The synthesis and application of the SiO2@Fe3O4@MBT nanocomposite as a new magnetic sorbent for the adsorption of arsenate from aqueous solutions: Modeling, optimization, and adsorption studies

Sheikhmohammadi, Amir and Dahaghin, Zohreh and Mohseni, Seyed Mohsen and Sarkhosh, Maryam and Azarpira, Hossein and Atafar, Zahra and Abtahi, Mehrnoosh and Rezaei, Shoheila and Sardar, Mahdieh and Masoudi, Hassan and Faraji, Majid and Nazari, Shahram and Rokhsane Hosseini, Pouya and Almasian, Mohammad (2018) The synthesis and application of the SiO2@Fe3O4@MBT nanocomposite as a new magnetic sorbent for the adsorption of arsenate from aqueous solutions: Modeling, optimization, and adsorption studies. JOURNAL OF MOLECULAR LIQUIDS, 255. pp. 313-323. ISSN 0167-7322

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Abstract

This study was conducted for the purpose of showing that the mercaptobenzothiazole (MBT)-functionalized SiO2@Fe3O4 nanocomposite can be applied as a new adsorbent for the adsorption of As (V) ions from aqueous solutions. SiO2@Fe3O4@MBT synthesized via a two-stage process was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), the transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). The SEM showed good adsorbing capacity for SiO2@Fe3O4@ MBT due to the average core size 40 nm with a vast surface. The appearance of bands attributed to the C-H stretch of methylenes of the alkyl chain in FTIR analysis showed SiO2@Fe3O4 was successfully modified by MBT. The XRD spectrum clearly demonstrates the occurrence of two phases of iron oxide/hydroxide and silica oxide, and also the spinal structure of SiO2@Fe3O4@ MBT reveals the presence of SiO2, by revealing the specific peaks at 2 theta = 26.62, 39.44, 42.41, 54.83.The TEM micrograph of SiO2@Fe3O4@ MBT showed the Fe3O4 nanopartide anchored on SiO2 and formed a large amount of Fe3O4 with different size. Surface area of SiO2@Fe3O4@ MBT was investigated and determined 5835 m(2)/g. Response surface methodology (RSM) was employed to model the effects of the operating parameters, such as pH (2-8), adsorbent dosage (10-100 mg L-1), initial As (V) concentration (1-10 mg L-1), and contact time (2-180 min) using the R software. Based on the results obtained from the analysis of variance (ANOVA), the reduced full second-order model demonstrated satisfactory adjustment with the experimental data. The Solver "Add-ins" were applied using the effective parameters to optimize important operating variables. The optimum operating points were established at the initial As (V) concentration of 10 mg L-1, the adsorbent dosage of 82.7 mg L-1, the time of 169.1 min, and the pH of 5.07, corresponding to the maximum predicted As (V) removal percentage of 93.89%. Based on the reported results, the experimental isotherm data best fit the Freundlich model rather than the other isotherms. The maximum adsorption capacities calculated from the Langmuir equation were 10.38, 11.35, and 17.5 mg g(-1) for 291 K, 301 K and 311 K. The followed kinetic model was the pseudo-first order kinetic model in nature and intraparticle diffusion was the dominant mechanism. (C) 2018 Elsevier B.V. All rights reserved.

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