Study on the Performance of Lignin-Based Iron-Copper Bimetallic MOF Composite Materials and Their Ultra-Fast Adsorption Application for Cr(VI) in Wastewater

To address the challenge of treating high-toxicity hexavalent chromium (Cr(VI)) pollution in industrial wastewater, this study innovatively used lignin as the precursor and constructed iron-copper dual-metal (Fe-Cu) organic framework materials (ILCB-MOFs-1) through in-situ self-assembly strategy. Using multiple-dimensional characterization methods such as SEM, XRD, FTIR, TEM, Raman spectroscopy, and XPS, the three-dimensional multi-level pore structure and the synergistic adsorption mechanism of the dual-metal active sites of the material were revealed. The results showed that when the molar ratio of Fe³⁺ to Cu²⁺ was 1:1, ILCB-MOFs-1 could self-assemble to form a three-dimensional multi-level pore structure. In the range of (Cr(VI)) concentration of 50 mg·L⁻¹ and pH 1-7, with an ILCB-MOFs-1 dosage of 0.1 g·L⁻¹ and a reaction time of 1 min, complete (100%) rapid adsorption of Cr(VI) could be achieved. The coexisting ions such as SO₄²⁻, NO₂⁻, Cl⁻, Na⁺, and Ca²⁺ in the system had no effect on the adsorption and removal of Cr(VI). Mechanism analysis indicated that Fe³⁺ oxidized and reduced Cr(VI) to low-toxicity Cr(III), while Cu²⁺strengthened the adsorption process of Cr(VI) through Lewis acid action. This study provides a new idea for the development of green lignin resources and the treatment of heavy metal pollution in water.