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

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 H2O2 or with all SOC removed from the original soil by 600 degrees C ignition. The results showed that all of the sorption-desorption isotherms of PCE were non-linear within the experimental range, and the H2O2-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 H2O2-treated and 600 degrees 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 degrees 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 degrees 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 degrees C-heated samples. (C) 2015 Elsevier Ltd. All rights reserved.