MASS AND SURFACE CHANGES OF ACTIVATED CARBON TREATED WITH NITRIC-ACID- THERMAL-BEHAVIOR OF THE SAMPLES

The mass and surface changes produced when a commercial activated carb on is treated with HNO3 solutions and in the subsequent heat treatment of the resulting samples are investigated. In the preparation of samp les, acid solutions of varying concentration were used. The outgassing , first of activated carbon, and the contact, then of the acid solutio n with the resulting intermediate product, were effected under control led temperature and temporal conditions. The starting carbon and some HNO3-treated samples were examined by Fourier transform-infrared spect roscopy. Brunauer-Emmett-Teller (BET) surface areas were determined by nitrogen adsorption at -196 degrees C. Heat treatments were carried o ut between 30 degrees and 800 degrees C in nitrogen. The oxidation of the activated carbon resulted in a significant mass increase. This was dependent on the method of preparation of the samples. Also, the surf ace chemistry of the activated carbon modified. Additionally, the surf ace area of the carbon underwent slight changes, this textural paramet er increasing for a number of samples. The mass loss in the heat treat ment of the samples was higher than the mass gain produced in their pr eparation. The mass loss was greater in the 30 degrees-180 degrees C r ange than in the 180-500 degrees and 500-800 degrees C ranges. In the various temperature ranges, the mass loss generally increased with inc reasing concentration of the HNO3 solution and the outgassing and cont act temperature or time.