Ozonation of bezafibrate promoted by carbon materials

Two carbon materials (multi-walled carbon nanotubes, MWCNT, and activated carbon, AC) were investigated as ozonation catalysts for the mineralization of bezafibrate (BZF) in water. For comparative purposes, kinetic results obtained in the absence of catalyst (single zonation) and adsorption experiments were also presented. Removal of BZF in the presence of MWCNT is mainly due to a catalytic process, contrarily to what occurs in the presence of activated carbon, which acts mainly as adsorbent. 3-[(4-chlorophenyl)formamido]propanoic acid (BBR), 4-chorobenzoic acid (pCBA) and 4-chloro-N-[2-(4-hydroxyphenyl)ethyl]benzamide (BBV) were detected as primary products of single and catalytic ozonation of BZF, whereas oxalic, pyruvic and oxamic acids were identified as refractory final oxidation products. The original chlorine of BZF is completely converted to chloride ion and part of nitrogen is converted to NH4+, NO3- and NO2-. The presence of the radical scavenger tert-butanol during catalytic and single ozonation evidenced the participation of HO center dot radicals in the oxidation process, especially in the mineralization of several intermediates. Microtox tests revealed that simultaneous use of ozone and AC originated lower acute toxicity, which may be due to the contribution of adsorption for the removal from the solution of BZF and its oxidation compounds. The time course of all detected compounds is studied and, as a result, the transformation pathway for the complete mineralization of BZF by single and catalytic ozonation in the presence of the selected carbon materials is also elucidated. Successive experimental runs of BZF degradation carried out with MWCNT show that the catalyst suffers some deactivation as a result of the introduction of oxygenated surface groups on the surface. (C) 2013 Elsevier B.V. All rights reserved.