Biomass-derived paper-based nanolignin/palladium nanoparticle composite film for catalytic reduction of hexavalent chromium

Abstract

In this study, paper-based catalytic composite films were prepared by synthesizing nanolignin on a filter paper (FP) and in situ reducing Pd ions to Pd nanoparticles (NPs). Alkaline lignin (AL) NPs were controllably prepared using industrial AL via two routes: “loading and then regeneration” and “regeneration and then loading.” The NPs prepared using the former method were labelled as LAL NPs, and those prepared using the latter were labelled as RAL NPs. The as-prepared NPs were loaded into the fiber framework of the FP to obtain paper-based AL NP composite material. The results showed that the AL NPs could be successfully prepared through both routes with similar dispersity and uniformity that were improved by the presence of FP. In addition, the size range of LAL NPs (26.6–92.7 nm) was broader than that of RAL NPs (37.3–85.0 nm). The AL NPs on FP were then employed as a reducing agent for the reduction of Pd2+. The concentration of the AL solution (0.43 %–3.07 %) influenced the content of AL NPs on the FP, and a higher AL NP content resulted in higher Pd NP content. Furthermore, the obtained paper-based nanolignin/palladium nanoparticles (AL-Pd NPs/FP) composite films were used for the catalytic reduction of Cr6+. They efficiently reduced the highly toxic Cr6+ to the less toxic Cr3+, and among them, the RAL-Pd NPs/FP film with a Pd NP content of 0.18 mg/mL required only 5 min to completely catalyze the reduction of Cr6+.