A comparison between undrained shear strength of clayey soils acquired by “PMT” and laboratory tests

© 2020, Saudi Society for Geosciences. A pressuremeter test (PMT) is one of the in situ tests, which is used to evaluate deformation and strength parameters of soils for various projects, including subway projects. The limit pressure (PL) and undrained shear strength (Su) are the key parameters that are obtained directly and indirectly from the pressuremeter testing results. This research was carried out using geotechnical information obtained from a subway project in Qom city, Iran. Based on 44 PMT and uniaxial tests on very stiff to hard saturated clayey soils, a linear empirical equation between Su − PL and Su − PL* = (PL − σH) with R2 = 0.68 was proposed and it was found that σH had an insignificant effect on the proposed relationship. The effect of physical properties of soil, including plastic index (PI), liquid limit (LL), and water content (ω), was evaluated, and a multivariate equation was proposed between them. A comparison between the equations obtained in this research and those proposed by other researchers reveals that the empirical relationships between Su and PL are associated with the consistency of soils; the stiffer the soil is, the slope of relationship between Su and PL is less

Exceptionally High Gravimetric Methane Storage in Aerogel-Derived Carbons

Storage of natural gas in highly porous materials provides a safer and more energy-efficient solution to energy-intensive compression and liquefaction options for advancing natural gas vehicular systems. Herein, we investigate the potential of highly porous aerogel-derived mesoporous carbons for storage of methane under the conditions relevant to adsorbed natural gas (ANG) tanks. Analysis of high-pressure isotherms indicated that EC-RF with a 2355 m2/g surface area and a 6.77 cm3/g total pore volume exhibited an exceptionally high gravimetric methane uptake with a deliverable capacity of 261 cm(STP)3/g in the pressure range of 5.8-65 bar and 25 °C which was 48% higher than that of the benchmark HKUST-1 material. Such behavior is attributed to its ultrahigh pore volume, large surface area, and low bulk density. In addition, our investigations demonstrated that upon desorbing the stored methane at 50 °C instead of 25 °C, both the methane deliverable capacity and the amount of methane recovered over EC-RF can be further increased to 305 cm(STP)3/g and 17%, respectively. Moreover, cyclic charge-discharge profiles revealed stable storage performance for this material. However, despite high gravimetric uptake, the volumetric uptake was only 89 cm(STP)3/cm3, which was 50% that of HKUST-1. The results reported herein demonstrate that for aerogel-based carbons to be considered suitable as ANG adsorbents, their properties should be optimized to yield high volumetric storage capacity, balanced with their exceptionally high gravimetric uptake capacity

PDMS/PAI-HF Composite Membrane Containing Immobilized Palladium Nanoparticles for 4-Nitrophenol Reduction

Catalytically active asymmetric membranes were developed by crosslinking a polydimethylsiloxane (PDMS) thin layer onto a porous polyamide‐imide hollow fiber (PAIHF) support, followed by grafting of aminosilane with hydroxyl derived-PDMS/PAIHF, and finally palladium nanoparticles (PdNPs) immobilization using salicylic aldehyde. Aminosilane and salicylic aldehyde linkers were used to permanently immobilize PdNPs onto the PDMS surface through metal coordination chelation, which prevented their agglomeration and leaching from the catalytic membrane reactor (CMR) module. The obtained CMRs were used for hydrogenation of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in a continuous-flow fashion. The effects of 4-NP concentration (0.5-4 mM) and flow rate (0.01-0.08 cm3 min-1) on 4-NP conversion and 4-AP selectivity were evaluated in both batch and continuous-flow systems. The newly developed continuous flow 4-NP hydrogenation module exhibited a good operating stability after six cycle run for 6 h’ time on stream, where complete 4-NP conversion (100%) was achieved in short residence time (2-3 s) via a single-pass-through the CMR module. Overall, the designed and developed method described herein offers an alternative platform to address PdNPs’ leaching issues that are commonly encountered in continuous-flow chemical transformation processes