A new method for incorporating polyethyleneimine (PEI) in algal beads: High stability as sorbent for palladium recovery and supported catalyst for nitrophenol hydrogenation

Abstract The incorporation of glutaraldehyde crosslinked polyethylenimine (PEI) in algal beads (ABA/PEI) increases its Pd(II) sorption capacity. However, the large size of dispersed agglomerates introduces limitations of sorption performance in terms of availability and accessibility of reactive groups. The homogeneous incorporation of PEI in alginate/algal mixture prior to inotropic gelation and glutaraldehyde crosslinking (HABA/PEI) improves sorption performance: HABA/PEI beads have a higher maximum sorption capacity (1.49 ± 0.02 mmol g −1 ) than ABA/PEI (1.13 ± 0.03 mmol g −1 ), probably due to more uniform dispersion of PEI in HABA/PEI beads. The comparison of 5 consecutive cycles of sorption-desorption shows that HABA/PEI beads are physically stable with no mass loss, while ABA/PEI bead loses up to 30% of its weight. The potential of these materials as precursors for the synthesis of supported catalysts has been investigated. Pd(II) sorbed on ABA/PEI and HABA/PEI has been reduced to Pd(0) using hydrazine hydrate or hydrogen gas (generated in situ). A simple hydrogenation reaction of 3-nitrophenol (with sodium formate as hydrogen donor) was tested for comparing their catalytic properties. Catalytic tests show that HABA catalyst exhibits similar catalytic activity, but better stability and reusability compared with ABA catalyst. Their rate constants are lower than conventional nanostructured catalysts, probably due to intra-diffusion limitation.