Efficient removal of methylene blue dye using cellulose capped Fe3O4 nanofluids prepared using oxidation-precipitation method

Unfixed dyes discharged into water bodies by textile industries is a major concern. Cellulose capped magnetite nanoparticles in the size ranging from 21 to 41 nm have been synthesized using oxidation-precipitation method by varying the reaction temperature and used for cationic dye removal. The particle size is tuned by adding appropriate amount of carboxymethyl cellulose at the nucleation stage, thereby controlling steric hindrance. The synthesized particles were characterized by X-ray powder diffraction, transmission electron microscopy, dynamic light scattering, atomic force microscope, vibrating sample magnetometer, phase contrast optical microscopy, UV-vis spectroscopy, Fourier transform infrared spectroscopy, thermo gravimetric analysis and differential scanning calorimeter. The crystallite size is found to increase with increasing reaction temperature due to poor sorption of polymers on nanoparticle at elevated temperatures and faster particle growth. The HRTEM images show lattice fringes run across the entire flower shaped particle, indicating lattice-oriented attachment of multiple primary nanocrystals. The FTIR spectra indicate that the interaction of carboxylate of cellulose with magnetite is bidentate chelating. The cellulose capped particles were found to be efficient for methylene blue dye removal. The underlying sorption mechanisms were evaluated by different models and the adsorption results were best described by Dubinin-Radushkevich (D-R) isotherms model for microporous material. The observed value of mean free energy of the adsorption per mole, of similar to 0.56 kJ/ mol, indicates that the methylene blue is physisorbed on cellulose capped nanoparticles. The influence of concentration of adsorbate, size of particles, time and adsorption mechanism were also studied along with reusability studies by recycling experiments. This approach of tuning particle size close to superparamagnetic limit, through the oxidation precipitation, provides a new platform for efficient magnetic separation technology.