Abstract: Al³⁺ composite polymeric flocculant （PAM-AA） was synthesized by  aqueous solution polymerization with acrylamide (AM), acrylic acid (AA) and Al₂(SO₄)₃ as raw materials. The optimum ploymerization conditions were determined by orthogonal experiment  as  m(AM)∶m(AA）=5∶3, reaction temperature  65 ℃ and  stirring time  5 h. The yield could reach  96.3% when the amount of the initiator was 3% of the mass of monomer.  On this basis, Ca²⁺,Mg²⁺ and Fe³⁺ composite polymeric flocculant were synthesized. The structure and morphology of Al³⁺ composite polymeric flocculant were characterized by infrared spectrum (IR), X-ray diffraction (XRD), scanning electron microscope (SEM), respectively. Al³⁺ composite polymeric flocculant and N,N-dimethyl, dodecyl, benzyl ammonium chloride (1227) were applied in municipal sludge dewatering. Through the filter cake moisture content (FCMC) and the specific resistance in filtration (SRF), we compared the effects of  the commercial flocculant polyaluminium chloride (PAC),  the mixture between Al₂(SO₄)₃ and PAM-AA on the dewatering performance of municipal sludge. The results show that the combination of Al³⁺ composite polymer flocculant and 1227 can reduce the FCMC of sludge filter cake to 63.8%, and the effect is good.

Key words: composite , flocculant,  , flocculation,  , polyacrylamide-acrylic acid,  , metal ion, sludge dewatering,  , polymerization