Processing method of polarizing plate manufacturing waste liquid

The invention provides a processing method of a polarizing plate manufacturing waste liquid, which can easily and efficiently recover a potassium iodide solution from the polarizing plate manufacturing waste liquid. The processing method of the polarizing plate manufacturing waste liquid for recovering the potassium iodide solution from the polarizing plate manufacturing waste liquid includes: a concentration step 1 of performing evaporation and concentration while maintaining the pH of the polarizing plate manufacturing waste liquid at 3.5 to 8.0, and producing a precipitate containing a boric acid and polyvinyl alcohol; and a solid-liquid separation step 3 of recovering the filtrate obtained by solid-liquid separation of the precipitate from the polarizing plate manufacturing waste liquid. 本发明的课题在于提供种能够容易且高效地从偏光板制造废液回收碘化钾溶液的偏光板制造废液的处理方法。种从偏光板制造废液回收碘化钾溶液的偏光板制造废液的处理方法，包括：边将偏光板制造废液的pH维持在3.5～8.0，边进行蒸发浓缩，生成含有硼酸和聚乙烯醇的析出物的浓缩工序1；和回收使上述析出物从偏光板制造废液固液分离得到的滤液的固液分离工序3。