Functional Nano-materials Used For The Analysis Of Trace Cadmium Ion

With the rapid economic development, industrial pollution has become more and more serious. As one of the important environmental pollutants, heavy metal cadmium has a damage effect on the liver, kidney, bone. The determination of heavy metals accurately and quickly has always attracted the attention of people. Duo to that the matrix is complex and the concentration of cadmium is low, it is usually necessary to enrich the sample before analyzing. The traditional techniques, such as liquid-liquid extraction is time-consuming, inefficient and labor-intensive. Therefore, the development of the determination of cadmium with a sensitive, well selective, simple and quick pre-treatment method is of great significance.Solid phase extraction (SPE) is a very important tool for sample pretreatment, which improve sensitivity and eliminate interference for the determination. However, the classical SPE has a few kinds of filler, poor selectivity and a long extraction time. Consequently, it is necessary to develop a new kind of material for SPE.As nonmaterial show strong adsorption ability, shorter equilibrium time and higher adsorption capacity, the selectivity was increased after surface modification. Also the magnetic nanoparticles gather quickly in the magnetic field, as they are super-paramagnetic.In this paper, two kinds of silica-coated magnetic nanoparticles modified with dithizone or ionic liquid was prepared. The functional materials were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM) and thermogravimetric analyzer (TGA).The modified magnetic nanoparticles was then used as the sorbent for solid phase extraction of trace amount of Cd2+from water samples by flame atomic absorption spectrometry (FAAS). Two new methods for preconcentration of Cd2+in aqueous solution were developed. The major contents are described as follows:1. Clarified the background and significance of the study, summarized the main analysis methods of the cadmium, and introduced solid phase extraction, nanometer materials and their application in environmental analysis profiles.2. The silica-coated magnetic nanoparticles modified with dithizone were prepared. Ferroferric oxide was coated with silica by sol-gel method, and doped with dithizone. The modified nanoparticles were characterized by SEM, FT-IR and VSM. The result showed that the prepared material has nano-size dimensions, which was modified with dithizone successfully and exhibits apparent superparamagnetism.3. A new method for detection of Cd2+in aqueous solution was developed, which using Dithizone modified magnetic nano-material based SPE-FAAS. The influential factors on the recovery of Cd were investigated. Under the optimized conditions, the limit of detection (LOD) for Cd2+was found to be0.15μg/L with the relative standard deviation (RSD) of5.2%. The method was successfully applied to the determination of cadmium in the lake and river. The standard recoveries were between83.3%and87.9%.4. The silica-coated magnetic nanoparticles modified with ionic liquid were prepared. Ferroferric oxide was coated with silica by sol-gel method, then modified with1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM]PF6). The modified nanoparticles were characterized by SEM, FT-IR, VSM and TGA.The result showed that the prepared material were nano-size particles, which exhibits apparent superparamagnetism.5. Another new method for detection of Cd2+in aqueous solution was developed, which using [OMIM]PF6modified magnetic nano-material based SPE-FAAS. The influential factors on the recovery of Cd2+were investigated. Under the optimized conditions, the LOD for Cd2+was found to be0.20μg/L with the RSD of2.5%. The method was successfully applied to the determination of cadmium in the lake and river, and the standard recoveries were between84.3%and99.6%.