Modification of CaCO and CaCO pin-coated cellulose paper under supercritical carbon dioxide-ethanol mixture for enhanced NO capture.

In this work, we examine two modifications of fine-ground calcium carbonate material (GCC) in order to enhanced sorption of NO and subsequent reaction properties toward NO/NO formation by firstly exposing the GCC to supercritical (sc) CO in order to increase particle surface area, a choice specifically made to avoid altering the surface chemistry, and secondly considering the potential advantage of using a surface coupling agent toward NO. The modification by the coupling agent amino silane (AMEO silane) was applied in a supercritical CO-ethanol mixture. The samples were characterised before and after modification by field emission scanning electron microscopy (FESEM), specific surface area determination (BET nitrogen adsorption), ATR-FTIR spectroscopy and ion chromatography to reveal the effects of the surface modification(s) on the morphology, surface textural properties and sorption versus reaction properties with NO. The performance of the treated sorbents for NO capture was evaluated at room temperature. Results show that reactivity of NO with GCC was observed to increase as a function of increased surface area resulting from scCO exposure, but that the presence of AMEO silane on the surface, while enhancing initial adsorption of NO was seen subsequently to act to block reactivity. Thus, judicious use of coupling agent can provide desired rapid initial adsorption of the gas, but the goal of long-term CaCO-consuming reactivity, so as to prolong the uptake of NO beyond surface saturation alone, is achieved by increasing surface area while retaining chemical-free exposed CaCO surface.