Synthesis, characterization of magnetic Fe3O4-chitosan micro/nanoparticles and determination of their Bromothymol Blue removal capacities from aqueous solution

In this study, firstly magnetic nanoparticles (MNP) were synthesized using co-precipitation method and the synthesized particles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA), Dynamic Light Scattering (DLS) and Vibrating Sample Magnetometry (VSM). According to the results, it was seen that the sizes of these nanoparticles are smaller than 10 nm and they exhibit superparamagnetic properties. In the next step, magnetic Fe3O4-chitosan micro/nanoparticles were synthesized using iron oxide nanoparticles. For this purpose, two different methods, ionic gelation and suspension cross-linking, were used and particles, which have different structural, morphological and magnetic properties, were obtained. All of the particles were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), FTIR, TGA, DLS and VSM. According to the characterization results, the particles were classified as the nanoparticles, which was synthesized by ionic gelation method (Fe3O4-KNP1); the nanoparticles (Fe3O4-KNP2) and microparticles (Fe3O4-KMP), which were synthesized by suspension cross-linking method. According to characterization results, it was determined that the Fe3O4-KNP1 have an average diameter size in the range of 85-114 nm depending on the conditions of synthesis, they contain 94.5 % Fe3O4 by weight, the value of saturation magnetization is 46.7 emu/g and they exhibit superparamagnetic characteristics. Besides, it was observed that Fe3O4-KNP2 have an average diameter size in the range of 18-423 nm depending on the conditions of synthesis and contain 52.1 % Fe3O4 by weight. Finally, it was determined that in the size distribution of Fe3O4-KMP ivby volume, the majority of particles are micro-sized beside nano-sized particles and they contain 29.8 % Fe3O4 by weight. Also, in suspension cross-linking method, saturation magnetization significantly reduced by coating the Fe3O4 with chitosan.In the second part of the study, dye adsorption properties of the synthesized three different adsorbents from aqueous solution were investigated. For this purpose, Bromothymol Blue, a dye, was used and the parameters affecting adsorption of Bromothymol Blue (adsorbent dosage, initial Bromothymol Blue concentration, temperature, pH etc.) was investigated. When the optimum adsorption conditions were provided for each adsorbent, the adsorption capacities of Fe3O4-KNP1, Fe3O4-KNP2 and Fe3O4-KMP were 40.7 mg/g, 82.2 mg/g and 193.3 mg/g, respectively.In the final part of the study, after adsorption process, the reusability of the particles was investigated by desorption experiments. It was observed that Fe3O4-KNP1 exhibited higher desorption efficiency than Fe3O4-KNP2 and Fe3O4-KMP.Key Words: Chitosan, Magnetic nanoparticles, Adsorption, Bromothymol Blue