【作者】 许健；

【导师】 姬泓巍；

【作者基本信息】 中国海洋大学 ， 应用化学， 2008， 硕士

【摘要】 铁是人体及动植物所必需的微量元素，同时也是造成环境污染的元素。目前国内外测定痕量铁的分析方法大多需要进行预富集才能进行测定，操作较为复杂繁琐，有些分析方法需要使用昂贵的分析仪器及试剂，分析成本较高。本论文建立了一种利用催化动力学原理直接测定水体中痕量铁的新方法，初步探讨了反应机理，同时利用新建立的分析方法对淡水样品及海水体系的铁进行测定，实验取得了满意的结果，得到的主要成果有以下几点：1．建立了一种直接测定痕量铁的新的催化动力学分析方法。本论文利用催化动力学原理对铁（Ⅲ）催化高碘酸钾氧化弱酸性艳蓝褪色的反应体系进行了研究，通过正交实验和单因素实验，确定了最佳分析条件：RAWL浓度为40mg／L，pH值为3．15，KIO₄浓度为1．2×10^-4mol／L，时间为7min,邻菲罗啉浓度为8．0×10^-4mol／L，温度为25．0℃。在最佳分析条件下，所建分析方法的相对标准偏差RSD为1．9％～3．1％，加标回收率为98．0％-100．5％，检出限为4．10×10^-10g／mL Fe³⁺，线性范围为0-20．0 ng／mL。干扰离子实验表明：大多数阳离子及阴离子均不干扰测定。本论文所建立分析方法的特点为：高准确度，高精密度，高灵敏度，高选择性，检出限低，线性范围宽，而且仪器价廉、操作简单、在室温下进行，便于船上操作。2．对该方法的动力学参数进行了测定，得到了反应的动力学方程。本论文对催化反应体系的反应级数、表观活化能及表观速率常数进行测定。实验得到：高碘酸钾的反应级数α=0．5015≈1／2，弱酸性艳蓝的反应级数β=0．6407≈1／2，Fe³⁺的反应级数γ=0．5516≈1／2，邻菲罗啉的反应级数θ=0．092≈0；反应体系的表观活化能Ea=19．72 kJ／mol，表观反应速率常数K=0．0560 min^-1。通过实验得到本反应的动力学方程为：-dC_k/dt=kC_K^1/2C_R^1/2C₍Fe^3+1/2C_p⁰3．将所建立的分析方法成功地应用于淡水体系中痕量铁的测定。用所建立的分析方法分别对自来水、矿泉水水样进行测定，得到样品测定的相对标准偏差在0．33％-1．68％之间，回收率在96．1％-103．0％之间。将本法的测定结果与原子吸收法的测定结果进行比较，测定结果基本一致。4．将所建立的分析方法成功地应用于海水体系中痕量铁的测定。用所建立的分析方法分别对胶州湾六个站点海水样品进行测定。测定的相对标准偏差在0．33％-1．86％之间，回收率在96．9％-103．3％之间。将本法的测定结果与原子吸收法的测定结果进行比较，测定结果基本一致。因此本分析方法能成功应用于海水体系中痕量铁的测定。更多还原

【Abstract】 Iron is considered as an essential micronutrient for animals, plants and human beings. And this element is also considered as an ambient contaminant in the environment. Some conventional determination methods of iron （Ⅲ） can be applied only after preliminary treatment and pre-concentration; the operation is more tedious and they need expensive instruments and reagents. In recent years, the analysis method based on catalyzed kinetic reaction has been developed and been proved to be an attractive means for trace analysis.In this paper a new analysis method is established for determination of trace iron （Ⅲ） based on the catalytic kinetic theory. The mechanistic of the reaction is studied, the iron in fresh water and sea water are determined with the new method. The main results of the research are as follows:1. A new catalytic kinetic spectrophotometric method is established for thedetermination of trace iron （Ⅲ）.A new kinetic spectrophotometric method has been developed for the determination of iron （Ⅲ）. The method is based on the catalytic effect of iron （Ⅲ） on the oxidation of weak acid brilliant blue dye （RAWL） by KIO₄ in acid medium. The results from the orthogonal experiments and the single experiments show that the optimal experimental conditions are as following: 40mg/L RAWL, pH 3.15, 1.2×10^-4mol/L Potassium periodate solution, reaction time 7minutes,8.0×10^-4 mol/L phenanthroline, reaction temperature 25℃. Under the optimum conditions, the proposed method allows the determination of iron （Ⅲ）in the range 0²0. 0ng/mL and the detection limit is down to 4.10×10^-10g/mL. The recovery efficiency in determining the standard iron （Ⅲ） solution is in the range of 98.0% - 100.5% and the RSD is the range of 1.9% - 3.1% .Moreover, it is found that most cations and anions do not interfere with the determination of iron （Ⅲ）. Compared with other kinetic catalytic methods and instrumental methods, it is found that the proposed method shows fairly good selectivity and sensitivity, simplicity, cheapness, low detection limit and rapidity. It can be operated on the boat easily.2. In the paper the kinetic parameters of the reaction are studied and the mechanism of the reaction is investigated.The reaction orders with respect to each reagent are determined and are found to be 1/2,1/2,1/1 and 0 for potassium periodate, RAWL, iron （Ⅲ） and phenanthroline, respectively. On the basis of these values the kinetic equation of the reaction may bewritten as:-dC_k/dt=kC_K^1/2C_R^1/2C₍Fe^3+1/2C_p⁰ The mean value of the apparentactivation energy of the reaction is found to be -19. 72 kJ/mol, and the apparent reaction rate constant is 0.0560 min^-1.3. The new method has been successfully applied for the determination of iron （Ⅲ） in fresh water samples.The iron （Ⅲ） in the tap water and mineral water has been detemined respectively with the new method. The RSD of the method is the range of 0.33% - 1.68%, and the recovery rate of the method is in the range of 96.1% - 103.0%. The results are compared to those obtained by the AAS method. Good agreement is achieved. It proves that the new method can be successfully applied for the determination of iron （Ⅲ） in fresh water samples.4. The new method has been successfully applied for the determination of iron （Ⅲ） in seawater samplesThe iron（Ⅲ） in the seawater of the Jiaozhou Bay have been detemined respectively with the new method. The RSD of the method is the range of 0.33%-1.86% and the recovery rate of the method is in the range of 96.9%- 103.3%. The results are compared to those obtained by the AAS method. Good agreement is achieved. It proves that the new method can be successfully applied for the determination of iron（Ⅲ） in different seawater samples.更多还原