Jingwan Huo, Chris Yuan Synthesis and characterization of Fe 3 O 4 -TiO 2 three- dimensional ordered macroporous nano-absorbent material for heavy metal removal Jingwan Huo, Chris Yuan Heavy metal removal processes Solid/liquid separation Absorption High efficiency Low cost Insensitivity to toxic substances Ion exchange Biological removal Figure 1. Schematic of synthesis process of Fe 3 O 4 -TiO 2 magnetic composite for heavy metal removal Mechanism of absorption: Take Cu 2+ for example, its adsorption onto Fe 3 O 4 surface hydroxyl groups in the pH region of 2-6 can be described as below: -FeO - + H + = -FeOH -FeOH + H + = -FeOH 2+ -mFeOH + Cu 2+ = -(Fe-O) m Cu (2-m)+ + mH + Where –FeOH is the surface hydroxyl site. The preparation of Fe 3 O 4 -TiO 2 3DOM absorbent are consist of 3 steps: 1) preparation of 3DOM TiO 2 structure, 2) synthesis of Fe 3 O 4 nanopartilces, 3) assemble Fe 3 O 4 nanoparticles onto 3DOM TiO 2

Methods and Results Figure 2 SEM image of PMMA colloidal crystals Figure 3 SEM image of 3DOM TiO 2 material The large pores have a size of 300 nm, and in each large pores there are three circular windows formed where the PMMA spheres were contacted to each other. PMMA spheres have an average diameter of 310 nm with a narrow distribution, and the spheres were close-packed into an fcc lattice

Results Fe 3 O 4 nanoparicles with size ~40 nm were successfully synthesized through hydrothermal method. From Figure 3 b) and c), Fe 3 O 4 nanoparticles were dispersed onto walls of 3DOM TiO 2 material, and the loading amount need further optimization. Figure 3 SEM image of a) amino-functionalized Fe 3 O 4 nanoparticles, b) Fe 3 O 4 -TiO 2 composite under high magnification, c) Fe 3 O 4 -TiO 2 composite under low magnification Figure 5 Copper ion removal at different pH The capacity of Cu (II) adsorbed was monitored by measuring Cu (II) concentrations of the initial and final solutions, which is shown in Figure 4 below. At pH=10, the Cu (II) removal efficiency reached ~98%