Continuous flow synthesis of phosphate binding h-BN@magnetite hybrid material

Abstract

Hexagonal boron nitride (h-BN) is rendered magnetically responsive in aqueous media by binding superparamagnetic magnetite nanoparticles 8.5–18.5 nm in diameter on the surface. The composite material was generated under continuous flow in water in a dynamic thin film in a vortex fluidic device (VFD) with the source of iron generated by laser ablation of a pure iron metal target in the air above the liquid using a Nd:YAG pulsed laser operating at 1064 nm and 360 mJ. Optimum operating parameters of the VFD were a rotational speed of 7.5k rpm for the 20 mm OD (17.5 mm ID) borosilicate glass tube inclined at 45 degrees, with a h-BN concentration at 0.1 mg mL⁻¹, delivered at 1.0 mL min⁻¹ using a magnetically stirred syringe to keep the h-BN uniformly dispersed in water prior to injection into the base of the rapidly rotating tube. The resulting composite material, containing 5.75% weight of iron, exhibited high phosphate ion adsorption capacity, up to 171.2 mg PO₄³⁻ per gram Fe, which was preserved on recycling the material five times.