Adsorption of Zirconium Ions by X-Type Zeolite

Dependence of zirconium adsorption value on agitation time, solution acidity, equilibrium concentrations of zirconium cations, and zeolite NaX particle size was investigated. The two most common adsorption theories Langmuir and Freundlich, were used to analyzing equilibrium adsorption data. Nonlinear approximation shows that the Freundlich adsorption theory provides higher R2 and lower χ2 for zirconium adsorption by NaX than the Langmuir adsorption theory. Experimental maximum adsorption values of NaX toward zirconium and strontium cations are 75 mg·g-1 and 156 mg·g-1, respectively. The desorption studies of zirconium ions from the surface of NaX by 1% oxalic acid and 10% HNO3 were performed. Degradation of the adsorbent in nitric acid was studied in a batch mode. The recovered suspended particles filter cake was investigated by X-ray fluorescence analysis. Alumina oxide (Al2O3) fraction decreases, and MgO is completely washed out from the adsorbent matrix in concentrated HNO3.

Improved Analysis of Nuclear-Magnetic-Resonance Measurements in Organic-Rich Mudrocks Through Experimental Quantification of the Hydrocarbon/Kerogen Intermolecular-Interfacial-Relaxation Mechanism

Summary Nuclear-magnetic-resonance (NMR) measurements have become a popular choice for estimating hydrocarbon saturations in organic-rich mudrock reservoirs. Previous publications have shown that the dominant mechanism for surface relaxation during NMR measurements in organic pores is intramolecular dipolar coupling among hydrocarbon protons. However, the influence of kerogen/hydrocarbon intermolecular interactions and kerogen thermal maturity on the surface relaxivity has not been reliably quantified. The objectives of this paper are to experimentally quantify the influence of intermolecular coupling on kerogen surface relaxivities; compare the experimentally determined surface relaxivities with those obtained from our previously published analytical model; and quantify the effect of intermolecular coupling on estimates of the adsorbed-hydrocarbon phase volume in simple geometries. First, we selected two organic-rich mudrock formations with different kerogen thermal maturities and extracted pure kerogen from them. The extracted-kerogen samples were synthetically matured by increasing the temperature at 4°C/min from 25 to 450°C under a controlled environment. The petrophysical properties of kerogen samples at different thermal maturities were quantified using pyrolysis and Brunauer-Emmett-Teller (BET) measurements. The untreated and thermally mature kerogen samples were then saturated with protonated and partially deuterated chloroform mixtures. Consequently, we performed longitudinal (T1) and transverse (T2) measurements on the kerogen/chloroform mixtures. Then, we compared the surface relaxivities estimated from T1/T2 and BET surface-area measurements with those predicted by a previously published theoretical model derived from generalized adsorption theory. Finally, we performed a sensitivity study demonstrating the effect of intermolecular dipolar coupling on estimates of adsorbed-hydrocarbon volume by modeling kerogen pores as synthetic spherical objects. Results indicate that synthetic maturation of kerogen samples relatively increased their specific surface areas by up to 97.1%. When chloroform deuteration is kept constant and kerogen samples were heat treated from temperatures of 25 to 450°C, the T1 and T2 surface relaxivities relatively decreased by up to 70.1 and 80.3%, respectively. Our recently introduced analytical model was able to reliably quantify the kerogen surface relaxivities estimated from experimental measurements with a relative error of 30.5%. The results of the sensitivity analysis showed that improved assessment of kerogen surface relaxivity by including intermolecular coupling enhanced the NMR-based adsorbed-hydrocarbon-volume estimates relatively by up to 41.9% when kerogen pores were modeled as synthetic spherical objects. The results of the experimental measurements support the observations of the analytically developed surface-relaxivity model derived from the generalized adsorption theory. Accurately quantifying the mechanism contributing to surface relaxation helps in providing accurate temperature and frequency corrections for T2 and T1/T2 cutoff values. Such cutoff values can then be extended to in-situ conditions improving downhole estimates of NMR-based hydrocarbon saturations in organic-rich mudrocks.

Fluctuation adsorption theory: quantifying adsorbate–adsorbate interaction and interfacial phase transition from an isotherm

Adsorbate–adsorbate interaction can be determined directly from an adsorption isotherm via a rigorous statistical thermodynamic theory.

Global impact of mineral dust on cloud droplet number concentration

The importance of wind-blown mineral dust for cloud droplet formation is studied by considering (i) the adsorption of water on the surface of insoluble particles, (ii) particle coating by soluble material (atmospheric aging) which augments cloud condensation nuclei (CCN) activity, and (iii) the effect of dust on inorganic aerosol concentrations through thermodynamic interactions with mineral cations. The ECHAM5/MESSy Atmospheric Chemistry (EMAC) model is used to simulate the composition of global atmospheric aerosol, while the ISORROPIA-II thermodynamic equilibrium model treats the interactions of K+-Ca2+-Mg2+-NH4+-Na+-SO42−-NO3−-Cl−-H2O aerosol with gas-phase inorganic constituents. Dust is considered a mixture of inert material with reactive minerals and its emissions are calculated online by taking into account the soil particle size distribution and chemical composition of different deserts worldwide. The impact of dust on droplet formation is treated through the unified dust activation parameterization that considers the inherent hydrophilicity from adsorption and acquired hygroscopicity from soluble salts during aging. Our simulations suggest that the presence of dust increases cloud droplet number concentration (CDNC) over major deserts (e.g., up to 20 % over the Sahara and the Taklimakan desert) and decreases CDNC over polluted areas (e.g., up to 10 % over southern Europe and 20 % over northeastern Asia). This leads to a global net decrease in CDNC by 11 %. The adsorption activation of insoluble aerosols and the mineral dust chemistry are shown to be equally important for the cloud droplet formation over the main deserts; for example, these effects increase CDNC by 20 % over the Sahara. Remote from deserts the application of adsorption theory is critically important since the increased water uptake by the large aged dust particles (i.e., due to the added hydrophilicity by the soluble coating) reduce the maximum supersaturation and thus cloud droplet formation from the relatively smaller anthropogenic particles (e.g., CDNC decreases by 10 % over southern Europe and 20 % over northeastern Asia by applying adsorption theory). The global average CDNC decreases by 10 % by considering adsorption activation, while changes are negligible when accounting for the mineral dust chemistry. Sensitivity simulations indicate that CDNC is also sensitive to the mineral dust mass and inherent hydrophilicity, and not to the chemical composition of the emitted dust.