YIC-IR  > 中科院烟台海岸带研究所知识产出
海岸带水体铁形态电分析方法研究
林明月1,2
学位类型博士
导师潘大为
2017-05-20
学位授予单位中国科学院大学
学位授予地点北京
学位专业环境科学
关键词 形态分析 海岸带水体 电分析方法 电极
其他摘要

铁是海洋生态体系中有机生物体所必需的微量元素。海水中的痕量铁是限制海洋初级生产力的关键因素,其形态和有效性与海洋浮游动植物的吸收有密切关系,因此铁在海洋地球化学循环中起着重要作用。及时、快速、准确地进行海水中铁的形态分析是目前海洋环境科学中的难点和热点。

目前,国际上已发展了多种检测海水中痕量铁的方法,例如原子吸收光谱法、电感耦合等离子体质谱法、分光光度法等。但这些方法大都存在仪器设备昂贵、操作复杂、分析测试及维护费用高等缺点,无法进行现场检测,且无法进行形态分析。电化学方法具有操作简单、测试费用低、携带方便、灵敏度高、可现场分析等优点,在痕量铁的检测和铁形态分析方面占有越来越重要的地位。电极材料是电化学传感器的核心部件,直接决定分析检测性能。本文基于不同的电极材料,发展了一系列用于痕量铁和铁形态分析的电化学方法,并对Fe3+/2+Fe(II)-2,2'-联吡啶络合物的电极反应机理进行了系统理论探究。主要内容包括以下七个方面:

1. 还原氧化石墨烯/亚甲基蓝/纳米金复合材料修饰玻碳电极用于Fe(III)的检测。基于还原氧化石墨烯和亚甲基蓝作为基底材料,原位、自催化合成了还原氧化石墨烯/亚甲基蓝/纳米金复合材料。该新型纳米复合材料修饰电极对Fe(III)有很好的响应,电极反应受吸附控制且是准可逆反应,线性范围为0.3~100 μM,检出限为15 nM,已成功应用于实际海水和河水中溶解态总铁的检测。

2. 纳米碳化钛/全氟磺酸修饰玻碳电极用于Fe(III)的检测。纳米碳化钛具有优异的电化学性能和催化性能,能够加快电子传递速率。全氟磺酸作为一种阳离子交换膜,不仅能够快速在电极表面成膜,而且可以为Fe(III)的吸附提供位点。基于纳米碳化钛和全氟磺酸的协同作用,以及H2O2的催化氧化作用,该方法对Fe(III)有很好的检测灵敏度。方法线性范围为0.07~70 μM,检出限为7.2 nM,已成功应用于实际海水和河水中溶解态总铁的测定。

3.锡铋合金电极吸附阴极溶出伏安法灵敏检测Fe(III)。新型锡铋合金电极环境友好,与汞电极电化学性能相似且优于铋膜修饰电极,是一种极具潜力的电极材料。实验以锡铋合金电极作为工作电极,引入Fe(III)的络合剂1-2-吡啶偶氮)-2-萘酚(PAN)提高检测的选择性和灵敏度。在-0.3 V富集电位,60 s富集时间下,此方法的线性范围为1~900 nM,检出限为0.2 nM。此外,该方法具有很好的抗干扰能力,已成功应用于实际近岸海水和河水中溶解态总铁的检测。

4. 纳米碳化钛-全氟磺酸/铂纳米花修饰玻碳电极用于Fe(II)的检测。实验以立方体结构的纳米碳化钛作为电沉积三维立体铂纳米花的基底。全氟磺酸的存在有助于将纳米碳化钛固定在电极表面,并能降低铂纳米花在电沉积过程中的成核速率,使花形更饱满,活性位点更多。基于纳米碳化钛和全氟磺酸的协同作用,结合铂纳米花的催化作用,该体系对Fe(II)-2,2'-联吡啶络合物的氧化电流具有很好的响应,且该反应是一个可逆过程。方法采用吸附阳极溶出伏安法,在-0.1 V富集电位,60 s富集时间下,该方法的线性范围为1 nM~6 μM,最低能够检测到的Fe(II)0.1 nM,该方法已成功应用于实际近岸海水和河水样品中Fe(II)的检测。

5. Fe3+/2+的电极反应过程研究。实验运用常规直流电(DC)循环伏安法对Fe3+/2+在不同电解质中(盐酸、双(三氟甲烷磺酰基)酰亚胺、高氯酸、硅钨酸)和不同电极上(玻碳电极、硼掺杂金刚石电极)的电极反应过程进行了系统地理论探究。实验结果表明,扩散系数D与电解质溶液阴离子半径呈反比。在硼掺杂金刚石电极上的电极反应速率k0小于在玻碳电极上的k0,且k0受电解质溶液离子配对的影响。根据可逆电位的比较,双(三氟甲烷磺酰基)酰亚胺被认为是比通常使用的高氯酸更为适用于得出可信k0的电解质溶液。超灵敏大振幅傅里叶变换交流电伏安法(FTACV)受背景电流影响很小,被用来研究Fe3+/2+双(三氟甲烷磺酰基)酰亚胺和硅钨酸中和在玻碳电极上的电极反应过程,以及硼掺杂金刚石电极表面的结构异质性对Fe3+/2+在硅钨酸中的电极反应动力学的影响。

6. Fe(II)-2,2'-联吡啶络合物的电子转移反应研究。实验运用常规直流电(DC)循环伏安法和超灵敏大振幅傅里叶变换交流电伏安法(FTACV)对2,2'-联吡啶(Bp)与二价铁形成的Fe(II)-Bp络合物在不同电极(玻碳电极、硼掺杂金刚石电极、铂电极、金电极)上的电极反应动力学进行了系统的探究。实验结果表明,Fe(II)-Bp在不同电极上均为单电子转移过程,且受扩散控制。Fe(II)-Bp在电极表面遵循的是外层传质过程,电极反应速率较快,与玻碳电极和金属电极相比,硼掺杂金刚石电极上获得的k0最低,这可能与电极的电子态密度有关。此外,实验还给出了2,2'-联吡啶可以用于在含有二价铁和三价铁的溶液中检测二价铁的电化学依据。

7. 近岸海水中不同形态铁的检测分析研究。实验基于催化吸附阴极溶出伏安法以及不同的预处理方法,采用2,3-二羟基萘作为三价铁络合剂,在采样过程中加入二价铁的特异性络合剂2,2’-联吡啶掩蔽活性二价铁,并在测试过程中加入催化剂KBrO3以大幅度提高检测灵敏度,实现了烟台近岸海水中总活性铁、活性三价铁、活性二价铁、溶解态总铁以及有机络合态铁五种形态铁的检测。该方法已成功用于烟台近岸海水连续5天(每隔一天采一次样)的检测。此外,实验对20172月和3月烟台四十里湾溶解态总铁的浓度及其形态分布进行了研究。; Iron is one of the essential micro-nutrient elements for all organisms in marine ecosystems. Trace iron in seawaters has been considered to be a key factor of phytoplankton growth limitation. Besides, iron's speciation has a close relationship with its uptake of microorganisms, thus iron plays an important role in marine biogeochemistry. Therefore, accurate and fast analysis of trace iron and its speciation in time is now a difficult and hot spot in marine environmental sciences.
To date, many analytical methods have been developed for determination of trace iron in seawaters, such as atomic absorption spectrometry, inductively coupled plasma-mass spectrometry, spectrophotometry, and so on. However, these methods are relatively not only cumbersome and expensive, but also require complicated operation and high cost of testing and maintenance, which can not meet the growing demands of the fast and real-time detection of iron. Most importantly, these methods can only determine total iron. As a low cost, simple, fast, portable, high sensitivity and in situ analytical technique, electrochemical method has shown great prospects in rapid analysis of trace iron and its speciation in seawater. Working electrode material is the core component of electrochemical sensor, directly determining the analysis of detection performance. In this paper, a series of electrochemical methods based on different working electrodes have been developed for trace iron and iron speciation analysis. In addition, the electrode process of Fe3+/2+ and Fe(II)-2,2'-bipyridyl complex have been systematically studied. The main contents are as follows:
1. Determination of Fe(III) at reduced graphene oxide/methylene blue/gold nanoparticles modified glassy carbon electrode. The reduced graphene oxide and methylene blue were chosen as the materials to help gold nanoparticles to grow in situ and self catalysis. Taking the advantage of gold nanoparticles'  fast electron transfer rate, the modified electrode showed a very good reduction signal of Fe(III). This is an adsorption controlled and quasi-reversible electrode process. The response to Fe(III) is in the linear range of 0.3~100 μM with a detection limit of 15 nM. This method has been successfully applied to determine total dissolved iron in real coastal seawaters and river waters.
2. Determination of Fe(III) at titanium carbide nanoparticles/Nafion modified glassy carbon electrode. Titanium carbide nanoparticles possess promising electrochemical and catalytic properties which can accelerate electron transfer rate. Nafion, as a typical cation-exchange polymer, can easily form a thin film on solid electrode and facilitate the preconcentration of Fe(III). Based on the synergistic effect of titanium carbide nanoparticles and Nafion, with the catalytic amplifying effect of H2O2, an excellent cathodic signal of Fe(III) can be obtained. The linear range of this sensor is from 0.07 to 70 μM and the detection limit is 7.2 nM. This method has been successfully used to sensitively determine total dissolved iron in real coastal waters.
3. Adsorptive cathodic stripping voltammetric determination of Fe(III) at tin-bismuth alloy electrode. The novel home-made tin-bismuth alloy electrode has the similar electrochemical properties with mercury electrode and is better than bismuth film electrode. This environmental-friendly tin-bismuth alloy electrode has great potentials for stripping analysis of iron. In this system, tin-bismuth alloy electrode was employed as working electrode, and a ligand of Fe(III) called 1-(2-piridylazo)-2-naphthol (PAN) was introduced to improve the selectivity and sensitivity. Under an accumulation potential of -0.3 V and an accumulation time of 60 s, a linear range of 1-900 nM and a detection limit of 0.2 nM can be obtained based on adsorptive cathodic stripping voltammetry. This method has been applied to determine total dissolved iron in coastal waters.
4. Determination of Fe(III) at titanium carbide nanoparticles-Nafion/platinum nanoflowers modified glassy carbon electrode. Cubic structure titanium carbide nanoparticles were used as the growth template of three-dimensional platinum nanoflowers. Nafion was used to help titanium carbide nanoparticles to be better attached onto the electrode surface and to slow down the crystal rate of platinum nanoflowers during the electrodeposition which resulted in more active surface sites. Taking the advantage of synergistic effect of titanium carbide nanoparticles and Nafion as well as the catalytic amplifying effect of platinum nanoflowers, an excellent anodic stripping responses to the oxidation of Fe(II)-2,2'-bipyridyl complex can be obtained under an accumulation potential of -0.1 V and an accumulation time of 60 s. The linear range of this sensor is from 1 nM to 6 μM with the lowest detectable concentration of 0.1 nM. This method has been successfully applied for sensitive determination of Fe(II) in coastal waters.
5. Theoretical study of Fe3+/2+ electrode process. The heterogeneous electron transfer kinetics (k0 values) and thermodynamic properties associated with Fe3+/2+ process in different electrolytes (HCl, bis(trifluoromethanesulfonyl)imide (HNTf2), HClO4, and silicotungstic acid (H4[α-SiW12O40])) and at different electrodes (glassy carbon and boron doped diamond electrodes) have been systematically studied based on direct current (DC) cyclic voltammetry and large amplitude Fourier transformed alternating current voltammetry (FTACV). The diffusion coefficient (D) values for Fe3+/2+ are dependent on the radius of the electrolyte anion. The k0 values are found to be smaller at boron doped diamond electrode (BDD) than glassy carbon electrode (GCE), and influenced by the ion-pairing effect. Based on the reversible potential, HNTf2 is suggested to be a more innocent electrolyte than commonly used HClO4 to obtain the true k0 values. FTACV with a favorable signal to background ratio, was used to determine k0 values associated with the Fe3+/2+ process in electrolyte of H4[α-SiW12O40] and HNTf2 at GCE and probe the influence of the heterogeneity of the BDD surface on k0 values in H4[α-SiW12O40].
6. The study of the electrode process of Fe(II)-2,2'-bipyridyl. The electrode transfer process of Fe(II)-2,2'-bipyridyl (Bp) complex at different electrodes (glassy carbon, boron doped diamond, platinum and gold electrodes) have been studied by direct current (DC) cyclic voltammetry and large amplitude Fourier transformed alternating current voltammetry (FTACV). This is a one-electron, diffusion-controlled process at all electrodes. The slower electron transfer kinetics (k0 value) at BDD, relative to the other electrode materials, are discussed in terms of the density of electronic states. Moreover, the electrochemical evidence for 2,2'-bipyridyl can be used to separate Fe(II) and Fe(III), thus to determine Fe(II) in solutions containing Fe(III) that has been reported.
7. Determination of different iron speciation in coastal waters. The concentrations of total reactive iron, reactive Fe(III), reactive Fe(II), total dissolved iron and iron complexed with natural organic matters in Yantai coastal waters can be obtained based on catalytic adsorptive cathodic stripping voltammetry and suitable pretreatments. 2,3-dihydroxynaphthalene (DHN) was chosen as the complexing ligand to Fe(III). 2,2'-bipyridyl was added during the sampling to mask Fe(II) in order to determine reactive Fe(II), and KBrO3 was utilized to catalytically improve the reduction current of Fe(III)-DHN. This method has been successfully used for 5 days' (every second day) determination of iron speciation in Yantai coastal waters. Besides, the concentration and distribution of total dissolved iron and iron speciation in Sishili Bay in February 2017 and March 2017 have also been investigated in this study.

 
学科领域环境化学
语种中文
文献类型学位论文
条目标识符http://ir.yic.ac.cn/handle/133337/21982
专题中科院烟台海岸带研究所知识产出
作者单位1.中国科学院烟台海岸带研究所
2.中国科学院大学
第一作者单位中国科学院烟台海岸带研究所
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林明月. 海岸带水体铁形态电分析方法研究[D]. 北京. 中国科学院大学,2017.
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