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A novel amidoxime-functional sorbent was synthesized using discarded polypropylene (PP) fabric as the base material for removing hexavalent chromium from water. In this work, the PP fabric was first exposed to a pre-irradiation process, which enabled the subsequent grafting of acrylonitrile (AN). The grafting step was performed at 80 °C for four hours in a water bath, employing sulfuric acid as a reaction promoter, with 60% AN and a radiation dose of 30 kGy. Conversion of the AN-grafted PP (AN-g-PP) into its amidoxime form was achieved through reaction with hydroxylamine hydrochloride. The resulting adsorbent was examined using FTIR, SEM, TGA, and DMA to verify changes in structure, morphology, and thermal behavior. The ability of the modified PP to capture Cr(VI) ions was evaluated by varying pH, temperature, contact duration, and metal-ion concentration. Adsorption behavior conformed well to both Langmuir and Freundlich isotherm descriptions, while the kinetic trends closely matched a pseudo-first-order model, showing strong agreement between theoretical and measured uptake values. Thermodynamic analysis demonstrated that the adsorption process was spontaneous and endothermic, accompanied by an increase in system disorder. Desorption and reusability studies further revealed that the material retained effective performance over multiple cycles, indicating its suitability for sustainable removal of Cr(VI) from aqueous environments.