Resin functionalized with 2-(hydroxymethyl)-12-crown-4 ether for selective adsorption of lithium ions from desilication solution of coal-based solid waste

Coal-based solid waste, as a secondary resource, contains significant quantities of aluminum, silicon, and lithium resources. The desilication solution is a waste solution with low concentrations of lithium ions, which is produced during the resource utilization process of coal-based solid waste. Developing adsorbents with high lithium selectivity and alkaline stability is important for the recovery of lithium in coal-solid waste alkaline leachate. In this study, resin functionalized with 2-hydroxymethyl-12-crown-4 (2H12C4) is prepared by esterification. The reaction conditions, including resin type, reaction temperature, time, and catalyst dosage, are optimized. The selective adsorption of 2H12C4-D113 is evaluated in a simulated desilication solution. The results show that 2H12C4-D113 with high selectivity for Li+ adsorption is successfully synthesized at 1 g of 2H12C4 per g of resin, 110 degree celsius reaction temperature, 6 h reaction time, 0.5 g of catalyst per g of resin and 1 mol of anhydrous lithium chloride per mol of 2H12C4. The adsorption rate of the 2H12C4-D113 resin is relatively rapid, and its adsorption kinetics satisfy the proposed second-order kinetic curve, and its Li+ adsorption capacity is greatly influenced by Li+ concentration. The peaking adsorption capacity of this resin is 58.71 mg/g in pure lithium solution (Li+=200 mg/L) with high alkalinity, and the peaking adsorptive capacity is 9 mg/g in the pre-desilication solution (Li+=274 mg/L, Na+=101 g/L). Furthermore, density functional theory (DFT) is utilized to study the selective adsorption mechanisms, geometrical characteristics, and thermodynamic parameters of the complexes between crown ether and different ions. DFT simulation reveals that 2H12C4-D113 has high selectivity for Li+ adsorption with a Li+-O bond length of 1.86-1.88 & Aring;, and an adsorption energy of 2H12C4-Li+ (-369 KJ/mol) being the highest among the mental ions.