Sorption-desorption behaviour of hydrophobic organic compounds on Danube sediment

The sorption-desorption hysteresis of naphthalene and phenanthrene onto Danube sediment was investigated. Hysteresis indices (HI) are calculated for three equilibrium concentration (Ce=1%, 5% i 50% of the solubility in water). The results of sorption-desorption hysteresis indicated that it exists for both investigated sorbates on the Danube sediment. For more hydrophobic compound, phenanthrene (logKOW< 4.55) hysteresis is less pronounced in comparison with naphthalene (logKOW< 3.36). In the case of naphthalene, the existence of hysteresis may be due to irreversible pore deformation of the sorbent which causes the formation of meta-stable states in the sorbate mesopores