<p>Heavy metal contamination of water resources is one of the most serious problems affecting human health and ecosystems. To remove heavy metal ions from polluted water, a bio-based cross-linked copolymer comprising vegetable oil-derived <i>n</i>-octadecyl acrylate and acrylic acid was synthesized via reversible addition-fragmentation chain transfer polymerization using multifunctional calix[4]resorcin-arene thioester as an initiator. Its amphiphilic structure, featuring both hydrophilic and hydrophobic domains, ensured efficient hazardous adsorption. Several techniques, including nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller analysis, and thermogravimetric analysis, were used to characterize and confirm the formation of the polymeric adsorbent. This copolymer has been evaluated for its ability to remove some common risky metal cations, including cadmium, nickel, and cobalt ions from aqueous solutions, which showed high adsorption efficiency. Optimization studies were conducted to maximize ion adsorption. In addition, pseudo-first-order and pseudo-second-order models were used to analyze adsorption kinetics, and Langmuir and Freundlich models were applied to study adsorption isotherms. The thermodynamics of adsorption was also investigated. As a result, high adsorption efficiency and effective ion desorption capability emphasize its recoverability and reusability.</p> Graphical abstract <p></p>