Rationally engineered core-shell structured Fe0@FeS towards the efficacious synergistic Cr(VI) and Ni(II) removal

As one category of promising and efficacious purification material toward environmentally harmful heavy metals, sulfidated amorphous zero-valent Iron (S@AZVI) exhibits unparalleled removal performance. Due to the disruptive crystal growth however, the irreversible loss of Fe0 component during conventional synthesis route poses a substantial hindrance to its industrial application. To address this, we propose a post-sulfidation strategy to hinder the transformation of Fe0 by altering the shell composition of AZVI from Fe2O3 to FeS, which maintains a remarkable Fe0 content up to 75.7 % over finally obtained S@AZVI, far higher than the material obtained through the one-step sulfidation. Attributing to the synergy of FeS shell and substantial Fe0, S@AZVI demonstrates impressive performance as the lowest free corrosion potential (−1.050 V) and work function (4.058 eV), and subsequently exhibits a notable enhancement in the removal efficiency of Cr(VI) and Ni(II), surpassing AZVI by 1.8 and 2.0 times, respectively. Results reveal that the adsorption, reduction, and coprecipitation constitute the mechanisms governing the removal of Cr(VI) and Ni(II). In practical electroplating wastewater experiments, S@AZVI effectively removes Cr(VI) and Ni(II) within a 60-min timeframe, meeting established emission standards. These findings provide valuable insights for future AZVI material synthesis for heavy metal elimination.