By this article, we continue studying weak polyelectrolyte hydrogels and their application as a desalination agent. We modeled the desalination process as a four-step reversible thermodynamic cycle transferring ions from a low salinity solution to a high salinity one. The cycle implies reversibility at any stage, therefore the method can achieve the maximum thermodynamic efficiency, comparable to the reverse osmosis. As a driving force for ions movement, we use the fact that compression of the gel leads to a decrease in the gel ionization degree, and therefore to a release of ions entrapped in the gel. We considered the gel composed of ionogenic units modified by hydrophobic pendants and showed that this modification significantly increases the number of transferred ions. This increase is caused by a first-order phase transition originated from an interplay between repulsive electrostatic and attractive steric interactions. The transition happens during hydrogel compression. At a certain pressure, the gel collapses abruptly, changing its volume almost to that of a dry state, and releases almost all ions collected inside. Employing the phase transition allows us to model the desalination cycle, which transfers a much larger number of ions and works at rather low pressures <10 bar.

通过本文，我们将继续研究弱聚电解质水凝胶及其在脱盐剂中的应用。我们将脱盐过程建模为四步可逆热力学循环，将离子从低盐溶液转移到高盐溶液。该循环意味着在任何阶段都具有可逆性，因此该方法可以实现与反渗透相当的最大热力学效率。作为离子运动的驱动力，我们利用以下事实：凝胶的压缩会导致凝胶离子化程度的降低，并因此释放截留在凝胶中的离子。我们考虑了由疏水侧基修饰的离子化单元组成的凝胶，并表明这种修饰显着增加了转移离子的数量。这种增加是由一阶相变引起的，该一阶相变源自排斥静电和吸引力空间相互作用之间的相互作用。该转变发生在水凝胶压缩期间。在一定压力下，凝胶突然崩塌，其体积几乎变为干燥状态，并释放几乎所有收集在其中的离子。利用相变，我们可以对脱盐循环进行建模，该过程可转移大量离子，并在<10的较低压力下工作 酒吧。