Amine impregnated porous silica gel sorbents synthesized from water-glass precursors for CO2 capturing

In this work, porous silica gel-solid beads have been made from economically affordable water-glass precursors via sol-gel nano casting technique. A stable nanometric silica sol was prepared first from water glass and studied for surface potential and sol to gel transition. A free-flow, injectable gel was obtained upon aging the sol which was then assembled into spherical silica beads in a chemical bath. A surface area of 304.7m2g-1 was obtained for water glass derived silica gel beads. These gel beads were impregnated with 3-aminopropyltrimethoxysilane (APTMS) and polyethylenimine (PEI) active functional groups at different percentages for turning the gel beads as sorbents for CO2 gas adsorption. The effect of amine loading on the thermal stability, morphology as well as porosity was studied and was correlated with CO2 adsorption values. Depending upon the amount of amine loaded in the gel support CO2 uptake was found varied. These amine modified silica gel porous adsorbents showed CO2 adsorption capacity at temperatures as low as 100°C; samples modified with 15wt% PEI had CO2 adsorption capacity of 1.16mmolg-1 at 50°C. © 2015 Elsevier B.V

Germanium-incorporated lithium silicate as highly efficient low-temperature sorbents for CO2 capture

© 2018 The Royal Society of Chemistry. Carbon dioxide emission from massive point sources such as industries and power plants is perceived to be a major contributor towards global warming and associated climate changes. Although lithium silicate has the highest capacity for CO2sorption (8 mmol g-1), it is kinetically limited during the sorption process, particularly at temperatures below 500 °C. Herein, we report a facile strategy for the development of germanium-incorporated lithium silicate composites, which display enhanced CO2absorption capacity as well as kinetics in the temperature range of 150-680 °C. The absorption capacity of 324 mg g-1at the rate of 117 mg g-1min-1was measured at 680 °C, and 49 mg g-1at the rate of 36 mg g-1min-1was measured at 300 °C for samples with a Si:Ge molar ratio of 1:0.183. This study thus highlights the possibility of employing germanium-incorporated lithium silicates for the absorption of CO2at a wide range of temperatures, including the in situ removal of CO2from chemical and petrochemical reactions, such as the water-gas shift reaction occurring at low temperature ranges of 150-450 °C, that has hitherto been not possible with pure Li4SiO4

Investigation of the mechanism of chromium removal in (3-aminopropyl)trimethoxysilane functionalized mesoporous silica

We are proposed that a possible mechanism for Cr(VI) removal by functionalized mesoporous silica. Mesoporous silica was functionalized with (3-aminopropyl)trimethoxysilane (APTMS) using the post-synthesis grafting method. The synthesized materials were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), N-2 adsorption-desorption analysis, Fourier-transform infrared (FT-IR), thermogravimetric analyses (TGA), and X-ray photoelectron spectroscopy (XPS) to confirm the pore structure and functionalization of amine groups, and were subsequently used as adsorbents for the removal of Cr(VI) from aqueous solution. As the concentration of APTMS increases from 0.01 M to 0.25 M, the surface area of mesoporous silica decreases from 857.9 m(2)/g to 402.6 m(2)/g. In contrast, Cr(VI) uptake increases from 36.95 mg/g to 83.50 mg/g. This indicates that the enhanced Cr(VI) removal was primarily due to the activity of functional groups. It is thought that the optimum concentration of APTMS for functionalization is approximately 0.05 M. According to XPS data, NH3+ and protonated NH2 from APTMS adsorbed anionic Cr(VI) by electrostatic interaction and changed the solution pH. Equilibrium data are well fitted by Temkin and Sips isotherms. This research shows promising results for the application of amino functionalized mesoporous silica as an adsorbent to removal Cr(VI) from aqueous solution

Unbiased surveys of dust-enshrouded galaxies using ALMA

The ALMA lensing cluster survey (ALCS) is a 96-hr large program dedicated to uncovering and characterizing intrinsically faint continuum sources and line emitters with the assistance of gravitational lensing. All 33 cluster fields were selected from HST/Spitzer treasury programs including CLASH, Hubble Frontier Fields, and RELICS, which also have Herschel and Chandra coverages. The total sky area surveyed reaches $\sim$133 arcmin$^2$ down to a depth of $\sim$60 $\mu$Jy beam$^{-1}$ (1$\sigma$) at 1.2 mm, yielding 141 secure blind detections of continuum sources and additional 39 sources aided by priors. We present scientific motivation, survey design, the status of spectroscopy follow-up observations, and number counts down to $\sim$7 $\mu$Jy. Synergies with JWST are also discussed.Comment: 6 pages, 4 figures, Proceedings of the 7th Chile-Cologne-Bonn-Symposium: Physics and Chemistry of Star Formation, V. Ossenkopf-Okada, R. Schaaf, I. Breloy (eds.

A Radio-to-mm Census of Star-forming Galaxies in Protocluster 4C23.56 at Z = 2.5:Gas Mass and Its Fraction Revealed with ALMA

We investigate gas contents of star-forming galaxies associated with protocluster 4C23.56 at z = 2.49 by using the redshifted CO (3-2) and 1.1 mm dust continuum with the Atacama Large Millimeter/submillimeter Array. The observations unveil seven CO detections out of 22 targeted Hα emitters (HAEs) and four out of 19 in 1.1 mm dust continuum. They have high stellar mass ({M}\star > 4× {10}10 M ⊙) and exhibit a specific star-formation rate typical of main-sequence star-forming galaxies at z˜ 2.5. Different gas-mass estimators from CO (3-2) and 1.1 mm yield consistent values for simultaneous detections. The gas mass ({M}{gas}) and gas fraction ({f}{gas}) are comparable to those of field galaxies, with {M}{gas}=[0.3,1.8]× {10}11× ({α }{CO}/(4.36× A(Z))) {M}⊙ , where {α }{CO} is the CO-to-H2 conversion factor and A(Z) is the additional correction factor for the metallicity dependence of {α }{CO}, and < {f}{gas}> =0.53+/- 0.07 from CO (3-2). Our measurements place a constraint on the cosmic gas density of high-z protoclusters, indicating that the protocluster is characterized by a gas density higher than that of the general fields by an order of magnitude. We found ρ ({H}2)˜ 5× {10}9 {M}⊙ {{Mpc}}-3 with the CO(3-2) detections. The five ALMA CO detections occur in the region of highest galaxy surface density, where the density positively correlates with global star-forming efficiency (SFE) and stellar mass. Such correlations possibly indicate a critical role of the environment on early galaxy evolution at high-z protoclusters, though future observations are necessary for confirmation

Surface engineered silica mesospheres – A promising adsorbent for CO2 capture

Carbon dioxide adsorption capacities of amine modified sol-gel SiO2 mesospheres were evaluated. The sorbents were prepared from readily available sodium metasilicate via sol-gel process. Three amines were used for surface modification purpose, namely Tetraethylenepentamine (TEPA), Tetraethylenepentamine acrylonitrile (TEPAN) and a mixture of Aminopropyltrimethoxysilane (APTMS) coupled with the two amines individually. The sorbents were characterized and carbon dioxide adsorption studies at 50 and 75 °C were conducted. CO2 adsorption isotherms of the functionalized samples at both the temperatures showed that the sorbents coupled with APTMS gave better adsorption performance than with individual amines. The sample with mixture of APTMS and TEPA showed the best performance among the samples studied with a CO2 adsorption capacity of 3.26 mmol g-1 at 75 °C. The TEPAN immobilized sorbents exhibited faster kinetics at both the temperatures of 50 and 75 °C; henceforth it appears that in addition to the amine content present in the sample, effective distribution of the amines on the surface and inside the pores that are accessible to CO2 determine the actual working capacity of the adsorbent