Upcycling aluminum machining shavings into sacrificial electrodes for electrocoagulation of wastewater

Cork-washing wastewater is a complex industrial effluent with high organic loads, phenolic compounds, suspended solids, and poor biodegradability, which limit the effectiveness of conventional treatment methods. To the best of our knowledge, this study reports the first direct upcycling of AW7075 aluminum (Al) machining shavings into binder-free, compacted sacrificial electrocoagulation (EC) electrodes, without remelting or thermal post-treatment, for treating cork-washing wastewater. Two cork-washing wastewaters (A and B) with distinct physicochemical characteristics were evaluated to assess electrode performance and matrix variability. Under identical operating conditions, Al-shavings electrodes achieved COD removal comparable to commercial AW5754 Al-plates (57-60%), while reducing specific energy consumption (SEC) by 10-17%. Screening carbon-footprint results suggested lower material-related impacts for waste-derived Al electrodes. Optimizing the Al-shavings/stainless-steel system using wastewater B, the selected operating conditions were an initial pH of 3.0, a current intensity of 0.13 A, and an interelectrode distance of 0.50 cm. After 30 min of treatment, removals of 91% COD, 81% TOC, 17% TN, and 80% TPC were achieved, with a SEC of 3.5 kWh·m −3 and high apparent dissolution efficiency. Using Al-shavings as both anode and cathode further reduced residual dissolved Al concentrations to near regulatory limits ( ≤ 10 mg L −1 ) and enabled stable short-term reuse cycles. Surface and sludge characterization supported the interpretation that pollutant removal was associated with controlled anodic dissolution, formation of Al-rich oxygenated flocs, adsorption, and co-precipitation mechanisms. By integrating metal waste valorization with wastewater treatment, this work provides a cleaner-production route for converting AW7075 Al-shavings into functional sacrificial electrodes for EC, while indicating that residual metal release, acid/base demand, long-term electrode durability, and matrix-specific process robustness require further validation before scale-up.