In recent years, metal contamination originating from industrial wastewater, particularly trivalent chromium ions (Cr³⁺), has been recognized as a serious threat to the environment and human health. The development of magnetic nanostructured adsorbents with high adsorption capacity and easy recoverability, especially through green and sustainable synthesis routes, is of great importance. In this study, cobalt ferrite (CoFe₂O₄) nanoparticles were synthesized via a self-combustion method based on green synthesis using date extract (COF-D), apple extract (COF-A), recycled rubber extract (COF-R), and a conventionally synthesized sample (COF-Cs). The aim was to investigate the influence of these extracts on the structural characteristics, morpHology, magnetic properties, and Cr³⁺ adsorption performance. XRD analysis revealed that all samples possessed an inverse spinel structure with a pure cobalt ferrite pHase; the use of extracts led to a reduction in crystallite size and lattice strain. FESEM images demonstrated that the extracts improved particle morpHology and increased the effective surface area of the nanoparticles. VSM analysis indicated an increase in saturation magnetization and a decrease in coercivity when plant extracts were used, with the highest Ms observed for COF-A. FTIR spectra confirmed that hydroxyl, carboxyl, and pHenolic functional groups originating from the extracts played a significant role in Cr³⁺ adsorption, while in the COF-R sample, the dominant mechanism was mainly pHysical adsorption and ion entrapment. Adsorption optimization was carried out using Response Surface Methodology (RSM) and an Adaptive Neuro-Fuzzy Inference System (ANFIS). The optimal conditions were determined (in single-variable evaluation) as pH ≈ 6 for COF-D, COF-A, and COF-Cs, and pH ≈ 4 for COF-R, with a contact time of 60 minutes and a temperature of 50°C; increasing the temperature to 55°C resulted in a decrease in adsorption efficiency. Additionally, increasing the ini