Preparation of Iron Oxide Adsorbent Modified by Chitosan Biomaterials and Its Adoption in the Adsorption of Heavy Metals

Abstract

Heavy metals in water leads to many ecological and environmental problems. All kinds of new magnetic adsorbents are used to adsorb the heavy metals in the aqueous solution, which has the advantages of high efficiency, low consumption, simplicity, convenience, and industrialization. Firstly, Fe3O4 is dissolved, and polyethylene glycol (PEG) and anhydrous sodium acetate are added. The dissolved product is placed in the reaction kettle lined with Teflon and reacts at a high temperature to obtain the Fe3O4 magnetic microspheres. The product is dissolved again. After the ultrasonic water bath, 1 mL tetraethyl orthosilicate (TEOS) is added drop by drop to obtain the SiO2/Fe3O4 magnetic microspheres by the ultrasonic and water-bath stirring. The magnetic microspheres are dissolved in 10 mL 3% chitosan solution. Chitosan/SiO2/Fe3O4 (CSF) magnetic adsorbent is obtained after ultrasonic agitation, and chitosan-biomodified iron oxide adsorbent (EDCSF) is obtained by the ethylene diamine tetraacetic acid (EDTA) modification. After the adsorbent is obtained, the biomaterial is characterized, and its performance of adsorbing heavy metals in water is tested as an adsorbent. In the experiment, the Fourier Transform Infrared Spectroscopy (FTIR) is used to verify that EDTA successfully modifies the surface of the CSF magnetic adsorbent. Through the morphology analysis and nitrogen adsorption–desorption test, EDTA cross-linked with the amino group of chitosan through carbodiimide can cause a decrease in the related physical indexes of the material. Thermogravimetric analysis (TGA) and hysteresis loop tests show that although the magnetism of CSF and EDCSF decreases, the solid–liquid separation is achieved in a relatively short time under the action of magnets. In the adsorption test, EDCSF shows an ideal adsorption performance for Cu(II), Cd(II), and Pb(II) in aqueous solution. With pH = 4.7 and at normal temperature, the maximum saturated adsorption capacity of EDCSF for Cu(II), Cd(II), and Pb(II) is 0.696 mmol/g, 0.586 mmol/g, and 0.562 mmol/g, respectively.