Fabrication of a recyclable magnetic halloysite-based cobalt nanocatalyst for the efficient degradation of bisphenol A and malachite green

Abstract

Worsening water quality has drawn considerable attention from the scientific fraternity owing to its serious impact on human health and environmental ecosystem. In this regard, magnetic halloysite-based organic–inorganic hybrid materials with a hollow nanotubular structure and surface tunable chemistry have emerged as an excellent platform for the efficient removal of recalcitrant water contaminants. The fabrication of nanocatalyst involves a simple yet versatile covalent immobilization strategy, wherein a chelating ligand, 2-benzoylpyridine (2-BPy) was grafted onto silane-functionalized magnetic halloysite nanotubes with subsequent anchoring of cobalt ions. Various physico-chemical techniques such as FT-IR spectroscopy, P-XRD, VSM, FE-SEM, TEM and XPS provided valuable insights into the crystallinity, magnetic attributes and morphology of the designed nanocomposites. The experimental results indicated that a Co(II)@2-BPy@APTES@MHNTs/H₂O₂ catalytic system not only exhibits immense catalytic potential in accelerating the degradation process but also shows impressive features such as shorter reaction time and ambient reaction conditions. With the assistance of coumarin fluorescent probe technique and radical scavenging studies, the mechanistic pathway has been proposed, and it has been found that in situ generated highly reactive hydroxyl radicals play a crucial role in achieving outstanding degradation efficiency. The kinetic characteristics of the degradation profile demonstrate that pseudo-first-order kinetics is followed with an apparent rate constant of 0.1179 min⁻¹ for BPA and 0.1242 min⁻¹ for MG. Fascinatingly, the splendid magnetic properties of the designed Co(II)@2-BPy@APTES@MHNTs furnished their facile recovery and reusability for nine subsequent runs. Remarkably, the new findings demonstrated here will deepen our understanding of the fabrication and utilization of heterogeneous catalysts for wastewater treatment via a greener approach.