Li~+ Recovery From Brine By Ion Exchange Resin

Lithium is an important metal in energy sources. Usually, lithium metal was produced mostly from brines and ores containing Li+, recently, more attention was paid to Li+ recovery from brine and seawater. However, it was difficult to recover Li+from brine with a high Mg2+/Li+ ratio in the solution. In this thesis, based on the research of the thermodynamics/kinetics for Li+ adsorption on ion exchange resins, and the Li+ adsorption/desorption process in the fixed bed, the Li+ recovery process from brines by ion exchange resins was evaluated.According to the functional groups on resins, ion exchange resins could be divided into acid resin, basic resin, amphoteric resin and chelate resin. In this thesis, the Li+ adsorption capacities on 21 ion exchange resins were tested, including 9 acid resins,9 chelate resins,2 basic resins and one amphoteric resin. It was found that the Li+ adsorption capacities on resins were more dependent on the functional groups and structures of resins. Strong acid resin had the higher Li+ adsorption capacity than those of weak acid resin, basic resin and amphoteric resin. The infra-red spectra of typical acid resin Amberlyst 35, amphoteric resin Retardion 11A8, chelate resin Amberlite IRC748 and anion resin 201*7 were analyzed to study the interaction mechanism between adsorbed ions and functional groups of resins.Usually there were many metal ions in brine, such as Li+, Na+, K+, Mg2+, Ca2+ et al, so there existed the competitive adsorption among these metal ions on ion-exchange resins when recovering Li+ from the brine. The Li+ adsorption capacities on resins would be reduced due to the competitive adsorption of metal ions. Here, the competitive adsorption between Li+ and Mg2+ on the above-mentioned 21 resins was tested. It was found that the Li+ adsorption capacity decreased quickly due to Mg2+ competitive adsorption.Strong acid resin Amberlyst 35 and amphoteric resin Retardion 11A8 were selected to research the thermodynamics/kinetics of Li+ adsorption on the resins and the adsorption/desorption processes in fixed bed, respectively. The experimental data for the Li+ adsorption equilibrium isotherms and adsorption kinetics were fitted by the relevant mathematical models. The effect of pH values and temperature on Li+ adsorption capacity was also studied. The Li+ breakthrough/elution curves were measured in various operation conditions, to evaluate the feasibility and efficiency of the Li+ adsorption/desorption process in fixed bed packed with Amberlyst 35 and Retardion 11A8 resin, respectively.In addition, an integrated process for Li+ recovery from brine with a high Mg/Li ratio in solution was developed, which included (1) to reduce the Mg/Li ratio in solution by the ion exchange on acid resin (such as G-26) packed columns, (2) to remove Mg2+ in the recovered solution by chelate resin (such as Amberlite IRC748) packed columns, (3) precipitation and crystallization of Li2CO3. Moreover, the Mg2+ adsorption thermodynamics and kinetics on Amberlite IRC748 resin and its adsorption/desorption process in fixed bed were also studied, in order to provide the fundamental data for industrial design in the future.