Antimony (Sb) Recycling from Wastewater to Supercapacitor Electrode Using Ordered Porous Amidoxime‐Polyacrylonitrile: Chemical Evolution and Transformation Mechanism

Abstract Exhausted adsorbents from Sb‐laden wastewater are hazardous and generally landfilled. This study presents that exhausted Sb adsorbents can be thermally reduced and recycled as supercapacitor electrode. Specifically, ordered hierarchical porous amidoxime‐polyacrylonitrile (OHPAPAN) is synthesized for highly efficient Sb(V) ions adsorption and then thermal conversion of exhausted OHPAPAN to Sb‐contained char, rendering excellent electrochemical activity. Sb 0 atom clusters are found to form during recycling process by X‐ray absorption spectroscopy (XAFS), along with Sb oxide with average valence of +2.63. The 4d and 4p orbital of Sb cluster exhibits abundant electron state in Fermi level and valence band, making a pseudocapacitive contribution. Moreover, ordered hierarchical pore is confirmed to be inherited in the char from OHPAPAN, further enhancing electrical double layer capacitance. Coordination configuration of Sb and N/O becomes more stable from sexadentate (coordinate atom distance of 1.98 and 2.66 Å) in OHPAPAN to ≈2 N/O ligands in Sb‐contained char (1.97 Å), underlining the shorter atom distance and higher orbital energy for Sb immobilization. Consequently, the capacitance maintains 96.1% after 6000 cycles, indicating that its excellent stability can rival relevant commercial electrode. This study offers a novel insight that Sb mineral sources can be derived from industrial wastewater, not just mining activity.