Simona Caprarescu

San copolymer membranes with ion exchangers for Cu(II) removal from synthetic wastewater by electrodialysis.

Heterogeneous membranes were obtained by using styrene-acrylonitrile copolymer (SAN) blends with low content of ion-exchanger particles (5wt.%). The membranes obtained by phase inversion were used for the removal of copper ions from synthetic wastewater solutions by electrodialytic separation. The electrodialysis was conducted in a three cell unit, without electrolyte recirculation. The process, under potentiostatic or galvanostatic control, was followed by pH and conductivity measurements in the solution. The electrodialytic performance, evaluated in terms of extraction removal degree (rd) of copper ions, was better under potentiostatic control then by the galvanostatic one and the highest (over 70%) was attained at 8V. The membrane efficiency at small ion-exchanger load was explained by the migration of resin particles toward the pores surface during the phase inversion. The prepared membranes were characterized by various techniques i.e. optical microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and differential thermal analysis and contact angle measurements.

Separation of Copper Ions from Synthetically Prepared Electroplating Wastewater at Different Operating Conditions using Electrodialysis

The removal of ionic copper from electroplating wastewater was investigated using a five-compartment electrodialysis cell. The experiments were carried out using two different types of ion-exchange membranes (Purolite A500, Purolite PPC100). The effects of initial copper ions concentration, solutions conductivity, solutions pH on the duration of electrodialysis, massic flow (the amount of copper deposited on the cathode lead), and extraction percentage of copper ions were determinated. The electrodialysis unit operates under the constant applied voltage (7.5 V), with the electrolyte recirculation. When initial copper ions concentration is high (4 g/L), the extraction percentage of copper ions increased (>85%). Chemical stability of ion exchange membranes was investigated by Fourier transformed infrared spectroscopy. The results show that the membranes were not damaged during the electrodialysis, after three hours.

Influence of hydrophobic characteristic of organo-modified precursor on wettability of silica film

The objective of this study is to design new hybrid silica materials as templates with hydrophobic properties, prepared at room temperature by a base catalyzed sol–gel process. As silica sources, organoalkoxysilanes functionalized with short hydrophobic chains were used: tetraethylorthosilicate (TEOS), methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), octyltriethoxysilane (OTES) and isobutyltriethoxysilane (iTES). It was shown that hydrophobicity of the functionalized silica nanoparticles increased as a function of length of the aliphatic chains (MTES < iTES < OTES) or when, instead of a hydrophobic alkyl chains (substituting group of silica precursors), a monounsaturated group was used (VTES). It was observed that the samples responded in a specific way to each type (hydrophilic or hydrophobic) of the dropped liquid. Even though the experiments were limited to short hydrocarbon chains, they showed that there is a threshold to reach high hydrophobicity of the hybrid surface.

Considerations on Reducing the Experimental Duration of Electrochemical Impedance Spectroscopy Measurements Used for the Evaluation of Ionic Conductivity in Polymer Electrolyte Membrane Electrolysers and Fuel Cells

In this paper one attempted to discuss the effect of reducing the experimental duration of electrochemical impedance spectroscopy (EIS) measurements by reducing the sampling frequency without affecting the measured parameters. The experimental setup is based on a novel cell consisting of two electrodes or three electrodes cell configuration. The experimental layout allows a precise evaluation of the membrane thickness, at micrometer resolution, during the determination of the electrochemical impedance spectra.