Fe₃O₄ Nanoparticles Coated with EDTA and Ag Nanoparticles for the Catalytic Reduction of Organic Dyes from Wastewater

This study was undertaken to design a stable easy-recoverable Fe3O4@EDTA-Ag hybrid with rich catalytic sites via wet-chemical method for the catalytic reduction of multiple dyes in wastewater. The amorphous ethylenediaminetetraacetic acid (EDTA) layer plays an important role by strongly pinning the Ag nanoparticle (NP) catalytic sites on the surface of the Fe3O4 core with a very high ratio of 10.8%. In addition, an improved surface area from 42 to 72 and 81 m2 g–1 was achieved after the decoration of Fe3O4 by EDTA and EDTA-Ag NPs, respectively. Finally, catalytic tests showed that Fe3O4@EDTA-Ag hybrid exhibits an ultrafast catalytic reduction of azo, heterocyclic, and cationic dyes with a reduction rate of about 0.05 mM/150 s. Moreover, the catalyst demonstrated a high efficiency for the simultaneous reduction of mixed dyes (N.R+MB+AY and MB+Rh–B+AY). Recycling tests showed that Fe3O4@EDTA-Ag has an excellent stability wherein the catalyst was recycled 10 times with a slight decrease in the reduction rate of only ∼4.5%. The dissolution of Fe from Fe3O4@EDTA-Ag was very small compared to bare Fe3O4 due to protective EDTA coating. The high catalytic activity, the magnetic recoverability, along with the excellent stability of Fe3O4@EDTA-Ag make it a potential candidate for the reduction of multiple dyes in real textile wastewaters.