Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, 46556, USA.
Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA.
Nat Commun. 2021 Jan 19;12(1):437. doi: 10.1038/s41467-020-20706-y.
Seawater desalination plays a critical role in addressing the global water shortage challenge. Directional Solvent Extraction (DSE) is an emerging non-membrane desalination technology that features the ability to utilize very low temperature waste heat (as low as 40 °C). This is enabled by the subtly balanced solubility properties of directional solvents, which do not dissolve in water but can dissolve water and reject salt ions. However, the low water yield of the state-of-the-art directional solvent (decanoic acid) significantly limits its throughput and energy efficiency. In this paper, we demonstrate that by using ionic liquid as a new directional solvent, saline water can be desalinated with much higher production rate and thus significantly lower the energy and exergy consumptions. The ionic liquid identified suitable for DSE is [emim][TfN], which has a much (~10×) higher water yield than the currently used decanoic acid. Using molecular dynamics simulations with Gibbs free energy calculations, we reveal that water dissolving in [emim][TfN] is energetically favorable, but it takes significant energy for [emim][TfN] ions to dissolve in water. Our findings may significantly advance the DSE technology as a solution to the challenges in the global water-energy nexus.
海水淡化在应对全球水资源短缺挑战方面发挥着关键作用。定向溶剂萃取（DSE）是一种新兴的非膜脱盐技术，其特点是能够利用非常低的温度废热（低至 40°C）。这是通过定向溶剂微妙平衡的溶解度特性实现的，定向溶剂不溶于水，但可以溶解水并排斥盐离子。然而，最先进的定向溶剂（癸酸）的低产水率显著限制了其吞吐量和能源效率。在本文中，我们证明通过使用离子液体作为一种新的定向溶剂，可以以更高的产率对盐水进行脱盐，从而显著降低能源和火用消耗。确定适合 DSE 的离子液体是[emim][TfN]，其产水率比目前使用的癸酸高约 10 倍。通过使用分子动力学模拟和吉布斯自由能计算，我们揭示了水在[emim][TfN]中溶解是能量有利的，但[emim][TfN]离子溶解在水中需要大量能量。我们的发现可能会极大地推动 DSE 技术作为解决全球水-能源关系挑战的一种解决方案。
