Hexachlorobenzene removal efficiencies in different solvents by electron beam irradiation were investigated. Several factors that might affect the removal efficiencies were further examined. At 10 kGy, HCB degradation value was 85.8% in the solvent of acetone: water mixture (20:80, v/v), while at the same dose, the reduction value of 42.6% was achieved in hexane solvent. In the solvent of acetone:water mixture (20:80, v/v), Na2CO3 as additive could enhance the degradation efficiency by 4.5%. However, Triton X-100, NaNO3, NaNO2 and H2O2 as additives reduced the degradation value by 20.0%, 6.3%, 85.7% and 20.5%, respectively. Furthermore, the increase of these additives would result in the decrease of the degradation efficiencies. The pH value of the solvent of acetone:water mixture (20:80, v/v) could affect HCB removal efficiency. At pH 11.8, reduction value of 90.2% was achieved at 10 kGy, while at the same dose, at pH 2.7 and 6.8, the reduction values were only 82.4% and 86.9%, respectively. At the same time, the degradation value of pentachlorobenzene was 94.7% at 10 kGy. In the presence or absence of additives, pH value of the solvent of acetone:water mixture (20:80, v/v) became lower with increasing dose after electron beam irradiation. (c) 2006 Elsevier B.V. All rights reserved.