Highly porous and doping Li/Al-LDHs derived from metal-organic frameworks for recovery of lithium

Abstract

The lithium/aluminum layered double hydroxides (Li/Al-LDHs) have been demonstrated as the promising adsorbents for industrial lithium extraction from brines. However, it is still highly desired to develop Li/Al-LDHs with high adsorption capacity and cycling stability. Here, the highly porous and doping Li/Al-LDHs adsorbents were prepared through the in-situ transformation of multimetallic Al-based metal–organic frameworks (MOFs) followed by granulation with poly (ethylene-co-vinyl alcohol) (EVAH). The granulated Li/Al-LDHs (GLDH) combined porous MOFs precursor, multi-metal doping, and polymer granulation to increase porosity, promote adsorption capacity and maintain structural stability. First, a series of Li/Al-LDHs with two-dimensional stacked flake structure were adhered and embedded into polymer framework with numerous porosities. Then, GLDH and doping GLDH exhibited excellent Li⁺ adsorption capacity, high cycling ability and good structural stability without significant loss of components. The enhancement of oxygen defects derived from Mn-doping reduced the diffusion energy of Li⁺, thus accelerating the diffusion of Li⁺ within Mn-GLDH. Moreover, The Li⁺ dynamic adsorption capacity for column experiment in simulated brine were 1.42 mg/g, 1.49 mg/g, and 2.23 mg/g by GLDH, Fe-GLDH, Mn-GLDH, respectively. Furthermore, Mn-GLDH showed highly selective adsorption for Li⁺ with the separation factor between Li⁺ and Mg²⁺ reached up to 33.67 and Mg²⁺/Li⁺ ratio reducing from 98 in real brine to 3 in the stripping solution. This work will offer new views for developing effective and long-term recycling adsorbents for industrial lithium extraction from brines.