The effect of liquid-phase oxidation of porous carbon composite material (PCCM) with nitric acid on its structural and physicochemical characteristics has been investigated. As shown by low-temperature nitrogen adsorption, the oxidation of PCCM with 50 wt.% nitric acid results in a 2-fold decrease in the volume of pores with sizes 4–20 nm and a 1.5-fold increase in the volume of larger pores (20–50 and 50–130 nm). It is shown by Raman spectroscopy that the oxidation of PCCM results in a 6.5-fold decrease in the ID1/IG and ID3/IG ratios, indicating structure ordering and removal of amorphous carbon. Furthermore, the oxidation of PCCM leads to a reduction in the crushing strength of single granules to ca. 80 kg/cm2, representing a 28% decrease compared to the original PCCM.
Knyazheva et al. (Sun,) studied this question.