Synthesis and performance of acrylamide-based aluminium flocculant

Abstract

Polymeric flocculants of aluminium hydroxide-poly[acrylamide-co-(acrylic acid)], AHAMAA, were synthesized by solution crosslinking polymerization using aluminium hydroxide as a coagulant in the presence of acrylamide and acrylic acid as a comonomer pair, N, N’- methylenebisacrylamide (N-MBA) crosslink agent, ammonium persulphate (APS) and N, N, N’, N’-tetramethylethylenediamine (TEMED) as an initiator and co-initiator pair, respectively. The reaction was stirred with a stirring speed of 250 rpm at 40-50℃ for 1 h. The reaction products were dewatered by precipitation with acetone, dried in an oven at 50℃ for 24 h and milled. The water absorbency, the direct dye removal efficiency and the turbidity reduction of a synthetic wastewater of suspending kaolin with a variety of poly[AM-co-(AA)] and AHAMAA were investigated. From the results, it was found that the water absorbency of poly[AM-co-(AA)] is always higher than AHAMAA for all synthesized polymers. The water absorbency can be related to the storage modulus of the polymers. The storage modulus of AHAMAA is higher than that of poly[AM-co-(AA)], in good agreement with its lower absorbency. The efficiency of Congo red removal by AHAMAA is better than that of poly[AM-co-(AA)] synthesized by 4x10⁻³, 2.3x10⁻⁴, 1.6x10⁻⁴ and 12x10⁻⁴ mol of the acrylic acid, crosslinking agent, initiator, and co-initiator, respectively. The AHAMAA can remove Congo red which obeys the Freundlich adsorption isotherm, whereas poly[AM-co-(AA)] can adsorb Congo red by the transportation of dye molecules into its hydrogel porous structure. In the case of direct blue 71, all the synthesized AHAMAAs can remove the dye and obey the Freundlich isotherm whereas poly[AM-co-(AA)] cannot remove it. The AHAMAA is far more effective to reduce turbidity of the kaolin suspending wastewater than poly[AM-co- (AA)].