| A series of prominent environmental pollution problems have emerged accompanied by the rapid development of industry and agriculture. Among them, the pollution of heavy metal ions has draw much more attention recently. Heavy metal ions exist in drinking water in various forms. It is not biodegradable and even trace concentration has detrimental risk to human health. It also has the continuity, amplification and the function of enrichment. To explore new materials and experimental methods to detect and handle the heavy metal ions in water is critical. Among them are metal oxides, especially the iron oxides with super adsorption capacity. Thus, in recent years, widespread attention has been paid to metal oxide materials. Iron-based metal oxides exhibit great potential in application of heavy metal ions removal and detection. Besides, they have great application prospect in various research fields, especially in the field of water purification and testing. Secondly, electrochemical detection technology is more and more popular due to the advantages of simple operation, short time and high detection efficiency. Challenges are that the inner relationship between adsorption and electrochemical response, also the internal mechanism of the interaction, is not so clear. Undoubtedly, it is a major research goal faced by us to understand the internal mechanism, which is beneficial for us to design new nanosensors to detect heavy metal ions.To solve the problems and challenges we encountered, this paper present three main research work as follows.Firstly, we successfully prepared plate-stacked Fe3O4, with which we realized individual and simultaneous electrochemical detection of five heavy metal ions, such as Zn(Ⅱ), Cd(Ⅱ), Pb(Ⅱ), Cu(Ⅱ) and Hg(Ⅱ). In addition, this material showed a high detection sensitivity and selectivity towards Pb(Ⅱ). The good stability and reproducibility of the modified electrodes made it possible for practical application. All the results helped to broaden the application of the square wave anodic stripping voltammetry in heavy metal ions detection in the environment. It is preliminary discussion of great guiding significance for the subsequent research.Secondly, different crystalline phases of rod-like FeOOH have been synthesized. These two crystalline phases of FeOOH nanorods were applied to electrochemical detection of heavy metal ions. Results showed that the a-FeOOH nanorods exhibited better electrochemical and adsorption performance towards heavy metals than β-FeOOH, especially for Pb (Ⅱ). The different hydroxyl of these two kinds of phases played an important role in the process of ion exchange. Hence, this study not only further explored the relationship between electrochemical and adsorption performance but also provided excellent evidence for the understanding of the internal mechanism of this difference.Thirdly, cubic and octahedral Fe3O4with the exposure of (100) and (111) crystal planes were synthesized. They were utilized in the electrochemical detection of five heavy metal ions under the open circuit accumulation. Results showed that enhanced electrochemical performance was closely related with its larger adsorption capacity. In order to further validate our theory, we adopted the means of theoretical calculation at the atomic level to analyze the causes of the difference between electrochemical detection and adsorption. The results found that the theoretical calculation results were in strict accordance with our electrochemistry and adsorption results. The study of this mechanism could be used to design nanoadsorbent with high performance and reveal the essence of how nanomaterials enhance the electrochemical response performance. It provided us with theory for understanding the electrochemical and adsorption behavior. Moreover, it provided us new method and strategy in developing newscale nanomaterials in the field of electrochemical sensing of heavy metal ions.Finally, we made a summary for the research work of this paper and put forward the outlook of the following work. |
PDF Full Text Request