Fabrication of Ag/halloysite nanotubes/Fe3O4 nanocatalyst and their catalytic performance in 4-nitrophenol reduction

Ag/halloysite nanotubes/Fe3O4 (Ag/HNTs/Fe3O4) nanocatalyst was synthesized in our work. The structure of the as-prepared composite catalyst was that Fe3O4 nanoparticles with the size of 5.0–8.0 nm were loaded in the internal hollow lumen of HNTs and Ag nanoparticles with a mean diameter of 20 nm were randomly deposited on the external surface of HNTs/Fe3O4. The resultant Ag/HNTs/Fe3O4 exhibited satisfied catalytic activity (with conversion of 100% in 38 min) to the reduction of 4-nitrophenol (4-NP) with sodium borohydride. The catalytic activity was markedly enhanced when the catalysts concentration was increased (the rate constant was gradually increased from 0.40 to 20.18 × 10−3 s−1). Also, the advantage of the obtained magnetic composite catalyst in terms of their fast separation and simple reuse was identified through five successive catalytic and separation process cycles. It could be concluded that Ag/HNTs/Fe3O4 showed satisfied catalytic activity, recoverability, and reusability, which showed great potential for practical application for water treatment.