Specific Surface Area of Carbon Materials Based on Hydrated Cellulose and Polyacrylonitrile Fibres Calculated by Sorption and Electrochemical Methods

Abstract

In many sorbates, water, toluene, benzene, n-hexane, the minimum limiting volume of water sorbed by carbon fibre materials is correlated with the minimum saturated vapor pressure and the maximum molecule size. Water at saturated vapor pressure at 20°C is primarily sorbed in the form of (H₂O)₄ clusters whose diameter is 681 pm. The industrially acceptable duration and completeness of desorption are attained at a temperature above the boiling point of the given sorbate but within the limits of the thermal stability of CFM. Electrochemical studies of CFM showed that in polarization in aqueous 0.3% NaCl solution in the range of −0.2 to +0.6 V on the hydrogen scale, the limiting current values are a function of the phase contact area and polarity: in cathodic polarization, the absolute current value in the circuit is much higher than the current in anodic polarization and is higher the more slowly the potential of the CFM changes. The CFM-solution contact area determined with electrochemical measurements is comparable to the specific surface area determined by sorption of saturated water vapors.