Carbon-based sorbents impregnated with iron oxides for removing mercury in energy generation processes

Abstract

Gaseous phase mercury emissions into the atmosphere from fossil fuel combustion processes for energy production are a matter of serious environmental concern. Several technologies have been studied and proposed to address this problem, but none of them is mature enough from a commercial point of view. This study aims to provide new insights into the interaction between mercury and iron oxides in order to enable the design of cost-effective mercury capture technology based on regenerable sorbents. Different iron oxides supported on an activated carbon were prepared and tested for the removal of elemental mercury (Hg0). It was found that 1) maghemite promoted the removal of mercury to a greater extent than goetite/hematite achieving 100% efficiencies and 2) the mercury-sorbent interaction is determined by the oxygen vacancies present in the iron oxide. The mercury retention efficiency is maintained after the sorbent is regenerated and it is not deactivated by the presence of acid gases. The results obtained with the sorbent loaded with maghemite open new perspectives for the retention of gaseous Hg0, combining high efficiency, good regenerability and lower price in comparison with sorbents developed to date. Once the regeneration capacity is assessed, the adsorption process will be scaled.