Synthesis and Characterization of Porous Magnetite Nanosphere Iron Oxide as a Novel Adsorbent of Anionic Dyes Removal from Aqueous Solution

Abstract

Porous magnetite Fe3O4 nanospheres (PMNs) are synthesized for removal from an aqueous solution of anionic dyes Acid Red 57 (AR57) and Remazol Red (RR) and are used as a high-performance adsorbent. Characterization of PMNs was carried out using various techniques, such as Fourier-transform infrared spectroscopy, the surface area measured by Brunauer Emmett-Teller (BET), and it was found 143.65m2g-1, and were spherical-shaped as determined by TEM. Surface modification was calculated using electron microscopy (SEM) scanning. The spherical morphology of the PMNs is very uniform, with an average particle size of ~25,84 nm in diameter. Variables such as initial pH, the dosage of adsorbent, contact time, and temperature were analyzed to find the optimal adsorption conditions for extracting Acid Red 57 (AR57) and Remazol Red (RR) from aqueous solutions. For respective AR57 and RR, the optimal pH for the extraction of the anionic dyes examined from water solutions was 3 and 4. The maximum adsorption potential expected for AR57 and RR dyes was 888.68 and 808.43 mgg−1, respectively. The effects of the initial solution pH, temperature, initial concentration, contact time, salinity, and dosing of PMNs were systematically analyzed. These dyes were suitable for acid pH adsorption, as the PMNs Zero-charge point (pHPZC) equals 4.3. Adsorption findings were based on the Langmuir, Freundlich, Dubinin – Radushkevich, and Temkin adsorption isotherms. The adsorption isotherm had been found to follow the Langmuir model for both dyes. The mean adsorption energy (Ea) is 20.24 and 31.3 kJmol−1 for AR57 and RR, respectively, indicating a chemisorption process. The adsorption kinetics had been found to follow the pseudo-second-order kinetic model. The adsorption process was verified to be endothermic and spontaneous by thermodynamic studies. Using ethanol as a solvent, it was also studied the process of desorption of the adsorbed anionic dyes.