Abstract
A new synthesis method for organic–inorganic hybrid Poly(vinylidene fluoride)-SiO2 cation-change membranes (CEMs) is proposed. This method involves mixing tetraethyl orthosilicate (TEOS) and 3-mercapto-propyl-triethoxy-silane (MPTES) into a polyvinylidene fluoride (PVDF) sol-gel solution. The resulting slurry was used to prepare films, which were immersed in 0.01 M HCl, which caused hydrolysis and polycondensation between the MPTES and TEOS. The resulting Si-O-Si polymers chains intertwined and/or penetrated the PVDF skeleton, significantly improving the mechanical strength of the resulting hybrid PVDF-SiO2 CEMs. The -SH functional groups of MPTES oxidized to-SO3H, which contributed to the excellent permeability of these CEMs. The surface morphology, hybrid structure, oxidative stability, and physicochemical properties (IEC, water uptake, membrane resistance, membrane potential, transport number, and selective permittivity) of the CEMs obtained in this work were characterized using scanning electron microscope and Fourier transform infrared spectroscopy, as well as electrochemical testing. Tests to analyze the oxidative stability, water uptake, membrane potential, and selective permeability were also performed. Our organic–inorganic hybrid PVDF-SiO2 CEMs demonstrated higher oxidative stability and lower resistance than commercial Ionsep-HC-C membranes with a hydrocarbon structure. Thus, the synthesis method described in this work is very promising for the production of very efficient CEMs. In addition, the physical and electrochemical properties of the PVDF-SiO2 CEMs are comparable to the Ionsep-HC-C membranes. The electrolysis of the concentrated CoCl2 solution performed using PVDF-SiO2-6 and Ionsep-HC-C CEMs showed that at the same current density, Co2+ production, and current efficiency of the PVDF-SiO2-6 CEM membrane were slightly higher than those obtained using the Ionsep-HC-C membrane. Therefore, our novel membrane might be suitable for the recovery of cobalt from concentrated CoCl2 solutions.
Highlights
Ion exchange membranes (IEMs) are widely used for industrial separation, energy generation, and water desalination [1,2,3,4,5,6,7,8,9]
Organic–inorganic polyvinylidene fluoride (PVDF)-SiO2 hybrid cation exchange membranes (CEMs) were prepared by the sol-gel method, during which
The initial amount of the MPTES significantly affected the physicochemical and electrochemical properties of the resulting organic–inorganic PVDF-SiO2 hybrid CEMs. -SO3 H functional groups were introduced to the membrane via the oxidation of existing
Summary
Ion exchange membranes (IEMs) are widely used for industrial separation, energy generation, and water desalination [1,2,3,4,5,6,7,8,9]. Materials 2019, 12, 3265 the main property of IEMs, makes all these industrial applications possible and efficient Such membranes belong to a class of dense polymeric membranes with charges present in the polymer matrix, which selectively permits counter-ions while blocking co-ions [10]. During the electrolysis of the concentrated CoCl2 solutions, the CEMs can be damaged by HClO (formed from Cl2 generated at the anode) and by OH and HO2 ·radicals (formed from incomplete reduction of oxygen diffusing through the membranes) [11] This damage might severely affect the ion-exchange point of the membrane, which might lead to lower IEC values and, as a result, poor CEM performance
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