A composite inorganic polymer coagulant, polyferric aluminum chloride (PFAC) was prepared by using hydrochloric pickle liquor and calcium aluminate as main materials. The optimum conditions for preparing PFAC with the hydrochloric pickle liquor and the calcium aluminate were studied. The coagulation performance of PFAC was investigated by studying the turbidity, COD, total phosphate (TP) and NH3-N removal efficiency in municipal sewage treatment. Results indicated that the effective composition, basicity (simplified as B, B = [OH]/(3[Fe-T + Al-T) x 100%). coagulation performance and stability of PFAC were affected by calcium aluminate dosage, reaction time, reaction temperature and stabilizing agents. The COD and turbidity removal efficiency of PFAC was better than that of PFS and FeCl3, and the TP and NH3-N removal efficiency of PFAC was much better than that of PFS, FeCl3 and PAC. PFAC not only possessed a good coagulation performance. but also had good stability when stored. (C) 2008 Elsevier B.V. All rights reserved.