Experimental Study On Physical And Mechanical Properties And Electrochemical Impedance Spectroscope Of Silt Contaminated By Cadimium Nitrate

In this paper,silt of contaminated by cadmium nitrate was selected as the research object,which physical,mechanical properties and electrochemical impedance spectroscopy were studied by means of geotechnical test and electrochemical impedance spectroscopy,and the relationship between physical,mechanical properties and parameters of electrochemical impedance spectroscopy of heavy metal contaminated soils are briefly analyzed.Compared and analyzed the physical properties of contaminated silt in different contents.It was shown that the clay content and the porosity ratio of the contaminated soil decreased,but the dry density increased with the increase of cadmium nitrate content.Compared with the uncontaminated silt,the liquid limit,the plastic limit and the plasticity index of the contaminated silt all decreased,indicating that the invasion of cadmium nitrate would reduce the plasticity of the silt.Through the indoor compression test and direct shear test,it can be concluded that the compressibility index and shear strength index ofcontaminated silt.The compressibility and shear strength of the silt before and after the addition of heavy metals were analyzed.The experimental results show that with the increasing of cadmium nitrate content,the engineering properties of the contaminated silt deteriorated,the compression coefficient and compression modulus increased,and the cohesion and internal friction angle decreased.This shows that the intrusion of cadmium nitrate can increase the compressibility of silt,and decrease the shear strength.By means of electrochemical impedance spectroscopy of six kinds of cadmium nitrate contaminated silt,the results were obtained that the Nyquist map of uncontaminated silt and cadmium nitrate contaminated silt showed a capacitive arc with a time constant.With the increasing of cadmium nitrate contents,the intercept of Nyquist map and real axis was getting smaller and smaller,and was the arc radius.In the Bode diagram,the impedance modulus |Z|decreased with the increasing of the concentration of cadmium pollution,and decreased with the increasing of the frequency.In the phase diagram,as the contents of cadmium nitrate contamination increases,the value of phase angle is increasing.Through the electrochemical impedance spectroscopy of the contaminated silt with the same cadmium nitrate contents,we know that the Nyquist map of different compaction work was also appeared as a capacitive arc,with the increasing of compaction power,the intercept of the Nyquist diagram and the real axis becomed smaller and the radius of the arc decreased gradually.The equivalent circuit model of cadmium nitrate contaminated silt is RL(QR1).It was used to fit the electrochemical impedance spectroscopy,and the following conclusions were obtained.With the increasing of the concentration of cadmium nitrate contamination,the pore resistance RL and the solid-liquid interface resistance R1 showed a decreasing trend,the electric double layer capacitance Q showed an increasing trend.Analysising fitting parameters of equivalent circuit,the solution resistance RL can be used to measure the concentration of ions in the pore water of the soil,and the solid-liquid interface resistance R1 and the electric double layer capacitance Q can be used to measure the adsorption capacity of soil particles to heavy metals.