It has been proposed that Virtual Sorbent Bed (VSB) provide an efficient way to increase gas particle mass transfer of Mercury. A prototype of the VSB has already been constructed by current student Nekheel Gajjar. I am currently working with him on calibrating the VSB. Once this is done, I will be working on developing a VSB performance map to determine its optimal operating conditions. In addition, I am developing a further model of mass transfer within ESPs that seeks to better understand the differential behavior or powdered activated carbon as compared to fly ash. Preliminary indications from bench-scale ESP tests have suggested that the electrical properties of powdered activated carbon may cause its collection in an ESP to be significantly different from that of fly ash, including the potential for significant collection on charging electrode wires. Such collection would constitute a previously unidentified mercury capture mechanism within ESPs, and could explain the often-observed slow recovery of mercury concentrations at ESP outlets after cessation of sorbent injection.