Physico-chemical factors affecting mercury elimination from solution using fern as sorbent have been analysed. It was demonstrated that interaction of mercury with this biomass follows two processes, adsorption by the functional groups in the biopolymers of the cell wall and reduction by easily oxidized compounds of the biomass. Batch experiments have been done to analyse the effect of pH, ionic strength of the media or competition with other metals. Ionic strength did not show a significant influence in the process, but mercury speciation with the formation of negatively charge complexes represented an important drawback in metal elimination. Continuous flow conditions were also analysed since many industrial applications will require them. These studies allowed distinguishing the two processes: mercury sorption was observed but also reduction of this metal occurs. Reduction to mercury (I) and metallic mercury has been confirmed by scanning electron microscopy analysis of the column filling after the continuous flow experiments. (C) 2010 Elsevier Ltd. All rights reserved.