Conversion of fern (Pteris vittata L.) biomass from a phytoremediation trial in sub- and supercritical water conditions

Uncontaminated and As-contaminated fronds of Pteris vittata L., an As-hyperaccumulator fern used to phytoextract As from contaminated soils and water, were converted by subcritical water (300 degrees C, 25 Pa) and supercritical water (400 degrees C, 25 Pa) treatments. Frond biomass was reduced between 70 and 77%. Compared to sub-critical conditions, supercritical conditions decreased C and inorganic contents in both the solid and liquid phases for uncontaminated and contaminated fronds and promoted CH4 formation. Higher As, Fe and Zn contents in contaminated fronds promoted decreasing C contents and the formations of cyclopentenones and benzenediols in the liquid phase. Al, Fe, P, Zn and Ca mainly remained in the solid phase whereas As and S were transferred to the liquid phase for both phytomasses. As the temperature increased from 300 degrees C to 400 degrees C, the concentrations of cyclopentenones and phenols in the liquid phase rose while those of guaiacols and other compounds decreased for both phytomasses. Arsenic in the liquid phase was removed by sorption on hydrous iron oxide. (C) 2010 Elsevier Ltd. All rights reserved.