<p>In this study, a novel composite flocculant was prepared using sodium silicate, aluminum sulfate, and thiosemicarbazone as experimental raw materials. The successful synthesis of the composite flocculant was verified through Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM–EDS), and X-ray photoelectron spectroscopy (XPS). The influence of pH levels in water samples, initial heavy metal ion concentrations, and flocculant dosage on copper ions removal efficiency was systematically studied. The experimental results demonstrate that the removal of Cu²⁺ under optimum conditions reached 96.88%. The Langmuir isotherm model predicts a maximum Cu²⁺ adsorption capacity reaching 1568.6&#xa0;mg/g. The adsorption kinetics indicate that the removal of heavy metal ions by this flocculant is dominated by chemisorption. When combined with zeta potential analysis of the flocculation mechanism, charge neutralization emerged as the controlling factor during flocculation, and additional mechanisms such as chelating and precipitation, adsorption and bridging, and sweep flocculation are also involved.</p>