Abstract Carbon nanotube (CNT) has a great potential as membrane material for water distillation because of its smooth and hydrophobic surface. We numerically investigated the distillation performance of CNT membrane for direct contact membrane distillation using non-equilibrium molecular dynamics (NEMD) simulation by varying diameters and lengths of the CNT and system operating conditions such as temperature, temperature difference between feed (hot) and permeate (cold) reservoirs, and sodium chloride (NaCl) concentration in the feed reservoir. It was found from the NEMD simulations that the distillation performance is enhanced by increasing system temperature, reservoir temperature difference, and CNT diameter, and decreasing CNT length, atomic attraction strength between water molecules and CNT, and NaCl concentration. The NEMD simulation overpredicts the water vapor transport by approximately an order of magnitude as compared with the results from the Knudsen diffusion model. The simulated flooding pressure is in good agreement with the theoretical prediction by the Young-Laplace equation using the MD-calculated contact angle. Most importantly, the permeability of the CNT membrane is two orders-of-magnitudes higher than a common polymer-based membrane made of Polytetrafluoroethylene (PTFE) due to almost two order-of-magnitude higher Knudsen diffusion of the CNT membrane than that of the PTFE membrane.

中文翻译：

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碳纳米管膜的水蒸馏性能：非平衡分子动力学模拟

摘要 碳纳米管（CNT）表面光滑、疏水，在作为水蒸馏膜材料方面具有巨大的潜力。我们使用非平衡分子动力学 (NEMD) 模拟通过改变 CNT 的直径和长度以及系统操作条件，如温度、进料（热）和渗透物之间的温差，对直接接触膜蒸馏的 CNT 膜的蒸馏性能进行了数值研究。冷) 储罐，以及进料储罐中的氯化钠 (NaCl) 浓度。从 NEMD 模拟中发现，通过增加系统温度、储层温差和 CNT 直径，以及减少 CNT 长度、水分子与 CNT 之间的原子吸引力强度和 NaCl 浓度，可以提高蒸馏性能。与 Knudsen 扩散模型的结果相比，NEMD 模拟高估了大约一个数量级的水蒸气传输。模拟的洪水压力与使用 MD 计算的接触角的 Young-Laplace 方程的理论预测非常一致。最重要的是，CNT 膜的渗透率比由聚四氟乙烯 (PTFE) 制成的普通聚合物基膜高两个数量级，因为 CNT 膜的 Knudsen 扩散比聚四氟乙烯膜。模拟的洪水压力与使用 MD 计算的接触角的 Young-Laplace 方程的理论预测非常一致。最重要的是，CNT 膜的渗透率比由聚四氟乙烯 (PTFE) 制成的普通聚合物基膜高两个数量级，因为 CNT 膜的 Knudsen 扩散比聚四氟乙烯膜。模拟的洪水压力与使用 MD 计算的接触角的 Young-Laplace 方程的理论预测非常一致。最重要的是，CNT 膜的渗透率比由聚四氟乙烯 (PTFE) 制成的普通聚合物基膜高两个数量级，因为 CNT 膜的 Knudsen 扩散比聚四氟乙烯膜。