Lithium ion recovery from brine using granulated polyacrylamide–MnO2 ion-sieve

• PAM is taken as the binder material, and the granulation does not affect Li+ uptake capacities and rate.
• The granulated ion-sieve has a high stability.
• The maximum Li+ concentration in the eluant is 13.74 times higher than that in the feed solution.
• A mathematical model was built to calculate the film and pore diffusion coefficients.

The granulated polyacrylamide (PAM)–MnO2 ion-sieve with 0.3–0.7 mm diameter was prepared using the inverse suspension polymerization method, where the precursor was the Li4Mn5O12 ultrafine powder synthesized in our laboratory, the binder was acrylamide, the cross-linker was N,N′-methylenebisacrylamide (MBA), and the initiator was ammonium persulfate (APS). And then Li+ in the granulated material was exchanged with H+ in a 0.5 M HCl solution to obtain PAM–MnO2 ion-sieve for Li+ adsorption. The adsorption equilibrium isotherms of Li+ on the granulated PAM–MnO2 ion-sieve were measured at 293, 298, 303, and 318 K, respectively. The Langmuir model was used to fit the experimental data, and the model parameters were estimated with the nonlinear regression method. The uptake curves of Li+ adsorption were measured. The film mass-transfer coefficient (kf) and Li+ pore diffusivity (Dp) in the granulated PAM–MnO2 ion-sieve were estimated using a mathematical model to fit the experimental data. Furthermore, the Li+ adsorption–desorption behaviors in the granulated PAM–MnO2 ion-sieve packed column were investigated for three kinds of feedstock, namely brine, LiCl solution with and without impurities of Na+, K+, Ca2+, and Mg2+, respectively, and the regenerability of the granulated PAM–MnO2 ion-sieve for the multicyclic Li+ adsorption from brine and desorption was assessed.