This study investigates the adsorptive removal of heavy metals (Cadmium, Lead, and Chromium) from wastewater using a novel cobalt-diphenylamine (Co-DPA) complex. The Co-DPA complex was synthesized from cobalt nitrate hexahydrate and diphenylamine, characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), and tested for its efficiency in removing heavy metals. The adsorption capacity and efficiency were evaluated by adjusting parameters such as adsorbent dose, pH, initial metal concentration, and contact time. The results showed that the Co-DPA complex effectively reduced the heavy metal concentrations from 0.267 mg/L, 0.075 mg/L, and 0.125 mg/L for Cd²⁺, Pb²⁺, and Cr³⁺, respectively, to 0.0129 mg/L, 0.00028 mg/L, and 0.00054 mg/L after 80 minutes, with removal efficiencies of 95.6%, 99.5%, and 99.5% for Cd²⁺, Pb²⁺, and Cr³⁺, respectively. The adsorption process followed the Freundlich isotherm model, and the kinetics were best described by the pseudo-second-order model for Cd²⁺ and Cr³⁺, and the pseudo-first-order model for Pb²⁺. The study concludes that the synthesized Co-DPA complex is a promising material for the adsorptive removal of heavy metal ions from wastewater.This study investigates the adsorptive removal of heavy metals (Cadmium, Lead, and Chromium) from wastewater using a novel cobalt-diphenylamine (Co-DPA) complex. The Co-DPA complex was synthesized from cobalt nitrate hexahydrate and diphenylamine, characterized by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR), and tested for its efficiency in removing heavy metals. The adsorption capacity and efficiency were evaluated by adjusting parameters such as adsorbent dose, pH, initial metal concentration, and contact time. The results showed that the Co-DPA complex effectively reduced the heavy metal concentrations from 0.267 mg/L, 0.075 mg/L, and 0.125 mg/L for Cd²⁺, Pb²⁺, and Cr³⁺, respectively, to 0.0129 mg/L, 0.00028 mg/L, and 0.00054 mg/L after 80 minutes, with removal efficiencies of 95.6%, 99.5%, and 99.5% for Cd²⁺, Pb²⁺, and Cr³⁺, respectively. The adsorption process followed the Freundlich isotherm model, and the kinetics were best described by the pseudo-second-order model for Cd²⁺ and Cr³⁺, and the pseudo-first-order model for Pb²⁺. The study concludes that the synthesized Co-DPA complex is a promising material for the adsorptive removal of heavy metal ions from wastewater.