Abstract
Solid phase extraction using magnetic nanoparticles has represented a leap forward in terms of the improvement of water quality, preventing the contamination of industrial effluents from discharge in a more efficient and affordable way. In the present work, superparamagnetic iron oxide nanoparticles (MNP) with different surface charges are tested as nanosorbents for the removal of chromium(VI) in aqueous solution. Uniform magnetic nanoparticles (~12 nm) were synthesized by a microwave polyol-mediated method, and tetraethyl orthosilicate (TEOS) and (3-aminopropyl) triethoxysilane (APTES) were grafted onto their surface, providing a variation in the surface charge. The adsorptive process of chromium was evaluated as a function of the pH, the initial concentration of chromium and contact time. Kinetic studies were best described by a pseudo-second order model in all cases. TEOS@MNP barely removed the chromium from the media, while non-grafted particles and APTES@TEOS@MNP followed the Langmuir model, with maximum adsorption capacities of 15 and 35 mgCr/g, respectively. The chromium adsorption capacities abruptly increased when the surface became positively charged as the species coexisting at the experimental pH are negatively charged. Furthermore, these particles have proven to be highly efficient in water remediation due their 100% reusability after more than six consecutive adsorption/desorption cycles.
Highlights
Many developed countries have decided to strengthen their environmental policies to minimize water pollution by regulating industrial activities regarding the discharge of hazardous chemicals, including heavy metals, as wastewater into the environment [1,2]
The magnetic nanoparticles (MNPs) were synthesized by a microwave-assisted method that presents greater efficiencies in comparison with other approaches such as thermal decomposition with conventional heating
The X-ray diffraction (XRD) pattern of the MNP was obtained and is displayed in Figure 1d, in which it can be seen that there was no extra reflection of other iron oxide phases such as hematite or iron hydroxides
Summary
Many developed countries have decided to strengthen their environmental policies to minimize water pollution by regulating industrial activities regarding the discharge of hazardous chemicals, including heavy metals, as wastewater into the environment [1,2]. One of the main advantages of this interesting approach is that microwave radiation allows a simple and controlled source of selective heating by ionic conduction and dipolar polarization allows a simple and controlled source of selective heating by ionic conduction and dipolar that takes place at the same time for all of the reaction volume [20] This is a highly reproducible polarization that takes place at the same time for all of the reaction volume [20]. The. MNP were functionalized with silica-based compounds (tetraethyl orthosilicate and (3-Aminopropyl) prepared MNP were functionalized with silica-based compounds (tetraethyl orthosilicate and (3triethoxysilane) to adjust the material surface charge from negative to positive for the removal of Cr(VI).
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