Rapid Ti(III) reduction of perchlorate in the presence of β-alanine: Kinetics, pH effect, complex formation, and β-alanine effect

Abstract

Ti(III) reduction of perchlorate might be a useful method for the treatment of highly perchlorate-contaminated water. Though the reaction rate was usually low, we observed that β-alanine (HOOCCH 2CH 2NH 2) could significantly promote the reaction. A complete (>99.9%) perchlorate removal was obtained in a solution containing [ClO 4 −] = 1.0 mM, [Ti(III)] = 40 mM, and [β-alanine] = 120 mM after 2.5 h of reaction under 50 °C. The effects of both pH and complex formation on the reaction were then studied. The results showed that without β-alanine the optimal pH was 2.3. When pH increased from 1.6 to 2.3, the reduction rate increased remarkably. In the pH range >2.3, however, the reduction was significantly inhibited, attributed to the formation of Ti(III) precipitate. The presence of β-alanine at a molar ratio of [β-alanine]:[Ti(III)] = 3:1 significantly increased the reduction rate of perchlorate even at near neutral pH. This is because β-alanine formed complexes with Ti(III), which greatly improved the total soluble [Ti(III)] in the pH range between 3.5 and 6. The findings may lead to the development of rapid treatment methods for intermittent and small stream of highly perchlorate-contaminated water, which are resulted from the manufacturing, storage, handling, use and/or disposal of large quantities of perchlorate salts.