Removal of Cu(II) and Cr(VI) from electroplating wastewater by magnetic Fe3O4@SiO2-UiO-66-EDTA : Adsorption behavior and mechanism

The heavy metals discharged from electroplating wastewater, represented as copper and chromium ions, is harmful to aquatic lives and human beings, and will break the ecological balance. In this work, magnetic hybrid porous structure adsorbent of Fe 3 O 4 @SiO 2 -UiO-66-EDTA is prepared for recycling copper and chromium ions. The adsorbent exhibits a maximum adsorption capacity of 212.10 mg/g for Cu(II) and 118.10 mg/g for Cr(VI). Notably, it shows excellent regenerability of 87.12% after 5 cycles. The adsorption of Cu(II) and Cr(VI) on Fe 3 O 4 @SiO 2 -UiO-66-EDTA follows the pseudo-second-order model, where chemical adsorption is dominant and it occurs spontaneously and exothermally. Based on XRD, FTIR, XPS, and DFT calculations, the adsorption mechanisms are driven by electrostatic attraction, chelation, and redox reactions. This work provides a novel and promising strategy for designing highly efficient adsorbents, paving the way for more effective treatments of electroplating wastewater contaminated with Cu(II) and Cr(VI).