Synthesis Of Functionalized Nano-Adsorbent Material And Its Applications In Trace Metal Ions Analysis

With the continuous development of the economy, the growing incidence of environmental pollution, air pollution, water pollution, global warming, energy shortages, solid waste pollution and species extinction and other issues have threated our living environment. Especially water, soil and food contamination caused by the heavy metal ions have maken our life destroyed once again. However, because complex matrix interference is complex and the sensitivity of the exsiting methods is not enough, it’s difficult to analyze trace and ultra-trace element in actual samples. Thus, it is very important to open efficient methods for detecting metal ions in the environment. In this paper, in order to separate trace metals from the environmental samples, we designed the new SPE adsorbents and analytical methods. Through the modification of multiwall carbon nanotubes, graphene oxide and halloysite nanotubes, we obtained several new SPE adsorbents material, and systematically studied the selective adsorption property of the material. At the same time, according to characteristics of graphene oxide, we developed a fluorescence sensor to directly analysis trace Th4+in the solution samples. Our work is divided into the following five parts:1. Highly selective solid-phase extraction of trace Pd(Ⅱ) by murexide functionalized halloysite nanotubesThe originality on the high efficiency of murexide modified halloysite nanotubes (HNTs-Mu) as a new solid-phase extractant has been reported to preconcentrate and separate Pd(Ⅱ) in solution samples. The structure of HNTs-Mu was confirmed by FT-IR, XRD, SEM, TEM and BET. Effective determination conditions of Pd(Ⅱ) were examined using column procedures before detection by inductive coupled plasma atomic emission spectrometry (ICP-AES). The effects of pH, sample flow rate and volume, amount of adsorbent, elution condition and interfering ions were optimized. Under the optimized conditions, trace Pd(Ⅱ) could be retained on the column at pH1.0and quantitatively eluted by2.5mL of0.01mol L-1HCl-3%thiourea solution at a flow rate of2.0mL min-1.An enrichment factor of120was achieved. Common interfering ions did not interfere in determination and separation. The maximum adsorption capacity of HNTs-Mu at optimum conditions was42.86mg g-1for Pd(II). The detection limit (3a) of the method was0.29ng mL-1, and the relative standard deviation was3.1%(n=11). The method was validated using certified reference material, and then has been applied for the determination of trace Pd(II) in actual samples with satisfactory results.2. Functionalized halloysite nanotubes with2-hydroxybenzoic acid for selective solid-phase extraction of trace iron(III)Functionalized halloysite nanotubes with2-hydroxybenzoic acid (HNTs-HBA) has been synthesized and characterized by FT-IR, XRD, TEM and Elemental analysis. The capability of HNTs-HBA has been developed for selective separation and preconcentration of trace Fe(III) before detection by ICP-AES. The effects of pH, shaking time, flow rate and volume of the sample, elution condition and interfering ions were examined using column and batch procedures. An enrichment factor of75was obtained. HNTs-HBA exhibited fairly fast kinetics for the adsorption of Fe(Ⅲ) and common coexisting ions did not interfere in the determination. The maximum adsorption capacity of HNTs-HBA for Fe(Ⅲ) was45.54mg g-1at optimum conditions. The detection limit (3σ) of the method was0.21ng mL-1. The relative standard deviation under optimum condition was2.7%(n=11). The developed method has been successfully applied for the determination of trace Fe(Ⅲ) in biological and natural water samples.3. Multiwalled carbon nanotubes modified with2-aminobenzothiazole for uniquely selective solid-phase extraction and determination of trace Pb(Ⅱ) ion in water samplesA solid phase extraction method is presented for the selective preconcentration and/or separation of trace Pb(Ⅱ) by2-aminobenzothiazole modified multiwalled carbon nanotubes (MWCNTs-ABTZ). ICP-AES was used for detection. The effects of pH, shaking time, sample flow rate and volume, elution condition and interfering ions were examined by column and batch procedures. An enrichment factor of100was obtained. Common coexisting ions did not interfere in the determination. The maximum adsorption capacity of MWCNTs-ABTZ for Pb(Ⅱ) was60.32mg g-1. The detection limit (3σ) of the method was0.27ng mL-1. And the relative standard deviation was1.6%(n=8). The method was validated using a certified reference material, and has been applied for the determination of trace Pb(II) in water samples with satisfactory results.4. Fluorescence determination based on graphene oxideGraphene oxide (GO) has been prepared and the structure of the prepared GO was characterized by XRD, UV-Vis, FT-IR and TEM, respectively. And then we demonstrated that GO could quench the fluorescence of Rhodamine6G (Rh6G) in aqueous solution. According to the UV-vis absorption spectrum of GO and the fluorescence spectrum of Rh6G, we found that GO quenched the fluorescence of Rh6G due to two factors. Firstly, the electrons moved from the Rh6G to the surface GO; secondly, Rh6G adsorbed onto the GO surface. However, trace Th4+enhanced the fluorescent signal of Rh6G, which was quenched by GO prior to metal ions addition.5. Adsorption of trace Cr(Ⅲ)and Pb(Ⅱ) by diethylenetriamine functionalized graphene oxideGraphene oxide chemically modified with diethylenetriamine (GO-DETA) was fabricated and used to determine trace metal ions in solution. The results showed that the material exhibited a highly selective adsorption of trace Cr(Ⅲ) and Pb(Ⅱ) at pH4. The maximum adsorption capacity of GO-DETA was be60.9mg g-1and142.86mg g-1for Cr(Ⅲ) and Pb(Ⅱ), respectively. The facile chemical route and high adsorption capacity made this material practically useful for waste water treatment.