Abstract A hydrate-based technology is suggested for the desalination of industrial effluents, especially electroplating effluents including NiCl2. To decrease the required energy for operating a hydrate-based desalination (HBD) process, chlorodifluoromethane (CHClF2) was used as a guest for hydrate formation at relatively mild conditions. The phase equilibria of CHClF2 hydrates formed in aqueous NiCl2 solutions were investigated to identify the effect of NiCl2 on the thermodynamic stability of CHClF2 hydrates. The dissociation phase boundary of CHClF2 hydrates in the presence of NiCl2 was shifted to higher pressures and lower temperatures as the salinity of aqueous solutions increased. To confirm the feasibility of NiCl2 separation from wastewaters via the HBD process, X-ray diffraction and Raman spectroscopic measurements were performed. The results showed that the Ni2+ and Cl− ions did not participate in the hydrate framework, which revealed that the HBD process could be used to remove NiCl2 from effluents. The formation kinetics of CHClF2 hydrates were analyzed by a new kinetic model adopting transient time-dependent apparent rate constants, which significantly depends on the sub-cooling temperature and the concentration of NiCl2 in the aqueous solutions. Thermodynamic approximations regarding the Ni2+ and Cl− ion exclusion from the clathrate framework and the full occupancy of CHClF2 molecules in the large cages of structure I clathrate hydrate were confirmed by comparing the calculated Ni2+ concentrations in the liquid phase in equilibrium with CHClF2 clathrate hydrates with the experimental measurements. These results provide good information for separating metal ions from wastewater streams by HBD processes.

中文翻译：

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NiCl2存在下CHClF2水合物的热力学稳定性和形成动力学

摘要 建议采用水合物技术对工业废水进行脱盐，尤其是电镀废水，包括NiCl2。为了降低操作基于水合物的脱盐 (HBD) 过程所需的能量，氯二氟甲烷 (CHClF2) 被用作在相对温和的条件下形成水合物的客体。研究了在 NiCl2 水溶液中形成的 CHClF2 水合物的相平衡，以确定 NiCl2 对 CHClF2 水合物的热力学稳定性的影响。随着水溶液盐度的增加，在 NiCl2 存在下 CHClF2 水合物的解离相界转移到更高的压力和更低的温度。为了证实通过 HBD 工艺从废水中分离 NiCl2 的可行性，进行了 X 射线衍射和拉曼光谱测量。结果表明 Ni2+ 和 Cl- 离子不参与水合物骨架，这表明 HBD 工艺可用于从流出物中去除 NiCl2。采用瞬态时间相关表观速率常数的新动力学模型分析了 CHClF2 水合物的形成动力学，该模型显着取决于过冷温度和水溶液中 NiCl2 的浓度。通过比较计算出的与 CHClF2 笼形水合物平衡的液相中的 Ni2+ 浓度与实验测量。