电解质和阳离子表面活性剂对MMH/粘土体系胶体性能的影响

Effects of Electrolytes and Cationic Surfactant on Colloidal Properties of MMH/Mt System

通过流变参数、电泳淌度和ｐＨ值的测定，研究了ＮａＣｌ、ＭｇＣｌ２、Ｎａ２ＳＯ４等电解质和阳离子表面活性剂（十六烷基三甲基溴化铵）对铝镁混合金属氢氧化物（ＭＭＨ）／钠土（Ｍｔ）悬浮体胶体性能的影响．发现所研究的电解质和表面活性剂都能使ＭＭＨ／Ｍｔ悬浮体的Ｂｉｎｇｈａｍ屈服值降低，但不同处理剂影响ｐＨ值和滤失量的变化趋势却不同．认为电解质中的阳离子以影响粘土颗粒间的缔合为主，而阴离子以影响ＭＭＨ的荷电性能为主，前者使滤失量上升，ｐＨ值下降；后者使滤失量下降，ｐＨ值上升．电解质对ＭＭＨ／Ｍｔ悬浮体滤失量和ｐＨ值的影响取决于二者相对能力的大小．阳离子表面活性剂由于在粘土上吸附后不仅影响颗粒之间的缔合，也能使其润湿性反转，导致ＭＭＨ／Ｍｔ悬浮体的滤失量和Ｂｉｎｇｈａｍ屈服值的变化幅度明显高于无机电解质．

The effects of electrolytes (NaCl, Na 2SO 4 and MgCl 2) and cationic surfactant (cetyltrimethylammonium bromide) on colloidal properties of mixed metal hydroxide (MMH)/montmorillonite (Mt) suspension were studied through measurements of electrophoretic mobilities, rheology and pH. The results show that all the electrolytes and surfactant studied in this work decreased Bingham yield point (YP) of MMH/Mt system, but exerted different effects on fluid loss (FL) and pH of MMH/Mt system. The results are interpreted as means that the cationic ions of electrolytes mainly displace the charge balancing ions of Mt particles, such as H + and Na +, so enhance their aggregation, leading to the decrease of pH and the increase of FL, but the anionic ions of these electrolytes mainly displace the charge balancing ions of MMH particles, such as OH - and Cl -, so weaken the aggregation effects of MMH on Mt particles, therefore, cause the increase of pH and the decrease of FL. In another word, the overall effects of electrolytes on MMH/Mt system depend on the relative ability of anionic and cationic ions to exert the opposite effects on FL and pH. As for cetyltrimethylammonium bromide (CTAB), the adsorption of CTAB on Mt particles does not only displace H + and cause the aggregation of Mt particles but also reverses their wetting ability, therefore, CTAB decrease FL and YP of MMH/Mt system to a larger extent than inorganic electrolytes although it can only decrease pH slightly.