氯化钠盐渍砂土电化学特性的试验研究

为分析盐含量对氯化钠盐渍砂土电化学特性的影响,通过配置4组不同浓度的氯化钠溶液与标准砂混合形成氯化钠盐渍砂土。采用CS350电化学工作站获取氯化钠盐渍砂土的电化学阻抗谱图,运用Zview、ZsimDemo进行拟合其等效电路,研究各个参数的变化规律及探讨其机理分析。结果表明:不同盐含量对氯化钠盐渍砂土的Nyquist图均影响较小,均表现为高频区的平扁容抗弧半圆和低频区的近45°斜线的图谱特征;且随着盐渍砂土中氯化钠含量的增加,容抗弧和扩散半径都呈减小的趋势。Bode图中阻抗模值随着盐渍砂土中氯化钠含量的增加和频率的增大都表现为减小的趋势。通过计算、分析和模拟其等效电路,得到盐渍砂土的等效电路元件主要包括:溶液电阻、砂土多孔层电容和电阻、固液界面形成的双电层电容和法拉第阻抗。由于氯化钠含量增大,盐渍砂土的孔隙溶液离子浓度上升,可自由移动的正负离子增多,致使体系中的电荷分离以及电荷转移等过程更加容易,促使体系反应速度加快,表现出溶液电阻、多孔层电阻和电荷转移电阻均呈减小趋势,导电能力增强,多孔层电容和双电层电容均呈增加趋势,储存电荷能力增强。

Experimental Study on Electrochemical Characteristics of Sodium Chloride Saline Soil

In order to analyze the effect of salt content on the electrochemical characteristics of sodium chloride saline soil, NaCl saline soils with different salt concentrations were configured. The electrochemical impedance spectroscopies (EIS) of NaCl saline soils were tested on the CS350 electrochemical workstation and the results were fitting by Zview and ZsimDemo. And the variation of parameters and the mechanism were analyzed. The results show that the salt concentration slightly affects the shape of Nyquist diagram of NaCl saline soils, which exhibits flat semi-circle arc (high-frequency region) and nearly 45 ° oblique line (low-frequency region). However, the radius decrease with the increasing salt concentration. Bode plots show that the impedance modulus also decreases with the increase of salt concentration and frequency. The equivalent components were obtained by equivalent circuit fitting, which include solution resistance, capacitance and resistance of sand porous layer, and the electric double-layer capacitance and Faraday impedance formed at the solid-liquid interface. When the salt concentration is high, ion concentration of pore solution is larger, and the charge separation and charge transfer processes in reaction is easy. Solution resistance, resistance of sand porous layer and charge transfer resistance are all small. The increase of porous and electric double layer capacitors indicate the increase of storage charge capacity.