Optimization and application of boron-doped diamond electrooxidation for landfill leachate treatment and mixed antibiotic removal from wastewater

Abstract

This thesis investigated boron-doped diamond (BDD) electrooxidation as an advanced treatment option for mature landfill leachate and antibiotic-contaminated wastewater. The first phase examined real mature landfill leachate collected from the Brady Road Resource Management Facility in Winnipeg, Canada. Niobium (Nb) based BDD electrooxidation was conducted in a batch reactor, and response surface methodology was applied to optimize current density and pH for the simultaneous removal of COD, color, ammonium, and phosphate. Current density, treatment time, and pH strongly influenced treatment performance. The optimum condition was obtained at 125 mA/cm2 and pH 8, achieving removal efficiencies of 95.47%, 80.27%, 71.15%, and 47.15% for color, NH4+, COD, and PO43-, respectively. The second phase evaluated Nb/BDD electrooxidation for removing a ternary antibiotic mixture containing sulfanilamide (SN), tetracycline hydrochloride (TC-HCl) and sulfamethazine (SMZ). Acidic conditions and higher current density improved parent-compound removal and mineralization. At pH 3.5, 35 mA/cm2, 4000 µg/L, and 60 min, the removals reached approximately 77%, 77–80%, and 79% for sulfanilamide, tetracycline hydrochloride, and sulfamethazine, respectively. TOC decreased from 160 to 75 mg/L, corresponding to 53.13% mineralization. The final phase optimized H2O2-supplemented Nb/BDD electrooxidation using central composite design-based response surface methodology. The optimum condition was 30 mA/cm2, pH 4.95, 2.5 mM H2O2, and 6000 µg/L at 90 min. Experimental validation confirmed removals of 97%, 95.50%, and 88% for sulfanilamide, tetracycline hydrochloride, and sulfamethazine, respectively. TOC decreased from 85 to 20 mg/L, indicating 76.47% mineralization. The process required 66 kWh/m3, with an estimated electrical cost of 6.51 CAD/m3. Overall, BDD electrooxidation showed strong potential as a targeted polishing process for refractory leachate contaminants and mixed antibiotics.