Green recovery of low concentration of lithium from geothermal water by a novel FPO/KNiFC ion pump technique

Abstract As a unique and indispensable element in modern battery and energy industries, the recovery of lithium has attracted wide attention worldwide. In this work, the recovery of low concentration of Li+ in geothermal water was carried out by a green and novel FePO4/K2NiFe(CN)6 [FPO/KNiFC] electrochemical ion pump technique. Different K2MFe(CN)6 (M = Cu, Co, or Ni) was synthesized and used to construct an electrochemical ion pump with FePO4. It was found that K2NiFe(CN)6 has excellent electrochemical properties, and the recovery of Li+ is mainly restricted by the insertion capacity and rate of the FePO4 electrode. This problem was successfully solved by the modification of electrode using multiwalled carbon nanotube. Even though the optimized ion pump system has a low single insertion capacity for low concentrations of Li+, a cycle extraction method was developed and successfully realized high-effective recovery of Li+ from geothermal water. Subsequently, a multi-stage extraction device was designed and proposed for the continuous recovery of low concentrations of Li+.