Comparison of Pd Nanoparticle-Decorated Softwood and Hardwood Activated Carbon in Catalytic Reduction of High-Concentrated Industrial 4-Nitrophenol

Carbon-based catalyst from natural wood recently shows a great potential in environmental remediation due to its naturally hierarchical and anisotropic porous structure. However, few studies have focused on the difference in structure-property-function between the two categories of hardwood and softwood. Herein, Pd nanoparticles decorated softwood (Pd/SAC) and hardwood activated carbon (Pd/HAC) were fabricated for catalytic reduction of high-concentrated 4-nitrophenol (4-NP, 2.0 g L-1). The results show that the developed Pd/HAC has larger specific surface area (474 m2 g-1), more abundant pits and nanopores than Pd/SAC (412 m2 g-1), offering Pd/ HAC with abundant interpenetrating channels for efficient mass transfer. As a result, Pd/HAC demonstrates outstanding performance in catalytic reduction of 4-NP, with the turnover frequency value up to 1.25 mol4-NP mol-1 min-1, much higher than Pd/SAC (0.92 mol4-NP mol- 1 min-1), even at lower Pd nanoparticles loading (0.551 % vs. 0.573 %). The mesopores/micropores ratio of wood-based activated carbon is considered to be an important parameter affecting the mass transfer process. Pd/HAC also demonstrates superior catalytic stability and reusability, with the shedding degree of decorated Pd nanoparticles much lower than Pd/SAC when subjected to 9 cycles. Hardwood is demonstrated to be a promising activated carbon precursor, and exhibits unique hierarchical porous structure that can highly promotes the catalytic performance in industrial wastewater treatment.