Pointeau Ingmar, Reiller Pascal, Macé Nathalie, Landesman Catherine, Coreau Nathalie
CE Saclay, DEN/DANS/DPC/SECR, Laboratoire de Mesures et Modélisation de la Migration des Radionucléides, Bât. 450, BP 11, 91191 Gif-sur-Yvette Cedex, France.
J Colloid Interface Sci. 2006 Aug 1;300(1):33-44. doi: 10.1016/j.jcis.2006.03.018. Epub 2006 May 2.
Hydrated cement pastes (HCP) have a high affinity with a lot of (radio)toxic products and can be used as waste confining materials. In cementitious media, elements are removed from solution via (co)precipitation reactions or via sorption/diffusion mechanisms as surface complexation equilibria. In this study, to improve the knowledge of the surface charge evolution vs the degradation of the HCP particles, two cements have been studied: CEM-I (ordinary Portland cement, OPC) and CEM-V (blast furnace slag and fly ash added to OPC). Zeta potential measurements showed that two isoelectric points exist vs HCP leaching, i.e., pH. Zeta potential increases from -17 to +20 mV for pH 13.3 to pH 12.65 (fresh HCP states) and decreases from 20 to -8 mV for pH 12.65 to 11 (degraded HCP states). The use of a simple surface complexation model of C-S-H, limited in comparison with the structural modeling of C-S-H in literature, allows a good prediction of the surface potential evolution of both HCP. Using this operational modeling, the surface charge is controlled by the deprotonation of surface sites (>SO(-)) and by the sorption of calcium (>SOCa(+)), which brings in addition a positive charge. The calcium concentration is controlled by portlandite or calcium silicate hydrate (C-S-H) solubilities.
水化水泥浆体（HCP）对许多（放射性）有毒产物具有高亲和力，可作为废物固化材料。在水泥基介质中，元素通过（共）沉淀反应或作为表面络合平衡的吸附/扩散机制从溶液中去除。在本研究中，为了增进对HCP颗粒表面电荷演变与降解关系的了解，研究了两种水泥：CEM-I（普通硅酸盐水泥，OPC）和CEM-V（在OPC中添加了高炉矿渣和粉煤灰）。zeta电位测量表明，相对于HCP浸出（即pH值）存在两个等电点。在pH值从13.3降至12.65（新鲜HCP状态）时，zeta电位从-17 mV增加到+20 mV；在pH值从12.65降至11（降解HCP状态）时，zeta电位从20 mV降低到-8 mV。使用一个简单的C-S-H表面络合模型（与文献中C-S-H的结构模型相比有限），可以很好地预测两种HCP的表面电位演变。使用这种实用模型，表面电荷受表面位点（>SO(-)）的去质子化和钙（>SOCa(+)）的吸附控制，钙的吸附还会带来正电荷。钙浓度受氢氧化钙或硅酸钙水合物（C-S-H）溶解度的控制。
