Green recovery of lithium from water by a smart imprinted adsorbent with photo-controlled and selective properties

Recently, the development of electronic devices and electric vehicles has promoted the demand for lithium resources. To realize green recovery of lithium from water, we designed novel photo-responsive lithium ion imprinted polymers (P-IIPs) based on the surface of mesoporous C3N4 by using the mixture of crown ethers and azobenzene derivatives as functional monomers. The effects of light irradiation, pH, contact time, temperature and initial concentrations on the Li+ adsorption capacity of P-IIPs were investigated in detail. The results show that UV irradiation led to Li+ desorption of P-IIPs, and visible irradiation promoted their adsorption. The experimental data could be well fitted by the Langmuir adsorption isotherm, and the maximum adsorption capacity of 3280.5 μmol/g was reached at solutions of 400 mg/L under visible irradiation. The equilibrium adsorption was achieved after 30 min under visible irradiation that was shorter than in darkness. The kinetic data can be well explained by pseudo-second-order kinetic model. In the presence of Na+, K+ and Mg2+, P-IIPs exhibited ideal selectivity and adsorption properties for Li+. In addition, the saturated P-IIPs with Li+ could be regenerated with UV light. Therefore, the present research provides a green and feasible strategy for the recovery of lithium resources.