Functional group-assisted green synthesised superparamagnetic nanoparticles for the rapid removal of hexavalent chromium from aqueous solution

Superparamagnetic nanoparticles (NPs) prepared using the capping agent derived from the Lantana camara fruit extract were used to study the adsorption of chromium ions. Characterisation techniques such as scanning electron microscope, energy-dispersive X-ray, Fourier transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer and thermo gravimetric analysis (TGA) were used to study the NP features and adsorption mechanisms. The maximum monolayer adsorption capacity calculated from the Langmuir isotherm was found to be 41mg/g. The chemical nature of the adsorption is confirmed with the results of Dubinin-Radushkevich model and thermodynamic studies. In addition, thermodynamically favourable and spontaneous adsorption is considered to be a good indication for the removal of metal ions. Out of the kinetic models investigated, the experiments exhibited the best fit to pseudo-second-order model, advocating for surface-based adsorption, involving both physical and chemical interactions. It is also significant to note that 85% of the adsorption occurs in the first 10min, and hence the selected adsorbent is also claimed for rapid removal of metal ions. The newly synthesised adsorbent hence possesses remarkable properties in terms of simple synthesising technique, low cost, rapid uptake and improved efficiency without generating harmful byproducts.