Leachate treatment via electrocoagulation-coal-based powdered activated carbon process: Efficiencies, mechanisms, kinetics, and costs.

Abstract

This study aims to improve COD, NH₃-N, and turbidity removal from Bingöl's leachate using a single-reactor integrated electrocoagulation (EC)-coal-based powdered activated carbon (CBPAC) process under various experimental conditions. In the EC-CBPAC process, three stainless-steel cathodes and three aluminum electrodes were connected to the negative and positive terminals of the power supply, respectively. The initial concentrations in the leachate were 1044 mg O₂/L for COD, 204 mg/L for NH₃-N, and 57 NTU (or 71.25-mg (NH₂)2H₂SO₄/L) for turbidity, respectively. After a 40-min EC-CBPAC process, with a CBPAC dosage of 5 g/L and pH of 5 for COD and turbidity, and 9.5 for NH₃-N, the optimum removal efficiencies for COD, NH₃-N, and turbidity were achieved at 92%, 40%, and 91%, respectively. When the EC process was applied without CBPAC under the same experimental conditions, the removal efficiencies of COD, NH₃-N, and turbidity were 87%, 28%, and 54%, respectively. Before and after the EC-CBPAC process, the Brunauer-Emmett-Teller (BET) surface area, pore volume, and mean pore diameter of the CBPAC were found to be (888 m²/g, 0.498 cm³/g, and 22.28 Å) and (173 m²/g, 0.18 cm³/g, and 42.8 Å), respectively. The optimum pseudo-first-order (PFO) rate constants for COD, turbidity, and NH₃-N were determined to be 3.15 × 10^-2, 4.77 × 10^-2, and 8.8 × 10^-3 min^-1, respectively. With the current density increasing from 15 to 25 mA/cm², energy consumption, unit energy consumption, and total cost increased from 68.7 to 122.4 kWh/m³, 6.948 to 15.226 kWh/kg COD, and 0.85 to 1.838 $/kg COD, respectively. PRACTITIONER POINTS: EC-CBPAC process has greater COD, NH₃-N, and turbidity removal efficiency than EC process. COD and turbidity achieved their optimum disposal efficiencies at 92% and 91%, respectively, at pH 5 The most efficient disposal efficiency for NH₃-N was observed to be 40% at pH 9.5. EC-CBPAC process increased removal efficiencies for COD, NH₃-N, and turbidity by 20%, 19%, and 38%, respectively, compared with EC alone. The turbidity, NH₃-N, and COD disposal fitted PSO model due to high correlation values (R² 0.94-0.99).