Role of CuO in improving NH3 and SO2 capture on nanoporous Fe2O3 sorbents.

In this work, mixed Fe/Cu oxides as sorbents for SO2 and NH3 removal were investigated. Nanoporous iron oxide mixed with 10, 20 and 30 at.% CuO were prepared by thermal decomposition of the corresponding oxalates at 250 °C for 5 h in air. The mixed Fe/Cu oxalates were obtained from the co-precipitation of iron/copper sulfate and ammonium oxalate during ultrasonication. The physical properties of the oxalate precursors and the resulting mixed Fe/Cu oxides were characterized with SEM, TGA-DSC, FTIR, powder XRD and Mössbauer spectroscopy. The porosity was studied by N2 adsorption-desorption isotherms and small angle X-ray scattering. Evenly dispersed CuO hindered the crystallization of Fe2O3, which significantly increased the specific BET surface area from 211 m2/g for Fe2O3 to 354 m2/g for Fe0.8Cu0.2Ox. As a result, SO2 and NH3 adsorption on Fe0.8Cu0.2Ox were enhanced by about 70% compared to Fe2O3. Compared to Fe2O3-impregnated activated carbons, nanoporous Fe0.8Cu0.2Ox could capture five times more SO2 per unit weight, which will be attractive for applications in respirators with lower weight and smaller size.

Novel nanoporous MnOx (x=∼1.75) sorbent for the removal of SO2 and NH3 made from MnC2O4·2H2O.

In this work, nanoporous manganese oxides (MnOx) were prepared by thermal decomposition of MnC2O4·2H2O at 225°C for 6h in air. The manganese oxalate dihydrate precipitate was made from manganese sulfate and ammonium oxalate during ultrasonication and stirring. The physical properties of the oxalate precursors and the resulting MnOx samples were characterized with SEM, TGA-DSC, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point BET and multi-point N2 adsorption-desorption measurements. The amorphous MnOx from oxalate prepared by sonication showed a specific surface area as large as 499.7m(2)/g. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx, especially for SO2, can be increased by increased surface area. Compared to the best Mn3O4-impregnated activated carbon adsorbent, nanoporous MnOx could remove approximately three times as much SO2 and a comparable amount of NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users.

Evaluation of the SO(2) and NH(3) gas adsorption properties of CuO/ZnO/Mn(3)O(4) and CuO/ZnO/NiO ternary impregnated activated carbon using combinatorial materials science methods.

Impregnated activated carbons (IAC) are widely used materials for the removal of toxic gases in personal respiratory protection applications. The combinatorial method has been employed to prepare IACs containing different types of metal oxides in various proportions and evaluate their adsorption performance for low molecular weight gases, such as SO(2) and NH(3), under dry conditions. Among the metal oxides used for the study, Mn(3)O(4) was found to have the highest capacity for retaining SO(2) gas under dry conditions. NiO and ZnO were found to have similar NH(3) adsorption capacities which are higher than the NH(3) capacities observed for the other metal oxide impregnants used in the study. Although Cu- or Zn-based impregnants and their combinations have been extensively studied and used as gas adsorbents, neither Mn(3)O(4) nor NiO have been incorporated in the formulations used. In this study, ternary libraries of IACs with various combinations of CuO/ZnO/Mn(3)O(4) and CuO/ZnO/NiO were studied and evaluated for their adsorption of SO(2) and NH(3) gases. Combinations of CuO, ZnO, and Mn(3)O(4) were found to have the potential to be multigas adsorbents compared to formulations that contain NiO.

SO2 and NH3 gas adsorption on a ternary ZnO/CuO/CuCl2 impregnated activated carbon evaluated using combinatorial methods.

Ternary libraries of 64 ZnO/CuO/CuCl(2) impregnated activated carbon samples were prepared on untreated or HNO(3)-treated carbon and evaluated for their SO(2) and NH(3) gas adsorption properties gravimetrically using a combinatorial method. CuCl(2) is shown to be a viable substitute for HNO(3) and some compositions of ternary ZnO/CuO/CuCl(2) impregnated carbon samples prepared on untreated carbon provided comparable SO(2) and NH(3) gas removal capacities to the materials prepared on HNO(3)-treated carbon. Through combinatorial methods, it was determined that the use of HNO(3) in this multigas adsorbent formulation can be avoided.

Gas adsorption properties of the ternary ZnO/CuO/CuCl(2) impregnated activated carbon system for multigas respirator applications assessed through combinatorial methods and dynamic adsorption studies.

A ternary library of 64 ZnO/CuO/CuCl(2) impregnated activated carbon samples was synthesized and screened automatically using a combinatorial (combi) method. The ability of the samples to adsorb toxic gases was screened gravimetrically. The stoichiometric ratio of reaction (SRR) between the moles of toxicant and the total moles of impregnant was obtained from the calculated mass increase of the samples after chemisorption, with a high SRR indicating high efficiency of toxicant removal. The combi samples that exhibited good dry SO(2) and NH(3) adsorption were prepared in bulk using the incipient wetness method and were evaluated for multigas respirator function by dynamic adsorption studies of SO(2), NH(3), HCN, and C(6)H(12) gases in either dry or humid conditions at ambient temperature. The bulk samples showed equivalent gas adsorption capacities when exposed to the different challenge gases indicating the value of the combi method for initial screening. Cu(2)Cl(OH)(3) was identified to be a potential multigas adsorbent.

Integrating near-edge X-ray absorption fine structure (NEXAFS) microscopy and crystallography: the effects of molecular order.

The carbon K-edge near-edge X-ray absorption spectra (NEXAFS) of oriented single crystals of N,N"-ethylenebis(N'-2-methylphenyl)urea have been recorded using scanning transmission X-ray microscopy (STXM). The single-crystal structure has been determined by X-ray crystallography. A strong polarization dependence (linear dichroism) has been observed and interpreted with the aid of the single-crystal structure and crystal alignment. These results demonstrate the ability of STXM to determine molecular orientation on a submicrometre spatial scale.