Abstract: High purity boric acid product was prepared by complex crystallization using industrial boric acid as raw materials.Impurities were selectively separated from boric acid by using that way.Different kinds of analysis methods,such as complex formation titration,thermogravimetry (TGA),ICP-AES,and UV analysis  were used to characterize the purity and performance of boric acid.Influences of the factors,such as kinds and dosages of oxidant and complexing agent and crystal series,on the purity of boric acid during the process of purification were investigated.Optimal conditions were obtained as follows:2% (volume fraction) H₂O₂ was added in saturated solution of boric acid,stirred and hot-filtrated,0.2% (mass fraction) aminocarboxyl chelating agent (H₂Y) was added in the filtrate at 80 ℃,and then hot-filtrated,slowly cooling to form boric acid crystal,after recrystallization and drying,the 99.99% boric acid was produced.

Key words: boric acid, purification, complexing, crystallization