Soil remediation by Fenton-like process: Phenol removal and soil organic matter modification

In situ chemical oxidation (ISCO) seems to be a powerful technology for soil remediation. In this work the application of Fenton's like oxidation treatment (H2O2 + natural ferrous species present in soil) has been evaluated to two different soils (S1 and S2) contaminated with phenol (qPhOHS1o = 360 mg g−1, qPhOHS2o = 160 mg g−1). They were categorized as calcareous loamy sand soils with different soil organic matter content (SOMS1 = 15.1%, SOMS2 = 10%). A refractory fraction of PhOH remained in the solid phase after treatment with H2O2 (CH2O2o=1   and   2%CH2O2o=1   and   2%), probably due to an entrapment phenomenon of the contaminant and because of the competition of SOM for the oxidant. Consequently, lower remediation efficiencies are obtained as SOM increases.It has also been paid attention to the effect of the oxidant on the SOM. It was found that H2O2 does not produce any important modification of both SOM content and distribution. This was in agreement with the oxygen obtained after hydrogen peroxide had reacted. Only a slight degradation of the humic and fulvic acids and a partial removal of the quinone and carbonyl groups were noticed, while carbonate groups and most of the SOM remain the same. However, a decrease in the sorption capacity of PhOH in the treated soils is observed. Therefore, it can be assumed that the oxidation of SOM could modify the external surface of SOM. Moreover, the oxidation of SOM by H2O2 could create more hydrophilic sites and thus decreases the sorption ability.