Nitrogen adsorption and X-ray scattering on porous carbons derived from polyethyleneterephthalate by nitric acid treatment

摘要

Surface functionalisation by nitric acid is a means of increasing the interaction of activated carbon with polar molecules.rnThe purpose of the present study is to examine the effects on the morphology of such chemical treatment. Measurementsrnare reported on activated carbon prepared from polyethyleneterephthalate (PET) and treated with nitric acid both at roomrntemperature and at the boiling point of the suspension. The BET surface area of the resulting material was studied byrnnitrogen adsorption. The (micro)porous character is described using the DR, HK and DFT approaches. Small angle andrnwide angle X-ray scattering (SAXS and WAXS) measurements were performed on the same samples.rnIt was found that the products obtained after room temperature acid treatment are similar, with a BET surface area in thernneighbourhood of 1200 m2/g. However, the high temperature acid treatment produces a major decrease both in thernsurface area and in the microporosity, accompanied by a decrease in the helium density.rnAll samples were found to be amorphous, with no detectable crystalline order. The upper end of the SAXS response,rnhowever, reveals significant short range ordering in the region q≥1 nm-1, where the microporous structure contributes tornthe scattering. This feature, which is probably associated with the distance between basic structural units (BSUs), isrnmodified when the material is mechanically ground. Its presence modifies the apparent Guinier radius deduced from thernSAXS data.rnIn all cases the ratio of the BET surface area to the apparent surface area obtained from fitting the SAXS curves isrnapproximately 50 %. For the sample treated with hot acid, however, this ratio is 30 %, suggesting that regions withrninaccessible voids preferentially survive the attack.