碳酸氢钠饱和盐渍砂土的电化学特性试验研究

为分析碳酸氢钠含量对饱和盐渍砂土的电化学特性影响,通过配置4组不同浓度的碳酸氢钠溶液与标准砂混合形成碳酸氢钠饱和盐渍砂土;运用三电极体系下电化学阻抗谱法研究了不同含量的碳酸氢钠饱和盐渍砂土的电化学特性。研究结果表明:不同含量碳酸氢钠饱和盐渍砂土的Bode图中的阻抗模值随着碳酸氢钠含量的增加和频率的增加都呈现减小的趋势;Nyquist图主要包括高频区的圆弧、中频区的直线段及低频区的圆弧;且等效电路含有两个时间常数。碳酸氢钠饱和盐渍砂土的等效电路由电极与溶液界面的电荷转移电阻、扩散电阻、常相位角元件、砂粒固液界面电阻、砂粒固液界面电容以及溶液电阻六部分组成。碳酸氢钠含量的增加使得孔隙液中的离子浓度增加、扩散层内的离子向砂粒表面的转移能力增强、土水离子交换更频繁,导致溶液电阻和砂粒固液界面电阻随着含量的增大而减小;砂粒固液界面电容、常相位角元件的电容随着碳酸氢钠浓度的增大而增大。

Experimental Study on the Electrochemical Characteristics of Saturated Sand with Sodium Sicarbonate

In order to analyze the effect of sodium bicarbonate content on electrochemical properties of saturated saline soils, four different concentrations of sodium bicarbonate solution and standard sand soil were configured to form the saturated saline soils with sodium bicarbonate, respectively. The electrochemical properties of satu-rated saline soils with different contents of sodium bicarbonate were studied by electrochemical impedance spectroscopy. The results show that the impedance modulus of saturated saline soils in the Bode diagram de-creases with the increase of sodium bicarbonate and the frequency. The Nyquist diagram of sodium bicar-bonate saturated saline soil under different levels includes the circular arc in high frequency area, the straight line segment in the intermediate frequency area and the arc in the low frequency, which contains two time constant. The equivalent circuit model of sodium bicarbonate saturated saline soil mainly includes six kinds of equivalent components, namely the charge transfer resistance in the electrode and solution interface, diffu-sion resistance, the constant phase angle element, the sand-liquid interface resistance, sand-liquid interface re-sistance capacitance and solution resistance. The increase of the sodium bicarbonate make the ion concentra-tion in the pore fluid increase and the transfer capacity of ions in the diffusion layer is enhanced at the same time. The ion between soil and water exchange more frequently all these lead to the solution resistance and sand-liquid interface resistance decreases with the increase of content. The capacitance of the solid-liquid in-terface and the constant phase angle element increase with the increasing concentration of sodium bicarbonate.