Titanium-based lithium ion-sieves (HTiO) with the layered structure is an excellent adsorbent for lithium recovery from brines, since it has a high theoretical Li ions adsorption amount (∼142 mg/g) and a stable structure under acid regeneration. However, the formation of the strong H–O bonds in HTiO leads to a greater energy barrier for re-adsorption of lithium ions, so it would be difficult to reach the theoretical lithium adsorption capacity in practical application. Moreover, the influence of H content in brine (pH value) on the Li ion adsorption amount is obvious, that limits the lithium recovery efficiency from brines. In this work, Li/H ion-exchange mechanism of layered HTiO (HTO) ion-sieve is investigated through DFT calculation, where the Li ion adsorption energies for three kinds of Li/H ion-exchange pathways are calculated, and the order of priority for Li/H ion-exchange is deduced and validated based on the experimental data of Li ions adsorption on the prepared nanometer HTO ion-sieve. Then, a quantitative relationship between Li ion adsorption amounts on HTO ion-sieve and pH values in Li-containing solution is developed on the basis of the experimental data. When the nanometer HTO ion-sieve powders are formed into the millimeter PVB-HTO ion-sieve granules for industrial application, it is found that the formation of an acidic micro-environment inside of this PVB-HTO granule obviously reduces the Li ions adsorption rate, especially in the initial stage of Li/H ion-exchange process. Finally, an improved strategy of Li/H ion-exchange rate on PVB-HTO granules from a carbonate-type brine is experimentally demonstrated utilizing a batch and a fixed-bed adsorber, respectively.

中文翻译：

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钛基锂离子筛Li+/H+离子交换的DFT计算与实验


具有层状结构的钛基锂离子筛（HTiO）是一种优异的从盐水中回收锂的吸附剂，因为它具有较高的理论锂离子吸附量（~142 mg/g）和在酸再生下稳定的结构。然而，HTiO中形成的强H-O键导致锂离子重吸附的能垒较大，因此在实际应用中很难达到理论锂吸附容量。此外，盐水中的H含量（pH值）对锂离子吸附量的影响明显，限制了盐水中锂的回收效率。本文通过DFT计算研究了层状HTiO（HTO）离子筛的Li/H离子交换机理，计算了三种Li/H离子交换途径的Li离子吸附能，并给出了根据制备的纳米HTO离子筛上Li离子吸附的实验数据，推导并验证了Li/H离子交换的优先性。然后，根据实验数据建立了HTO离子筛上锂离子吸附量与含锂溶液pH值之间的定量关系。当纳米HTO离子筛粉末成型为毫米级PVB-HTO离子筛颗粒进行工业应用时，发现PVB-HTO颗粒内部形成酸性微环境，明显降低了锂离子的吸附率，特别是在Li/H离子交换过程的初始阶段。最后，分别利用间歇式吸附器和固定床吸附器对来自碳酸盐型盐水的 PVB-HTO 颗粒进行 Li/H 离子交换率的改进策略进行了实验论证。