Heterogeneous Fenton oxidation of trichloroethylene catalyzed by sewage sludge biochar: Experimental study and life cycle assessment.

Heterogeneous Fenton oxidation of trichloroethylene (TCE) catalyzed by sewage sludge biochar was studied. The highest TCE removal efficiency was 83% at pH 3.1, catalyzed by 300 W biochar. The biochars produced at higher microwave power levels provided better catalytic effect, due to higher iron contents and specific surface areas. Reactivity of sewage sludge biochar maintained after several uses, which provides an advantage for using as a permeable reactive barrier to remediate groundwater pollution. Chromium, copper, nickel, lead, and zinc were found in the leachate generated from sewage sludge biochar, and most of the concentrations were lower than the standards for non-drinking water use. Besides, copper, zinc, and iron were found in the reaction solutions of Fenton oxidation. Because of the highest dosage required for Fenton oxidation, the environmental impact caused by 200 W biochar is highest. The environmental impact caused by 300 W biochar is lowest. Among the four endpoint impact categories in the life cycle assessment (LCA), human health is the highest concern, whereas ecosystem quality is the least. According to experimental and LCA results, the optimum microwave power level would be 300 W. The primary impact source is microwave pyrolysis because of high energy usage.