Nano silver decorating three-dimensional porous wood used as a catalyst for enhancing azo dyes hydrogenation in wastewater

The natural wood can be used as a multifunctional material e.g. a reducing agent and a stabilizer due to the reducing functional groups and three-dimensional network structure. In this work, a wood catalyst decorated with silver nanoparticles (Ag NPs) was prepared and used to catalyze the hydrogenation of azo dyes. The systematic characterizations revealed that the Ag NPs were uniformly present on the wood surface. The Ag NP/wood exhibited an excellent catalytic activity for hydrogenating methyl orange (MO), congo red (CR) and erichrome black T (EBT), and their reaction rate constants were calculated as 1.533, 0.969 and 0.707 min−1, respectively. The factors affecting the hydrogenation efficiency of azo dyes were elucidated by the density functional theory (DFT). The catalyst had a good reusability, for instance the hydrogenation efficiency of MO retained as 90% in 5 min after six recycles. In addition, the mechanism of MO hydrogenated by NaBH4 catalyzed with the Ag NPs/wood was proposed.