| 其他摘要 | Turbid water generally refers to the water turbidity value of more than 10 NTU or suspended particulate matter concentration (SPM) of more than 10 g/L. As one of the necessary parameters for environmental monitoring, pH value is closely related to the development and change of estuarine and the coastal environment. However, in the estuarine and coastal zone, river water and seawater exchange violently, resulting in the increase of suspended sediment particles. The turbid water containing suspended particles such as sediment is easy to damages the traditional glass pH
electrode and affects the optical path dispersion in pH optical detection. Therefore, direct, accurate, and stable pH monitoring is of great significance in estuarine and coastal turbid water. The common preparation methods of solid iridium-based pH electrode include electrodeposition and thermal oxidation. These methods require expensive equipment and complex deposition solution, which limits the application of iridium-based electrodes. Therefore, in view of the importance of pH monitoring and the difficulty of direct monitoring in estuarine and coastal turbid water, a new type of solid iridium-based pH electrode was developed. The electrode can effectively reduce the friction effect of suspended sediment particles by virtue of the close binding ability of iridium oxide particles and electrode matrix, maintain long-term stability and rapid response-ability, and realize rapid, accurate, and stable pH monitoring of turbid water.
(1) Fabrication and characterization of iridium needle pH electrode by self-electrodeposition. In this chapter, the copper wire and iridium wire were packaged and combined by AB glue, and the exposed iridium wire was scanned by cyclic voltammetry in alkaline sodium hydroxide solution for 4 cycles. The micro iridium needle pH electrode with the size of 1 cm×0.25 mm was prepared. The
surface structure, stability, response slope, and stability of the prepared electrode were investigated. The total weight of the microelectrode is about 10 g, and the particle size of the oxide film on the surface of the working electrode is between 50~200 nm. The average Nernst linear response of three iridium needle electrodes is -59.67 mV/pH, which is close to Nernst linear response. The relative standard deviation (RSD) was 2.2%. The maximum deviation of the electrode is about 0.1 pH.
(2) Construction and performance of Ir/IrO2 pH electrode with high stability and accuracy. The self-electrodeposited iridium needle electrode has good response-ability and fast balance ability, but there are still some problems in the test process, such as large deviation and poor stability. Therefore, this chapter is devoted to optimizing the self-electrodeposited iridium needle electrode to improve the performance of the electrode. The results showed that the optimal conditions of self-electrodeposition were pH 13 and 20 cycles. Scanning electron microscopy (SEM) and X-ray
photoelectron spectroscopy (XPS) was used to analyze the surface morphology of the optimized electrode. It was confirmed that the surface product was IrO2. Furthermore, the preparation and response mechanism of self-electrodeposited iridium-based pH electrodes were discussed. The performance of the optimized iridium-based electrode was tested, and the results showed that the average response slope of the electrode was -65±3.5 mV/pH in the range of pH 1.83~11.97. The deviation of the electrode in three kinds of the standard buffer is 0.05 pH (pH 9.18), 0.01 pH (pH 6.86), and 0.02
pH (pH 4.00), and the measurement accuracy was effectively improved. The measurement of turbid water in the laboratory shows that the optimized electrode can reach the measurement equilibrium faster than the two traditional glass pH electrodes. The long-term life of the electrode is up to 30 days, and the drift is 3.1 mV (0.38 mV/h) for 8 hours.
(2) Construction and performance of Ir/IrO2 pH electrode with high stability and accuracy. The self-electrodeposited iridium needle electrode has good response-ability and fast balance ability, but there are still some problems in the test process, such as large deviation and poor stability. Therefore, this chapter is devoted to optimizing the self-electrodeposited iridium needle electrode to improve the performance of the electrode. The results showed that the optimal conditions of self-electrodeposition were pH 13 and 20 cycles. Scanning electron microscopy (SEM) and X-ray
photoelectron spectroscopy (XPS) was used to analyze the surface morphology of the optimized electrode. It was confirmed that the surface product was IrO2. Furthermore, the preparation and response mechanism of self-electrodeposited iridium-based pH electrodes were discussed. The performance of the optimized iridium-based electrode was tested, and the results showed that the average response slope of the electrode was -65±3.5 mV/pH in the range of pH 1.83~11.97. The deviation of the electrode in three kinds of the standard buffer is 0.05 pH (pH 9.18), 0.01 pH (pH 6.86), and 0.02
pH (pH 4.00), and the measurement accuracy was effectively improved. The measurement of turbid water in the laboratory shows that the optimized electrode can reach the measurement equilibrium faster than the two traditional glass pH electrodes. The long-term life of the electrode is up to 30 days, and the drift is 3.1 mV (0.38 mV/h) for 8 hours. monitoring and navigation monitoring in the wet season and dry season respectively. In the wet season, the pH value of turbid yellow river water with a turbidity of 750 NTU fluctuates between 8.01 and 8.15 after online monitoring for 1 h; in the dry season, the pH value of turbid yellow river water near estuary with a turbidity of 20.6~60.5 NTU fluctuates between 7.50 and 7.61 after navigation test for 3 h. Besides, the pH value of the Gangdang River (turbidity value 16.3~53.1 NTU) in Yantai city was also detected. The results showed that the pH value of the Gangdang River fluctuated from 7.74 to 8.00. |
修改评论