Degradation of 2-methylisoborneol in drinking water by bauxite catalyzed ozonation

Raw mineral bauxites with and without thermal treatment were used as catalysts in a catalyzed ozonation process for the degradation of a typical taste and odour compound 2-Methylisoborneol (MIB). Compared with the sole ozonation or catalyst adsorption, raw mineral bauxite without further thermal treatment did not exhibit remarkable catalytic activity. But all bauxite catalysts with further thermal treatment exhibited some catalytic activity. Changing of the crystalline form during the thermal treatment played an important role in enhanced ozonation efficiency. Bauxite calcined at 450°C (Bauxite450), which is composed of γ-Al₂O₃, exhibited the most remarkable catalytic activity among all the bauxite catalysts with thermal treatment. Catalyzed ozonation with Bauxite450 could remove MIB effectively and reduce MIB concentration to below its taste and odour threshold concentration. The catalyzed ozonation of MIB followed an indirect oxidation mechanism by hydroxyl radical (·OH). This result was confirmed by tert-butyl alcohol inhibiting the catalytic activity and R_ct value between the sole ozonation and catalyzed ozonation. As a natural mineral catalyst, bauxite with thermal treatment has supplied an economical and feasible choice for the catalyzed ozonation of MIB in drinking water.