Mineralization of Bisphenol A from water by an ozonation process enhanced by Electric Arc Furnace Slag

INCHAURRONDO, N.; BOCERO, F.; FASCE, L.

Congreso; CIBIQ2023 - II IBEROAMERICAN CONGRESS OF CHEMICAL ENGINEERING; 2023

Bisphenol A (BPA) is classified as an endocrine disrupting chemical widely found in different natural water reserves because of human activity. Ozonation is an oxidation process capable to remove BPA from wastewater, but toxic by-products are often generated, and complete mineralization cannot be achieved economically [1]. The present study was encouraged by the appealing potential of electric arc furnace slag (EAFS), a by-product of the steel industry, to enhance BPA mineralization, due to its composition rich in Fe oxides, with traces of Cu and Mn, elements which have shown catalytic activity in ozonation processes [1]. Heterogeneous catalytic ozonation of BPA aqueous solution (20 ppm) was performed during 3 h in a semi-batch stirred-tank reactor (1L) at room temperature, inlet ozone concentration and flow rate of 10 mg/L and 0.7 L/min, EAFS content of 0.5 g/L, initial pH of 3 and 9-10. The evolution of pH, BPA, leached species and TOC conversion (XTOC) was determined. Catalytic heterogeneous ozonation results were compared with single ozonation. EAFS stability at pH 9 was also studied. Main results are shown in Figure 1. BPA disappeared after the first 20 min of reaction in all experiments. Mineralization is enhanced at basic media because of the formation of •OH species that are less selective than ozone. Then, XTOC was markedly enhanced from 20 to 50% by increasing pH from 3 to 9, in single ozonation. EAFS is alkaline by nature mainly due to the presence of CaO, and it raises the pH of BPA solution up to 9-10. However, the mineralization enhancement at this pH in the presence of EAFS, resulted higher than the mineralization levels reached with single ozonation, at basic pH. Moreover, the catalytic process showed similar mineralization levels at pH 3 and 9. Therefore, the activity can be mostly attributed to the presence of transition metals in EAFS, which may react with O3 generating reactive oxygen species.The catalyst maintained its activity over 4 cycles at pH 9, although leached species such as Fe (ca. 0.22 ppm), Cu (ca. 0.1 ppm) and Mn (ca. 0.06 ppm) were detected. Further studies will be performed to evaluate the contribution of leached species and the presence of hydroxyl radicals (tert-butanol tests).