Avaliação de desempenho de eletrodos de titânio e aço inox em reator de eletrocoagulação em batelada aplicado ao tratamento de esgoto sanitário sintético

Abstract

The inadequate treatment of domestic wastewater in Brazil remains a significant concern for environmental protection and public health. Electrocoagulation has been investigated as a complementary treatment technology based on the electrochemical generation of coagulant species for pollutant removal; however, the limited durability of conventional electrodes motivates the search for more stable materials. This study evaluated the performance of titanium (anode) and stainless steel (cathode) electrodes in a batch reactor (8.9 L) applied to the treatment of synthetic domestic wastewater. The effects of current intensity (1.5–10 A), electrolysis time, aeration, conductivity (NaCl), number of electrodes, submerged anodic area, settling time, and electrode mass loss were investigated. Process performance was assessed in terms of chemical oxygen demand (COD) and total phosphorus removal, with monitoring of pH, turbidity, and electrical conductivity, comparing raw and centrifuged samples. High phosphorus removal efficiency was achieved, exceeding 98% within 30 min (≥ 5 A), with rapid and stable behavior. In contrast, COD removal was limited, reaching a maximum of 41% (5 A; 60 min). Aeration (Q_ar = 0.5 L·min⁻¹) enhanced initial COD removal, likely due to improved hydrodynamic conditions and floc formation. The addition of NaCl (1–2 g·L⁻¹) did not improve COD removal in centrifuged samples, while phosphorus removal remained nearly complete under the evaluated conditions. Increasing the anodic area and settling time primarily promoted solid removal, reducing turbidity, without a significant increase in dissolved organic matter removal. Gravimetric analysis confirmed the non-sacrificial behavior of titanium, with anodic wear of 4.65 mg/cm² and negligible mass loss of the stainless steel cathode (0.02 mg/cm²), indicating high operational stability. Overall, the Ti–stainless steel system shows potential for phosphorus removal; however, dissolved organic matter removal remained limited under the investigated operating conditions.