title: Isotope microscopy visualization of the adsorption profile of 2-methylisoborneol and geosmin in powdered activated carbon.
abstract: Decreasing the particle size of powdered activated carbon may enhance its equilibrium adsorption capacity for small molecules and micropollutants, such as 2-methylisoborneol (MIB) and geosmin, as well as for macromolecules and natural organic matter. Shell adsorption, in which adsorbates do not completely penetrate the adsorbent but instead preferentially adsorb near the outer surface of the adsorbent, may explain this enhancement in equilibrium adsorption capacity. Here, we used isotope microscopy and deuterium-doped MIB and geosmin to directly visualize the solid-phase adsorbate concentration profiles of MIB and geosmin in carbon particles. The deuterium/hydrogen ratio, which we used as an index of the solid-phase concentration of MIB and geosmin, was higher in the shell region than in the inner region of carbon particles. Solid-phase concentrations of MIB and geosmin obtained from the deuterium/hydrogen ratio roughly agreed with those predicted by shell adsorption model analyses of isotherm data. The direct visualization of the localization of micropollutant adsorbates in activated carbon particles provided direct evidence of shell adsorption.
authors.affiliation: Faculty of Engineering, Hokkaido University , N13W8, Sapporo 060-8628, Japan.
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Matsui
authors.forename: Asuka
authors.initials: A
authors.lastname: Sakamoto
authors.forename: Soichi
authors.initials: S
authors.lastname: Nakao
authors.forename: Takuma
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Taku
authors.initials: T
authors.lastname: Matsushita
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Shirasaki
authors.forename: Naoya
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Hisayoshi
authors.initials: H
authors.lastname: Yurimoto
mesh_terms: D000327:Adsorption; D001892:Camphanes / Q000737:chemistry / Q000302:isolation & purification*; D002247:Carbon Isotopes; D002606:Charcoal / Q000737:chemistry*; D008853:Microscopy / Q000379:methods*; D009284:Naphthols / Q000737:chemistry / Q000302:isolation & purification*; D010316:Particle Size; D011208:Powders; D013696:Temperature
chemical_list: D001892:Camphanes; D002247:Carbon Isotopes; D009284:Naphthols; D011208:Powders; D002606:Charcoal; C005536:2-methylisoborneol; C001278:geosmin