| Precipitation is a way of atmospheric wet deposition.A part of heavy metal ions combines with precipitation to enter the earth,oceans,rivers and lakes.The content of heavy metal ions in precipitation can reflect the quality of the atmospheric environment in a sort of way.Therefore,detection of the content of heavy metal ions in precipitation is of great significance to industries such as environmental protection and meteorology.At present,the detection of heavy metal ion content in precipitation usually requires to collect rainwater first,and then send it to the laboratory for test,which cannot be detected online.The existing heavy metal ion detection instruments are high-cost,bulky,and non-portable.Thus,in this paper,a portable detection device is designed for online detection of heavy metal ion content in natural precipitation.A three-electrode sensor is self-made based on the screen printing;and the electrochemical performance of the sensor is improved by surface modification.The rainwater collection/storage component and mixing component are designed and fabricated using 3D printing;the detection component is designed based on STM32 microcontroller.Finally,an on-line detection device,which is with small size,low cost and easy disassembly,is integrated to enable on-line detection of heavy metal ion content in natural precipitation.The work is as follows:(1)This paper first discusses the significance of on-line detection of the content of heavy metal ions in natural precipitation;summarizes the research status of the detection of heavy metal ions in water;compares the methods and related instruments of heavy metal detection;and clarifies the significance of the research and main content.(2)The principle of measuring the content of various heavy metal ions based on electrochemical dissolution method is elaborated.The three-electrode sensor is designed according to the measurement principle.The material used for working electrode and counter electrode is carbon;and the material used for reference electrode is silver/silver chloride.According to the requirements of portable and online testing,the structure of the device is designed.The sensor is fabricated based on screen printing.The performance of the fabricated sensor is tested using an electrochemical workstation.The working electrode surface of the sensor is modified by the same-position rhodium plating.According to the experiments,the sensitivity of the sensor is improved by 3.68 times after plating.(3)The mechanical structures of the rainwater collecting component,the rainwater and electrolyte mixing component,and the overall casing are designed;and they are manufactured by 3D printing.Specifically,the mixing effect of the helix tube was simulated and the color mixing experiment was carried out.The experiment proves that the mixer can effectively mix the liquid to be tested and the electrolyte.(4)Based on the STM32 microcontroller,the detection component is designed,including the detection circuit,data transmission circuit and display circuit in accordance with the principle of stripping voltammetry.Data processing and display are realized throμgh software design.Finally,the whole device is assembled and its performance is tested. |
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