Alkaline Resins Enhancing Li<sup>+</sup>/H<sup>+</sup> Ion Exchange for Lithium Recovery from Brines Using Granular Titanium-Type Lithium Ion-Sieves
Jianchuan Liu, Yunbo Zhang, Miao Yao, Ying Yang, Ping Li
Abstract
The mechanism of lithium ion-sieve adsorbing Li+ ions from brines is based on the Li+/H+ ion exchange, where Li+ ions in brines are adsorbed on ion-sieves to displace H+ ions, and the displaced H+ ions are released in brines in turn. If the released H+ ions are accumulated in brines, then brines become acidic, not conducive to Li+ ions adsorption on ion-sieves. Therefore, it is important to regulate the pH value in brines to be more than 7 during the lithium recovery from brines using ion-sieves. Instead of the addition of the traditional ammonia buffer solution, the alkaline anion exchange resins are used to regulate the pH value of brines in this work since the addition of ammonia buffer solution in brines would cause the secondary pollution in Salt Lake with a high ammonia nitrogen emission value. The alkaline anion exchange resins contain the amine functional groups to neutralize the released H + ions in brines that enhance the adsorption performance of lithium ion-sieves. Like ammonia buffer, the amine functional groups of alkaline resins without more free OH– ions in brine will avoid the precipitation of high content of magnesium in brines. Here, seven kinds of alkaline anion exchange resins are used to neutralize the released H+ ions during lithium recovery from brines using homemade granular titanium-type lithium ion-sieves (PVB-HTO ion-sieves). The process intensification for lithium recovery from brine by lithium ion-sieves with the addition of alkaline anion exchange resins is evaluated based on experimental results, and a green lithium recovery technology from brine with a high Mg/Li ratio will be developed.