盐溶液对膨润土微观结构的影响

Effects on bentonite microstructure by salt solution

将蒸馏水和不同浓度的NaCl溶液浸泡过的膨润土试样进行氮分子吸附,测得试样在77 K温度下N_2等温吸附线,根据等温吸附数据采用BET法、BJH法和Neimark热力学方法分别测算出各试样的比表面积、孔隙体积和表面分维.计算结果表明,随着浸泡溶液浓度的增加,膨润土试样的孔隙体积逐渐减小,而比表面和表面分维呈先增大后减小的趋势.对比发现这是由于浓度不同,膨润土表面吸附的Na^+量不同所引起的.NaCl溶质浓度越高,膨润土吸附的Na^+量越大,在试样烘干后吸附在膨润土表面的Na^+堵塞了试样的孔隙引起孔隙体积的减小,但相比于高浓度的NaCl溶液,少量的Na^+分散于膨润土表面则会引起表面粗糙度的增加,导致在低浓度NaCl溶液中的比表面积和表面分维较大.

Nitrogen adsorption was conducted at 77 K to obtain the adsorption isotherm on the bentonite specimens inundated with distilled water and sodium chloride with different concentrations. Then, according to the adsorption data, the specific surface area, the pore volume, and the surface fractal dimension of bentonite specimens were calculated by BET, BJH and the Neimark thermody- namics methods, respectively. The test results show that with the increase of inundating solution con- centration, the pore volume of bentonite decreases, and the specific surface and surface fractal dimension firstly decreases after an increased. It is found that this is due to the amount of Na ^＋ coating the bentonite surface is different in different NaCl solutions. When the concentration of NaCl solution is higher, the Na ^＋ adsorbed on bentonite surface is higher, and the Na ^＋ will block the pore, leading to a smaller pore volume. Compared with the highly concentrated NaCl solution, a little of Na ^＋ coating on the surface is more likely to cause a higher surface roughness, thus resulting in a high specific surface area and surface fractal dimension in NaCI solution with low concentration.