Application of citric acid as eluting medium for titanium type lithium ion sieve

The titanium type lithium ion sieve (Ti-LIS) is usually considered as a promising lithium ion sieve (LIS) by the virtue of its superiorities in both stable structure and high adsorption capacity. Acidification process is a significant and necessary step for LIS application in the lithium adsorption from brine, which has raised two problems including partly dissolution of the Ti-LIS structure and the low lithium ions enrichment in elution solutions. Many reported works about the Ti-LIS focused on reducing the amount of loss of Ti-LIS but ignored the lithium ions enrichment in elution solutions. In this manuscript, an effective strategy that employing a proper weak polyprotic acid to replace the most widely eluting medium of hydrochloric acid was proposed, and the citric acid was selected on the basis of its superior properties containing low damage to the structure of Ti-LIS (titanium loss ≤0.05%) and high lithium ions concentration enrichment (4.06 g L−1) with 0.2 mol L−1 in elution solutions. Meanwhile, the adsorption performance of Ti-LIS treated with citric acid was also investigated by batch experiments, and the results revealed the adsorptive ability of the Ti-LIS could reach up to 52 mg g−1 in LiOH solutions (1.8 g L−1 Li, pH 12). Furthermore, the competitive absorbing and recycling results demonstrated that the Ti-LIS treated with citric acid still has a remarkable selectivity to Li+ and stable adsorptive function. Consequently, it elucidated that the citric acid was an effective eluting medium in the application of LIS.