Lamorena Rheo B, Lee Woojin
Department of Civil and Environmental Engineering Korea Advanced Institute of Science and Technology, 335 Gwahangno, Yuseong-Gu, Daejon 305-701, Korea.
Environ Sci Technol. 2009 Aug 1;43(15):5908-14. doi: 10.1021/es901066h.
We investigated the effect of pH on CO2 hydrate formation in the presence of phyllosilicate mixtures. Different pH conditions of phyllosilicate suspensions (Na-montmorillonite-rich and phyllosilicate-rich suspensions) with and without NaCl (3.5%) were prepared and controlled by the addition of an acid or base before the dissolution of CO2. The formation of CO2 hydrates was observed in all phyllosilicate suspensions (30 bar and 273.45 K). The temperature-time plot results showed that hydrate formations were suppressed more in acidic mineral suspensions than in basic suspensions. The fastest hydrate induction time can be observed in Na-montmorillonite-rich and phyllosilicate-rich suspensions with and without NaCl at near neutral conditions (pH 6-8), followed by basic (approximately pH 12.0) and acidic (approximately pH 2.0) pHs. Hydrate induction time can be significantly affected by various chemical species forming under different suspension pHs. The distribution of chemical species in each mineral suspension was estimated by a chemical equilibrium model, PHREEOC, and used for the identification of hydrate formation characteristics in the suspension. Particle-particle and particle-water interactions may possibly contribute to the delay of hydrate formation. NaCl was not an efficient inhibitor but a possible promoter for hydrate formation when pH-dependent solid surfaces were present in the system.
我们研究了在层状硅酸盐混合物存在的情况下，pH值对二氧化碳水合物形成的影响。在二氧化碳溶解之前，通过添加酸或碱来制备和控制含NaCl（3.5%）和不含NaCl的层状硅酸盐悬浮液（富含钠蒙脱石和富含层状硅酸盐的悬浮液）的不同pH条件。在所有层状硅酸盐悬浮液（30巴和273.45K）中均观察到了二氧化碳水合物的形成。温度-时间曲线结果表明，与碱性悬浮液相比，酸性矿物悬浮液中水合物的形成受到的抑制作用更大。在接近中性条件（pH 6-8）下，无论有无NaCl，在富含钠蒙脱石和富含层状硅酸盐的悬浮液中均可观察到最快的水合物诱导时间，其次是碱性（约pH 12.0）和酸性（约pH 2.0）pH条件。不同悬浮液pH值下形成的各种化学物质会显著影响水合物诱导时间。通过化学平衡模型PHREEOC估算了每种矿物悬浮液中化学物质的分布，并用于确定悬浮液中水合物的形成特征。颗粒间和颗粒与水之间的相互作用可能会导致水合物形成的延迟。当体系中存在依赖于pH值的固体表面时，NaCl不是一种有效的抑制剂，而是水合物形成的一种可能的促进剂。
