Facile synthesis of lignin Schiff base-copper complex as a catalyst for methylene blue and 4-nitrophenol removal

초록

Pure metal catalysts can cause environmental risks when they are released into lakes or rivers and difficulty in removing them from the catalyst system. Recently, several studies have focused on biopolymer-based catalysts owing to advantages such as biodegradability, high efficiency, and low cost. In this work, a novel lignin Schiff base-copper complex (L-SB-Cu) catalyst was synthesized and used for methylene blue (MB) and 4-nitrophenol (4NP) reduction in aqueous solutions. The catalysts were characterized using elemental analysis (EA), Fouriertransform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance spectroscopy (1H NMR) proved that the lignin Schiff base (L-SB) was successfully synthesized. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometry (EDS)-mapping proved that the copper ions were coordinated with L-SB, thus forming the L-SB-Cu catalyst. The catalyst exhibited a high catalytic reduction ability toward the organic pollutants MB and 4-NP with sodium borohydride (NaBH4) as the reducing agent. Even after three iterations of reusing the L-SB-Cu catalyst for MB and 4-NP reduction, the percentage reductions achieved were 87.3% and 75.65%, respectively. This work presents a new strategy for utilizing a biobased material as a highly efficient catalyst for degrading organic pollutants.

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