Characteristics and influencing factors of tetrachloroethylene sorption–desorption on soil and its components

Abstract To investigate the effects of soil structure, soil organic carbon (SOC), minerals, initial tetrachloroethylene (PCE) concentration ( C 0 ), and ionic strength ( C i ) on PCE sorption–desorption, six types of soil were adopted as adsorbents, including two types of natural soil and four types of soil with most of the “soft carbon” pre-treated by H 2 O 2 or with all SOC removed from the original soil by 600 °C ignition. The results showed that all of the sorption–desorption isotherms of PCE were non-linear within the experimental range, and the H 2 O 2 -treated samples exhibited higher non-linear sorption isotherms than those of the original soils. The hysteresis index of PCE sorption to original soil is less pronounced than that of the H 2 O 2 -treated and 600 °C-heated samples due to the entrapment of sorbate molecules in the “hard carbon” domain, together with the meso- and microporous structures within the 600 °C-heated samples. Both SOC and minerals have impacts on the sorption–desorption of PCE, and the sorption–desorption contribution rate of minerals increased with decreasing SOC content. C 0 has almost no influence on the sorption to minerals of the soils, but the contribution rate of minerals decreased with increasing C 0 in the desorption stage. As a result of the salting-out effect, PCE sorption capacity was increased by increasing C i , especially when C i  ≥ 0.1 M. Moreover, desorption increased and hysteresis weakened with increasing C i , except for the 600 °C-heated samples. In addition, no significant effect of C i on desorption of PCE and no hysteresis was observed in this experimental range for the 600 °C-heated samples.