Simultaneous removal of nitrobenzene, benzoic acid, flunixin meglumine and aspirin by CaO2/Fe(III) system: Enhanced degradation by crystal boron

In this study, Fe(III) catalyzed calcium peroxide (CaO2 , CP) Fenton-like process assisted by crystal boron (Cboron) was applied for in situ chemical oxidation. Flunixin meglumine (FMME), aspirin (ASA), nitrobenzene (NB) and benzoic acid (BA) were selected as target contaminants. Pollutants decomposition by the CP/Fe(III) and C-boron/CP/Fe(III) systems was proposed in terms of diverse parameters, including C-boron dosage, pH, and temperature, with regard to the pseudo-first-order kinetic model (R-2 > 0.95). About 26.8% of 20 mu M FMME was removed by 0.5 mM CP and 0.5 mM Fe(III) after 20 min at pH 4.0, whereas 90.4% of FMME was decomposed in the C-boron/CP/Fe(III) system with 100 mg/L C-boron. The removal rates of the other three pollutants were also improved to varying degrees. The k(obs) of the C-boron/CP/Fe(III) system for these four pollutants degradation at pH 4.0 was approximately 4.1 - 5.3 times higher compared to the CP/Fe(III) system. Electron paramagnetic resonance and quenching experiments indicated that (OH)-O-center dot, O-2(center dot-) and O-1(2) were present in both systems and contribution of (OH)-O-center dot was 71.3% at initial pH 4.0 in C-boron/CP/Fe(III) system, suggesting that it was the main reactive oxygen species for the contaminants elimination. Furthermore, experiments on the characterization of C-boron showed great reactivity and stability. This work manifested the promotion mechanism of pollutant degradation in the C-boron/CP/Fe(III) system.