Quantitative effects of Fe3O4 nanoparticle content on Li+ adsorption and magnetic recovery performances of magnetic lithium-aluminum layered double hydroxides in ultrahigh Mg/Li ratio brines.

The quantitative effects of magnetic Fe3O4 nanoparticle content on Li+ adsorption and magnetic recovery performances of magnetic lithium-aluminum layered double hydroxides (MLDHs) were investigated systematically. MLDHs with different Fe3O4 nanoparticle contents were synthesized by a staged chemical coprecipitation method. The property disparities of these MLDHs were analyzed by various characterizations and results proved the existence of magnetic nanoparticles had no impairment on MLDHs crystal structure stability while the mesopores were lessened with the increasing Fe3O4 contents. In adsorption experiments using Qarhan Salt Lake brine with Mg/Li mass ratio of 284, the Li+ adsorption capacity of MLDHs presented a downtrend with the increasing Fe3O4, while the increased magnetic components had positive influence on the Li+ separation with Mg2+ on account of the steric effect. MLDHs presented excellent Li+ selectivity that the Mg/Li mass ratio of desorption solution was significantly decreased below 7.0. Relying on the superparamagnetism, MLDHs recovery all exceeded 97 % in the external magnetic field for only 10 min, and the magnetic recovery performance was promoted with more Fe3O4 nanoparticles. Furthermore, on the basis of experimental data, precise models were built and described well the correlations of Fe3O4 contents of MLDHs with Li+ adsorption capacity and magnetic recovery rate, respectively.