Remediation of soils contaminated with polychlorinated biphenyls by microwave-irradiated manganese dioxide

The removal of polychlorinated biphenyls (PCBs) using microwave-irradiated manganese dioxide (MnO2) in PCB-contaminated soils under different conditions is investigated. The removal of PCB77 in two actual soil samples exhibits strong pH-dependent behavior, and the removal efficiency is higher in acidic soil (Ali-Perudic Ferrosols) than that in neutral soil (Udic Argosols). The removal kinetics of PCB77 using microwave-irradiated MnO2 under different experimental conditions fits a pseudo-first-order kinetic model well. Both the removal efficiency and the kinetic constant (k) values of PCB77 in Ali-Perudic Ferrosols considerably increase, although in a nonlinear fashion, as the initial amount of MnO2 is increased, as the treated soil mass is increased, and as the microwave power is increased. The reactivity of three PCBs (PCB28, PCB77, and PCB118) did not present as a function of the degree of chlorination in the reaction with microwave-irradiated MnO2. The pronounced removal of three PCBs in contaminated soil (all above 95%) indicates that MnO2 in combination with microwave irradiation is promising for technological applications that seek to remediate sites critically polluted with PCBs.