Preparation Of Novel Functionalized Adsorbent And Their Application In Metal Ion Analysis

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.