Facile solvothermal synthesis of Fe3O4/magnetic grapefruit peel for adsorptive removal of congo red, humic acid and phosphate from aqueous solutions

An environment-friendly and economical magnetic composite, namely Fe3O4/GP, was produced from grapefruit peel (GP) and ferric chloride via the solvothermal method in one easy step, and was used to remove Congo red (CR), humic acid (HA), and phosphate (P) from aqueous solutions. The Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscope (SEM) procedures and specific surface area and zeta potential determination were applied to describe the structure of Fe3O4/GP composite. The results shown the Fe3O4 particles, which fabricated during the solvothermal reaction, were distributed evenly on the surface of GP. Then Fe3O4/GP composite also presented a high level of magnetism, and thus could be separated quickly from suspension by an external magnet. The adsorption efficiencies of Fe3O4/GP for CR, HA, and P were 92.88%, 47.45%, and 99.02%, which were found uninfluenced by the initial solution pH and attained the equilibrium state within 10 min. The kinetic and isothermal tests were performed and the data were consistent with the pseudo-second-order kinetic equation and the Freundlich model.