Preparation and characterization of magnetic chitosan nanoparticles and its application for Cu(II) removal

https://doi.org/10.1016/j.cej.2011.01.006Get rights and content

Abstract

The magnetic chitosan nanoparticles were prepared by a simple one-step in situ co-precipitation method and characterized by means of X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier Transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM) and energy dispersive X-ray spectrometer (EDS). The sorption performance of the nanoparticles for removing Cu(II) from aqueous solution was investigated. The experimental results showed that the particles were super-paramagnetic, with the saturation magnetization of about 36 emu/g and the size was in the range of 8–40 nm. The EDS images confirmed the presence of Cu(II) on the surface of magnetic chitosan nanoparticles. The maximum sorption capacity was calculated to be 35.5 mg/g using the Langmuir isotherm model. The mechanism of Cu(II) sorption onto the magnetic chitosan nanoparticles was tentatively proposed.

Introduction

Toxic heavy metal pollution is one of the most significant environmental problems due to their hazards to human being and ecological systems. The treatment methods used for removing metal ions from aqueous solution include physical, chemical and biological technologies. Biosorption, defined as to remove various pollutants from aqueous solution by biological material such as fungi, yeast, algae, etc., has received increasing attention in recent years, because it has several advantages in comparison with physical and chemical methods, such as membrane separation, ion exchange and chemical precipitation [1]. Chitosan is produced from N-deacetylation of chitin, a major component of crustacean shells and fungal biomass and it is readily available from seafood processing wastes. Chitosan, because of its high amino content, has been found to possess good sorption capacity for many heavy metal ions through complexation with the amine groups. It has been widely used as biosorbent for removing various metal ions from wastewater [2], [3].

Magnetic separation technique has some advantages, such as high efficiency, cost-effectiveness. Magnetic carriers are usually composed of the magnetic cores to ensure a strong magnetic response and a polymeric shell to provide favorable functional groups and features for various applications [4], [5], [6].

Compared to the traditional micro-sized magnetic supports used in separation process, nano-sized magnetic carriers possess quite a good performance due to higher specific surface area and lower internal diffusion resistance [7], [8]. In addition, magnetite (Fe3O4) has been widely used as magnetic material due to their excellent magnetic properties, chemical stability and biocompatibility. Therefore magnetic chitosan nanoparticles are a promising biosorbent for removing heavy metals. This material has not only strong metal chelating capability due to presence of the amine and hydroxyl groups in chitosan chain, but also the feature of nano-materials. In addition, due to magnetic properties, it can easily be separated from the sorption system by using magnetic field.

Copper is one of the most common pollutants in industrial effluents. Several industries, for example, dyeing, paper, petroleum, copper/brass plating and copper–ammonium rayon, discharge Cu(II)-containing wastewater. In the copper-cleaning, plating and metal-processing industries, Cu(II) concentration was about 100–120 mg l−1 [9]. It has been a major concern because of its toxicity to aquatic life, human beings and the environment.

Low-cost biosorbents may be an alternative material for wastewater treatment [10], [11], [12], [13], [14]. It would be of great interest to develop a novel biosorbent with a large sorption surface area, less diffusion resistance, higher specific sorption capacity and fast separation for large volumes of solution.

Recently, many researches have reported the preparation of the magnetic chitosan/Fe3O4 composites and their applications for removing metal ions. However, to our knowledge, there have been a few reports on preparation, characterization and adsorption properties of magnetic nanosized chitosan composite adsorbent. For the preparation of magnetic chitosan beads, most of the researchers applied two-step method, and the size of the particles was mostly in micrometer scale.

In this paper, a novel magnetic chitosan nanoparticles was prepared through a simple one-step in situ co-precipitation method. Their performance was characterized, and the sorption property for removing Cu(II) from aqueous solution was investigated.

Section snippets

Chemicals and materials

Chitosan flakes (85% deacetylated) used in the experiments were purchased from Sinopharm Chemical Reagent Co., Ltd., Shanghai, China. FeSO4·7H2O (≥99.0%), FeCl3·6H2O (≥99.0%), CH3COOH (≥99.5%) were purchased from Beijing Modern East Fine Chemical Ltd. NaOH (≥96.0%) was supplied by Beijing Chemical Works. Cu(NO3)2·3H2O (99.0–102.0%) was supplied by Sinopharm Chemical Reagent Ltd.

Synthesis of chitosan–magnetite nanocomposites

Magnetic chitosan nanoparticles were prepared by chemical co-precipitation of Fe2+ and Fe3+ ions by NaOH in the

Preparation of magnetic chitosan nanoparticles

For the preparation of magnetic chitosan beads, two-step method was widely used. The first step is to synthesize Fe3O4 particles, and the second one is to bind them with chitosan. There are two binding methods: verse-phase suspension cross-linking method [16], [17], [18], and precipitation method [6], [19], [20]. The size of the particles was mostly in micrometer scale. Comparing with the verse-phase suspension cross-linking method, the precipitation method is quite simple and facile to be

Conclusions

In this study, a novel magnetic chitosan nano-biosorbent was prepared, characterized and used for the removal of Cu(II) from aqueous solution. The particles size varied from 8 nm to 40 nm, with superparamagnetic property. The equilibrium data could be described by the Dubini–Radushkevich (D–R) and the Langmuir isotherms. The maximum sorption capacity for Cu(II) was calculated to be 35.5 mg/g from the Langmuir isotherm. More than 90% Cu(II) ions adsorbed could be eluated from magnetic chitosan

Acknowledgements

The authors are grateful to the precious comments and careful correction made by anonymous reviewers. The authors also would like to thank the financial support provided the National Natural Science Foundation of China (Grant No. 50830302).

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