Silica- Iron Oxide Nanocomposite Enhanced with Porogen Agent Used for Arsenic Removal

Georgiana Mladin; Mihaela Ciopec; Adina Negrea; Narcis Duteanu; Petru Negrea; Paula Ianasi; Cătălin Ianași

doi:10.3390/ma15155366

Silica- Iron Oxide Nanocomposite Enhanced with Porogen Agent Used for Arsenic Removal

Materials (Basel). 2022 Aug 4;15(15):5366. doi: 10.3390/ma15155366.

Authors

Georgiana Mladin¹, Mihaela Ciopec¹, Adina Negrea¹, Narcis Duteanu¹, Petru Negrea¹, Paula Ianasi², Cătălin Ianași³

Affiliations

¹ Faculty of Industrial Chemistry and Environmental Engineering, Polytechnic University of Timişoara, Victoriei Square, No. 2, 300006 Timisoara, Romania.
² National Institute for Research and Development in Electrochemistry and Condensed Matter, 144th Dr. A. P. Podeanu Street, 300569 Timisoara, Romania.
³ Coriolan Drăgulescu' Institute of Chemistry, Bv. Mihai Viteazul, No. 24, 300223 Timisoara, Romania.

Abstract

This study aims to remove arsenic from an aqueous medium by adsorption on a nanocomposite material obtained by the sol-gel method starting from matrices of silica, iron oxide and NaF (SiO₂/Fe(acac)₃/NaF). Initially, the study focused on the synthesis and characterization of the material by physico-chemical methods such as: X-ray diffraction, FT-IR spectroscopy, Raman spectroscopy, atomic force microscopy, and magnetization. Textural properties were obtained using nitrogen adsorption/desorption measurements. The zero load point, pHpZc, was also determined by the method of bringing the studied system into equilibrium. In addition, this study also provides a comprehensive discussion of the mechanism of arsenic adsorption by conducting kinetic, thermodynamic and equilibrium studies. Studies have been performed to determine the effects of adsorbent dose, pH and initial concentration of arsenic solution, material/arsenic contact time and temperature on adsorption capacity and material efficiency. Three theoretical adsorption isotherms were used, namely Langmuir, Freundlich and Sips, to describe the experimental results. The Sips isotherm was found to best describe the experimental data obtained, the maximum adsorption capacity being ~575 µg As(III)/g. The adsorption process was best described by pseudo-second order kinetics. Studies have been performed at different pH values to establish not only the optimal pH at which the adsorption capacity is maximum, but also which is the predominantly adsorbed species. The effect of pH and desorption studies have shown that ion exchange and the physiosorption mechanism are implicated in the adsorption process. From a thermodynamic point of view, parameters such as ΔG°, ΔH° and ΔS° were evaluated to establish the mechanism of the adsorption process. Desorption studies have been performed to determine the efficiency of the material and it has been shown that the material can be used successfully to treat a real-world example of deep water with a high arsenic content.

Keywords: adsorption; arsenic; iron oxide; nanocomposite; silica matrix; sol–gel method.

Grants and funding

This work was supported by a grant of the Romanian Ministry of Research, Innovation and Digitalization, project number PFE 26/30.12.2021, PERFORM-CDI@UPT100- The increasing of the performance of the Polytechnic University of Timișoara by strengthening the research, development and technological transfer capacity in the field of “Energy, Environment and Climate Change” at the beginning of the second century of its existence, within Program 1-Development of the national system of Research and Development, Subprogram 1.2-Institutional Performance—Institutional Development Projects-Excellence Funding Projects in RDI, PNCDI III”.