An optical fiber sensor for detecting lead ions in industrial wastewater from battery production

Abstract

The present invention relates to an optical fiber sensor for detecting lead ions in industrial wastewater from battery production, which is composed of a multimode optical fiber, a coreless optical fiber, a microsphere, a chromium film, a silver film, and a modified chitosan film. The end face of the coreless optical fiber is processed into a microsphere shape, and the surface of the coreless optical fiber is successively coated with a chromium film, a silver film, and a modified chitosan film to form an optical fiber cladding. The present invention utilizes the adsorption of lead ions in industrial wastewater from battery production by the modified chitosan film, which causes a change in the refractive index of the modified chitosan film layer, and further leads to a change in the wavelength of the SPR signal loss peak. By analyzing the wavelength of the SPR signal, the detection of lead ion concentration is realized, meeting the actual requirements for the detection of heavy metal ions. The preparation method of the present invention uses simple equipment, steps, and processes, can effectively excite the SPR signal, realize the high-sensitivity and high-precision detection of lead ions, and effectively evaluate the pollution situation of lead ions in industrial wastewater from battery production.

Description

Technical Field

[0001] The present invention belongs to the field of optical fiber sensing detection, and particularly relates to an optical fiber surface plasmon resonance (hereinafter referred to as optical fiber SPR) sensor for detecting lead ions in industrial wastewater from battery production. Background Art

[0002] With the serious damage to the ecological environment, especially the water environment, the country has gradually paid sufficient attention to the problem of water environmental pollution. At present, lead is widely used as an industrial raw material in industrial production, and most of it is discharged into the environment in various forms such as waste gas, wastewater, and waste residue, causing large-area pollution. The industrial wastewater from the battery production industry is one of the main sources of lead pollution. Lead ions in the water environment will be enriched through the food chain and continuously deposited in the human body, which is likely to cause lead poisoning and will harm multiple systems such as the nervous, hematopoietic, digestive, kidney, cardiovascular, and endocrine systems. How to effectively solve the problem of lead pollution is an important task currently faced by our country. Moreover, it is necessary to detect whether the lead content in the industrial wastewater meets the discharge standard before discharging the industrial wastewater. Therefore, it is particularly important to develop a simple, practical, easy-to-operate lead ion detection method that can meet the needs of future development.

[0003] At present, the main methods for detecting lead ions include atomic absorption spectrophotometry, atomic fluorescence spectrometry, inductively coupled plasma emission spectrometry, anodic stripping voltammetry, oscillopolarography, and biological stain test paper method. The existing detection methods have a wide analysis range, high sensitivity, high precision, and fast analysis speed, but they have the disadvantages of cumbersome steps (requiring pretreatment of samples), high detection method cost, large investment cost, narrow linear range, high detection limit, and being easily interfered. Summary of the Invention

[0004] The object of the present invention is to solve the defects of the above-mentioned prior art and provide an optical fiber SPR sensor for detecting lead ions. The sensor has the advantages of low cost, convenient operation, high sensitivity, small background interference, and no need for pretreatment of the analyte. When chitosan is dissolved in an aqueous solution of acetic acid, the amino groups in chitosan are protonated, and chitosan becomes a kind of polymer salt and dissolves. Then, it reacts with the added glutaraldehyde to undergo a cross-linking reaction. The stability and viscosity of the cross-linked chitosan increase, and a uniform semi-transparent chitosan film is formed on the silver film. When a lead ion solution is introduced, the lead ions chelate with the unprotonated amino groups on the chitosan, the structure and composition of the chitosan change, and its refractive index also changes accordingly. Eventually, the SPR sensing signal changes. At the same time, the greater the lead ion concentration, the greater the adsorption rate. The higher the concentration of the introduced lead ion solution, the greater the refractive index change, and the more the resonance peak of the SPR signal deviates. The sensor uses the modified chitosan film to adsorb lead ions in the industrial wastewater from battery production, causing the refractive index of the modified chitosan film layer to change. The SPR effect occurs at the silver film interface on the outer surface of the coreless optical fiber by using an optical signal, and the SPR signal is excited. The SPR signal is received by a multimode optical fiber for transmission, and an SPR curve is obtained. The noise is filtered by wavelet transform using MATLAB software to obtain a smoother fitting curve, and the resonance peak of the SPR signal is obtained. The lead ion concentration is judged according to the standard curve.

[0005] The optical fiber SPR sensor for detecting lead ions according to the present invention is connected by a multimode optical fiber and a coreless optical fiber. The end face of the coreless optical fiber is processed into a microsphere shape, and a chromium film, a silver film, and a modified chitosan film are sequentially coated on the surface of the coreless optical fiber to form an optical fiber cladding.

[0006] A tungsten halogen lamp is selected as the experimental light source.

[0007] The end face of the coreless optical fiber is processed into a microsphere shape by the process of discharging with a fusion splicer. The optical signal is reflected multiple times in the microsphere and returns to the coreless optical fiber, increasing the light energy effect.

[0008] The thickness of the modified chitosan film is preferably 50 nm, where the chitosan content is 0.8% and the acetic acid content is 99.2%. At this time, the modified chitosan film has the strongest ability to adsorb lead ions, causing the refractive index of the modified chitosan film layer to change.

[0009] During operation, an optical signal is incident from a multimode optical fiber onto the interface between the multimode optical fiber and the coreless optical fiber and scatters within the coreless optical fiber. When the light reaches the outer interface of the coreless optical fiber, the SPR effect occurs on the silver film, exciting an SPR signal, which is received by the transmitting multimode optical fiber. When there are lead ions in the water sample to be measured, chitosan adsorbs the lead ions, resulting in a change in refractive index, which in turn causes a change in the wavelength of the SPR signal loss peak. The SPR signal is received by the transmitting multimode optical fiber to obtain an SPR curve. The noise is filtered by wavelet transform using MATLAB software to obtain a smoother fitting curve, and the resonance peak of the SPR signal is obtained. The lead ion concentration is judged according to the standard curve.

[0010] The object of the present invention can be achieved by adopting the following technical solutions:

[0011] The multimode optical fiber is a quartz series optical fiber.

[0012] The surface of the coreless optical fiber is first coated with a chromium film to increase the adhesion of the optical fiber to the silver film, and then coated with a silver film. The thickness of the chromium film is preferably 3 nm; the thickness of the silver film is preferably 30 nm; the thickness of the modified chitosan film is preferably 10 nm; the length of the coated film is preferably 15 mm.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] (1) The structure of the present invention is simple and delicate, using a single-end design, and the preparation process and technology are simple;

[0015] (2) The present invention is convenient to operate. When in use, only the optical fiber SPR sensor needs to be placed into the sample to realize the detection of the sample. The sample does not need pretreatment and the dosage is small, eliminating various cumbersome sample operation steps and improving the detection efficiency;

[0016] (3) The modified chitosan film can adsorb 98% of the lead ions in the water sample, and can effectively produce the SPR effect to form an SPR curve, realizing the high-sensitivity and high-precision detection of lead ions. At the same time, it has strong anti-interference ability and can effectively evaluate the pollution situation of lead ions in sewage. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of an optical fiber surface plasmon resonance (abbreviated as optical fiber SPR) sensor for detecting lead ions in industrial wastewater from battery production of the present invention;

[0018] Figure 2 is a schematic optical path diagram of the present invention. Detailed Embodiments

[0019] The present invention will be specifically described below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be presented more clearly therefrom. These specific embodiments and examples are used to illustrate the present invention, rather than limiting the present invention.

[0020] The structure of an optical fiber SPR sensor for detecting lead ions in industrial wastewater from battery production is as Figure 1 shown. A quartz series optical fiber is selected and consists of a multimode optical fiber (1), a coreless optical fiber (2), a chromium film (3), a silver film (4), and a modified chitosan film (5). The end face of the coreless optical fiber (2) is processed into a microsphere shape, and the surface of the coreless optical fiber (2) is successively coated with a chromium film (3), a silver film (4), and a modified chitosan film (5) to form an optical fiber cladding.

[0021] As Figure 2 shown, when in use, the modified chitosan film can adsorb lead ions, causing a change in the refractive index of the modified chitosan film layer and a change in the SPR signal peak on the silver film. The optical path is as follows: The light emitted by a broadband light source is incident on the interface between the multimode optical fiber and the coreless optical fiber through the multimode optical fiber and scattered in the coreless optical fiber. When the light reaches the outer interface of the coreless optical fiber, the SPR effect occurs on the silver film, exciting an SPR signal. The SPR signal is received by the transmitting multimode optical fiber to form an SPR curve. The noise is filtered by wavelet transform using MATLAB software to obtain a smoother fitting curve, and the resonance peak of the SPR signal is obtained. The concentration of lead ions is judged according to the standard curve.

[0022] The preparation method of the optical fiber SPR sensor for detecting lead ions in the present invention includes the following steps:

[0023] (1) Fuse the transmitting multimode optical fiber and the coreless optical fiber;

[0024] (2) Deposit a chromium film and a silver film successively on the surface of the coreless optical fiber described in step (1); place it in a 10 - 20% glutaraldehyde solution for 15 - 25 hours, and rinse with water;

[0025] (3) Dissolve chitosan with acetic acid at a concentration of 1 - 5% to obtain a chitosan solution with a concentration of 0.8%, and coat it on the silver film described in step (2);

[0026] (4) After the optical fiber obtained in step (3) is dried, place it in a 1 - 10% glutaraldehyde solution for 1 - 10 minutes. The mass ratio of chitosan to glutaraldehyde is 100:1 - 10, and then dry it.

[0027] The preferred solutions are as follows:

[0028] To improve the coating effect, the coreless optical fiber after fusion in step (1) is placed in an ultrasonic cleaning tank and cleaned with absolute ethanol 3 to 5 times for 1 to 3 minutes, and then the surface of the fiber cladding is wiped clean with absorbent cotton dipped in absolute ethanol and dried; the drying in step (4) is preferably vacuum drying, that is, the optical fiber obtained in step (3) is dried in vacuum for 1 to 3 hours and then placed in a 1-10% glutaraldehyde solution for 1 to 10 minutes, and the mass ratio of chitosan to glutaraldehyde is 100:1-10, and dried for 20-24 hours.

Claims

1. An optical fiber sensor for detecting lead ions in industrial wastewater from battery production, characterized in that: It consists of a multimode optical fiber (1), a coreless optical fiber (2), a chromium film (3), a silver film (4), and a modified chitosan film (5); the multimode optical fiber (1) is a quartz series optical fiber, which is connected to the coreless optical fiber (2). The end face of the coreless optical fiber (2) is processed into a microsphere shape. The surface of the coreless optical fiber is successively coated with a chromium film (3), a silver film (4), and a modified chitosan film (5) to form an optical fiber cladding. The light emitted by a broadband light source is incident on the coreless optical fiber (2) through the multimode optical fiber (1) and scatters. When the light penetrates the chromium film (3) on the surface of the coreless optical fiber (2) and reaches the interface of the silver film (4), total reflection occurs and the SPR effect occurs on the silver film (4). The optical signal is reflected multiple times in the microsphere and returns to the coreless optical fiber. The generated SPR signal is received by the transmitting multimode optical fiber (1) and transmitted to a spectrometer. When there are lead ions in the water sample to be measured, the modified chitosan film (5) adsorbs the lead ions, resulting in a change in refractive index, and further causing a change in the wavelength of the SPR signal loss peak. By analyzing the wavelength of the SPR signal, the concentration of lead ions can be determined.

2. The optical fiber sensor for detecting lead ions in industrial wastewater from battery production according to claim 1, characterized in that: The cladding diameter of the multimode optical fiber (1) is 125 μm, and the core diameter is 110 μm.

3. The fiber optic sensor for detecting lead ions in the industrial wastewater of battery production according to claim 1, characterized in that: The end face of the coreless optical fiber (2) is processed into a microsphere shape by the process of discharging with a fusion splicer, with a length of 20 mm and a diameter of 130 - 150 μm.

4. The optical fiber sensor for detecting lead ions in the industrial wastewater of battery production according to claim 1, wherein: The function of the chromium film (3) is to increase the bonding force between the surface of the coreless optical fiber (2) and the silver film (4), and it has no influence on the SPR effect, with a thickness of 3 nm.

5. The optical fiber sensor for detecting lead ions in industrial wastewater from battery production according to claim 1, wherein: The thickness of the silver film (4) is 30 nm.

6. The optical fiber sensor for detecting lead ions in industrial wastewater from battery production according to claim 1, characterized in that: The modified chitosan film (5) has a strong ability to adsorb lead ions, with a chitosan content of 0.8% and an acetic acid content of 99.2%, and a thickness of 50 nm.

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