Preparation and Application of Amino-Terminated Hyperbranched Magnetic Composites in High-Turbidity Water Treatment

Abstract

In order to separate the colloidal in high-turbidity water, a kind of magnetic composite (Fe₃O₄/HBPN) was prepared via the functional assembly of Fe₃O₄ and an amino-terminal hyperbranched polymer (HBPN). The physical and chemical characteristics of Fe₃O₄@HBPN were investigated by different means. The Fourier Transform infrared spectroscopy (FTIR) spectra showed that the characteristic absorption peaks positioned at 1110 cm^-1, 1468 cm^-1, 1570 cm^-1 and 1641 cm^-1 were ascribed to C-N, H-N-C, N-H and C=O bonds, respectively. The shape and size of Fe₃O₄/HBPN showed a different and uneven distribution; the particles clumped together and were coated with an oil-like film. Energy-dispersive spectroscopy (EDS) displayed that the main elements of Fe₃O₄/HBPN were C, N, O, and Fe. The superparamagnetic properties and good magnetic response were revealed by vibrating sample magnetometer (VSM) analysis. The characteristic diffraction peaks of Fe₃O₄/HBPN were observed at 2θ = 30.01 (220), 35.70 (311), 43.01 (400), 56.82 (511), and 62.32 (440), which indicated that the intrinsic phase of magnetite remained. The zeta potential measurement indicated that the surface charge of Fe₃O₄/HBPN was positive in the pH range 4-10. The mass loss of Fe₃O₄/HBPN in thermogravimetric analysis (TGA) proved thermal decomposition. The -C-NH₂ or -C-NH perssad of HBPN were linked and loaded with Fe₃O₄ particles by the N-O bonds. When the Fe₃O₄/HBPN dosage was 2.5 mg/L, pH = 4-5, the kaolin concentration of 1.0 g/L and the magnetic field of 3800 G were the preferred reaction conditions. In addition, a removal efficiency of at least 86% was reached for the actual water treatment. Fe₃O₄/HBPN was recycled after the first application and reused five times. The recycling efficiency and removal efficiency both showed no significant difference five times (p > 0.05), and the values were between 84.8% and 86.9%.

Keywords: Fe3O4; coating; hyperbranched polymer; magnetic separation; water treatment.

Figure 1

FTIR spectra of Fe₃O₄ and Fe₃O₄/HBPN.

Figure 2

X-ray diffraction pattern of Fe₃O₄/HBPN.

Figure 3

X-ray photoelectron spectra (XPS) of Fe₃O₄ and Fe₃O₄/HBPN in the survey scan (a) and high-resolution XPS spectra of Fe 2p (b), C 1s (c), N 1s (d) and O 1s (e) peaks on the surfaces of Fe₃O₄/HBPN.

Figure 3

X-ray photoelectron spectra (XPS) of Fe₃O₄ and Fe₃O₄/HBPN in the survey scan (a) and high-resolution XPS spectra of Fe 2p (b), C 1s (c), N 1s (d) and O 1s (e) peaks on the surfaces of Fe₃O₄/HBPN.

Figure 4

SEM images of Fe₃O₄ (a–c) and Fe₃O₄/HBPN (d–f).

Figure 5

Thermogravimetric curves of Fe₃O₄ and Fe₃O₄/HBPN.

Figure 6

Magnetization hysteresis loops of Fe₃O₄ and Fe₃O₄/HBPN.

Figure 7

Zeta potential of Fe₃O₄ and Fe₃O₄/HBPN.

Figure 8

The effect of different dosages on kaolin suspension treatment at diverse times (a) and fixed times (b). (Ph = 5.6, kaolin suspension concentration was 1.0 g/L, magnetic field intensity was 3800 G).

Figure 9

The effect of different pH on kaolin suspension treatment (the dosage was 2.5 mg/L, kaolin suspension concentration was 1.0 g/L, magnetic field intensity was 3800 G).

Figure 10

The treatment effect of different kaolin concentrations (the dosage was 2.5 mg/L, pH = 5.6, magnetic field intensity was 3800 G).

Figure 11

The effect of different magnetic fields intensity on kaolin suspension treatment (the dosage was 2.5 mg/L, pH = 5.6, kaolin suspension concentration was 1.0 g/L).

Figure 12

The actual water application effect in two lakes of Fe₃O₄/HBPN (the dosage was 2.5 mg/L, and the magnetic field intensity was 3800 G).

Figure 13

The recycling (a) and reusing (b) effect of Fe₃O₄ and Fe₃O₄/HBPN (pH = 5.6, kaolin suspension concentration was 1.0 g/L, magnetic field intensity was 3800 G).