Synthesis Of Iron Oxide Based Magnetic Microspheres And Its Adsorption Properties

In recent years, adsorption is successfully applied in the treatments of wastewater and wastegas. Porous materials with large specific surface area have been the best choice of the adsorbents. Biomaterials is low cost, widely exist in the nature, many for which have natural porous structure and the structure could be preserved intact during calcination. Moreover, LDH is widely used in adsorption field, because of its high surface area, good thermal stability, and interlayer ion interchangeability. But these two kinds of material also exists some problems such as different to recycle after adsorbed. In this word, the iron oxide was introduced to the two kinds of material, the synthetic adsorbent is not only a large specific surface area with the porous structure, but also has a excellent magnetic adsorption performance. The main works include the following two parts:1. The magnetic ?-Fe₂O₃ was synthesized by pine pollen as biological template, and then put it in Mg precursor solution, using hydrothermal method to synthesis MgFe₂O₄/?-Fe₂O₃. The micro morphology and physical properties were characterizated by SEM, TEM, IR, XRD, Raman, surface area analysis, and the adsorption performance of Congo red solution and minocycline solution were studied. SEM displayed that the MgFe₂O₄/?-Fe₂O₃ maintained the original micro morphology of pine pollen. The MgFe₂O₄/?-Fe₂O₃ was successfully synthesized according to analyze the results of XRD, IR, and Raman. The MgFe₂O₄/?-Fe₂O₃ material had bigger surface area and pore volume than ?-Fe₂O₃. The adsorption kinetics equilibrium and thermodynamics of Congo red?CR? and minocycline?MC? onto MgFe₂O₄/?-Fe₂O₃ and ?-Fe₂O₃ were investigated. Adsorption experiments displayed that the as-synthesized magnetic microspheres exhibited excellent adsorption performances. Maximum adsorption capacities of 259.1 mg/g and 200.8 mg/g were obtained for Congo red and minocycline, respectively. The adsorption kinetics and isotherm of Congo red and minocycline onto the as-synthesized samples followed the pseudo-second-order and Langmuir monolayer model, and the adsorption processes were spontaneous and endothermic in nature. The adsorbed samples could be regenerated by methanol or NaOH solution, and easily magnetically seperated from aqueous solution. H-bond formation and electrostatic attractions were conceived as the main adsorption mechanisms of CR, and chemisorption was conceived as the main adsorption mechanism of MC.2. Fe₃O₄ was synthesized using the solvothermal method, then the Fe₃O₄@MgAl-LDH magnetic microsphere was prepared by coprecipitation method. The micro morphology and physical properties were characterizated by SEM, TEM, IR, XRD, surface area analysis, and the adsorption performance of Congo red solution solution was studied. The Fe₃O₄@MgAl-LDH magnetic microsphere was successfully synthesized according to analyze the results of XRD and IR. SEM displayed that the as-prepared novel hierarchically porous Fe₃O₄@MgAl-LDH exhibited vertically/slantly/horizontally oriented platelets-coated morphology. The adsorption kinetics equilibrium and thermodynamics of Congo red?CR? onto the Fe₃O₄, MgAl-LDH and Fe₃O₄@MgAl-LDH magnetic microspheres were investigated. Adsorption experiments displayed that the Fe₃O₄@MgAl-LDH magnetic microspheres exhibited excellent adsorption performances, and the maximum adsorption capacities of Fe₃O₄@MgAl-LDH reached up to 813.0 mg/g. The adsorption kinetics and isotherm of Congo red onto the as-synthesized samples followed the pseudo-second-order and Langmuir monolayer model, and the adsorption processes were spontaneous and endothermic in nature. The adsorbed samples could be regenerated by methanol, and easily magnetically seperated from aqueous solution. Electrostatic attraction and anion exchange were conceived as the main adsorption mechanisms.Thus, the as-synthesized iron oxide based magnetic microspheres is a kind of green, efficient, fast recovery adsorbent.