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The catalytic ozonation of bisphenol A (BPA) was performed using an industrial solid waste as catalyst: electric arc furnace slag (EAFS). The characterization of the catalyst (SEM/EDS, XRD, surface area, pHPZC and Mössbauer spectroscopy) showed low surface area, alkaline nature and a composition rich in Fe, Ca, Si, C oxides, with minor content of Mg, Mn and Al. Ozonation experiments were carried out in a semi-batch reactor at room temperature at different initial pH conditions: from alkaline (natural pH 10.5) to acidic (controlled pH 3) aqueous media. Catalytic ozonation experiments showed complete BPA removal and remarkable total organic carbon conversions (62–80 %) over the broad pH range explored. The highest mineralization levels were obtained under basic pH, which was attributed to the generation of hydroxyl radical given by the presence of OH− and precipitation reactions of intermediates promoted by Ca oxides. Under acidic conditions the presence of EAFS notoriously enhanced BPA mineralization compared to single ozonation, due to the activity of leached species. The stability of the material was tested in 4 ozonation cycles. EAFS activity was mostly sustained under acidic conditions while a reduction was observed under uncontrolled pH condition, which was associated with a marked pH decrease. However, the residual activity still allowed complete BPA degradation and high mineralization levels (> 50 %). EAFS is a low-cost material that exhibits high activity and reasonable stability in catalytic ozonation of BPA. The valorization of this waste constitutes a technological alternative that could benefit both metallurgical and water treatment plants. |
