Exclusion of heavy cations from wastewater using activated carbon/NiFe2O4 nanocomposite prepared via co-precipitation method

mahdi ranjeh ¹ (Ph.D. student (Institute of Nano Science and Nano Technology, University of Kashan, Kashan) , Chemist in university of semnan)
Mehdi Mousavi-Kamazani ² (New Technology Faculty, Semnan University, Semnan, Iran.)

Submited date : 2018-08-21 accepted date : 2018-09-29

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Exclusion of heavy cations from wastewater using activated carbon/NiFe2O4 nanocomposite prepared via co-precipitation method

 

Abstract

First, crystalline NiFe2O4 powder was synthesized on a nanoscale dimension by a simple one-step co-precipitation chemical route, and then used to produce activated carbon/NiFe2O4 nanocomposite. The structure and morphology of the as-prepared composite was characterized by X-ray diffraction (XRD) pattern, transmission electron microscope (TEM) and fourier transform infrared (FT-IR) spectroscopy. Eventually, the as-prepared composite was used for exclusion of heavy cations from wastewater in different conditions. A significant absorption capacity (250 mg g-1) showed that this nanocomposite could be useful for the removal of heavy cations from wastewater.

 

Keywords: Carbon/NiFe2O4, Nanocomposite, Heavy cation, Exclusion

 

Introduction

The ecological crisis of environmental pollution has been blamed on different issues. Pollution due to metals or their species in the environment is the major one. Heavy metal pollution affects flora, fauna and other abiotic components of the ecosystem [1]. Many attempts have been made to remove them, which can be mentioned to "Low-cost adsorbents for heavy metals uptake from contaminated water: a review" [2]. Nano crystalline ferrites which possesses a general formula MFe2O4 (M = divalent metal ion, e.g. Ni, Co, Cu, Mn, Mg, Zn, Cd, etc.) is one of the most attractive class of materials for technological applications. Nickel ferrite has been intensively investigated as one of the magnetic nanomaterials. Nickel ferrite (NiFe2O4) has an inverse spinel structure. The location of the divalent cations (Ni2+) in the crystal structure is closely related to the magnetic properties of the nickel ferrite. However, nickel ferrite shows super-paramagnetic behaviour and it has various applications such as gas-sensor, magnetic fluids, catalysts, magnetic storage systems, photo magnetic materials, magnetic resonance imaging, site-specific drug delivery and microwave devices [3–11]. In one case, the removal of divalent cations of nickel and lead, and the oxyanions of hexavalent chromium was tested by the developed adsorbents. The adsorption equilibrium and kinetics data are fitted to various models to evaluate and compare the performance with an activated carbon [12]. In other case, the magnetic and electrical response of the sol-gel synthesized NiFe2O4 nanoparticles have investigated. Changes in the impedance plane plots with temperature have been discussed and correlated to the microstructure of material. Thermally activated hopping carriers between Fe3+-Fe2+ and Ni2+-Ni3+ ions have been determined for a decrease in the resistance of the sample and a change in the conduction mechanism around 318 K [13]. Chinnasamy et al. have shown that Nano crystalline NiFe2O4 exhibits a mixed spinel structure with Ni2+ ions occupying both (A) and (B) sites. NiFe2O4 nanoparticles with a mixed spinel structure have been shown to exhibit interesting electrical, magnetic, gas, and humidity sensing properties [14]. Nano-sized NiFe2O4 is one type of ferrite that has been studied extensively. It shows peculiar structural and magnetic properties. Small particle size promotes a mixed spinel structure whereas the bulk form is an inverse spinel. As far as the magnetic properties of these materials are concerned, spin glass like behavior can be considered as the most interesting property that leads to high field irreversibility, shift of the hysteresis loops, and anomalous relaxation dynamics [15]. In this work, we describe a new process based on the use of co-precipitation technique for the synthesis of pure NiFe2O4 nanoparticles and activated carbon/NiFe2O4 nanocomposite. Also we investigated the exclusion of heavy cations from wastewater. It is worth noting that in our opinion, we have not achieved good efficiency in the previous methods, but in our method, there was a good efficiency and less material was used, which is economically feasible.

 

Experimental

Materials and physical measurements

Fe(NO3)3.9H2O (Merck), Ni(NO3)2.6H2O (Aldrich), NaOH (Merck), and ethanol (Merck) were used as received. X-ray diffraction (XRD) patterns were recorded by a Philips-X’PertPro, X-ray diffractometer using Ni-filtered Cu Kα radiation at scan range of 10<2θ<80. Transmission electron microscopy is carried out using a model Philips EM208 field emission transmission electron microscope operated at 100 kV. Fourier transform infrared (FT-IR) spectra were obtained on Magna-IR, spectrometer 550 Nicolet with 0.125 cm-1 resolution in KBr pellets in the range of 400-4000 cm-1.

Synthesis of NiFe2O4 nanoparticles

2 g of NaOH was dissolved in 100 cc of distilled water and heated to boiling point. Then, a 50 cc solution of Fe(NO3)3.9H2O (5.494 g) and Ni(NO3)2.6H2O (1.977 g) in water was prepared and added to the boiling solution. The mixture solution was then refluxed at 100 °C for 2.5 h. Finally, the resulting product was separated from water and dried at 90 °C for 10 h.

Preparation of activated carbon/NiFe2O4 composite

Activated carbon/NiFe2O4 composite was synthesized by a facile refluxing route in solution of NaOH. In a typical procedure a certain amount of activated carbon was added into 150 mL alkaline solution containing 3.4 g sodium hydroxide, and stirred at room temperature for 35 min to get the activated carbon suspension. The suspension was then maintained at 120 °C to keep boiling state. 50 mL metal nitrate solution (aqueous) was prepared by dissolving Fe(NO3)3.9H2O (5.494 g) and Ni(NO3)2.6H2O (1.977 g) in distilled water. The solution was poured as quickly as possible into the above boiling suspension. The mixture solution was then refluxed at 100 °C for 2.5 h. By a simple magnetic procedure the resulting product was separated from water and dried at 90 °C for 10 h.

Removal of heavy cations by activated carbon/NiFe2O4 composite

For this work, 0.1 g of activated carbon/NiFe2O4 composite were added to 25 ml of a 50 ppm solution of heavy cations and stirred for 5 h. The solution was then smooth and reached 100 cc with 1% nitric acid. Ultimately, absorption was read by AAS (Atomic Absorption Spectroscopy). The results of the studies are shown in the Table 1.

 

Results and discussions

Fig. 1 shows XRD pattern of the as-synthesized NiFe2O4 nanoparticles. The diffraction peaks observed in Fig. 1 are in good agreement with cubic phase of NiFe2O4 (space group fd3m and JCPDS: 10-0325). The sharp and strong diffraction peaks in Fig. 1 indicate that the as-prepared product is well crystallized. Also, no diffraction peaks from other species such as Fe2O3 or NiO could be detected, which indicates the obtained sample is pure. The crystallite size diameter (D) of the as-obtained products has been calculated by Scherer equation [16]:

                                                                                                                           (1)

where D is the crystallite size, as calculated for the (hkl) reflection, k is the wavelength of Cu Kα radiation (0.154 nm), k is a constant related to the crystal shape (0.94), and β is the value of full width at half-maximum intensity (FWHM). Crystallite sizes of the as-prepared NiFe2O4 particles has been found to be 21 nm. The lattice constants of all the samples are calculated using the following relation [17, 18]. 

a = dhkl(h2 + k2 + l2)1/2

The values are in good agreement with earlier reported values of 0.833 nm for nano NiFe2O4 [19] and 0.8339 nm for the bulk NiFe2O4 [20], which prove the efficiency of our synthesis technique.

The FT-IR spectra of the as-prepared NiFe2O4 and activated carbon/NiFe2O4 nanocomposite are presented in Figs. 2a and b, respectively. A broad absorption band at about 3400 cm-1 represents a stretching mode of H2O molecules and OH groups [21, 22]. Two other principle absorption bands in the range of 400 - 600 cm-1 are also observed in the FT-IR spectra. The first band is around 500 cm-1 and the second one is around 585 cm-1, which are attributed to the long bond length of oxygen metal ions in the octahedral sites and shorter bond length of oxygen metal ions in the tetrahedral sites in the spinel structure, respectively [23]. The band of 1135 cm-1 in Fig. 2b shows the connection of NiFe2O4 to surface of activated carbon. The morphology of the as-prepared nanocomposite was investigated by TEM image. As shown in Fig. 3. It can be seen that NiFe2O4 particles deposited on the surface of activated carbon in the composite are uniform with the particle size in the range of 20–30 nm.

The effect of adsorption of nickel ferrite (NiFe2O4) nanoparticles and activated carbon/NiFe2O4 nanocomposite on heavy cations in different conditions were investigated. Here, the removal of Ag+, Cu2+, Zn2+, and Cd2+ ions from wastewater was evaluated. The results of the studies are presented in Table 1. According to the Table 1, it can be said that the absorption of copper by both nanoparticles and nanocomposite is higher than others, which may be due to a smaller ionic radius of copper. According to Table 2, the size of ion radii is as follows:

Cu2+﹥Zn2+﹥Cd2+﹥Ag+

With a smaller ionic radius more surface absorption can be expected. Another important point is that the empty nanoparticles have better efficiencies than composite and this can be attributed to the reduction of the hydroxyl group on the surface of the composite. The presence of hydroxyl groups is crucial for the absorption of cations. These groups are reduced by compositing and hence the reduction of efficiency can be attributed to this. NaCl molestation in present of heavy cations was also investigated. As can be seen, the absorption of Cd2+ ions in the presence of sodium ion has declined sharply and this is due to the occupation of the surface of the nanoparticles with sodium ions.

 

Conclusions

Summary, nickel ferrite and activated carbon/NiFe2O4 nanocomposite was synthesized by a simple co-precipitation method. The structure and morphology of the as-prepared composite was characterized by XRD, TEM, and FT-IR spectroscopy. The absorption of heavy ions by these synthetic materials was then investigated. According to the results, the nickel ferrite has a better absorption than its composite with active charcoal. The size of the ions affects the absorption rate and smaller ions are more absorbed. The presence of inhibitory ions is also important, and sodium ion strongly reduces the absorption of cadmium cations.

 

Acknowledgements

This research work has been supported by Department of Chemistry, Semnan University, Semnan, Iran.

 

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