Lithium Salt Refining for High-Impurity Battery-Grade Hydroxide

The patent extracts and removes impurity elements (sodium, potassium, calcium, magnesium, boron, etc.) from the lithium source through selective precipitation and ion exchange processes. By targeting specific impurities for removal rather than using multiple general purification steps, the process achieves battery grade purity with reduced complexity.

The patent employs controlled pH adjustment and temperature variations to selectively precipitate different impurities at specific stages. By changing physical-chemical parameters systematically, the process achieves sequential purification without requiring complex equipment for each purification step.

The patent performs preliminary impurity removal from the lithium source before carbonate precipitation. By pre-cleaning the lithium solution through ion exchange and selective precipitation, fewer post-carbonation purification steps are needed, reducing overall production time while maintaining product quality.

The patent implements continuous carbonation and crystallization processes where lithium carbonate precipitates continuously from the purified lithium solution. This continuous operation eliminates batch processing interruptions and reduces total production time compared to sequential batch operations.

The patent converts potential harmful impurities into beneficial separation opportunities. By using selective precipitation where impurities form insoluble compounds at controlled pH levels, the process removes impurities while keeping lithium in solution for recovery, thus improving both purity and recovery rate simultaneously.

The patent uses ion exchange resins as intermediaries to selectively bind and remove impurity ions from the lithium solution. These resins act as mediators that capture unwanted elements while allowing lithium ions to pass through, achieving purification without lithium loss.

The patent segments the purification process into distinct functional stages: preliminary filtration, selective precipitation, ion exchange, and final crystallization. Each stage targets specific impurities with dedicated simple operations, avoiding the need for expensive multi-step processes while achieving cumulative purification效果.

The patent employs cost-effective reagents such as conventional acids and bases for pH adjustment, and readily available ion exchange resins for impurity removal. These inexpensive materials replace expensive specialized chemicals, reducing production cost while maintaining effective purification.