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

•C-boron/CP/Fe(III) system presented great potential for ISCO.•EPR and quenching tests demonstrated the existence of OH, O2−, and 1O2.•Competitive kinetic method indicated a high contribution of OH.•Characterization of C-boron remained unchanged after the oxidation. In this study, Fe(III) catalyzed calcium peroxide (CaO2, CP) Fenton-like process assisted by crystal boron (C-boron) 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 (R2 > 0.95). About 26.8% of 20 μM 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 kobs 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, O2− and 1O2 were present in both systems and contribution of OH 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.