Facile strategy to fabricate palladium-based nanoarchitectonics as efficient catalytic converters for water treatment

Developing facile strategies for anchoring transition-metal nanoparticles (M-NPs) on support materials to make their easy handling, and nascent technologies to advance their applications towards large scale sustainable catalysis are highly demanding. Herein, one-pot strategy is reported for the in-situ immobilization of palladium nanoparticles (Pd-NPs) on highly porous polyurea (PPU). In this approach, Pd acetate (PdAc) solution in tolylene-2,4-diisocyanate (TDI) was gradually added in H₂O/acetone (3/7 wt%) mixture under stirring at ambient conditions, followed by the addition of NaBH₄ to get Pd/PPU. The combined outcomes of characterizations of resulting Pd/PPU by NMR, SEM, ICP-OES, XRD, XPS, TEM, and BET techniques revealed the successful immobilization of uniformly dispersed Pd-NPs (d_mean = 6.2 nm) on PPU having hierarchically porous morphology with specific surface area of 127.13 m²/g. The hybrid composite, Pd/PPU, was used in packed-bed reactor to evaluate its performance as the continuous flow catalytic converter for several toxic organic and inorganic pollutants, as well as their mixture in aqueous medium with the assistance of suitable reductants. The effects of Pd loading, feed concentrations, and permeation flux on the activity of Pd/PPU are discussed. A remarkable permeation flux of 21,000 Lm⁻² h⁻¹ (LMH) with > 99% of pollutant's reduction efficiency and high stability (no change for 20 h used) of Pd/PPU in packed-bed continuous flow catalytic converter were obtained, far better (>10 times) to compare with reported results (2000 LMH) so far. This work therefore provides facile strategy to get PPU-based Pd, a high-performance catalyst for continuous flow reduction of toxic contaminants from wastewaters.