The surface and interfacial properties of five zwitterionic surfactants, including three propyl sulfobetaines CSB (where the carbon atom number of the alkyl chain is 12, 14 and 16, respectively) and two hydroxypropyl sulfobetaine surfactants CHSB (where the carbon atom number of the alkyl chain is 12 and 14, respectively), were studied at both air-water and oil-water interfaces. The surface activity of these surfactants at the air-water interface in aqueous solutions was investigated by the Wilhelmy plate method at 30 C and ambient pressure. The values of the critical micelle concentration (CMC) and surface tension at CMC (g CMC ) were determined from the surface tension measurements. The obtained results indicate that CMC and surface tension strongly depend on the surfactant molecular structure. An increase in the alkyl chain length results in a decrease in the CMC and g CMC values. The presence of a hydroxyl group causes an increase in CMC values and a decrease in g CMC values. The hydroxypropyl sulfobetaine surfactants have better surfacial properties. In addition, the interfacial activity at the oilwater interface among the crude oil-reservoir water-surfactant systems was investigated by use of the spinning drop method under harsh reservoir conditions of high temperature (90 C) and high salinity (11.52 Â 10 4 ppm, including 7040 ppm Ca 2+ and 614 ppm Mg 2+ ). It is interesting that the transient minimum dynamic interfacial tension (DIT min ) could be observed in a specific concentration range. The time to reach DIT min is different with different surfactant molecular structures and surfactant concentrations. The hydroxypropyl sulfobetaine surfactant C 14 HSB shows excellent interfacial properties:it can reduce interfacial tension (IFT) between oil and water to an ultralow level at a very low concentration, and the ultralow IFT phenomenon only occurs in a specific concentration range from 0.03 to 0.10 wt%. In this work, hydroxypropyl sulfobetaine surfactants exhibit remarkable ability and are good candidates for chemical agents to enhance oil recovery in harsh reservoirs.
Lake Chaohu, which is a large, shallow, hypertrophic freshwater lake in southeastern China, has been experiencing lake-wide toxic Microcystis blooms in recent decades. To illuminate the relationships between microcystin (MC) production, the genotypic composition of the Microcystis community and environmental factors, water samples and associated environmental data were collected from June to October 2012 within Lake Chaohu. The Microcystis genotypes and MC concentrations were quantified using quantitative real-time PCR (qPCR) and HPLC, respectively. The results showed that the abundances of Microcystis genotypes and MC concentrations varied on spatial and temporal scales. Microcystis exists as a mixed population of toxic and non-toxic genotypes, and the proportion of toxic Microcystis genotypes ranged from 9.43% to 87.98%. Both Pearson correlation and stepwise multiple regressions demonstrated that throughout the entire lake, the abundances of total and toxic Microcystis and MC concentrations showed significant positive correlation with the total phosphorus and water temperature, suggesting that increases in temperature together with the phosphorus concentrations may promote more frequent toxic Microcystis blooms and higher concentrations of MC. Whereas, dissolved inorganic carbon (DIC) was negatively correlated with the abundances of total and toxic Microcystis and MC concentrations, indicating that rising DIC concentrations may suppress toxic Microcystis abundance and reduce the MC concentrations in the future. Therefore, our results highlight the fact that future eutrophication and global climate change can affect the dynamics of toxic Microcystis blooms and hence change the MC levels in freshwater.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.