Experimental research has indicated that magnetic materials in fly ash can arouse the catalytic oxidative capacity that facilitates mercury capture. In this work, external magnetic field (EMF), rather than magnetic sorbent, is conducted to evaluate the behavior between magnetism and mercury removal. The experimental tests are designed to study the influence of EMF on the mercury adsorption capacity of fly ash. The results show that the mercury removal efficiency of the fly ash with EMF increases by 15-25 percentage points as compared with that without EMF. This enhancement may be a result from energy level splitting of mercury derived from EMF and the magnetochemistry effect of magnetic materials in fly ash. (C) 2015 Elsevier Ltd. All rights reserved.