Microstructure formation phenomena in phase inversion membranes

Most structural studies of polymeric phase inversion membranes have focused on macrovoid formation, while the rich microstructure (size scale < 5 μm) has received little independent attention. We present a classification and qualitative description of possible microstructures on the basis of phase diagram, kinetic, and connectivity considerations. Special attention is given to the microstructural features resulting from a two-stage phase separation. Subsequently, our considerations are extended to the microstructure of the skin and that of the macrofinger boundaries. Finally, the features of actual phase inversion microstructures are described and interpreted

Hybrid [polysulfone-Zero Valent Iron] membranes: Synthesis, characterization and application for As^III remediation

Hybrid polysulfone membranes decorated with Zero Valent Iron (ZVI) nanoparticles were prepared and evaluated for AsIII uptake. The hybrid polysulfone/ZVI membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), mercury intrusion porosity measurements, thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The membranes are characterized by a macroporous structure with ZVI particles dispersed both inside the pores as well as at their surface. Electron Paramagnetic Resonance (EPR) spectroscopy reveals that the surface sulfide groups of polysulfone are readily accessible by extrinsic CuII cations. Moreover the polysulfone/ZVI membranes have a considerable electron-donating capacity to surface-adsorbed atoms, thus they are able to reduce CuII to CuI, and inhibit oxidation of ZVI from Fe0 to Fe3+. As a result, the Zero Valent Iron particles are stabilized against oxidation by ambient air and show appreciable AsIII adsorption capacity (26.6mgg-1). This renders them a significant stability, thus they can be reused at least four times for AsIII adsorption with a loss less than 1% of their As-uptake capacity. Based on a theoretical Surface Complexation Model we provide a consistent interfacial/structural picture that describes quantitatively all observed phenomena