Optimization of Preparation of Fe3O4-L by Chemical Co-Precipitation and Its Adsorption of Heavy Metal Ions

Abstract

To address the serious pollution of heavy metals in AMD, the difficulty and the high cost of treatment, Fe 3 O 4 -L was prepared by the chemical co-precipitation method. Based on the single-factor and RSM, the effects of particle size, total Fe concentration, the molar ratio of Fe 2+ to Fe 3+ and water bath temperature on the removal of AMD by Fe 3 O 4 -L prepared by chemical co-precipitation method were analyzed. Static adsorption experiments were conducted on Cu 2+ , Zn 2+ and Pb 2+ using Fe 3 O 4 -L prepared under optimal conditions as adsorbents. The adsorption properties and mechanisms were analyzed by combining SEM-EDS, XRD and FTIR for characterization. The study showed that the effects of particle size, total Fe concentration and the molar ratio of Fe 2+ to Fe 3+ are larger. Obtained by response surface optimization analysis, the optimum conditions for the preparation of Fe 3 O 4 -L were a particle size of 250 mesh, a total Fe concentration of 0.5 mol/L, and a molar ratio of Fe 2+ to Fe 3+ of 1:2. Under these conditions, the removal rates of Cu 2+ , Zn 2+ , and Pb 2+ were 94.52%, 88.49%, and 96.69% respectively. The adsorption of Cu 2+ , Zn 2+ and Pb 2+ by Fe 3 O 4 -L prepared under optimal conditions reached equilibrium at 180 min, with removal rates of 99.99%, 85.27%, and 97.48%, respectively. The adsorption reaction of Fe 3 O 4 -L for Cu 2+ and Zn 2+ is endothermic, while that for Pb 2+ is exothermic. Fe 3 O 4 -L can still maintain a high adsorption capacity after five cycles of adsorption-desorption experiments. Cu 2+ , Zn 2+ and Pb 2+ mainly exist as CuFe 2 O 4 , Zn(OH) 2 , ZnFe 2 O 4 and PbS after being adsorbed by Fe 3 O 4 -L, which is the result of the combination of physical diffusion, ion exchange and surface complexation reaction.