Mpofu Patience, Addai-Mensah Jonas, Ralston John
Ian Wark Research Institute, University of South Australia, Mawson Lakes, Adelaide, South Australia 5095, Australia.
J Colloid Interface Sci. 2003 May 15;261(2):349-59. doi: 10.1016/S0021-9797(03)00113-9.
The influence of hydrolyzable metal ions (Mn(II) and Ca(II)) adsorption on the surface chemistry, particle interactions, flocculation, and dewatering behavior of kaolinite dispersions has been investigated at pH 7.5 and 10.5. Metal ion adsorption was strongly cation type- and pH-dependent and significantly influenced the zeta potential, anionic polyacrylamide-acrylate flocculant (PAM) adsorption, shear yield stress, settling rate, and consolidation of kaolinite slurries. The presence of Mn(II) and Ca(II) ions alone led to a systematic reduction in zeta potential due to specific adsorption of positively charged metal ion-based hydrolysis products at the kaolinite-water interface. Metal ion-mediated zeta potential changes were reflected by lower dispersion shear yield stresses and improved clarification (higher settling rates) but had no detectable effect on dispersion consolidation. The adsorption of PAM was significantly improved by prior addition of the metal ions. In the presence of Mn(II) or Ca(II) ions, the flocculant adsorption density was enhanced at pH 7.5 for Mn(II) and pH 10.5 for Ca(II). Optimum flocculation conditions, involving partial rather than complete particle surface coverage by both metal ions and flocculant, were identified. As a consequence, the metal ions and flocculant acted synergistically to enhance dewatering, producing particle interactions that were more conducive to high settling rates and greater consolidation of kaolinite dispersions at pH 7.5 than 10.5.
在pH值为7.5和10.5的条件下，研究了可水解金属离子（Mn(II)和Ca(II)）吸附对高岭土分散体的表面化学、颗粒相互作用、絮凝和脱水行为的影响。金属离子吸附强烈依赖阳离子类型和pH值，并显著影响高岭土悬浮液的ζ电位、阴离子聚丙烯酰胺 - 丙烯酸酯絮凝剂（PAM）吸附、剪切屈服应力、沉降速率和固结。单独存在Mn(II)和Ca(II)离子会导致ζ电位系统性降低，这是由于带正电的金属离子基水解产物在高岭土 - 水界面的特异性吸附。金属离子介导的ζ电位变化表现为较低的分散体剪切屈服应力和更好的澄清效果（更高的沉降速率），但对分散体固结没有可检测到的影响。预先添加金属离子可显著改善PAM的吸附。在存在Mn(II)或Ca(II)离子的情况下，在pH值为7.5（对于Mn(II)）和pH值为10.5（对于Ca(II)）时，絮凝剂吸附密度增加。确定了最佳絮凝条件，即金属离子和絮凝剂对颗粒表面的覆盖是部分而非完全覆盖。因此，金属离子和絮凝剂协同作用以增强脱水效果，在pH值为7.5时比pH值为10.5时产生更有利于高岭土分散体高沉降速率和更大固结的颗粒相互作用。
