THE PREPARATION AND PROPERTIES OF SOME FLUORINATED ACTIVATED CARBONS

Granular activated carbons were modified by treatment with fluorine (5% vol in N2) at temperatures below 200-degrees-C. The nature and amounts of any gaseous products formed were dependent upon the type of carbon and the reaction temperature, but in each case the extent of carbon gasification was small. Nitrogen adsorption indicated that fluorination resulted in a progressive reduction in micropore volume and external surface area. Water adsorption-desorption isotherms suggested that the polarity of the carbon surface was not reduced as a consequence of fluorination and also that the modified carbons were unstable. Qualitative differences in the thermal stability of the modified carbons were noticeable, and it was apparent that the bulk of the fluorine was weakly adsorbed. Carbons fluorinated or outgassed below 350-degrees-C were acidic in nature, and liberated iodine from potassium iodide solution. The adsorption of chloropicrin from a humid air-stream by all the modified carbons was poor in comparison to control samples.