Resource Recycling and Wastewater Remediation: Application of Turning Metal Scrap as Anode in Electrochemical Treatment of Soluble Cutting Fluids

Soluble cutting fluids (SCFs) from metalworking processes pose significant treatment challenges. Here, SCFs were treated using a monopolar electrochemical (EC) system, using turning scrap generated from metalworking operations as the anode. The system was operated for 60 min under various conditions, including different anode materials, electrolyte addition, aeration, and initial pH. Treatment performance was evaluated in terms of chemical oxygen demand (CODCr) and total organic carbon (TOC) removal efficiencies and specific energy consumption (SEC) for CODCr removal. The Al scrap (20 g/L) showed the optimal overall performance, achieving CODCr and TOC removal efficiencies of 29.28% and 25.62%, respectively, with an SEC comparable to that of the Al electrode. Electrolyte addition improved the energy efficiency under all conditions, with NaNO3 10 mM yielding the lowest SEC (0.57 kWh/kg-CODCr), and aeration negatively affected both removal efficiency and energy consumption. Although acidic conditions (pH 2) resulted in high apparent removal, most of the reduction occurred during pre-treatment pH adjustment, and the highest energy efficiency was achieved at pH 7 (0.47 kWh/kg-CODCr). These results demonstrate that Al turning scrap is a promising alternative anode material for electrochemical treatment of SCFs with optimized electrolyte addition and operating pH enabling improved energy efficiency.