Elsevier

Chemosphere

Volume 90, Issue 2, January 2013, Pages 542-547
Chemosphere

Simple in situ functionalizing magnetite nanoparticles by reactive blue-19 and their application to the effective removal of Pb2+ ions from water samples

https://doi.org/10.1016/j.chemosphere.2012.08.025Get rights and content

Abstract

An in situ method for direct attachment of reactive blue-19 onto the surface of magnetite nanoparticles to prepare an efficient adsorbent for removal of Pb2+ ion from water samples was proposed. The produced modified magnetite nanoparticles (MMNP) were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and infrared spectroscopy. The synthesized MMNP showed high adsorption capacity to removal of Pb2+ from wastewater samples. Lead ion adsorption process has been thoroughly studied from both kinetic and equilibrium points of view for adsorbent. The adsorption isotherms were analyzed using the five different isotherm models and correlation coefficients were determined for each isotherm. It was found that the Langmuir isotherm showed better correlation with the experimental data than other isotherms. The adsorption kinetics was tested for the pseudo-first order and pseudo-second order kinetic models at different experimental conditions. The kinetic data showed that the process is very fast and the adsorption process follows pseudo second order kinetic models for modified magnetite adsorbents. Thus, the new nanoparticles are favorable and useful for the removal of this metal ion, and the high adsorption capacity makes them good promising candidate materials for Pb2+ ion removal from water samples.

Highlights

► Magnetite nanoparticles were modified using reactive blue 19. ► In situ functionalizing method was used to the direct attachment of modifier. ► The modified nanoparticles were characterized by different methods. ► The modified nanoparticles was used as an efficient adsorbent for the adsorption of Pb2+. ► The adsorption isotherm and kinetics were investigated using different models.

Introduction

Lead is an element which holds significant importance industrially and has been used by man since ancient times. All lead compounds are considered cumulative poisons. Acute lead poisoning can affect the gastrointestinal track and nervous system. Treatments for lead removal from solution include precipitation, coagulation, and adsorption (Deshpande et al., 2001, Deng et al., 2003, Zhang et al., 2005). The maximum allowable lead in drinking water has been set at a concentration of 15 ppb by the US Environmental Protection Agency (2002). Adsorption of lead from aqueous solutions by synthetic adsorbents is widely used to decrease lead concentration in aqueous solutions (Unob et al., 2007, Mahmoud et al., 2010, Afkhami et al., 2011). The principal success of such inorganic solid surfaces modified with organofunctional groups is the immobilization of the desired reactive atomic group, which causes a great versatility of this surface in developing various functions. The resulting functional materials can work effectively to remove specific toxic metal ions from aqueous media.

Nanometer-sized materials are widely used to the effective adsorption of different chemical species from water samples (Unob et al., 2007, Afkhami and Moosavi, 2010, Itskos et al., 2010, Koukouzas et al., 2010, Afkhami et al., 2011, Madrakian et al., 2011, Madrakian et al., 2012). Magnetic nanoparticles are widely used in the fields of biotechnology and biomedicine (Faye et al., 2004, Yang et al., 2004, Wiekhorst et al., 2006, Afkhami et al., 2010). These particles are superparamagnetic, which means that they are attracted to a magnetic field, but retain no residual magnetism after the field is removed. Therefore, suspended superparamagnetic particles adhered to the target can be removed very quickly from a matrix using a magnetic field, but they do not agglomerate after removal of the field. However, the basic disadvantages of this solid sorbent are the low metal sorption capacity and the lack of selectivity in removal of metal ions, which leads to other species interfering with the target metal ion(s). To overcome this problem, chemical or physical modification of the sorbent surface with some organic compounds, especially chelating ones, is usually used to load the surface with some donor atoms such as oxygen, nitrogen, sulfur and phosphorus (Takafuji et al., 2004). These donor atoms are capable of selective binding with certain metal ions (Zhang et al., 2009). When a modifier is immobilized at the surface of the sorbent, the target metals are not only removed by adsorption on the surface of the metal oxide but could be removed by a surface attraction/chemical bonding phenomenon on the newly added chemicals. Functionalization of magnetic nanoparticles also makes it possible to control their dispersion in an organic or aqueous medium.

Different methods have been reported for functionalizing magnetic nanoparticles using various groups (Rosensweig et al., 1969, Kataby et al., 1998, Rockenberger et al., 1999, Yee et al., 1999, Tadmor et al., 2000, Lu et al., 2003). But due to the hydrolysis in aqueous or protic media these groups are not stable. Recently a novel and facile methodology has been proposed for the in situ surface functionalizing of Fe3O4 nanoparticles, based on the use of diazonium salts chemistry for obtaining strong and stable linkages between the iron oxide nanoparticle surface and the organic coating (Griffete et al., 2011).

In this study, magnetite nanoparticles modified with reactive blue-19 (RB-MMNPs) was synthesized by a novel method. The fabricated adsorbent materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR) analysis. These magnetic nanoparticles were employed in batch process for removal of high concentrations of Pb2+ from water samples. Experimental data obtained from batch equilibrium tests have been analyzed different sorption isotherm models, namely Langmuir, Freundlich, Temkin, Sips and Redlich–Peterson isotherms. Also kinetic investigations were carried out using two kinetic models, pseudo-first order model and pseudo-second order model. On the other hand, the effects of various parameters such as initial concentration of adsorbates, pH of the solutions, and amount of adsorbent and contact time on the adsorption process were studied and interpreted.

Section snippets

Instrumentation

A Metrohm model 713 pH-meter was used for pH measurements. A Shimadzu AA-670 flame atomic absorption spectrophotometer (FAAS) equipped with a deuterium background corrector and a hollow cathode lamp for lead, operated at 5 mA (wavelength 283.3 nm, spectral bandwidth 1 nm) was used for lead measurements. A conventional air-acetylene burner (10 cm slit-fuel/oxidant 2/8) was used. Scanning electron microscope (SEM, VEGA, TESCAN Czech Republic) was used for preparation of SEM images. The crystal

Characterization of the adsorbent

The FT-IR spectra of magnetite nanoparticles, Fe3O4, RB-19 and RB-19 modified magnetite nanoparticles (RB-MMNPs) are presented in Fig. 1. As can be seen, after grafting RB on Fe3O4, a new peak at 1630 cm−1 was appeared that indicated the Cdouble bondC stretching of aromatic ring of RB-19 on the Fe3O4. At 1400.27 and 1384.95 cm−1 wavenumbers the Ssingle bondO groups were present, the peak at 3390 cm−1 corresponding to the Nsingle bondH stretching of RB-19 disappeared and the peak at 3400 cm−1 corresponding to Osingle bondH stretching was

Conclusion

In this study new modified, nanometer-sized RB-MMNPs has been prepared by a new in situ functionalizing method and the results indicated that the modified nanoparticles, could be used as an effective adsorbent for the removing of Pb2+ from water samples and the suggested method for in situ modification of magnetite nanoparticles is quite effective for this purpose. After the equilibrium, adsorption data were fitted with different isotherm models, the higher correlation factors of Langmuir model

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