Microwave-Assisted Hydrothermal Synthesis of Lithium Ion-Sieve for Adsorption of Lithium Ion in Coal Gangue Leaching Solution

A two-step method involving microwave-assisted hydrothermal synthesis and solid-phase calcination was employed to prepare the Li1.6Mn1.6O4 (LMO) precursor. Material characterization demonstrated the structural stability of LMO even after acid pickling, resulting in the creation of the ion-sieve H1.6Mn1.6O4 (HMO) with the most notable Li+ adsorption capacity of 29.45 mg·g-1. The adsorption isotherm behavior of HMO adhered to the Langmuir isothermal model (R2 = 0.9929), indicating a smooth and monolayer adsorption process. Simultaneously, the adsorption kinetics of HMO were consistent with the pseudo-second-order kinetic model (R2 = 0.9911), indicative of chemisorption. Upon undergoing five cyclic adsorption-desorption cycles, HMO's adsorption capacity remained above 22.32 mg·g-1. Evaluation of the distribution coefficient (Kd) and the separation factor (αMeLi) for HMO in both coal gangue leaching solution and simulated salt lake brine highlighted its exceptional selectivity. Notably, HMO achieved a remarkable 99.9% adsorption rate in the coal gangue leaching solution. These outcomes underscore the efficacy of the synthesized HMO in highly selective Li+ recovery from both coal gangue and salt lake brine, additionally emphasizing the potential of coal gangue as a valuable lithium resource with significant prospects for future development and utilization.