Method for producing boric acid from lithium-extracting boron-containing waste liquid

The invention provides a method for recovering boric acid from lithium-extracting boron-containing waste liquid, and belongs to the technical field of inorganic salt production processes. The method comprises the following steps: adjusting the pH value of the lithium-extracting boron-containing waste liquid to 3.5-4.5, and then discharging to a boron-dissolving salt field for evaporative crystallization to form a boric acid crystal and a boric acid mother liquid after water is evaporated; transferring the boric acid crystal and the boric acid mother liquid out of the boron-dissolving salt field in the form of mixed boric acid liquid, and performing thick thickening and deposition to obtain boric acid crystal slurry and a supernatant; refluxing the supernatant to the boron-dissolving salt field for further evaporative crystallization; performing solid-liquid separation on the boric acid crystal slurry to obtain boric acid and boron-containing liquid; and refluxing the boron-containing liquid to the boron-disso