Green synthesis of superparamagnetic maghemite nanoparticles using banana pseudo-stem: a reusable heterogeneous catalyst for Fenton-like degradation of tetracycline antibiotics

Ferric ion-loaded waste banana pseudo stem biomass was successfully converted to superparamagnetic maghemite nanoparticles (MNPs) by a simple one-pot heat treatment in a muffle furnace. But direct calcination of the ferric source, ferric nitrate nonahydrate, produced non-magnetic hematite nanoparticles (HNPs). The newly synthesized dark red iron oxide was characterized by multiple techniques, such as BET, SEM, HR-TEM, VSM, XRD, XPS and FT-IR. Having a high saturation magnetization of 47.17 emu g-1, the polycrystalline oxide had an average crystallite size of 13.38 nm. Apart from being highly dispersible in water and easily separable by an external magnet, it is also found to be very effective in the generation of SO4- radicals from persulphate, which helps efficient degradation of tetracycline (TC) from ideal and real environmental waters like river water, tap water and borewell water. More than 80% of TC is removed from a 50 mg L-1 solution with a very low catalytic dose of 0.05 g L-1. The material is highly stable and retained most of its activity even after five cycles of operation. Ferric ions impregnated in banana pseudo stem biomass are converted to superparamagnetic maghemite nanoparticles (MNPs) which activated persulphate towards the degradation of tetracycline antibiotic.