Low-cost removal of organic pollutants with nickel nanoparticle loaded ordered macroporous hydrogel as high performance catalyst

• A new poly(acrylamide-co-acryl acid) hydrogel with ordered macropores.
• A simple in situ fabrication of nickel nanoparticles under mild conditions.
• High-performance heterogeneous catalyst for removal of nitrophenol from water.
• Good recyclability of catalyst without any complicated regeneration process.

A facile route for the in situ preparation of catalytically active Ni nanoparticles (NPs) in ordered macroporous hydrogel (OMH) has been developed. The hydrogel was fabricated based on polystyrene colloid template. The electronegativity of amide and carboxyl groups on the poly(acrylamide-co-acryl acid) chains of the hydrogel caused strong binding of Ni2+ ions which made them distribute uniformly inside the hydrogel. When immersed in NaBH4 aqueous solution, the Ni2+ ions on the hydrogel were reduced to Ni NPs. The resultant Ni NPs loaded OMH showed good catalytic activity for the reduction of a common organic pollutant, 4-nitrophenol, with NaBH4. A kinetic study of the catalytic reaction was carried out. The rate constant per unit weight could reach 0.53 s−1 g−1, which is much better than many common hydrogel loaded nickel catalysts. Moreover, the current catalyst can be easily separated and recovered with stable catalytic activity.