitude. The confined structure method uses metal capillaries to confine liquid flow and plasma diffusion to reduce sputtering and improve signal stability; electrochemical enrichment combined with controlled spark discharge has also been used to enhance the detection signals of volatile elements such as As and Hg. Although these methods have certain effects, there are still obvious limitations: filter paper has low mechanical strength and is easily damaged; metal or nanomaterial substrates are expensive and have complex preparation processes; and the adsorption selectivity and enrichment efficiency of electrochemical enrichment for specific metal ions still need to be improved. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies, such as low mechanical strength of filter paper, easy breakage, high cost and complex preparation process of metal or nanomaterial substrates, and the need to improve the adsorption selectivity and enrichment efficiency of electrochemical enrichment for specific metal ions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A LIBS water quality testing method includes the following steps:

[0008] a. Immerse a wood-derived carbon substrate with a secondary pore structure in a water sample to be tested to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in the water sample.

[0009] b. Remove the substrate material that has adsorbed heavy metal elements and dry it to obtain the wood-derived carbon substrate sample to be tested;

[0010] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device, and the heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum.

[0011] Preferably, in step a, the substrate material is completely immersed in the water sample to be tested for 10 to 90 minutes.

[0012] Preferably, in step b, the substrate material is dried at a temperature of 50~80℃ for 5~15 minutes.

[0013] Preferably, in step c, the laser of the laser-induced breakdown spectroscopy (LIBS) device is applied with a voltage of 630~650V and a laser energy of 187.2~195.5mJ; the timing control parameters are set to a delay of 1~2μs and a gate width of 9~10μs.

[0014] Optionally, the secondary pore structure includes micropores and mesopores, and the secondary pore structure is formed by crystal growth of a chloride template.

[0015] Preferably, the wood used is fir.

[0016] Optionally, the preparation method of wood-derived carbon substrate includes the following steps:

[0017] 1) Dissolve glucose and sodium chloride in water to obtain a precursor solution;

[0018] 2) Cut wood chips of different thicknesses and immerse them in the precursor solution under negative pressure;

[0019] 3) Remove the wood chips and dry them to obtain the calcination precursor;

[0020] 4) The calcination precursor is calcined at high temperature in an inert gas atmosphere to obtain a wood-derived carbon substrate.

[0021] Optionally, the wood-derived carbon substrate obtained in step 4 is polished to a thickness of 0.5~0.7mm and then cleaned with deionized water.

[0022] Preferably, in step 1), the concentration of the dissolved sodium chloride solution is 1~3.5 mol / L, and the concentration of the dissolved glucose solution is 0.35~0.7 g / ml.

[0023] Preferably, in step 2), the wood chips are cut in the direction of wood growth, and the thickness of the wood chips is 1~5 mm.

[0024] Preferably, the drying in step 3) is constant temperature drying, with a drying temperature of 50~150 ℃ and a drying time of 1~3 days.

[0025] Preferably, the high-temperature calcination in step 4) is performed by heating to 600-900 ℃, holding at that temperature for 4-5 hours, and heating at a rate of 3-5 ℃ / min.

[0026] The beneficial effects of the present invention include at least the following:

[0027] 1) This invention proposes using wood-derived carbon materials as a novel LIBS (Liquid-Induced Bioassay) substrate for water quality detection. Utilizing its unique three-dimensional porous structure, it achieves efficient adsorption and enrichment of trace metal ions in aqueous solutions. Furthermore, by leveraging the excellent thermal stability and laser energy coupling characteristics of the wood-carbon substrate, it improves plasma excitation efficiency, ultimately enhancing the sensitivity and reliability of LIBS detection of heavy metals in water. The wood substrate used in this invention has high structural strength and is not easily broken. This invention not only provides an innovative solution for liquid-phase LIBS analysis but also opens up new avenues for the high-value utilization of wood resources, while using inexpensive wood.

[0028] 2) This invention utilizes the unique array-arranged through-pore structure of wood. A vacuum filling method is used to fill the through-pores of the wood with glucose / sodium chloride crystals, followed by simple high-temperature calcination to obtain an integrated wood-derived carbon substrate material. This eliminates the need for substrate fabrication and molding, making the operation simpler and less costly. Using sodium chloride templates and glucose, an ordered secondary pore structure is constructed within the wood through-pores. This unique structure provides the material with higher pore structure characteristics, structural stability, and more active sites. Thanks to its unique structural characteristics, water quality testing using this substrate revealed distinct characteristic peaks of heavy metal Mn (257.61, 259.37, and 260.57 nm) in the LIBS spectrum, demonstrating the excellent adsorption performance of this material's special secondary pore structure for heavy metal ions, exhibiting high adsorption selectivity and high enrichment efficiency.

[0029] 3) This invention is beneficial for expanding the application of wood-derived carbon materials in the LIBS field, especially in enhancing the accuracy and sensitivity of LIBS water quality detection, and has broad market prospects. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of SEM detection of wood-derived carbon substrate material in Example 1 of the LIBS water quality detection method of the present invention;

[0031] Figure 2 This is a schematic diagram of the ordered pore structure of a wood-derived carbon substrate material in Example 1 of the LIBS water quality detection method of the present invention, obtained by SEM analysis.

[0032] Figure 3 This is the nitrogen adsorption-desorption curve of the wood-derived carbon substrate material in Example 1 of the LIBS water quality detection method of the present invention;

[0033] Figure 4 This is a schematic diagram of the micropore distribution of the wood-derived carbon substrate material in Example 1 of the LIBS water quality detection method of the present invention;

[0034] Figure 5 This is a schematic diagram of SEM detection of wood-derived carbon substrate in Comparative Example 1 of the LIBS water quality detection method of the present invention.

[0035] Figure 6 These are LIBS spectra of water quality detection in Examples 1, 2, and 3 of the LIBS water quality detection method of the present invention.

[0036] Figure 7 These are LIBS spectra of water quality detection for Comparative Examples 1 and 2 of the LIBS water quality detection method of the present invention. Detailed Implementation

[0037] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0038] Furthermore, the terms “first,” “second,” “third,” etc., are used for descriptive purposes only and should not be interpreted as indicating or implying relative importance.

[0039] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0041] Unless otherwise specified, the raw materials and equipment used in this invention are all conventional raw materials and equipment in the art and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in this invention are all conventional methods in the art.

[0042] As used in the specification and appended claims of this invention, unless otherwise clearly stated, the term "or" is generally used in its meaning as including "and / or".

[0043] Unless otherwise indicated, all figures expressing characteristic magnitudes, quantities, and physical properties will be understood to be modified by the term “about”, regardless of whether the term “about” is immediately present. Therefore, unless indicated to the contrary, the numerical parameters presented are approximations that may vary depending on the desired properties sought by those skilled in the art using the teachings disclosed herein.

[0044] In this invention, LIBS stands for Laser-Induced Breakdown Spectroscopy.

[0045] This invention uses the Chenhua 660E electrochemical workstation as the power source.

[0046] The LIBS testing equipment of this invention is model LPS-1064-S.

[0047] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0048] a. Immerse a wood-derived carbon substrate with a secondary pore structure in a water sample to be tested to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in the water sample.

[0049] b. Remove the substrate material that has adsorbed heavy metal elements and dry it to obtain the wood-derived carbon substrate sample to be tested;

[0050] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device, and the heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum.

[0051] In some embodiments, in step a, the substrate material is completely immersed in the water sample to be tested for 10 to 90 minutes.

[0052] In some embodiments, the substrate material is dried at a temperature of 50-80°C for 5-15 minutes in step b.

[0053] In some embodiments, in step c, the laser of the laser-induced breakdown spectroscopy (LIBS) device is applied with a voltage of 630-650V and a laser energy of 187.2-195.5mJ; the timing control parameters are set to a delay of 1-2μs and a gate width of 9-10μs.

[0054] In some embodiments, the secondary pore structure includes micropores and mesopores, and the secondary pore structure is formed by crystal growth of a chloride template.

[0055] In some embodiments, the wood used is cedar.

[0056] In some embodiments, the method for preparing a wood-derived carbon substrate includes the following steps:

[0057] 1) Dissolve glucose and sodium chloride in water to obtain a precursor solution;

[0058] 2) Cut wood chips of different thicknesses and immerse them in the precursor solution under negative pressure;

[0059] 3) Remove the wood chips and dry them to obtain the calcination precursor;

[0060] 4) The calcination precursor is calcined at high temperature in an inert gas atmosphere to obtain a wood-derived carbon substrate.

[0061] Nitrogen is typically used as the inert gas here, but helium can also be used.

[0062] In some embodiments, the wood-derived carbon substrate obtained in step 4 is polished to a thickness of 0.5-0.7 mm and then cleaned with deionized water.

[0063] In some embodiments, the concentration of the dissolved sodium chloride solution in step 1) is 1~3.5 mol / L, and the concentration of the dissolved glucose solution is 0.35~0.7 g / ml.

[0064] In some embodiments, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 1~5 mm.

[0065] In some embodiments, the drying in step 3) is constant temperature drying, with a temperature of 50~150℃ and a drying time of 1~3 days.

[0066] In some embodiments, the high-temperature calcination in step 4) is performed by heating to 600-900 °C, holding at that temperature for 4-5 hours, and heating at a rate of 3-5 °C / min.

[0067] In this embodiment, the secondary pore structure of the wood-derived carbon substrate includes micropores and mesopores. The secondary pore structure is formed by crystal growth of a chloride template, and the wood used is cedar.

[0068] Example 1

[0069] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0070] 1) Dissolve 17.5g of glucose and 2.92g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0071] 2) Cut wood chips with a thickness of 3mm, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure for 2 days;

[0072] 3) Remove the wood chips and dry them at a constant temperature of 60 ℃ for 1 day to obtain the calcination precursor.

[0073] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to heat up to 750°C, hold for 4 hours, with a heating rate of 3°C / min and a calcination atmosphere of nitrogen, to obtain an integrated ordered porous wood-derived carbon substrate.

[0074] 5) The obtained wood-derived carbon substrate was polished to a thickness of 0.5 mm with 1200 grit sandpaper and then cleaned with deionized water.

[0075] In this embodiment, the wood chip cutting direction in step 2) is along the wood growth direction.

[0076] The wood-derived carbon substrate prepared in Example 1 is referred to as "Sample 1" in the accompanying drawings.

[0077] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0078] a. The wood-derived carbon substrate of “Sample 1” was completely immersed in a 0.4 mg / L Mn(NO3)2 solution for 15 min to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in the water sample.

[0079] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 60℃ for 10 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0080] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 630V, laser energy 187.2mJ; timing control parameters were set as follows: delay 2μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0081] Example 2

[0082] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0083] 1) Dissolve 17.5g of glucose and 5.85g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0084] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure for 2 days;

[0085] 3) Remove the wood chips and dry them at a constant temperature of 80 ℃ for 1 day to obtain the calcination precursor.

[0086] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to heat up to 750 °C, hold for 4 hours, with a heating rate of 3 °C / min and a calcination atmosphere of nitrogen, to obtain a wood-derived carbon substrate.

[0087] 5) The obtained wood-derived carbon substrate was polished to a thickness of 0.5 mm with 1200 grit sandpaper and then cleaned with deionized water.

[0088] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 3mm.

[0089] The wood-derived carbon substrate prepared in Example 2 is referred to as "Sample 2" in the accompanying drawings.

[0090] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0091] a. The wood-derived carbon substrate of “Sample 2” was completely immersed in a 0.4 mg / L Mn(NO3)2 solution for 15 min to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in the water sample.

[0092] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 60℃ for 10 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0093] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 650V, laser energy 195.5mJ; timing control parameters were set as follows: delay 2μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0094] Example 3

[0095] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0096] 1) Dissolve 35g of glucose and 5.85g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0097] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure for 2 days;

[0098] 3) Remove the wood chips and dry them at a constant temperature of 80℃ for 1 day to obtain the calcination precursor.

[0099] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to raise the temperature to 850 °C, hold for 4 hours, raise the temperature at a rate of 3 °C / min, and calcinate in a nitrogen atmosphere to obtain a wood-derived carbon substrate.

[0100] 5) The obtained wood-derived carbon substrate was polished to a thickness of 0.5 mm with 1200 grit sandpaper and then cleaned with deionized water.

[0101] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 3mm.

[0102] The wood-derived carbon substrate prepared in Example 3 is referred to as "Sample 3" in the accompanying drawings.

[0103] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0104] a. The wood-derived carbon substrate of “Sample 3” was completely immersed in 0.4 mg / L Mn(NO3)2 solution for 15 min and the immersion time was 90 min to obtain the wood-derived carbon substrate that adsorbed heavy metal elements in the water sample.

[0105] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 80℃ for 5 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0106] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 630V, laser energy 195.5mJ; timing control parameters were set as follows: delay 2μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0107] Example 4

[0108] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0109] 1) Dissolve 17.5g of glucose and 2.92g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0110] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure;

[0111] 3) Remove the wood chips and dry them at a constant temperature of 50 ℃ for 3 days to obtain the calcination precursor.

[0112] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to heat up to 600°C, hold for 4 hours, with a heating rate of 3°C / min and a calcination atmosphere of nitrogen, to obtain a wood-derived carbon substrate.

[0113] 5) The obtained wood-derived carbon substrate is polished to a thickness of 0.5 mm and then cleaned with deionized water.

[0114] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 1 mm.

[0115] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0116] a. The wood-derived carbon substrate with a secondary pore structure was completely immersed in a 0.4 mg / L Mn(NO3)2 solution for 15 min to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in a water sample.

[0117] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 50°C for 15 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0118] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 630V, laser energy 187.2mJ; timing control parameters were set as follows: delay 1μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0119] Example 5

[0120] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0121] 1) Dissolve 17.5g of glucose and 2.92g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0122] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure;

[0123] 3) Remove the wood chips and dry them at a constant temperature of 150 ℃ for 1 day to obtain the calcination precursor.

[0124] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to heat up to 900 °C, hold for 5 hours, with a heating rate of 5 °C / min and a calcination atmosphere of nitrogen, to obtain a wood-derived carbon substrate.

[0125] 5) The obtained wood-derived carbon substrate is polished to a thickness of 0.7 mm and then cleaned with deionized water.

[0126] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 5mm.

[0127] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0128] a. The wood-derived carbon substrate with a secondary pore structure was completely immersed in a 0.4 mg / L Mn(NO3)2 solution for 90 min to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in a water sample.

[0129] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 80℃ for 5 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0130] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 650V, laser energy 195.5mJ; timing control parameters were set as follows: delay 2μs, gate width 10μs; acquisition matrix 10×10, step size 0.6mm.

[0131] Comparative Example 1

[0132] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0133] 1) Dissolve 5.85g of sodium chloride in 50ml of deionized water to obtain a precursor solution;

[0134] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure for 2 days;

[0135] 3) Remove the wood chips and dry them at a constant temperature of 80℃ for 1 day to obtain the calcination precursor.

[0136] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to raise the temperature to 850 °C, hold for 4 hours, raise the temperature at a rate of 3 °C / min, and calcinate in a nitrogen atmosphere to obtain a wood-derived carbon substrate.

[0137] 5) The obtained wood-derived carbon substrate was polished to a thickness of 0.5 mm with 1200 grit sandpaper and then cleaned with deionized water.

[0138] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 3mm.

[0139] The wood-derived carbon substrate prepared in Comparative Example 1 is referred to as "Comparative Sample 1" in the attached figure.

[0140] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0141] a. The wood-derived carbon substrate of “Comparative Sample 1” was completely immersed in 0.4 mg / L Mn(NO3)2 solution for 15 min and the immersion time was 90 min to obtain the wood-derived carbon substrate that adsorbed heavy metal elements in the water sample.

[0142] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 80℃ for 5 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0143] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 630V, laser energy 195.5mJ; timing control parameters were set as follows: delay 2μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0144] Comparative Example 2

[0145] This invention discloses a method for preparing a wood-derived carbon substrate, comprising the following steps:

[0146] 1) Dissolve 35g of glucose in 50ml of deionized water to obtain a precursor solution;

[0147] 2) Cut wood chips of different thicknesses, place them in a vacuum chamber, and immerse them in the precursor solution under negative pressure for 2 days;

[0148] 3) Remove the wood chips and dry them at a constant temperature of 80℃ for 1 day to obtain the calcination precursor.

[0149] 4) The calcination precursor is subjected to high-temperature calcination. The high-temperature calcination sequence is to raise the temperature to 850 °C, hold for 4 hours, raise the temperature at a rate of 3 °C / min, and calcinate in a nitrogen atmosphere to obtain a wood-derived carbon substrate.

[0150] 5) The obtained wood-derived carbon substrate was polished to a thickness of 0.5 mm with 1200 grit sandpaper and then cleaned with deionized water.

[0151] In this embodiment, the wood chips are cut in step 2) along the growth direction of the wood, and the thickness of the wood chips is 3mm.

[0152] The wood-derived carbon substrate prepared in Comparative Example 1 is referred to as "Comparative Sample 2" in the attached figure.

[0153] This invention discloses a LIBS water quality testing method, comprising the following steps:

[0154] a. The wood-derived carbon substrate of “Comparative Sample 2” was completely immersed in 0.4 mg / L Mn(NO3)2 solution for 15 min and the immersion time was 90 min to obtain the wood-derived carbon substrate that adsorbed heavy metal elements in the water sample.

[0155] b. Remove the substrate material that has adsorbed heavy metal elements and dry it. The substrate material is dried at 80℃ for 5 minutes to obtain the wood-derived carbon substrate sample to be tested.

[0156] c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device. The heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum. The parameters of the LIBS device were set as follows: laser applied voltage 630V, laser energy 195.5mJ; timing control parameters were set as follows: delay 2μs, gate width 9μs; acquisition matrix 10×10, step size 0.5mm.

[0157] The wood-derived carbon substrate prepared in Example 1 was examined using a scanning electron microscope (SEM). Figure 1 As shown, SEM detection. Figure 2 As shown, local SEM analysis of the wood-derived carbon substrate prepared in Example 1 indicates that the secondary pore structure of the substrate material is caused by the crystal growth characteristics of the sodium chloride template.

[0158] like Figure 3 As shown, the abundant pore structure of the wood-derived carbon substrate provides a high specific surface area.

[0159] like Figure 4 As shown, the wood-derived carbon substrate has a large number of micropores.

[0160] The wood-derived carbon substrate prepared in Comparative Example 1 was examined using a scanning electron microscope (SEM). Figure 5 As shown, SEM analysis revealed that the wood-derived carbon substrate sample prepared in Comparative Example 1 had no special secondary channel structure within its wood through-hole structure.

[0161] like Figure 6 , Figure 7 As shown, from Figure 6 As can be seen, "Sample 1", "Sample 2", and "Sample 3" have obvious Mn element characteristic peaks at 257.61, 259.37, and 260.57 nm, while the Mn element characteristic peaks in the LIBS spectra of "Comparison Sample 1" and "Comparison Sample 2" are not obvious. Figure 7 Furthermore, under the same testing conditions, the characteristic peak intensity of Mn in the LIBS spectra of "Sample 1", "Sample 2", and "Sample 3" was significantly higher than that of "Comparative Sample 1" and "Comparative Sample 2". The results indicate that the wood-derived carbon substrate for LIBS water quality detection prepared using this patent has a better adsorption effect on the heavy metal Mn, resulting in higher detection sensitivity and accuracy for the substrate material prepared by this patent.

[0162] The above description is merely a preferred embodiment of the present invention and does not limit the scope of patent protection of the present invention. Any equivalent structural transformations made based on the description and drawings of the present invention, whether directly or indirectly applied to other related technical fields, are similarly included within the scope of protection of the present invention.

Claims

1. A LIBS water quality testing method, characterized in that, Includes the following steps: a. Immerse a wood-derived carbon substrate with a secondary pore structure in a water sample to be tested to obtain a wood-derived carbon substrate that adsorbs heavy metal elements in the water sample. b. Remove the substrate material that adsorbs heavy metal elements from the water sample and dry it to obtain the wood-derived carbon substrate sample to be tested; c. The wood-derived carbon substrate sample was tested using a laser-induced breakdown spectroscopy (LIBS) device, and the heavy metal elements were quantitatively analyzed by analyzing the plasma emission spectrum.

2. The LIBS water quality testing method according to claim 1, characterized in that, In step a, the substrate material is completely immersed in the water sample to be tested for 10 to 90 minutes.

3. The LIBS water quality testing method according to claim 1, characterized in that, In step b, the substrate material is dried at a temperature of 50~80℃ for 5~15 minutes.

4. The LIBS water quality testing method according to claim 1, characterized in that, In step c, the laser of the laser-induced breakdown spectroscopy (LIBS) device is applied with a voltage of 630~650V and a laser energy of 187.2~195.5mJ; the timing control parameters are set to a delay of 1~2μs and a gate width of 9~10μs.

5. The LIBS water quality testing method according to claim 1, characterized in that, The secondary pore structure includes micropores and mesopores, and the secondary pore structure is formed by crystal growth from a chloride template; or the wood is fir.

6. The LIBS water quality testing method according to claim 1, characterized in that, The method for preparing the wood-derived carbon substrate includes the following steps: 1) Dissolve glucose and sodium chloride in water to obtain a precursor solution; 2) Cut wood chips of different thicknesses and immerse them in the precursor solution under negative pressure; 3) Remove the wood chips and dry them to obtain the calcination precursor; 4) The calcination precursor is calcined at high temperature in an inert gas atmosphere to obtain a wood-derived carbon substrate.

7. The LIBS water quality testing method according to claim 1, characterized in that, The wood-derived carbon substrate obtained in step 4 is polished to a thickness of 0.5~0.7mm and then cleaned with deionized water.

8. A LIBS water quality testing method according to claim 1, characterized in that, In step 2), the wood chips are cut along the growth direction of the wood, and the thickness of the wood chips is 1~5 mm.

9. A LIBS water quality testing method according to claim 1, characterized in that, In step 3), the drying is constant temperature drying, with a temperature of 50~150 ℃ and a drying time of 1~3 days.

10. A LIBS water quality testing method according to claim 6, 7, 8, or 9, characterized in that, The high-temperature calcination sequence in step 4) is to raise the temperature to 600~900 ℃, hold it for 4~5 hours, and raise the temperature at a rate of 3~5 ℃ / min.

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