Shellac-coated iron oxide nanoparticles for removal of cadmium(II) ions from aqueous solution.

This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer, a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups, on the surface of iron oxide magnetic nanoparticles. Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm. Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution. Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g. SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions, and cadmium could easily be desorbed using mild organic acid solutions at low concentration.