Research paperInfluence of magnetic field on the adsorption of organic compound by clays modified with iron
Graphical abstract
Introduction
Pigments and dyes are disposed into wastewaters from various industries, mainly by the textile production (Fatimah et al., 2010, Hai et al., 2011). They are a serious problem when dealing with textile waste because they are water soluble, chemically and photolytically stable (Guimarães et al., 2012). Effluents containing dyes must not be disposed in natural bodies, because they do not allow solar light penetration and decrease the dissolved oxygen amount, damaging aerobic processes (Banković et al., 2012).
Clays have been used by humanity since ancient times for manufacturing, ceramic objects, and more recently in several technological applications. Clay has also become indispensable to modern life; it is the material of many kinds of applications and they are abundant in nature, inexpensive and environmentally friendly (Bergaya et al., 2006, Carretero and Lagaly, 2007). Their structural properties can be modified by simple methods such as pillaring, to produce materials with higher surface area, porosity, thermal stability and greater capacity for adsorption and/or degradation of contaminants (Bergaya et al., 2006, Kurian et al., 2012, Tong et al., 2009).
The pillared clays, also cited by the abbreviation PILC (Pillared InterLayered Clays), have achieved considerable interest in their use as catalysts and adsorbents in recent years (Gil et al., 2011). The pillarization promotes an increase in basal spacing and surface area, which provides better accessibility of the molecules to the active sites present inside of the clay structure (Gil et al., 2011, Yang et al., 2013). The list pertaining to the engineering and application of these materials is extensive; there are several publications with different aspects of the theme in the recent literature.
Materials containing iron, like iron oxide pillared clay, become very interesting when they display magnetic attraction in combination with high specific surface area. Furthermore, iron is usually employed for adsorbents fabrication, because of the low cost (Mubarak et al., 2013). These represent an innovative and promising class of new materials for removal of contaminants such as organic dyes (Banković et al., 2012, Hou et al., 2010) and contaminants in aqueous media (Mubarak et al., 2013, Rivagli et al., 2014, Zhang et al., 2010). In addition, attention was focused on utilizing magnetic materials (such as magnetite and magnetite silica composites) for wastewater treatment (Ferroudj et al., 2013, Tuutijärvi et al., 2009, Wu et al., 2012, Yu and Yang, 2010) mainly because of simplicity and speed of separation when these materials are used with aqueous media.
In this work a simple and rapid synthesis was performed for obtaining modified clay with magnetic iron phases exposed. Furthermore, the modified materials were tested for their ability to remove the organic dye methylene blue (MB) from an aqueous medium. The possibility of improving the removal process by implementing a magnetic field was also evaluated.
Section snippets
Materials and methods
The cation exchange capacity (CEC) of montmorillonite, determined by the ammonium acetate method, is 1.75 mEq/g. Mineralogical composition showed the presence of 5 wt.% of quartz and 10 wt.% of feldspar. Through chemical analysis it was determined that the principal exchangeable cation is sodium and the following is the chemical composition:M1.41 (Al0.20 Si7.80)IV (Al2.69 Fe0.15 Mg1.11 Mn0.02)VI O20 (OH)4
Structural characterization
The FTIR spectra of the clays are presented in Fig. 2. A strong absorption in the region around 3600 cm− 1 for the montmorillonite corresponds to the stretching of the hydroxyl groups and cations in the octahedral sheet. In these modified materials, this absorption appears overlapped with another in the region of 3400 cm− 1 that is related to the presence of adsorbed water on the surface of the clays. Also in 1645 cm− 1 the band can be ascribed to the vibration of water molecules (Zhao et al., 2012).
Conclusions
In this work, a montmorillonite was modified with iron; different heat treatments were responsible for the formation of materials with different characteristics and different iron phases. The magnetic clay was obtained by heat treatment in open furnace, and XRD indicated that the phase of iron present in this material is maghemite.
All clays showed high adsorption capacity of methylene blue, and the magnetic field positively influenced adsorption. For those which had no magnetism, the field
Acknowledgements
We greatly appreciate the Chemistry and Exact Science Departments of the Federal University of Lavras (UFLA), also the funding organizations for this project, National Counsel of Technological and Scientific Development (CNPQ) and Higher Education Co-ordination Agency (CAPES).
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