Stepwise no chemisorption processes on synthetic chrysotile asbestos : tubular crystals with acidic and basic surfaces
Abstract
Nitric oxide adsorption on synthetic chrysotile asbestos has been studied by a gravimetric method and F.t.i.r. spectroscopy at 303 K. The NO adsorptio isotherm on chrysotile had tow steps : the first step at low NO pressure arises from NO adsorption on the outer, basis Mg(OH)2 surfaces of tubular chrysotile crystals, and the second step at high NO pressure from that on the inner, acidic SiO2 surfaces. NO is adsorbed as an NO–2 species on Mg(OH)2 surfaces which gives rise to the pair of absorptions at 1140 and 1280 cm–1, and as an NO–3 species on SiO2 surfaces, which gives rise to the doublet peat at 1380 cm–1. The i.r. band at 1600–1720 cm–1 may be assigned to NO– or physisorbed H2O, produced by the surface reaction of NO with surface hydroxyls. Aslo the effect of surface modification a chrysotile on the NO adsorption supported the stepwise NO adsorption process.