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Abstract. Carbon dioxide (CO 2 ) injection into deep geologic formations could decrease the atmospheric accumulation of this gas from anthropogenic sources. Furthermore, by co-injecting H 2 S or SO 2 , the products respectively of coal gasification or combustion, with captured CO 2 , problems associated with surface disposal would be mitigated. We developed models that simulate the co-injection of H 2 S or SO 2 with CO 2 into an arkose formation at a depth of about 2 km and 75°C. The hydrogeology and mineralogy of the injected formation are typical of those encountered in Gulf Coast aquifers of the United States. Six numerical simulations of a simplified 1-D radial region surrounding the injection well were performed. The injection of CO 2 alone or co-injection with SO 2 or H 2 S results in a concentrically zoned distribution of secondary minerals surrounding a leached and acidified region adjacent to the injection well. Co-injection of SO 2 with CO 2 results in a larger and more strongly acidified zone, and alteration differs substantially from that caused by the co-injection of H 2 S or injection of CO 2 alone. Precipitation of carbonates occurs within a higher pH (pH > 5) peripheral zone. Significant quantities of CO 2 are sequestered by ankerite, dawsonite, and lesser siderite. The CO 2 mineral-trapping capacity of the formation can attain 40-50 kg/m 3 medium for the selected arkose. In contrast, secondary sulfates precipitate at lower pH (pH < 5) within the acidified zone.Most of the injected SO 2 is transformed and immobilized through alunite precipitation with lesser amounts of anhydrite and minor quantities of pyrite. The dissolved CO 2 increases with time (enhanced solubility trapping). The mineral alteration induced by injection of CO 2 with either SO 2 or H 2 S leads to corresponding changes in porosity. 2Significant increases in porosity occur in the acidified zones where mineral dissolution dominates. With co-injection of SO 2 , the porosity increases from an initial 0.3 to 0.43 after 100 years. However, within the CO 2 mineral-trapping zone, the porosity decreases to about 0.28 for both cases, because of the addition of CO 2 mass as secondary carbonates to the rock matrix. Precipitation of sulfates at the acidification front causes porosity to decrease to 0.23. The limited information currently available on the mineralogy of naturally occurring high-pressure CO 2 reservoirs is generally consistent with our simulations.

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New host lattice materials whose red phosphors for white LEDs have been investigated in the ternary system Ca 3 N 2 -AlN-Si 3 N 4 , just as Ca 2 Si 5 N 8 and CaSiN 2 : Eu were found in the binary system Ca 3 N 2 -Si 3 N 4 . A new red phosphor of CaAlSiN 3 : Eu which is effectively excited by blue-GaN and near UV-GaInN LED chips has been synthesized at 1600 °C for 2 h and subsequently at 1800 °C for 2 h under nitrogen pressure of 1 MPa. The host-compound has an orthorhombic structure with the space group Cmc2 1 (No. 36), which is isotypic with LiSi 2 N 3 and NaSi 2 N 3 . The red phosphor showed the emission peak around 650 nm which was assinged to 5d → 4f of Eu 2+ ion, and its color coordinates were estimated to be 0.667 and 0.327. The optimum concentration of Eu 2+ ion was 1.6 mol%. The phosphor also had a high chemical stability, high quantum output, and especially a good thermal property compared to the other phosphors, Ca 2 Si 5 N 8 :Eu 2+ and CaSiN 2 :Eu 2+ . CaAlSiN 3 :Eu 2+ maintained 83% of the initial efficiency above 150 °C.

The permeability of nine different polyimide membranes to H2, N2, O2, CH4, and CO2 has been determined at 35°C and at applied pressures of up to 9 atm. The dianhydride monomers used for the synthesis of the polymides were PMDA and 6FDA, whereas the diamine monomers were ODA, BDAF, and p‐PDA. The selectivities of the 6FDA polymides toward CO2 relative to CH4 are higher than those of the PMDA polyimides at comparable CO2 permeabilities. Both types of polyimides exhibit significantly higher CO2/CH4 selectivities than more common glassy polymers, such as cellulose acetate, polysulfone, and polycarbonate. The selectivities of the PMDA and 6FDA polyimides to O2 relative to N2 are of the same magnitude and generally higher than those of common glassy polymers with similar O2 permeabilities. The polymides are more permeable to N2 than to CH4, whereas the opposite is true for many other glassy polymers. Possible factors responsible for the above behavior, such as segmental mobility, mean interchain distance, and formation of charge transfer complexes, are examined. The relevance of the study to the development of more highly gas‐selective and permeable membranes for the separation of gas mixtures is also discussed.