【作者】 李振华；

【导师】 常希俊；

【作者基本信息】 兰州大学 ， 分析化学， 2011， 博士

【摘要】 当今社会,金属离子污染已存在于人类生活的各个领域,已严重威胁到了人类的生命安全,如何对环境中的痕量金属污染物进行有效治理就成为环境分析化学工作者所面临的一大挑战。尽管原子发射光谱和原子吸收光谱是应用最广泛的测定金属离子含量的方法,然而由于金属污染物体系比较复杂,且常以痕量、超痕量的状态存在于环境中,因而在进入仪器分析前,往往需要将实际样品进行一定的预处理。固相萃取技术(SPE)是目前样品前处理技术中最为灵活、高效的的一种手段,对于固相萃取技术而言,吸附剂的选择决定着方法的回收率和富集因子。为了解决固相萃取技术选择性不够高,容易对目标物质的分析造成干扰等缺点,一般通过物理或者化学手段对吸附剂的表面进行修饰,在吸附剂的表面引入0、N、S、P等配位原子从而提高方法的选择性和吸附容量。因此,本论文致力于合成新型的固相萃取剂并将其用于环境样品中痕量金属离子的分离富集,主要的研究工作如下：1.用2-羟基萘醛修饰凹凸棒得到了新型的固相萃取吸附剂,并将其应用于环境样品中痕量Cu(Ⅱ)的富集分离。通过静态和动态分析程序优化各种实验条件,得到最佳富集Cu(Ⅱ)的酸度为pH 4,使用2.0 mL 0.0lmol L-1的HCl可以实现对Cu(Ⅱ)的有效洗脱。该吸附剂对Cu(Ⅱ)的吸附容量为25.13 mg g-1。本方法对Cu(Ⅱ)的检出限为0.24 ng mL-1,富集因子为150。将本方法应用于国家标准样品和天然水样中痕量Cu(Ⅱ)的测定,结果令人满意。2.用香草醛修饰硅胶得到了两种新型的固相萃取吸附剂,并将其应用于环境样品中痕量Cr(Ⅲ)的富集分离。通过优化各种实验条件,得到在pH为4时,两种吸附材料均可以实现对Cr(Ⅲ)的定量吸附。2.0 mL 0.5 mol L-1 HCl可以实现对Cr(Ⅲ)的定量洗脱。两种吸附剂对Cr(Ⅲ)的吸附容量分别为0.700和0.538 mmolL-1。两种方法的检出线分别为0.87和0.64 ng mL-1。两种方法的富集因子分别为100和75。将这两种吸附剂应用于生物样品和环境样品中痕量Cr(Ⅲ)的富集分离,结果令人满意。3.用乙二胺成功修饰活性炭得到新型的固相萃取吸附剂并将其应用于环境样品中痕量Cr(Ⅲ)、Fe(Ⅲ)、Hg(Ⅱ)和Pb(Ⅱ)的测定。通过优化实验条件,得到最佳的实验酸度为pH 4,被吸附的离子可以被3.0 mL 2%硫脲和0.5 mol L-1 HCl混合溶液洗脱,该吸附剂对Cr(Ⅲ)、Fe(Ⅲ)、Hg(Ⅱ)和Pb(Ⅱ)的吸附容量分别为39.4、28.9、60.5和49.9 mg g-1。本方法的相对标准偏差小于4%(n=8),将本方法应用于国家标准样品GBW08301,、猪肝以及环境水样中痕量Cr(Ⅲ)、Fe(Ⅲ)、Hg(Ⅱ)和Pb(Ⅱ)的测定,结果令人满意。4.用锌试剂负载活性炭得到新型的固相萃取剂,将其用来分离富集液体样品中痕量的Cr(Ⅲ)和Pb(Ⅱ),用ICP-AES进行测定。实验结果表明,在优化的酸度下,本吸附剂对的吸附容量分别为17.9和26.7 mg g-1,1.0 mL 0.1 mol L-1 HCl可以实现对目标离子的有效洗脱。常见的共存离子不影响目标离子的分离富集,得到该方法对Cr(Ⅲ)和Pb(Ⅱ)的检出限分别为0.91和0.65 ng mL-1,相对标准偏差小于3.5%(n=8),该方法已成功应用于生物样品和黄河水样中痕量Cr(Ⅲ)和Pb(Ⅱ)的分离富集。5.用DCC作为脱水剂,使用L-丙氨酸成功修饰碳纳米管得到一种能够选择性吸附Au(Ⅲ)的固相萃取吸附剂材料。在优化的酸度条件下,该吸附剂对的吸附容量为101.3 mg g-1,该吸附材料制备过程简单,富集过程快速,易洗脱,将其应用于国家标准样品、和环境水样中痕量Au(Ⅲ)的测定,结果令人满意。更多还原

【Abstract】 In recent years, the toxicity and the effect of trace elements on human health and the environment are receiving increasing attention in pollution and nutritional studies. Therefore, it is crucial to develop simple, rapid, and efficient methods for monitoring metal ions in the environment. Although inductively coupled plasma atomic emission spectrometry (ICP-AES) and atomic absorption spectrometry (AAS) are among the most widely used methods for trace metal determination, they are usually insufficient due to the matrix interferences and the very low concentration of metal ions. For these reasons, an efficient separation and preconcentration procedure is often required prior to the measurement step. Recently, one of widely used and fast emerging preconcentrative separation techniques is the solid-phase extraction (SPE). In SPE procedure, the choice of appropriate adsorbent is a critical factor to obtain full recovery and high enrichment factor. However, the main drawback of SPE is the lack of selectivity, which leads to high interference of the other existing species with the target metal ion. To overcome this problem, a chemical or physical modification of the sorbent surface with some organic compounds, is usually used to load the surface with some donor atoms such as oxygen, nitrogen, sulfur and phosphorus. Based on it, this research paper is devoted to the design, synthesis and application of newly selective solid-phase extractors in order to pre-concentration and separation of trace metal ions. The detailed novelty of this study have been listed in the following:1. A new sorbent 2-hydroxy-l-naphthaldehyde-modified attapulgite was prepared as a solid-phase extractant and applied for separation, preconcentration and determination of Cu(Ⅱ) in aqueous solutions by ICP-AES. The optimum pH value for the separation of Cu(Ⅱ) on the newly sorbent was 4.0 and complete elution of Cu(Ⅱ) from the sorbent surface was carried out using 2 mL of 0.01 mol L-1 HCl. The adsorption capacity for Cu(Ⅱ) was 25.13 mg g-1. The detection limits of the method defined by IUPAC were found to be 0.24 ug L"1 with enrichment factor of 150. The method has been applied for the determination of Cu(Ⅱ) in certified reference materials and natural water samples with satisfactory results.2. A method is described for the selective extraction of chromium(Ⅲ) from aqueous solutions and natural water samples, based on the use of two newly synthesized solid-phase extractors via silica gel-immobilized-vanillin derivatives (Ⅰ,Ⅱ). The optimum pH values for the separation of Cr(Ⅲ) simultaneously on the newly sorbents were both 4.0 and complete elution of Cr(Ⅲ) from the sorbents surface was carried out using 2.0 mL of 0.5 mol L-1 HCl. The sorption capacity of phase I towards Cr(Ⅲ) was found to be 0.700 mmol g-1 where the sorption capacity of phaseⅡwas 0.538 mmol g-1. The detection limits (3б) of the method defined by IUPAC were found to be 0.87 and 0.64 ng mL-1 with enrichment factors of 100 and 75 for phasesⅠandⅡ, respectively. The method has been applied for the determination of Cr(III) in biological materials and water samples with satisfactory results.3. A new method that utilizes ethylenediamine-modified activated carbon (AC-EDA) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(Ⅲ), Fe(Ⅲ), Hg(Ⅱ) and Pb(Ⅱ) prior to the measurement by ICP-AES. The optimum pH value for the separation of metal ions simultaneously on the new sorbent was 4.0. Complete elution of adsorbed metal ions from the sorbent surface was carried out using 3.0 mL of 2% (%w/w) thiourea and 0.5 mol L-1 HCl solution. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be 39.4,28.9,60.5 and 49.9 mg g-1 for Cr(Ⅲ), Fe(Ⅲ), Hg(Ⅱ) and Pb(Ⅱ), respectively. The precision (RSD) of the method was lower 4.0% (n=8). The prepared sorbent as solid-phase extractant was successfully applied for the preconcentration of trace Cr(Ⅲ), Fe(III), Hg(Ⅱ) and Pb(Ⅱ) in natural and certified samples with satisfactory results.4. A new method that utilizes zincon-modified activated carbon (AC-ZCN) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(Ⅲ) and Pb(Ⅱ) prior to the measurement by ICP-AES. At pH 4, the maximum adsorption capacity of Cr(Ⅲ) and Pb(Ⅱ) onto the AC-ZCN were 17.9 and 26.7 mg g-1, respectively. The adsorbed metal ions were quantitatively eluted by 1 ml of 0.1 mol L-1 HCl. According to the definition of IUPAC, the detection limits (3б) of this method for Cr(Ⅲ) and Pb(Ⅱ) were 0.91 and 0.65 ng mL"1, respectively. The relative standard deviation under optimum condition is less than 3.5%(n=8). The method has been applied for the determination of Cr(Ⅲ) and Pb(Ⅱ) in biological materials and water samples with satisfactory results.5. A new method that utilizes L-Alanine-modified multiwalled carbon nanotubes as a solid phase extractant has been developed for simultaneous preconcentration of trace Au(Ⅲ) prior to the measurement by ICP-AES. The maximum adsorption capacity at optimum conditions was found to be 101.3 mg g-1 for Au(Ⅲ). The method was validated using two certified reference materials, and has been applied for the determination of trace Au(Ⅲ) in natural water samples with satisfactory results.更多还原