Phenanthrene decomposition in soil washing effluents using UVB activation of hydrogen peroxide and peroxydisulfate.

In this work, the decomposition of phenanthrene (PHE) in mimic and real soil washing (SW) effluents was investigated using UVB light assisted activation of hydrogen peroxide (H2O2) and peroxydisulfate (PDS) oxidation processes. The impact of oxidant concentration, initial pH, and coexisting inorganic anions (Cl-, HCO3- and NO3-) on PHE removal was evaluated. PHE degradation efficiency under UVB irradiation followed the order of UVB/PDS > UVB/H2O2 > UVB. The increase of PHE decomposition efficiency was observed with increasing oxidant dose in the range of 2-30 mM upon the two processes. It was found Cl- played different roles in the two activation systems depending on the solution pH and Cl- concentration. The influence of HCO3- on PHE elimination was negligible in the UVB/PDS process, while an inhibitory effect was observed in the UVB/H2O2 system. Nitrate inhibited the PHE decay in both UVB/H2O2 and UVB/PDS processes at the investigated pH 3.3, 7.1 and 8.6. Finally, the application of the two activation processes to the treatment of real SW effluents indicated that up to 85.0% of PHE degradation could be reached under 6 h UVB irradiation with PDS, indicating UVB/PDS process is a promising alternative for SW effluent treatment.