Method for purifying fluorine-containing lithium salt

The invention provides a fluorine-containing lithium salt purification method which comprises the following steps: S1, mixing fluorine-containing lithium salt powder with water to obtain a mixed system, and adding acid into the mixed system for reaction to obtain a first lithium-containing solution; s2, adjusting the first lithium-containing solution to be weakly acidic, and then adding a composite fluorine removal agent into the first lithium-containing solution for reaction to obtain a second lithium-containing solution; the composite fluorine removal agent comprises an aluminum fluorine removal agent, calcium hydroxide and lanthanum-loaded modified charcoal, and the mass ratio of the aluminum fluorine removal agent to the calcium hydroxide to the lanthanum-loaded modified charcoal is (5-8): (1-3): (1-5); s3, adjusting the pH value of the second lithium-containing solution to be neutral or alkalescent, continuing the reaction, and after the reaction is finished, carrying out solid-liquid separation to obtai