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Kinetics and Thermodynamic Study on Novel Modified–Mesoporous Silica MCM-41/Polymer Matrix Nanocomposites: Effective Adsorbents for Trace CrVI Removal

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posted on 26.06.2017, 11:33 authored by Mohammad Dinari, Roozbeh Soltani, Gholamhossein Mohammadnezhad
It is no longer news that the world is in the midst of a freshwater crisis, with the future health of both humans and the environment being threatened by heavy metal pollution. Accordingly, attempts at removing the toxic heavy metals from water are attracting considerable attention around the world. As a result, for the first time, amine-modified MCM-41/polymer matrix nanocomposites (m-MCM-41/PMNCs) have been applied to remove hexavalent chromium species (CrVI) from aqueous solution. Poly­(methyl methacrylate), poly­(vinyl alcohol), nylon-6, and polystyrene, which are environmentally benign and economically accessible polymer matrices, were used for fabricating four different types of m-MCM-41/PMNCs. Owing to the abundance of chemically active functional groups on the surface of these m-MCM-41/PMNCs, excellent adsorption performance was observed. Maximum metal removal was observed at low pH (2–3) and with the efficiency of CrVI removal being in the range of 61.78–85.71%. The kinetic modeling and equilibrium isotherm data were analyzed, and the results showed that various adsorption mechanisms, depending on the type of polymers, may occur. Also, the computed thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, suggested that the adsorption of CrVI onto the m-MCM-41/PMNCs is an endothermic, spontaneous, and physical adsorption process.