We previously reported that microscale Cu/Fe bimetal could be used for the dechlorination of hexachlorobenzene (HCB), a representative polychlorinated persistent organic pollutant (Pops). But slow reduction rate and rather incomplete dechlorination were reached. In this study, HCB dechlorination by nanoscale Fe and Cu/Fe was evaluated. It was found that HCB reduction by nanoscale Fe was rather slow, and the reduction was significantly increased by nanoscale Cu/Fe. Near complete reduction of HCB was obtained by nanoscale Cu/Fe for 48 h treatment. HCB was quickly dechlorinated to PeCB, TeCBs, TCBs and DCBs without selectivity via a stepwise process. The reduction rate and dechlorination extent were much higher compared with microscale Cu/Fe. Lowering pH during reduction showed slightly negative influence on HCB reduction by nanoscale Cu/Fe due to retarded co-precipitation. A catalytic hydrogenation process on Cu surface through iron oxide film was suggested for the increased HCB reduction by Cu coating on nanoscale Fe. This study proved that using a much cheaper bimetallic iron of nanoscale Cu/Fe than nanoscale Pd/Fe could also achieve the effective dechlorination of HCB. (C) 2009 Elsevier B.V. All rights reserved.