Liquid activated carbon (LAC) - Enhanced microwave remediation of PAH - Contaminated soils

A new Liquid Activated Carbon (LAC)-enhanced microwave (MW) treatment was studied in the remediation of PAH-contaminated soils. The role of different doses of LAC was studied at the bench-scale varying MW input and irradiation times. Laboratory transport tests were also designed to assess the potential mobility of LAC suspensions in unsaturated porous media under the effect of gravity, thus simulating field application via ground flooding and gravity-driven percolation.The main results revealed that the LAC can significantly increase the MW electric field absorbing performance of the irradiated medium, leading to very high soils temperatures up to similar to 1100 degrees C within 3-min irradiation time (LAC 10%). This resulted in largely shortened PAH removal kinetics. A LAC dose of 5% led to a total PAH removal in 5 min, whereas the maximum dose of 5% shorted this time to 2 min. Transport tests evidenced a good mobility of LAC when applied by gravity-driven percolation, without active injection. In 18 cm long columns, approximately 30% of LAC was retained, with a fairy homogeneous distribution along the bed length. Experimental and modelling results validate the concept of the LAC-enhanced MW heating and the fundamental role of the liquid enhancer for in situ remediation interventions.