Mannich-mediated synthesis of a recyclable magnetic kraft lignin-coated copper nanostructure as an efficient catalyst for treatment of environmental contaminants in aqueous media

Recently, the fabrication of heterogeneous catalysts using biopolymers has been considered due to some advantages such as biodegradability, easy handling, high efficiency and so on. In this work, 5-amino-1H-tetrazole modified kraft lignin/Fe3O4 supported highly catalytic active copper complex (Fe3O4@LigA/Cu) has been synthesized as a novel catalyst. The support was prepared by the Mannich reaction of 5-amino-1H-tetrazole and kraft lignin. The prepared catalyst was characterized by different techniques including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), Energy-dispersive X-ray spectrometry (EDX), elemental mapping, Brunauer-Emmett-Teller (BET) and vibrating sample magnetometry (VSM). The Fe3O4@LigA/Cu catalyst was used in the catalytic reduction of organic pollutants such as 4-nitrophenol (4-NP), methylene blue (MB), and congo red (CR) using sodium borohydride (NaBH4) as the reducing agent and the catalytic efficiency was studied by UV–visible spectroscopy. Fe3O4@LigA/Cu catalyst showed high yield (˃ 99%) in the reduction of 4-NP in four min. Moreover, Fe3O4@LigA/Cu catalyst showed good recyclability and reusability. This work provides a simple method for the preparation of lignin based catalysts with high catalytic activity and easy recovery to degrade organic pollutants from aqueous solution.