System and method for separating ions in waste acid

The invention discloses a system and a method for separating ions in waste acid, the system comprises a reaction tower, the top of the reaction tower is provided with a waste acid inlet for introducing waste acid, and the bottom of the reaction tower is provided with a hydrogen sulfide inlet for introducing hydrogen sulfide; a plurality of reaction units are arranged in the reaction tower along the height direction of the reaction tower; the waste acid reacts with hydrogen sulfide to generate different sulfides, and the different sulfides are separated out in different reaction units respectively; and each reaction unit with sulfide precipitation is connected with a precipitation separation device. By using a tower gas absorption reaction process, different elements in the waste acid are subjected to fractional separation by utilizing the characteristic that hydrogen sulfide gas is gradually dissolved in the waste acid in a graded manner and the difference of solubility products of different sulfides, so that