Integration of galvanic reactions and engineered nanoconfinement in iron-copper nanocomposites for highly-efficient remediation of Cr(VI)-contaminated acidic/alkaline water

To eliminate trace toxic hexavalent chromium (Cr(VI)) from water with different pHs, researchers focused on adsorption, reduction of Cr(VI) to trivalent chromium with followed precipitation while the complex and costly reactivity regulations via adjusting pHs was inevitable. Here we exploit Fe-Cu nanocomposites (CnZVI/Cu) with galvanic reactions and engineered nanoconfinement effect for removing Cr(VI) from acidic/alkaline water directly, consisting of phosphorylated cracked nanoscale zero-valent iron (CnZVI, crack width of 1–2 nm) anode and Cu aggregates cathode. The formed primary battery exhibits strong electrostatic interactions towards ions and outstanding reactivity of reduction and precipitation at acidic/alkaline conditions. The pH inside the cracks at neutral or alkaline conditions is calculated to turn lower for enhancing the dynamics relevant to remediation. Benefiting from those two effects, the removal efficiencies of Cr(VI) through CnZVI/Cu attain more than 99.5 % at pH ≤ 8 and even 96 % at pH of 12 in only 30 min, outperforming the previous works. Its protection on beings (water spinach, zebrafish, and cell) from suffering poisonous Cr(VI), control of adsorbed Cr from migration, and magnetic collectability demonstrate the admirable removal performance, biosafety, and stability, respectively. This work proposes highly-efficient, eco-friendly, convenient, and low-cost technology to scavenge Cr(VI) from acidic/alkaline water.