Controlled synthesis of samarium trifluoride nanoparticles in a water-in-oil microemulsion: Effects of water-to-surfactant ratio on particles and phosphate removal

Abstract

SmF3 nanoparticles with a hexagonal closed pack structure were synthesised by W/O microemulsions of water/Tween 20/1-butanol/toluene. The crystal structure, composition and purity of the sample, as well as the morphology of the produced nanoparticles were studied using Powder X-ray Diffraction, Energy Dispersive X-ray, elemental mapping, Transmission Electron Microscope and Field Emission Scanning Electron Microscope. According to Dynamic Light Scattering study, particle size distribution is governed by the water to surfactant mole ratio (W0), and increasing W0 causes an increase in particle size distribution (PSD). PSD of SmF3 nanoparticles produced at W0 = 50 is the widest compared to W0 = 10. W/O microemulsion method provides formed nanoparticles to attain a spherical form at both W0. The so formed nanoparticles can adsorb phosphate ions from aqueous solution via electrostatic interactions, and their adsorption effectiveness is dependent on particle size and surface area. Small sized nanoparticles, at W0 = 10 removed 98.5% of the phosphate because of its greater surface area while the comparatively larger nanoparticle at W0 = 50 removed 84.5% of the phosphate. The adsorption kinetic data for both W0 are better fitted by pseudo second order model than by pseudo first order model and the calculated equilibrium adsorption capacities is higher for W0 = 10 than for 50. Consequently, this approach yields the most cost effective pure synthesis of high-cost, size and shape controlled rare earth nanoparticles and therefore used in size dependent applied field.