• • Cl-ZVIbm achieved a 76.5-fold increase in Cr(VI) removal kinetics (0.0306 min−1 vs. 0.0004 min−1 for ZVIbm), enabling complete removal of 2 mg·L−1 Cr(VI) within 120 min, a critical improvement for practical water treatment throughput.
• • Chloride modification reduced Cr(VI) adsorption energy from –0.28 eV to –1.64 eV by switching to a bidentate binuclear configuration, enhancing surface affinity and facilitating subsequent reduction.
• • Surface Fe(II) content increased by 26.9% (from 53.2% to 67.5%) due to Cl− electron-withdrawing effect, driving direct electron transfer that reduced 99.5% of Cr(VI) to Cr(III), ensuring high detoxification efficiency.
• • Chloride leaching was only 0.0126 mmol·L−1, well below industrial discharge limits, confirming the material's environmental safety and potential for scale-up without secondary pollution.