CNT/PVP blend PVDF membranes for the removal of organic pollutants from simulated treated wastewater effluent

Abstract

In this work, we established a simple and effective way of immobilizing CNT onto polyvinylidene fluoride (PVDF) membrane by casting dual-layer membranes. We explored two different methods of dual-layer casting: (i) layer by layer and (ii) simultaneous dual layer fabrication. The influence of these methods on the characteristics of the prepared membranes were investigated. The hydrophilicity of the top surface was ensured by blending appropriate quantity of polyvinyl pyrrolidone (PVP) into the polymer dope so that the feed water and its organic pollutant content have adequate contact with the membrane surface containing the CNT. Dynamic contact angle data revealed that CNT blend PVDF membranes were highly hydrophilic when compared to their pristine counterparts. Single layer and simultaneous cast double layer blend membranes showed bigger pores (∼10 μm), whereas layer-by-layer cast double layer blend membrane showed acceptable lower mean pore size (∼0.25 μm). Adsorption experiments were done using methylene blue (MB) as a model adsorbate. Composite membranes performed better in the removal of MB, while also showing high rate of filtration. This was achieved due to better membrane wettability, more open structure and higher concentration of CNT on the top surface of the blend membranes. An almost complete desorption of MB off the membrane surface was successfully accomplished using ethanol solution at a pH of 2, indicating the possible cyclic application of these membranes.