Removal of methylene blue from aqueous solution with magnetite loaded multi-wall carbon nanotube: Kinetic, isotherm and mechanism analysis

doi:10.1016/j.jhazmat.2011.10.041

Journal of Hazardous Materials

Volume 198, 30 December 2011, Pages 282-290

https://doi.org/10.1016/j.jhazmat.2011.10.041 Get rights and content

Abstract

In this study, we have demonstrated the efficient removal of cationic dye, methylene blue (MB), from aqueous solution with the one-pot solvothermal synthesized magnetite-loaded multi-walled carbon nanotubes (M-MWCNTs). The as-prepared M-MWCNTs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopy. The effects of contact time, initial dye concentration, and solution pH on the adsorption of MB onto M-MWCNTs were systematically studied. It was shown that the MB adsorption was pH-dependent. Adsorption kinetics was best described by the pseudo-second-order model. Equilibrium data were well fitted to the Langmuir isotherm model, yielding maximum monolayer adsorption capacity of 48.06 mg g⁻¹. FTIR analysis suggested that the adsorption mechanism was possibly attributed to the electrostatic attraction and π–π stacking interactions between MWCNTs and MB.

Highlights

► M-MWCNTs were synthesized by a facile one-pot solvothermal method and used as an efficient adsorbent for removing toxic dye from aqueous solution. ► The adsorption process was characterized by kinetics and isotherm analysis. ► FTIR analysis was employed to investigate the interactions between M-MWCNTs and dye.

Introduction

Dyes are one of the most hazardous materials in industrial effluents which can cause severe health problems in human beings, since they exhibit high biotoxicity and potential mutagenic and carcinogenic effects [1], [2]. Therefore, the removal of dye from colored effluents has attracted increasing attention. Several technologies including biological treatment, adsorption, coagulation/flocculation, chemical oxidation, membrane separation and ion exchange have been developed [3], [4], [5], [6], [7], [8]. Among these methods, adsorption has been considered to be simple, highly efficient, and ease of operation. A wide range of materials have been reported for dye removal, including activated carbon, zeolite, clay, polymer, etc. [9], [10], [11], [12]. In view of pollutant control at present, it is still indispensible for the development of new adsorbent materials with high adsorption capacities and removal efficiencies.

Recently, carbon nanotubes (CNTs) have attracted great interest as a new type of adsorbent for removing environmental pollutants (e.g. small molecules, heavy metal ions, radionuclides, and organic chemicals) [13], due to their remarkable features of the large specific surface area, hollow and layered structures. However, recovery of this kind of adsorbent usually needs the complicated and time-consuming filtration and/or centrifugation, thus limiting the reusability and increasing the regeneration cost. In this regard, many researchers have focused on combining CNTs and magnetic oxides to create a promising novel adsorbent that possesses adsorptive and magnetic dual functionalities [14], [15], [16], which opens new opportunities for the achievement of desirable adsorption capacity and effective magnetic separation. For example, Luan et al. synthesized CNTs/iron oxide composites by a chemical coprecipitation method with a high performance for the removal of Pb(II) and Cu(II) from water [17]. Gong et al. demonstrated chemical coprecipitation derived MWCNTs/iron oxide composites can efficiently remove cationic dye from aqueous solution [18]. Mishra and Ramaprabhu also employed chemical coprecipitation method to synthesize MWCNTs/magnetite composites for the removal of high concentration of arsenic and desalination of seawater [19]. However, to the best of knowledge, there is little report on the adsorption behavior of the solvothermally synthesized MWCNTs/magnetite composites.

In the present work, we have demonstrated a one-pot solvothermal route to prepare the magnetite (Fe₃O₄)-loaded multi-walled carbon nanotubes (M-MWCNTs) as an efficient adsorbent for the removal of cationic dye, methylene blue (MB), from aqueous solution. The effect of various parameters such as contact time, solution pH and initial dye concentration on the adsorption of MB onto M-MWCNTs was systematically studied. Adsorption isotherm, kinetic and mechanism were also evaluated. Furthermore, the resulting M-MWCNTs presented high magnetic sensitivity under an external magnetic field, providing an easy and efficient way for the separation of adsorbent from aqueous solution.

Section snippets

Materials

FeCl₃·6H₂O, sodium acetate (NaAc), ethylene glycol (EG), methylene blue (MB) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China) and used without further purification. All chemicals used in this study were of commercially available analytical grade. Multi-walled carbon nanotubes were purchased from Shenzhen Nanotech Port Ltd. Co. (Shenzhen, China). The detailed parameters supplied by the manufacturer are as follows: length: 5–15 μm; diameter: 20–40 nm; purity: ≥95%; ash:

Characterization of the adsorbent

Fig. 1 shows the X-ray diffraction (XRD) patterns of MWCNTs, Fe₃O₄ and M-MWCNTs. As for MWCNTs (Fig. 1(a)), the strong diffraction peak at 2θ = 25.8° can be indexed as the (0 0 2) reflection of the hexagonal graphite structure. After loading of Fe₃O₄ (Fig. 1(b)), besides the diffraction peak of MWCNTs, the new peaks at 2θ values of 18.2° (1 1 1), 30.0° (2 2 0), 35.3° (3 1 1), 42.9° (4 0 0), 53.4° (4 2 2), 56.9° (5 1 1), and 62.5° (4 4 0) are observed, which are consistent with the standard XRD data for the cubic

Conclusions

In conclusion, magnetite-loaded multi-walled carbon nanotubes (M-MWCNTs) have been successfully synthesized by a facile one-pot solvothermal method. Adsorption ability of the M-MWCNTs is evaluated by choosing the methylene blue (MB) as an adsorbate. Batch adsorption tests demonstrate that the adsorption is affected by various conditions such as contact time, solution pH and initial dye concentration. Adsorption kinetics follows the pseudo-second-order model. The adsorption process is operated

Acknowledgements

This work was supported by the National Natural Science Foundation of China (21103141), Open Project of Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province (11CSPC-(1-7)), Program for Scientific and Technological Innovative Team in Sichuan Provincial Universities (2010008) and Program for Scientific Research Innovation Team of China West Normal University.

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Removal of methylene blue from aqueous solution with magnetite loaded multi-wall carbon nanotube: Kinetic, isotherm and mechanism analysis

Abstract

Highlights

Introduction

Section snippets

Materials

Characterization of the adsorbent

Conclusions

Acknowledgements

Bioresour. Technol.

J. Hazard. Mater.

Bioresour. Technol.

Desalination

J. Hazard. Mater.

J. Membr. Sci.

Chem. Eng. J.

J. Hazard. Mater.

J. Hazard. Mater.

Desalination

Synth. Met.

Chem. Eng. J.

J. Hazard. Mater.

J. Hazard. Mater.

Carbon

Colloid Surf. A

J. Hazard. Mater.

J. Solid State Chem.

J. Solid State Chem.

Carbon

Mater. Chem. Phys.

Chem. Eng. J.

Desalination

J. Colloid Interface Sci.

J. Environ. Manage.

J. Hazard. Mater.

Desalination