Preparation Of Long-period Fiber Grating Iron Ion Concentration Sensor And Its Application In MFC

Microbial fuel cell(MFC)is a new kind of clean energy to solveenvironmental pollution.It can be used in handling waste water,removing hydrogen sulfide,producing hydrogen and repairing groundwater.Compared with traditional waste water treatment process,MFC produce less mud and no methane.But the low power density affect the development of MFC,usually MFC is 3-4 grade level less than the hydrogen fuel cell.In order to improve the efficiency of MFC and reduce the cost,this thesis systematically analyzes the real-time monitoring technology of Fe3+ near the electrode during the process of biochemical reaction in MFC.Optical fiber sensing technology is a new type of sensor with fiber grating as the sensing unit.In this thesis,we use the electrostatic layer self-assembly technology to replace fiber cladding in the LPFG sensing area.Add iron ion indicator sulfosalicylic acid in sensitive membrane.Analyze how the thickness of the sensitive membrane and the amount of indicator affect the transmission spectrum and transmit light intensity.We test the concentration of Fe3+ in the MFC anode chamber,the experiment found:(1)Test the transmission spectrum of the fiber optic sensor by a spectrometer,found that the spectral transmission capacity has been enhanced,and the maximum absorbance of the sensor is linearly weakened with the number of coating layers.It is confirmed that the coating process is alternately deposited on a layer-by-layer basis.(2)Microscopic observation of the surface of the coated fiber with an electron microscope scanning instrument revealed that the appearance of the fiber was uniform and the surface was uniform.Can be used as a carrier for Fe3+ indicator.(3)The addition of 0.5% sulfosalicylic acid indicator showed a linear relationship with the intensity of the iron ions in different concentrations.The self-assembled sensitive film has good optical response ability to the iron ions in the liquid phase,and can be used as a sensor for real-time monitoring of the compound content of different components of the MFC anode interface matrix.(4)EDTA was used to test the reusability of the fiber optic sensor.It was found that the redistribution of 2.54 nm after EDTA was added to the desorption of iron ions and then shifted back to the original central wavelength by 2.5 nm,indicating that the optical fiber sensor State of the Fe3+ reaction to form a stable water-soluble complex,therefore,this pass LPFG-FBG sensor can be repeated many times to use.When the MFC operation is started,the biochemical reaction occurring during the production process changes the temperature and ion concentration in the reaction chamber,which affects the production power and also affects the accuracy of the sensor.Therefore,in order to eliminate the problem in the process of measurement,this thesis analyzes how to eliminate the cross-sensitivity of temperature,and uses the cascaded LPFG-FBG fiber grating sensor to measure the temperature and the refractive index of the sensor's external environment.The temperature sensing characteristics of FBG and LPFG and the refractive index of external environment are analyzed theoretically.FBG is not sensitive to ambient refractive index,combine FBG with LPFG,propose a new sensor with compensation function.