Desenvolvimento de catalisadores a partir de materiais residuais para aplicação nos processos Fenton


The Fenton process and its variants (eg, photo-Fenton) is an advanced oxidation process (POA) that follows the appearance of complex compounds, such as adsorbable halogenated organic compounds (AOX), in domestic wastewater and in effluents produced by the industries, and in the urgent search for their correct degradation. Associated with these POA are the consumption of chemicals, namely, hydrogen peroxide (H2O2, oxidizer) and ferrous ions (Fe2 +, catalyst), and also energy (especially in photo-Fenton), conditioning a broader industrial application. This work has as main objective the replacement, total or partial, of the iron catalyst (virgin), conventionally used, by residual materials rich in iron, and to evaluate their catalytic capacity when applied in the Fenton processes to remove AOX from the effluent of the bleaching stage (D0) of a pulp and paper industry. Five solid residual materials were selected as potential candidates for the catalysis of Fenton\'s processes, with iron powder being the one with the most promising results, it was studied in the three variants of the Fenton process, i.e, “homogeneous Fenton”, “homogeneous photo-Fenton” and \"Heterogeneous Fenton\". The replacement of the source of iron (virgin) by iron powder, implied the existence of a leaching step in a leaching/solid ratio (L/S) of 10 L/kg, for a time of 10 minutes, upstream of the reaction (or treatment), whose leacher is precisely the effluent (D0) to be treated. The overall removal of AOX in the “homogeneous Fenton”, “homogeneous photo-Fenton” and “heterogeneous Fenton” processes, for a treatment time of 10 minutes, was 65%, 74% and 81%, respectively. In the “conventional Fenton” processes, the overall AOX removal was, respectively, 92% and 85% in the Fenton tests with iron in the oxidation state 2+ and 3+, in turn in the photo-Fenton tests it was 96% and 88% , with iron in the oxidation state 2+ and 3+, respectively. Studied the reuse of iron powder with effluent D0_5, in a ratio (L/S) = 100 L / kg, for 5 successive leach cycles, there was an average removal of AOX at the end of the Fenton process of 58%. Throughout the experimental tests there was a need to use different batches, either of iron powder or D0 effluent, having proved that the batch of effluent D0 is determinant in the amount of iron mobilized for the leacher. The estimated operating costs of the “modified Fenton” processes were lower when compared to the “conventional Fenton” processes. In the “modified Fenton” processes without the addition of light, the estimated cost was 66.2 [€/m3effluent_treated] while in the “homogeneous photo-Fenton” process it was 69.7 [€/m3effluent_treated].\r\nAlthough this was an exploratory work, the results obtained were encouraging, in addition, they allow an alignment with the principles of a circular economy, since a waste (iron powder) is being valued.


Luana Sarinho

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Maria Isabel da Silva Nunes

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