Synthesis Of Novel Adsorption Materials And Their Application In Trace Metal Ion Analysis

The release of heavy metals into the environment is a potential threat to water and soil quality as well as to aquatic life and human health. Moreover, metal ions do not degrade biologically like organic pollutants, their presence in the environment is a public health problem due to their ingestion and therefore possible accumulation in living organisms. However, the direct determination of heavy metal ions by modern spectrometric techniques are usually insufficient due to the matrix interferences and the very low concentration of metal ions. Therefore, a separation/pre-concentration step is required.Nowadays, solid-phase extraction (SPE) becomes the most common technique for environmental sample pretreatment because of its advantages of high recovery, short extraction time, high enrichment factor, low cost, and lower consumption of organic solvents than liquid-liquid extraction. In SPE procedure, the choice of appropriate sorbent is a critical factor to obtain full recovery and high enrichment factor. Based on this, in our work, some newly selective solid-phase extractors were synthesized and characterized in order to pre-concentration and separation of trace metal ions in environment. The detailed novelty of this study have been listed in the following:1. A novel method that utilizes1-(2-formamidoethyl)-3-phenylurea-modified activated carbon (AC-1-(2-formamidoethyl)-3-phenylurea) as a solid phase extractant has been developed for simultaneous preconcentration of trace Cr(Ⅲ), Cu(Ⅱ), Fe(Ⅲ) and Pb(Ⅱ) prior to the measurement by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results showed that the optimum pH value for the separation of metal ions simultaneously on the new sorbent was4. The maximum static adsorption capacity of the sorbent at optimum conditions was found to be39.8,39.9,77.8and17.3mg g-1for Cr(Ⅲ), Cu(Ⅱ), Fe(Ⅲ) and Pb(Ⅱ), respectively. The relative standard deviation (RSD) of the method was lower than4.0%(n=8). The method was successfully applied for the preconcentration of trace Cr(Ⅲ), Cu(Ⅱ), Fe(Ⅲ) and Pb(Ⅱ) in natural and certified samples with satisfactory results.2. Ethyl-3-(2-aminoethylamino)-2-chlorobut-2-enoate modified activated carbon (AC-EAC) was synthesized and characterized. The new sorbent showed great affinity, relatively high adsorption capacity and less equilibrium time for Au(Ⅲ), Pd(Ⅱ) and Pt(Ⅳ). The influences of some analytical parameters on the quantitative recoveries of the analytes were investigated in detail. This method was applied to the preconcentration and determination of trace amount of Au(Ⅲ), Pd(Ⅱ) and Pt(Ⅳ) from actual samples with satisfactory results.3.1-(2-Aminoethyl)-3-phenylurea chemically modified silica gel (SG-AEP) was synthesized and characterized. The new sorbent showed great affinity, relatively high adsorption capacity, less equilibrium time and easy elution for Sc(Ⅲ). Parameters that affect the sorption and elution efficiency of the metal ions were also studied. The optimum pH value for the separation of Sc(Ⅲ) on the new sorbent was4and complete elution of Sc(Ⅲ) from the sorbent surface was carried out using1.0mL of0.1mol L-1HCl.Common coexisting ions did not interfere with the separation and determination of the analyte. The maximum static adsorption capacity of the sorbent under optimum conditions was found to be32.5mg g-1. The detection limit of present method was found to be0.091μg g-1, and the relative standard deviation (RSD) was lower than3.0%(n=8). Then, the method was applied to preconcentrate trace Sc(Ⅲ) from environmental samples with satisfactory results.4.2-(Aminothioxomethyl)hydrazine]acetylchloride modified silica gel was synthesized. The new sorbent showed great affinity, relatively high adsorption capacity, high enrichment factor, less equilibrium time and easy elution for Fe(Ⅲ) and Pb(Ⅱ). Parameters that affect the sorption and elution efficiency of the metal ions were also studied, the method was applied to preconcentrate trace Fe(Ⅲ) and Pb(Ⅱ) from environmental samples with satisfactory results.5.3-(4-Amino-phenylamino)-2-chloro-but-2-enoic acid ethylester modified multiwalled carbon nanotubes was synthesized. The new sorbent showed great affinity for Pb(Ⅱ). Parameters that affect the sorption and elution efficiency of the metal ion were also studied. the method was applied to preconcentrate trace Pb(Ⅱ) from environmental samples with satisfactory results.