Kinetics of the Organic Compounds and Ammonium Nitrogen Electrochemical Oxidation in Landfill Leachates at Boron-Doped Diamond Anodes

Electrochemical oxidation (EO) of organic compounds and ammonium in the complex matrix of landfill leachates (LLs) was investigated using three different boron-doped diamond electrodes produced on silicon substrate (BDD/Si)(levels of boron doping [B]/[C] = 500, 10,000, and 15,000 ppm-0.5 k; 10 k, and 15 k, respectively) during 8-h tests. The LLs were collected from an old landfill in the Pomerania region (Northern Poland) and were characterized by a high concentration of N-NH4+ (2069 +/- 103 mg center dot L-1), chemical oxygen demand (COD) (3608 +/- 123 mg center dot L-1), high salinity (2690 +/- 70 mg Cl-center dot L-1, 1353 +/- 70 mg SO42-center dot L-1), and poor biodegradability. The experiments revealed that electrochemical oxidation of LLs using BDD 0.5 k and current density (j) = 100 mA center dot cm(-2) was the most effective amongst those tested (C-8h/C-0: COD = 0.09 +/- 0.14 mg center dot L-1, N-NH4+ = 0.39 +/- 0.05 mg center dot L-1). COD removal fits the model of pseudo-first-order reactions and N-NH4+ removal in most cases follows second-order kinetics. The double increase in biodegradability index-to 0.22 +/- 0.05 (BDD 0.5 k, j = 50 mA center dot cm(-2)) shows the potential application of EO prior biological treatment. Despite EO still being an energy consuming process, optimum conditions (COD removal > 70%) might be achieved after 4 h of treatment with an energy consumption of 200 kW center dot m(-3) (BDD 0.5 k, j = 100 mA center dot cm(-2)).