Study On The Application Of Nanocomposite Materials In The Analysis Of Trace Metal Ions

In recent years,emissions of toxic and harmful metal ions in the environment are increasing as the economy rapidly develops.Metal ions eventually enter human body through food chains enrichment and further endanger human health.All of this means it is imperative to develop new,fast,and accurate methods for the separation,enrichment,and detection of metal ions in the environment.Carbon nanotubes and graphene oxides are typical nanomaterials,which have many potential applications due to their advantages such as great specific surface area and plentiful active sites.In this paper,an electrochemical sensor for detecting Cu²⁺was constructed based on a carbon nanotubes/molybdenum disulfide nanosheets composite.In addition,mercapto-modified graphene/multi-walled carbon nanotube aerogels（SH-GNAs）and amino-functionalized zeolite imidazolate framework material ZIF-90（NH₂-ZIF-90）were applied for separation and enrichment of precious metal ion Au（Ⅲ）.The specific contents are as shown in the blow:1.An electrochemical sensor is successfully developed based on 5-sulfosalicylic acid modified molybdenum disulfide nanosheets and oxidized multi-walled carbon nanotubes（SSA/MoS₂/o-MWCNTs）.The nanocomposites modified glassy carbon electrode（GCE）is used for the detection of Cu²⁺after characterization by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,X-ray photoelectron spectroscopy（XPS）,Raman spectroscopy,and electrochemical measurements.Electrochemical analysis of Cu²⁺was then studied by differential pulse voltammetry（DPV）,and the effects of pH,deposition potential,etc.were investigated.Therefore,the peak current linearly increased with increasing Cu²⁺concentration over a range of 0.1μM¹1μM.The curve was fitted with the linear equation I（μA）=8.503c+2.167（R²=0.996）,revealing a detection limit of0.057μM（S/N=3）.Finally,the developed sensor was applied to the analysis of Cu²⁺in lake water and dairy product,and the results were consistent with ICP–MS analysis.Therefore,this work demonstrates that the proposed electrochemical sensor can be easily used for the daily monitoring of Cu²⁺.2.In this study,SH-GNAs were facilely constructed by using L-cysteine as a cross-linking agent and modifier.The effective adsorption behaviors of Au（Ⅲ）from environmental samples by the SH-GNAs were investigated.The SH-GNAs were characterized by SEM,N₂ adsorption-desorption isotherms,XRD,FT-IR,XPS,and the influencing factors,such as pH value,adsorbent dosage were optimized.The pseudo-second-order model fitted kinetic data better,and the equilibrium data was well described by the Freundlich isotherm model.Moreover,the Au（Ⅲ）could be desorbed with 1 M HCl containing 4%thiourea.Finally,the SH-GNAs were used in lake water and soil samples for Au（Ⅲ）adsorption with recovery rate from 86.3%to 102%.The results indicate that the developed SH-GNAs is an excellent adsorbent for removing Au（Ⅲ）from samples and has significant application prospects in environmental field.3.The adsorption of Au（Ⅲ）from aqueous solutions employing NH₂-ZIF-90 has been systematically investigated in this work.The morphology and structure of NH₂-ZIF-90were analyzed by SEM,XRD,FT-IR,and XPS.The adsorption effect of Au（Ⅲ）onto NH₂-ZIF-90 was achieved best after 12 h of shaking in pH=5 aqueous medium with 2 mg mL^-1 NH₂-ZIF-90.The adsorption process accords with the pseudo-second-order model and Freundlich adsorption isotherm.Finally,NH₂-ZIF-90 was successfully applied to the adsorption of Au（Ⅲ）in environmental water samples with the recovery rate from 81.0%to 93.3%.This study shows a new way to solve the adsorption problem of Au（Ⅲ）.