Three-dimensional functionalized graphene oxide for enhanced hexavalent chromium remediation: Mechanistic insights...

In this study, GO-TETA, GO-PEI, and GO@TETA-PEI were synthesized using a modified Hummers' method, with the structural and chemical properties characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). GO@TETA-PEI featured a three-dimensional (3D) porous architecture, high surface area, and abundant -OH/-NH₂ groups, collectively contributing to superior Cr(VI) adsorption performance. The GO@TETA-PEI achieved an impressive adsorption capacity of 729.9 mg g^-1 at 303 K and pH 2, and demonstrated excellent regeneration stability with 84.19 % capacity retention after seven cycles. The adsorption kinetics adhered to the pseudo-second-order model, while the isotherms aligned with the Langmuir model, confirming monolayer adsorption on homogeneous surfaces. Advanced X-ray photoelectron spectroscopy (XPS) analysis, complemented by density functional theory (DFT) calculations, elucidated a proton transfer mechanism between protonated amine groups (-NH₂) and HCrO₄^-, facilitating the formation of hydrogen bonds. The proposed adsorption mechanism involved multiple interaction modes, including electrostatic attraction, chemical reduction, chelation, and hydrogen bonding. GO@TETA-PEI demonstrated exceptional adsorption and reduction capabilities, excellent reusability, and significant potential for practical deployment in the treatment of actual electroplating wastewater. Additionally, the material exhibited strong selectivity against common coexisting ions, with only moderate interference from PO₄^3-, SO₄^2-, and Cu²⁺, further showcasing its potential for practical wastewater treatment applications.