The present investigation used a lab-scale ESP to assess the collection behavior of powdered mercury sorbents to collect preferentially on discharge electrode wires.  The lab-scale results explored mixtures of sorbents and various fly ashes, building upon earlier work (Prabhu et al., Energy & Fuels, 2011) that examined only single-component powders.  The results confirm that when mixtures of fly ash and powdered activated carbon (PAC) are electrostatically precipitated, the material collected on the energized wire discharge electrode is enriched in PAC relative to both its concentration entering the ESP and the material collected on the collection electrodes.  Measuring LOI of the material collected on the discharge electrode revealed as much as a 50% enrichment in PAC as compared to the PAC concentration entering the ESP.    Particle size analysis (below) reveals that the material collected on the ESP discharge electrode, consisting of both fly ash and PAC, is slightly finer than the raw PAC material.  This suggests that a) the affinity of PAC for collection on the discharge electrode has a size-dependent nature that also influences fly ash collection, and b) such fine materials may constitute a significant challenge to overall collection efficiency, particularly when considering rapping resuspension behavior.   Experimental testing also explored the effects of applied ESP polarity, voltage, and power, composition of the PAC-fly ash mixtures, and total particulate matter loading entering the ESP.