Novel lignin-based phenolic nanosphere supported palladium nanoparticles with highly efficient catalytic performance and good reusability

Lignin, the most abundant aromatic biopolymer, has great potential as a sustainable phenol replacement in phenolic resin synthesis, which has been considered as one of the most promising options for lignin valorization. In this work, kraft lignin from bamboo was used as a phenol substitute for the fabrication of novel lignin-based phenolic resin (LPR) nanosphere using a facile hydrothermal process. The as-prepared LPR nanosphere was then used as a reducing agent and a stabilizing support for synthesis of Pd nanoparticles (NPs). It was found that 40 % replacement of phenol by lignin led to a significant decrease of the nanosphere size and enhancement of the nanosphere surface roughness, which eventually increased the specific surface area of LPR nanosphere. Owing to the enhanced specific surface area and the excellent reducing activity of lignin, the as-prepared LPR nanosphere had considerably higher Pd NPs loading amount compared with the lignin-free PR support. Therefore, the asprepared Pd@LPR nanocomposites demonstrated highly efficient catalytic ability for the reduction of toxic Cr (VI) and two typical dyes. Moreover, the Pd@LPR nanocomposites exhibited excellent reusability owing to the stable loading of Pd NPs on the lignin-based support. Consequently, the lignin-based nanosphere, prepared by a facile hydrothermal process, is used as a reducing agent and a support for Pd NPs synthesis, which presents a novel approach to develop lignin-functionalized catalyst materials.