Preparation And Characterization Of Nano-carbon Materials/Polyamide Reverse Osmosis Composite Membranes

Reverse osmosis has become one of the most economical technique in the desalination of seawater and brackish water and it has been developed to a mature stage. With the further development of reverse osmosis technology, the reverse osmosis membranes are expected to be more excellent in performance. It has been hoped to study and prepare the advanced composite membranes with high water flux, reject and low energy consumption. Nanomateirals has become the research focus resently. Carbon nanotubes and nano carbon powder are two different nano-materials with different structure which are made by the same elements. Nanotubes were widely used in many fields because of its one dimensional structure. Modified multi-wall carbon nanotubes were synthesized in this work. The Pristine Multi-wall carbon nanotubes, modified Multi-wall carbon nanotubes and nano carbon powder were dispersed into organic phase or water phase separately for the composite membrane preparation in order to improve the performance of the membrane.The biggest limitation to the application of carbon nanotubes was its disabled dispersion. The problems which include its large aspect ratio, high surface energy, huge molecular weight, and easy to reunite affected its dispersion seriously in solutions or in composite materials. But the problem can be solved by modifying the nanotubes to increase its reactivity. In this paper, a covalent modification method was presented to modify the Multi-wall carbon nanotubes. The multi-wall carbon nanotubes were first treated with mix-acids, than thionyl chloride and ethylene diamine was used to react with treated multi-wall carbon nanotubes separately to introduce acyl chloride groups and amido groups to the carbon nanotubes. The organic groups attached to carbon nanotubes were characterized by FT—IR, SEM, TGA and XRD to make sure if the modification were successful. The surface morphologies of the carbon nanotubes can be observed by SEM. The existence of organic groups through FT—IR spectrogram can make sure that the modification was successful. TGA analysis can be used to quantify the modification and XRD to ensure that the modification do not destroy carbon nanotubes'special structure.The Pristine Multi-wall carbon nanotubes, acyl chloride modified Multi-wall carbon nanotubes, amido modified Multi-wall carbon nanotubes and nano carbon powder were dispersed into organic phase or water phase separately for the composite membrane preparation, and the performance of so formed nano-composite membranes especially water flux was improved markedly, it was improved from 8.58 L/h·m~2 to 23.17 L/h·m~2, 26.26 L/h·m~2, 26.52 L/h·m~2 and 45.20 L/h·m~2 respectively. The surface morphologies of the membranes were observed by scanning electron microscope and it was shown characteristic ridge-and-valley structure, and the surface of the composite membranes were rougher than conventional composite membranes.