In this work, a heterogeneous oxidation of phenolic compounds was examined by impure bismuth ferrite (BiFeO3) nanoparticles synthesized by ultrasound. The nanoparticles were characterized by different techniques. The impure nanoparticles were more effective than pure one. The heterogeneous solar- Fenton catalytic degradation of phenolic compounds was used for the first time. A complete degradation of the phenolic compounds was achieved along with easy separation of the catalyst from the solution by an external magnetic field. The limitations of Fenton reaction such as iron sludge and slow regeneration of Fe(II) ions improved in this work. In the present work, a multivariate analysis has been used to assess the conditions for obtaining complete degradation in terms of the oxidant and catalyst concentrations. The response surface methodology (RSM) was performed to evaluate the effects of the two major factors (amount of impure BiFeO3 magnetic nanoparticles (BFO MNPS) and concentration of H2O2) during the process. The effect of other variables such as initial concentration of phenol and initial pH was also examined. Partial oxidation of phenol took place at dark and a complete degradation was achieved at light in 60 min. The Fenton catalytic degradation mechanism was determined in dark and light. New reaction sites can be generated on the solid surface by the conversion of Fe(III) to Fe(II) for the generation of hydroxyl radical (OH). The effect of different electron acceptors on the heterogeneous solar-Fenton catalytic degradation of phenol was examined too. In addition, the solar-Fenton catalytic degradation of derivatives of phenol such as 4-chlorophenol (4-CP), 2,4,6-trichlorophenol (2,4,6-TCP), biphenyl (BP), 4-nitrorophenol (4-NP), 2,4 dinitrophenol (2,4 DNP) and 2,4,6-trinitrophenol (2,4,6-TNP) was evaluated for the first time. Phenol and its derivatives completely degraded under solar light irradiation by the solar-Fenton catalyst in a short time with low concentration of H2O2.

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