Hollow silica nanoparticles synthesized from core-shell nanoparticles as highly efficient adsorbent for methylene blue and its invitro release: Mechanism and Kinetics study

In this study, hollow silica nanoparticles (HSNPs) were prepared by acidic etching of core of core-shell nanoparticles (ZnSe@SiO2 shell). HSNPs were confirmed from X-ray diffraction (XRD), transmission electron microscope (TEM) and Raman spectroscopy, demonstrating amorphous silica peak, hollow structure, and prominent D1 and D2 Raman peaks of silica. Langmuir and Freundlich model analysis showed adsorption of methylene blue (MB) by HSNPs to be of chemisorption type, with adsorption capacity of 64.06 mg/g. Reaction kinetics was found to be of pseudo-second-order, interparticle diffusion model and Byod's model predicts that adsorption mechanism follows both film and pore diffusion process, and external mass transport phenomenon. Moreover, adsorption study on bare and silica shell coated NPs of ZnSe and CdSe signifies that voids and hollow nature of HSNPs favors more adsorption of MB than its counterparts. Reusability experiments showed > 80% dye adsorption efficiency, after fifth cycle of reuse. Also, MB invitro release study form HSNPs was conducted, and different models like Higuchi, first order kinetic decay, Korsmeyer-Peppas model were applied suggesting a diffusion controlled mechanism of release. This study aims to provide knowledge about dye adsorption and its sustained release mechanism, finding applications in water treatment and invitro delivery process.