Room-temperature ionic liquids [C₄mim][PF₆], [C₆mim][PF₆], [C₆mim][BF₄] and [C₈mim][BF₄] have been used for the extraction of m-aminobenzene sul-fonic acid (m-ABSA) and p-aminobenzene sulfonic acid (p-ABSA) from aqueous solutions. The results showed that changes of temperature and phase ratio had no obvious effect on the dis-tribution ratio, whereas pH values of aqueous phase affected significantly the extraction equilibrium and the maximum distribution ratio was observed at pH＝4.20. Distribution ratio of ABSA was found to increase greatly in the presence of CaCl₂ or Na₂SO₄ in the aqueous phase. It was noted that the nature of anion of the ionic liquids had also remarkable effect on the distribution ratio, and the ionic liquids with [BF₄]^－anion had much higher extraction efficiency for ABSA than those with [PF₆]^－anion. The extraction efficiency was also affected to a certain extent by the length of alkyl chain of imidazolium cation. Among the ionic liquids studied, [C₆mim][BF₄] and [C₈mim][BF₄] had better extrac-tion efficiency for ABSA, and ABSA in the extraction phase could be retrieved, the ionic liquids reused.

Key words: room-temperature ionic liquid, aminobenzene sulfonic acid, aqueous solution extraction