Progressively more complex technological advancements have been made, particularly with the invention of ferrite material manufacture. In this evaluation, the co-precipitation method was used to assess the structure, morphological, and magnetic characteristics of cobalt nickel ferrite for heavy metal adsorbent in Cu, and Cr material. Synthesized cobalt nickel ferrite of Co_0.7Ni_0.3Fe₂O₄ was analyzed structurally and morphologically using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), and its room temperature hysteresis loops were measured using a vibrating sample magnetometer (VSM). Atomic absorption spectroscopy was then used to determine the metal content (AAS). XRD study that the six peaks and well-defined reflection planes of (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), and (4 0 0) at the 2θ values of 30.12°, 35.57°, 43.29°, 53.71°, and 62.72° and there is no secondary phase in cobalt–nickel ferrite. FE-SEM results confirmed the spherical shape of the ferrite nanoparticle. The average particle size of Co_0.7Ni_0.3Fe₂O₄ is found with a range of 80 to 120 nm. The peaks of Fe, Ni, Co, and O elements as energy dispersive X-ray (EDX) spectra studied the ratio of the chemical composition of metal ions (Co: Ni) and iron to oxygen (Fe:O), The magnetic properties from VSM results evaluated that Ms of 34.46 emu/g, Mr of 14.91 emu/g, Hc of 671.58 Oe, independently. Correspondingly, AAS results from a removal efficiency of 99.86 % with capacity adsorption of 11.23 mg/L of Co_0.7Ni_0.3Fe₂O₄.