In this study, new composite flocculants were prepared from iron salts and polydimethyldiallylammonium chloride (PDMDAAC). The Fe(III) species and zeta potential of the composite poly-ferric chloride (PFC) and PDMDAAC flocculant (PFC-PDMDAAC) and PFC wen, measured by a timed complexation spectroscopy method and the Malvern Zetasizer 3000, respectively. The results showed that when PDMDAAC fraction (Wp) was 7.0%. PFC-PDMDAAC contained the smallest content of Fe-c and had the highest zeta potential. The flocculation efficiency of PFC-PDMDAAC and the composite FeCl3 and PDMDAAC flocculant (FeCl3-PDMDAAC) for treating actual surface water or wastewater samples was compared with that of FeCl3, PFC and PDMDAAC. The results showed that for surface water from Yellow River, PFC-PDMDAAC produced the highest flocculation efficiency, while for papermaking intermediate wastewater, the flocculation efficiency of FeCl3-PDMDAAC was the highest. (C) 2007 Elsevier B.V. All rights reserved.