STUDY ON SORPTION AND DESORPTION OF PHENANTHRENE BY DIFFERENT KINDS OF GEOSORBENTS

Sorption and desorption of phenanthrene by some natural geosorbents(soils and sediments)were studied. Both sorption and desorption can reach steady state quickly. Under the test conditions, the sorption of phenanthrene followed linear isotherm well, which indicates that partition is the key process controlling the sorption. Distribution coefficients(Kd) ranged from 24.1 to 187.5 L·kg-1. Sequential desorption test revealed that desorption of phenanthrene from the geosorbents into aqueous solutions exhibited hysteresis to different extents. Desorption rate and hysteresis extent were influenced by both organic carbon(OC)content of the geosorbents and the initial concentration of phenanthrene. For example, the hysteresis index(HI)was 1.61 and 0.67 for Yulin soil with an OC content of 2.82% when the initial concentration of phenanthrene was 1 and 2 mg·l-1, respectively;whereas HI decreased to-0.06 for Teda soil with an OC content of 0.69% at 2 mg·l-1 initial phenanthrene concentration, indicating a reversible sorption.