Carbon dioxide (CO2) flooding holds immense potential for enhancing hydrocarbon recovery and facilitating geological carbon storage. Among CO2 flooding methods, miscible flooding demonstrates significantly higher production compared to immiscible flooding. However, in certain reservoirs, the high miscibility pressure presents a challenge for achieving miscibility under reservoir pressure conditions. Nonionic surfactants offer a solution by reducing the miscibility pressure in hydrocarbon-CO2 systems. In this study, eight nonionic surfactants were assessed, and two of the most effective surfactants were selected. These surfactants were combined to create a novel nonionic surfactant system aimed at lowering the miscibility pressure. The minimum miscibility pressure (MMP) of the hydrocarbon-CO2 system was measured using a slim-tube experiment, and a comparative analysis was conducted between the vanishing interfacial tension method (VIT) and the slim-tube method. Furthermore, the microscopic mechanism by which surfactants reduce the miscibility pressure was studied and analyzed. The findings indicate that the compound nonionic surfactant SF, with a total concentration of 1.0 wt% and a SMF to Span20 ratio of 1:1, reduces the miscibility pressure by 18.30%. The slim-tube data were processed to obtain a narrower range for MMP using criteria such as the crude oil recovery factor (ORF) and the break-over pressure (BOP). The maximum error between MMP measured by the VIT method and the slim-tube experiment is 5.86%, demonstrating the high accuracy of the VIT method in this study. The surfactant effectively reduces the miscibility pressure by decreasing the interfacial tension (IFT) between oil and gas, enhancing the CO2 extraction efficiency on intermediate hydrocarbons within the crude oil, and improving the solubility of CO2 in the crude oil. The findings of this study hold significant guidance for future investigations on the miscibility in the processes of geological CO2 utilization and storage.
The CO2 and Sodium Dodecyl Sulfate (SDS) assisted steam flooding technology was an effective approach addressed the persistent issues that have hindered the stable development of high-viscosity cold oil through steam injection. However, in the process of steam flow through porous media, the synergistic influence of the oil film adsorbed in near wellbore porous media, and the CO2-SDS on steam heat transfer has not been investigated. Steam heat transfer is the key factors affecting heavy oil recovery. The primary objective of this study was to research the effect of CO2-SDS on steam heat transfer and oil film stripping by designing experiments. The study results demonstrated that in the initial stage of displacement, the heat transfer resistance between the steam and the porous medium was increased by the oil film adsorbed in near wellbore area. In additional, the condensation mode of the steam was altered from bead condensing to film condensing by the composite thermal fluid flooding, preventing the steam heat dissipation near wellbore area and transferring more thermal to the long-distance area. At the later stage of displacement, the interfacial tension between oil-water and oil-gas was reduced by CO2-SDS, improving the fluidity of oil and providing the seepage channel for steam, and increasing the steam thermal sweep range. Compared to the sandpack experiment of steam flooding, the temperature at the output end of the sandpack model increased from 69.8 °C to 88.7 °C, indicating an expansion of the steam heat sweep range and successful long-distance heat transfer during composite thermal fluid flooding. In the process of composite thermal fluid flooding, the maximum displacement pressure difference increased from 2.28 MPa to 3.07 MPa, and the maximum oil recovery rate increased from 2.48 g/mL to 2.81 g/mL. The peak of the high production period was raised, resulting in a 40.97% to 51.86% increase in recovery rates.
ron/chromium hydroxide coprecipitation controls the fate and transport of toxic chromium (Cr) in many natural and engineered systems. Organic coatings on soil and engineered surfaces are ubiquitous; however, mechanistic controls of these organic coatings over Fe/Cr hydroxide coprecipitation are poorly understood. Here, Fe/Cr hydroxide coprecipitation was conducted on model organic coatings of humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA). The organics bonded with SiO2 through ligand exchange with carboxyl (–COOH), and the adsorbed amounts and pKa values of –COOH controlled surface charges of coatings. The adsorbed organic films also had different complexation capacities with Fe/Cr ions and Fe/Cr hydroxide particles, resulting in significant differences in both the amount (on HA > SA(–COOH) ≫ BSA(–NH2)) and composition (Cr/Fe molar ratio: on BSA(–NH2) ≫ HA > SA(–COOH)) of heterogeneous precipitates. Negatively charged –COOH attracted more Fe ions and oligomers of hydrolyzed Fe/Cr species and subsequently promoted heterogeneous precipitation of Fe/Cr hydroxide nanoparticles. Organic coatings containing –NH2 were positively charged at acidic pH because of the high pKa value of the functional group, limiting cation adsorption and formation of coprecipitates. Meanwhile, the higher local pH near the –NH2 coatings promoted the formation of Cr(OH)3. This study advances fundamental understanding of heterogeneous Fe/Cr hydroxide coprecipitation on organics, which is essential for successful Cr remediation and removal in both natural and engineered settings, as well as the synthesis of Cr-doped iron (oxy)hydroxides for material applications.
Biomolecule labeling in living systems is crucial for understanding biological processes and discovering therapeutic targets. A variety of labeling warheads have been developed for multiple biological applications, including proteomics, bioimaging, sequencing, and drug development. Quinone methides (QMs), a class of highly reactive Michael receptors, have recently emerged as prominent warheads for on-demand biomolecule labeling. Their highly flexible functionality and tunability allow for diverse biological applications, but remain poorly explored at present. In this regard, we designed, synthesized, and evaluated a series of new QM probes with a trifluoromethyl group at the benzyl position and substituents on the aromatic ring to manipulate their chemical properties for biomolecule labeling. The engineered QM warhead efficiently labeled proteins both in vitro and under living cell conditions, with significantly enhanced activity compared to previous QM warheads. We further analyzed the labeling efficacy with the assistance of density functional theory (DFT) calculations, which revealed that the QM generation process, rather than the reactivity of QM, contributes more predominantly to the labeling efficacy. Noteworthy, twelve nucleophilic residues on the BSA were labeled by the probe, including Cys, Asp, Glu, His, Lys, Asn, Gln, Arg, Ser, Thr, Trp and Tyr. Given their high efficiency and tunability, these new QM warheads may hold great promise for a broad range of applications, especially spatiotemporal proteomic profiling for in-depth biological studies.
In this paper, we present findings from four separate studies using different data sources and methods to examine Chinese attitudes toward the United States amid the COVID-19 pandemic. The empirical results consistently indicate a marked and significant decline in Chinese attitudes toward the US between late 2019 and the end of 2022. Using a quasi-experimental design and granular survey data that exploit daily variations in public opinion, we offer additional evidence that the decline in Chinese attitudes toward the United States followed a distinct pattern not true for Chinese attitudes toward other countries. Specifically, the rise in Chinese unfavorability toward the United States closely corresponded to the heightened Chinese attention to the pandemic’s progression in the United States. These results collectively suggest a causal effect of COVID-19, shedding light on how public health crises, international relations, and media jointly shape the increasing enmity between the two great powers.
Public transportation is important for older adults to meet their mobility needs and obtain external support. However, little is known about the elderly population with disabilities using public transportation. Using a nationally representative sample from the China Family Panel Studies (CFPS) for 2016, 2018, and 2020, we examined the elderly and public transportation disability (E&PTD) rate and its determinants in Chinese adults aged 45 years and above; the E&PTD rate in this population was 9.65%. The results showed that factors such as being female, age, and family size increased the likelihood of E&PTD in older adults. Married older adults with more education, better intelligence, higher incomes, receiving a pension, and living in urban areas and pilot provinces of healthcare reform were less likely to have E&PTD. This study provides an important policy reference for providing better public transportation services for E&PTDs.