【作者】 邓海强；

【导师】 王立世；

【作者基本信息】 华南理工大学 ， 环境科学， 2010， 硕士

【摘要】 液/液界面被认为是最简单的模拟生物膜模型,发生在该界面上的离子转移过程是目前电化学和电分析化学领域的研究热点之一。液/液界面的离子转移可以用于环境分析和环境毒理学评价中,而离子转移的动力学和热力学研究是这些应用的基础。傅里叶变换/逆傅里叶变换-方波伏安法(FT/IFT-SWV)是本世纪初由Bond等人提出并发展起来的研究电极过程机理的新技术,该技术具有在频域和时域同时分析电极过程的强大能力,使得同时研究离子转移的动力学和热力学成为可能。薄层及边平面热解石墨(EPPG)三相电极液/液界面装置具有简单、实用、使用常规三电极体系、宜于推广和环境污染小等诸多优点,因此被广泛应用于液/液界面的离子转移研究中。本文创造性地将FT/IFT-SWV结合薄层及EPPG三相电极液/液界面装置,研究了液/液界面的离子转移反应,得到的主要结果如下:1.采用FT-SWV结合薄层修饰电极在三电极体系下发展了测定液/液界面阴离子转移动力学的新方法。与只在每个脉冲末端采集电流的传统SWV不同,FT-SWV持续收集电流响应然后将其转换为频域频谱。出现在频谱里的偶次谐波频率来自于法拉第电流响应,偶次谐波频谱的轮廓呈现钟形,在某一特定频率处对应着一个最大值。这个最大值以及相应的频率分别相当于传统SWV里著名的“准可逆最大”和“临界频率”(fmax)。速率常数和离子转移系数α可以通过得到的fmax测定,同传统SWV相比,FT-SWV在离子转移动力学测定过程中更快更简单。2.利用循环伏安法对EPPG三相电极法的原理进行了研究,得到了比文献报道更理想的液/液界面离子转移热力学数据。本研究还首次观察到铬(Ⅵ)离子在水相/硝基苯相界面上的转移反应,并测定了铬(Ⅵ)的离子转移热力学;同时还分别利用SWV和FT-SWV结合“准可逆最大”现象对铬(Ⅵ)在水相/硝基苯相界面上的离子转移动力学进行了比较研究。3.使用FT/IFT-SWV结合EPPG三相电极法对液/液界面离子转移反应进行了系统地研究:一方面确认本方法具有同时研究离子转移动力学和热力学的能力,另一方面通过该方法研究不同种类离子和不同浓度的同一离子在液/液界面转移时的动力学和热力学规律,在动力学研究过程中还探讨了振幅ΔE对“准可逆最大”的影响。通过这些研究以优化该新方法在液/液界面离子转移反应机理研究中的测试条件,并希望得到该新方法有望在未来用于定量分析的潜在价值,因为在环境日益恶化的今天,不管是定量分析还是机理研究都对环境分析和环境毒理学的发展具有巨大的推动作用。更多还原

【Abstract】 A liquid/liquid interface has been considered as a simplest model for biological membranes and studies of ion transfer across this kind of interface is one of the hot topics in electrochemistry and electroanalytical chemistry at present. The ion transfer across the liquid/liquid interface can be applied in both environmental analysis and environmental toxicology assessment, where studies on kinetics and thermodynamics of ion transfer is fundamental for these applications mentioned above.A novel methodology of Fourier transformed/inverse Fourier transformed square-wave voltammetry (FT/IFT-SWV), initially developed by Bond and coworkers just since the beginning of this century, can be used to study the mechanism of electrode process. As FT/IFT-SWV has the power to resolve the electrode process in both frequency domain and time domain simultaneously, making it possible for simultaneous studies of kinetics and thermodynamics of ion transfer. The thin-film modified and edge plane pyrolytic graphite (EPPG) three-phase electrodes possess numerous merits of simplicity, practicality, being used in conventional three-electrode arrangement, popularity and mild environmental impact etc., hence they have been extensively used in studies of ion transfer across the liquid/liquid interface. In this paper FT/IFT-SWV was combined with thin-film modified and EPPG three-phase electrodes to study ion transfer across the liquid/liquid interface for the first time and the main results obtained were as follows:1. A novel method of FT-SWV in combination with thin-film modified electrode was employed to investigate the kinetics of anion transfer across the liquid/liquid interface using a conventional three-electrode arrangement. Other than traditional SWV in which currents are sampled only at the end of each pulse, FT-SWV continuously collects the current response and then transforms it into frequency domain. Even harmonic frequencies, which are derived from the faradaic current response, will emerge in the power spectrum. The profile of the even harmonic power spectrum is parabolic and shows a maximum at a certain frequency. The maximum and the corresponding frequency are equivalent to the well-known“quasireversible maximum”and“critical frequency”(fmax) in traditional SWV, respectively. The rate constant and ion transfer coefficientαcan be estimated by the obtained fmax. Compared with traditional SWV, FT-SWV is much simpler and faster in ion transfer kinetics estimation.2. The principle of EPPG three-phase electrode was investigated by cyclic voltammetry, and the obtained thermodynamic data of anions transfer across the water/nitrobenzene interface are more ideal, compared with those from published literature. The transfer of chromium (Ⅵ) ion across the water/nitrobenzene interface was observed for the first time and the thermodynamics of its transfer was determined. At the same time, SWV and FT-SWV associated with“quasireversible maximum”were comparatively used to study the kinetics of chromium (Ⅵ) transfer across the water/nitrobenzene interface.3. A systematical study of ion transfer across liquid/liquid interface was carried out by FT/IFT-SWV combined with EPPG three-phase electrode: on the one hand, testifying this method has the power to study kinetics and thermodynamics of ion transfer simultaneously; on the other hand, studying the effects of different kinds of ions and a kind of ion at different concentrations on kinetics and thermodynamics, besides, studying the effect of amplitude (ΔE) on“quasireversible maximum”. The investigation mentioned above was aimed to optimize the conditions employed during the studies of mechanism of ion transfer across liquid/liquid interface and explore the potential of this method in quantitative analysis in the future, since investigation on mechanism as well as quantitative analysis are both beneficial for the advancement of environmental analysis and environmental toxicology assessment while the environment is deteriorating increasingly.更多还原