The Sensitive Detection Of Heavy Metal Ions And Phosphate Anions In Soil By Chemically Modified Electrodes

Based on electrochemical voltammetry techniques with high sensitivity,strong selectivity,low operating cost and simple operation,chemically modified electrodes are applied for detecting different trace environmental pollutants effectively and quickly.This kind of method is of higher potential comparing with various conventional detection methods for environmental pollutants in water and soil.Focusing on various modification materials,modification methods of chemically modified electrodes and optimization of experimental parameters in the modification process,this paper describes two kinds of modified working electrodes by preparing novel metal oxide composite nanomaterials mixed with carbon-based nanomaterials as raw materials with the modification method of drop coating.Meanwhile,the study analyzed the electrochemical behavior of various heavy metal ions and inorganic phosphate ions on the surface of the working electrode respectively,and applied them to the analysis of the above substances in actual soil samples.The main contents are as follows:1.CuZrO3 nanocomposites were prepared by chemical deposition and high temperature oxidation(700?).The elemental composition and structural characteristics of CuZrO3 nanocomposites were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).The characterization results showed that a nanocomposites with nano-sized needle-like structure and high crystallinity was formed,and then the graphene nanomaterial was mixed so that CuZr03/Gr composite modified glassy carbon electrode(CuZrO3/Gr/GCE)was successfully constructed by drop coating.In the electrochemical behavior analysis process,0.2 mol L-1 acetic acid-sodium acetate buffer(pH=4.6)was used as the electrolyte solution,and different concentrations of Pb(?)and Cd(?)were detected by square wave anodic stripping voltammetry(SWV).In the synergistic effect of CuZrO3 nanoparticles and graphene,CuZrO3/Gr/GCE exhibited excellent ion transport performance,stability and sensitivity in the presence of Pb(?)and Cd(?)ions:the detection limits of Pb(?)and Cd(?)were 4.8×10-10 mol L-1 and 4.4×10-9 mol L-1,respectively.The prepared CuZrO3/Gr chemically modified electrodes was applied to the codetection of Pb(?)and Cd(?)contents in the soil samples.The test had considerable practical value.After the soil samples were pretreated according to the conventional method,the Pb(?)and Cd(?)contained therein were effectively extracted,and then CuZr03/Gr/GCE was used to carry out the detection of two heavy metal ions in the soil extract simultaneously.The detection results were compared with the results of inductively coupled plasma mass spectrometry(ICP-MS)for the same samples.The results showed that the detection values of the two methods for the two heavy metal ions are extremely similar,indicating that this modified electrode by voltammetry would have practical operability.2.A novel ZrO2-ZnO nanocomposite doped multi-walled carbon nanotube modified screen printing electrode(ZrO2-ZnO/MWCNTs/AMT/SPE)was developed and this electrochemical sensor was applied for rapid detection of inorganic phosphate ions.ZrO2-ZnO nanocomposites were also prepared by chemical deposition and high temperature oxidation(450 ?).The elemental composition and structural characteristics of the prepared materials were characterized by scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The results showed that the nanocomposite forms a nanorod-like structure with high crystallinity.Under the synergy of the nanocomposite doped multi-walled carbon nanotubes,under the complexation reaction between molybdate and phosphate,using 0.2 mol L-1 H2SO4/KCI as the electrolyte solution,and cyclic voltammetry(CV)was adopted.The electrochemical behavior of phosphomolybdate complexes on the surface of ZrO2-ZnO/MWCNTs/AMT/SPE was studied to indirectly obtain the concentration of addicted phosphate ions.The detection system demonstrated a low detection limit of phosphate ions at 2×10-8 mol L-1,outstanding reproducibility and anti-interference.In this study,ZrO2-ZnO/MWCNTs/AMT/SPE was applied to the determination of inorganic phosphate ions in actual soil samples.The extraction parameters of inorganic phosphate ions in soil samples including extractant type and extraction time were optimized.The feasibility of the electrochemical method for the determination of phosphate in soil was evaluated by the comparation of the concentration of inorganic phosphate in soil samples through standard colorimetric and cyclic voltammetry respectively.The results demonstrated that ZrO2-ZnO/MWCNTs chemically modified electrode can be effectively used for detecting inorganic phosphate in different soil sources with high-precision detection,which laid the foundation of situ measurement of inorganic phosphate ions in soil in the future.