Synthesis and characterization of Fe3O4-TiO2 three-dimensional ordered macroporous nano-absorbent material for heavy metal removal

Jingwan Huo, Chris YuanH

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Solid/liquid separation

Absorption

High efficiency

Low cost

Insensitivity to toxic substancesIon exchange

Biological removal

Figure 1. Schematic of synthesis process of Fe3O4-TiO2 magnetic composite for heavy metal removal

Mechanism of absorption:

Take Cu2+ for example, its adsorption onto Fe3O4 surface hydroxyl

groups in the pH region of 2-6 can be described as below:

-FeO- + H+ = -FeOH

-FeOH + H+ = -FeOH2+

-mFeOH + Cu2+ = -(Fe-O)mCu(2-m)+ + mH+

Where –FeOH is the surface hydroxyl site.

The preparation of Fe3O4-TiO2 3DOM absorbent are consist of 3 steps: 1) preparation of 3DOM TiO2

structure, 2) synthesis of Fe3O4 nanopartilces, 3) assemble Fe3O4 nanoparticles onto 3DOM TiO2

Methods and Results

Figure 2 SEM image of PMMA colloidal crystals

Figure 3 SEM image of 3DOM TiO2 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

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Fe3O4 nanoparicles with size ~40 nm were successfully synthesized through hydrothermal method. From Figure 3 b) and c), Fe3O4 nanoparticles were dispersed onto walls of 3DOM TiO2 material, and the loading amount need further optimization.

Figure 3 SEM image of a) amino-functionalized Fe3O4 nanoparticles, b) Fe3O4-TiO2 composite under high magnification, c) Fe3O4-TiO2

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%