Fabrication of Hierarchically Porous “Fish Cage”-like Carbonaceous Nanomaterials via Soft Template-assisted Strategy for Cr Removal: Accelerated Stepped Adsorption and Enhanced Coordination Effect

Abstract

The negative impact of heavy metal pollution, specifically chromium (VI), on human health is well-documented. To solve this issue, hollow anisotropic hierarchically porous “Fish Cage”-like carbonaceous nanomaterial (N,S-HFC-180) with multi-active groups is synthesized. Hierarchically porous structure provides stepped adsorption effect. The addition of K₂C₂O₄ leads to an increase in the specific surface area of N,S-HFC-180 to 1914.21 m² g⁻¹ (an increase of ~552 times compared to HFC-180). Thiourea introduces multi-active groups that act as “Barbs” in “Fish Cage”, further reducing Cr(VI) to Cr(III) and sequestrating Cr(III) by coordination effect. Subsequent batch studies suggest that N,S-HFC-180 exhibits a high removal capacity of 164.29 mg g⁻¹ for Cr(VI) at pH=2. The kinetics and isotherm analyses display an outstanding maximum adsorption capacity of 393.88 mg g⁻¹ at 298 K. In addition, even after seven cycles, the removal rate of Cr(VI) using N,S-HFC-180 remains>85.00 %, and it effectively reduces the concentration of electroplating wastewater from 55.82 to 0.14 mg L⁻¹. Pore filling, chemical reduction and chelation, hydrogen bond and electrostatic attraction are the primary adsorption drivers. The results suggest that, the recoverable N,S-HFC-180 highlights its viability for practical applications in wastewater treatment processes.