Synthesis, Characterization, and Modification of Alumina Nanoparticles for Cationic Dye Removal

Abstract

In the present study, alumina nanoparticles (nano-alumina) which were successfully fabricated by solvothermal method, were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), and Brunauer⁻Emmett⁻Teller (BET) methods. The removal of cationic dye, Rhodamine B (RhB), through adsorption method using synthesized nano-alumina with surface modification by anionic surfactant was also investigated. An anionic surfactant, sodium dodecyl sulfate (SDS) was used to modify nano-alumina surface at low pH and high ionic strength increased the removal efficiency of RhB significantly. The optimum adsorption conditions of contact time, pH, and adsorbent dosage for RhB removal using SDS modified nano-alumina (SMNA) were found to be 120 min, pH 4, and 5 mg/mL respectively. The RhB removal using SMNA reached a very high removal efficiency of 100%. After four times regeneration of adsorbent, the removal efficiency of RhB using SMNA was still higher than 86%. Adsorption isotherms of RhB onto SMNA at different salt concentrations were fitted well by a two-step model. A very high adsorption capacity of RhB onto SMNA of 165 mg/g was achieved. Adsorption mechanisms of RhB onto SMNA were discussed on the basis of the changes in surface modifications, the change in surface charges and adsorption isotherms.

Keywords: Adsorption isotherm; Alumina nanoparticles; Rhodamine B; SDS; Two-step model.

Figure 1

Chemical structures of Rhodamine B (RhB) (A) and sodium dodecyl sulfate (SDS) (B).

Figure 2

XRD pattern of synthesized γ-Al₂O₃ nanoparticles.

Figure 3

The FT-IR spectra of synthesized γ-Al₂O₃ nanoparticles.

Figure 4

TEM image of synthesized γ-Al₂O₃ nanoparticles.

Figure 5

Adsorption isotherm of N₂ onto synthesized nano-alumina.

Figure 6

Adsorption of SDS onto synthesized nano-alumina at different NaCl concentrations.

Figure 7

The effect of pH on RhB removal using synthesized nano γ-Al₂O₃ without SDS modification (Ci (RhB) = 10⁻⁶ M and with SDS modification (Ci (RhB) = 10⁻⁴ M).

Figure 8

The effect of contact time on RhB removal using synthesized nano γ-Al₂O₃ without SDS modification (Temperature 25 ± 2 °C, C_i (RhB) = 10⁻⁶ M and with SDS modification (C_i (RhB) = 10⁻⁴ M).

Figure 9

The effect of adsorbent dosage on RhB removal using synthesized nano γ-Al₂O₃ without SDS modification (C_i (RhB) = 10⁻⁶ M) and with SDS modification. (C_i (RhB) = 10⁻⁴ M).

Figure 10

Adsorption isotherms of RhB onto SDS modified nano γ-Al₂O₃ (SMNA) at different NaCl concentrations. The points are experimental data while solid lines are fitted by a two-step adsorption model.

Figure 11

The ζ potential of synthesized nano γ-Al₂O₃, SDS modified nano γ-Al₂O₃ (SMNA), and SMNA after RhB adsorption in 1 mM NaCl (pH 4).

Figure 12

The FT-IR spectra of SDS modified nano γ-Al₂O₃ (A) and SMNA after RhB adsorption (B).

Figure 13

Removal efficiency of RhB using SMNA after four regenerations. Error bars show standard deviation of three replicates.