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Abstract: We have developed activated carbon membranes (ACM) that can remove not only particulate matters but also dissolved organic matters. Recently, we succeeded in growing carbon whiskers on activated carbon membranes (W-ACM). We hypothesize that the whiskers prevent the flux from lowering due to particle blocking on the membrane surface. In this study, we compared the filtration properties and blocking characteristics of ACM and W-ACM using an artificial microsphere (polymethyl methacrylate) (PMMA), particle diameter=0.8, 5, and 10μm) to estimate the effect of whiskers on particle filtration. We found that the whiskers successfully prevented a reduction of penetration flux in all particle diameters; however, the prevention mechanism seems to be different according to the filtrated particle size. To clarify the mechanism, we performed numerical model analysis using a microfiltration model. In the case of 0.8μm particle filtration, whiskers seemed to inhibit the packing of particles into the microholes existing at the surface of activated carbon membrane, and with 5–10μm particle filtration, the packing density of the cake layer accumulated on the membrane would be reduced with the appearance of whiskers. [Copyright &y& Elsevier]

An 80-cm long tubular carbon coated membrane was fabricated by chemical vapor deposition (CVD) of methane on a multilayered porous ceramic substrate at a temperature of 1000 °C. The deposition of pyrocarbon on the membrane generated a carbon film, the nature of which not only reduced the pore size of the membrane but also changed the physical properties of the membrane, including its hydrophobicity, electrical conductivity, and thermal conductivity. To ensure a uniform deposition of carbon on the membrane, a CVD apparatus equipped with process piping was employed to periodically reverse the direction of the gas flow in the reactor. The CVD experiments were then conducted by varying parameters such as the rate of flow of the gas mixture (methane and nitrogen), the percentage concentration of methane, and so on. To analyze the uniformity of the carbon film, we measured the electrical resistance of the membrane and the permeation of six gases through the sectioned membranes. In the range of our study, it was found that the flow rate of the gas mixture and the alternation of the direction of the gas flow were two important factors for determining the uniformity of the carbon deposit in the membranes. Observation by scanning electron microscope (SEM) and measurement of the nitrogen permeation of the membranes revealed that fabrication of uniform carbon coated ceramic membranes with a desired pore size is possible for applications involving microfiltration, ultrafiltration, and nanofiltration. In addition, the utilization of the superior properties of the membranes such as hydrophobicity and electrical conductivity were suggested for enhancing the degree of separation of the membranes. [Copyright &y& Elsevier]