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Multi-stage hydraulic fracturing is a commonly used method to maximize production from shale gas reservoirs. However, the recovery of flowback water after hydraulic fracturing is relatively low, which gives rise to technical and environmental concerns. Although it is widely accepted that the water uptake is due to physicochemical fluid–shale interactions caused by the capillary forces, much of the studies up to now are just descriptive in nature and little attention has been paid to quantitatively characterize the fluid–shale interactions and, thus, surface forces from a geochemical perspective. In this study, we performed geochemical modeling to explain the results of spontaneous imbibition experiments by published work. We calculated the surface potential of organic matter, quartz, and calcite in the presence of 0.1–20 wt % NaCl. Moreover, we predicted the local pH using PHREEQC with consideration of ion exchange and mineral dissolution. We also computed the disjoining pressure under constant charge conditions. Results show that a low salinity drives the surface potential of organic matter and inorganic minerals to strongly negative at in situ pH. The disjoining pressure isotherm shows that air–brine–organic matter and air–brine–calcite systems give positive disjoining pressure regardless of salinity, implying a water-wet system. Moreover, a low salinity shifts the disjoining pressure to be more positive for organic matter, suggesting a wettability alteration process. However, the change of disjoining pressure on the calcite surface is negligible as a function of salinity. Our results confirm that capillary forces at least partially contribute to the water uptake, and the presence of organic matter likely further facilitates the water uptake as a result of wettability alteration. This explains in part why a low salinity causes shale expansion and microfracture generation in organic-rich reservoirs.

Calcium-looping technology has been identified as one of the most favorable CO 2 capture techniques for the implementation of carbon capture, utilization, and storage (CCUS); however, the rapid deactivation of CaO sorbents due to sintering is currently a major barrier of this technology. We report for the first time an environmentally benign and costeffective strategy to reduce sintering by adding waste-derived nanosilica, synthesized from photovoltaic waste (SiCl 4 ), into Cao-based sorbents through a simple dry mixing procedure. The as-synthesized sorbent (90% CaCO 3 −W) resulted in final CO 2 uptake of 0.32 g(CO 2 ) g(CaO) −1 within 5 min of carbonation. Even under the most severe calcination conditions (at 920 °C in pure CO 2 ), it still maintained a stable capture capacity, with CO 2 uptake of 0.23 g(CO 2 ) g(CaO) −1 after 30 cycles. Additionally, the CO 2 uptake percentage reached ∼90% in the fast carbonation stage (∼20 s), which is of great significance for real applications. The most likely stabilization mechanism was considered on the basis of N 2 physisorption isotherms and X-ray diffraction patterns. It was concluded that stable and refractory larnite (Ca 2 SiO 4 ) particles were formed during 2-h thermal pretreatment at 900 °C, leading to sintering resistance. This strategy significantly enhanced the cyclic stability and carbonation rate of CaO-based sorbents through the reuse of SiCl 4 and is thus a green technology for scaled-up fast CO 2 capture.

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A series of novel 1,2,4-triazolium derivatives was synthesized starting from commercially available 1H-1,2,4-triazole, 2,4-dichlorobenzyl chloride, or 2,4-difluorobenzyl bromide. Their antibacterial and antifungal activities were evaluated against Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Bacillus proteus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans ATCC 76615, and Aspergillus fumigatus. All structures of the new compounds were confirmed by NMR, IR, and MS spectra, and elemental analyses. The antimicrobial tests showed that most of synthesized triazolium derivatives exhibit significant antibacterial and antifungal activities in vitro. 1-(2,4-Difluorobenzyl)-4-dodecyl-1H-1,2,4-triazol-4-ium bromide and 1-(2,4-Dichlorobenzyl)-4-dodecyl-1H-1,2,4- triazol-4-ium bromide were the most potent compounds against all tested strains with the MIC values ranging from 1.05 to 8.38 microM. They exhibited much stronger activities than the standard drugs chloramphenicol and fluconazole which are in clinical use. The results also showed that the antimicrobial activities of triazolium derivatives depend upon the type of substituent, the length of the alkyl chain, and the number of triazolium rings.