This study addressed the high colority and toxicity of textile dyeing wastewater by developing a novel,efficient,and cost-effective composite flocculant.The material was synthesized through interface-controlled chemical bonding involving dicyandiamide,formaldehyde,ammonium chloride,urea,and polyaluminum chloride(PAC),resulting in,for the first time,a molecular-level composite of Dicyandiamide-Formaldehyde-Coated(DFC)and PAC.A synergistic"electrostatic neutralization-coordination complexation"mechanism was demonstrated.Response surface methodology was employed to optimize the conditions,which indicated that a PAC mass fraction of 62%,reaction temperature of 73℃,and reaction time of 2.5 h favored the selective binding of C2N+and Al3+to sulfonate groups(-SO3-)and hydroxyl groups on dyes,respectively.This led to a significant enhancement of the floc structure,evidenced by a 16.47%increase in viscosity,and an improved decolorization efficiency that exceeded that of conventional physical mixing methods by 12.58%.Fourier Transform Infrared Spectroscopy(FTIR)analysis confirmed that the synergistic removal mechanism involved electrostatic neutralization by C2N+functional groups and coordination interactions with Al3+,which strengthened the floc integrity through combined electrostatic and complexation effects.In practical wastewater treatment applications,the composite flocculant achieved removal rates of 98.23%for color and 77.49%for COD without pH adjustment,with the treatment cost reduced to only 0.53 yuan per ton of water,demonstrating a higher cost-performance ratio and greater application potential compared to single flocculants such as PAC and DFC.This work provided a theoretical foundation and practical methodology for the high-efficiency,low-cost treatment of textile dyeing wastewater,thereby contributing to sustainable water environment management and supporting the goals of"clean water"and environmental protection.