Lithium recovery from ultrahigh Mg2+/Li+ ratio brine using a novel granulated Li/Al-LDHs adsorbent

A novel granulation method with high hydrophilia and considerable mechanical strength was developed for the lithium aluminum double hydroxides (Li/Al-LDHs) to recover lithium from old brines with ultrahigh Mg2+/Li+ ratios. The granulated Li/Al-LDHs (GLDH) displayed a great structure stability and Li+ adsorption capacity could reach up to 4.92 mg/g without weakening on the encapsulated Li/Al-LDHs at 303 K. The pore volume diffusion model (PVDM) based on adsorption isotherms was conducted to confirm that the Li+ adsorption process was controlled by the pore volume diffusion in GLDH. Besides, GLDH showed a great selectivity to Li+ with an ion selective sequence of Li+ > Na+ > K+yMg2+ > Ca2+, especially alpha LiMg could reach to 156.1. The column experiments declared that the adsorbed Li+ could be easily eluted by neutral Li+-containing solution and the Mg2+/Li+ ratio could decrease significantly from 301.58 in old brine to 0.99 in the strip solution. The working Li+ adsorption capacity of packed GLDH column exceeded 2.6 mg/g when Qarhan old brine was fed at a flow rate of 15 mL/min. Moreover, it was found that the strip solution with Li+ concentration less than 150 mg/L would cause the structure collapse of Li/Al-LDHs.

Automated summary

A novel granulation method was developed to recover lithium from old brines with ultrahigh Mg2+/Li+ ratios. The granulated Li/Al-LDHs displayed great structure stability and selectivity, achieving high Li+ adsorption capacity and significant reduction in Mg2+/Li+ ratio. The study also found that Li/Al-LDHs could collapse when eluted with strip solutions with Li+ concentration below 150 mg/L.