Patent ID: 8721918

Claim:
A method for purifying fluoride etching solution, comprising: adjusting a pH value of the fluoride etching solution to pH 6.5-8.0 by using ammonia gas or ammonium hydroxide solution, wherein the fluoride etching solution comprises hydrogen fluoride (HF), ammonium fluoride (AF), boron ion (B 3+ ) and phosphate ion (PO 4 3− ); subjecting a basic anion exchange resin to a resin pretreatment, wherein the resin pretreatment is to pass a 0.5 weight percent to 10 weight percent of sodium hydroxide (NaOH) solution through the basic anion exchange resin; passing the fluoride etching solution with an adjusted pH through a pretreated basic anion exchange resin, so that the boron ion and the phosphate ion are absorbed in the pretreated basic anion exchange resin; and obtaining an effluent from the pretreated basic anion exchange resin, wherein the effluent is a purified fluoride etching solution, and in the purified fluoride etching solution, the boron ion has a concentration of 1 ppb to 200 ppb, and the phosphate ion has a concentration of 1 ppb to 200 ppb.