Natural surfactants that are present in complex crude oil may induce spontaneous emulsification in the oil and brine phases that co-exist in rock pores.This process is known to be affected by the salinity of brine.How...Natural surfactants that are present in complex crude oil may induce spontaneous emulsification in the oil and brine phases that co-exist in rock pores.This process is known to be affected by the salinity of brine.However,the role of salinity in water-oil micro-emulsification is not fully understood.In this paper,we report on our experimental studies of the effect of salinity on spontaneous emulsification in a“mixture”of dodecane and brine.The dodecane contains SPAN 80 surfactant and brine with different salinity values,varying from 0.2%to 20%(by weight).For our observations,we use dynamic light scattering(DLS)technique to capture nano-scale emulsion formation and pendant drop method to observe micro-scale emulsion dynamics.The DLS experiments show that small(2.2 nm)and medium-sized emulsions(100 nm)are formed at low salinities,while at higher salinities only smaller droplets are formed and emulsification is reduced.In pendant drop experiments,dodecane and heptane systems were tested over 13 h.Heptane exhibited faster emulsification at water-oil interfaces in the cases with pure water and low salinity brine(0.2%),where the changes at interfacial area occurring within two hours and significant droplet shrinkage by 13 h.Lower salinity enhances micelle activity and emulsification,while higher salinities(2%,5%,and 20%)stabilize the oil-water interface and suppress emulsion formation.Dodecane exhibits a similar trend in emulsification but forms more stable emulsions and maintains a more stable water-oil interface compared to heptane.Additionally,we present the theory of reverse micelle exclusion through a theoretical derivation,providing a deeper understanding of the emulsification mechanism.Four distinct scenarios are schematically presented to explain the influence of salinity on spontaneous emulsification,illustrating how varying salinity levels affect micelle formation and emulsion behaviour.This study provides valuable insights into optimizing salinity levels in enhanced oil recovery.展开更多
The aim of this study was to prepare arsenic trioxide （ATO）-loaded stealth PEGylated PLGA nanoparticles （PEG-PLGA-NPs） and to assess the merits of PEG-PLGA-NPs as drug carriers for ATO delivery. PEG-PLGA copolymer...The aim of this study was to prepare arsenic trioxide （ATO）-loaded stealth PEGylated PLGA nanoparticles （PEG-PLGA-NPs） and to assess the merits of PEG-PLGA-NPs as drug carriers for ATO delivery. PEG-PLGA copolymer was synthesized with methoxypolyethyleneglycol （Mw=5000）, D, L-lactide, and glycolide by the ring-opening polymerization method. Amorphous ATO was transformed into cubic crystal form to increase its solu-bility in the organic solvent. ATO-loaded PEG-PLGA-NPs were prepared by the modified spontaneous emulsification solvent diffusion （SESD） method, and the main experimental factors influencing the characteristics of nanopar- ticles were investigated, to optimize the preparation. To confirm the escape of PEG-PLGA-NPs from phagocytosis by phagocytes, PEG-PLGA-NPs labeled rhodamine B uptake by murine peritoneal macrophages （MPM） were analyzed by flow cytometry. The results showed that the physicochemical characteristics of PEG-PLGA-NPs were affected by the type and concentration of the emulsifiers, polymer concentration, and drug concentration. ATO-loaded PEG-PLGA-NPs, with particle size of 120.8nm, zeta potential of-10.73mV, encapsulation efficiency of 73.6%, and drug loading of 1.36%, were prepared under optimal conditions. The images of transmission electron micros-copy （TEM） indicated that the optimized nanoparticles were near spherical and without aggregation or adhesion. The release experiments in vitro showed the ATO release from PEG-PLGA-NPs exhibited consequently sustained release for more than 26d, which was in accordance with Higuchi equation. The uptake of PEG-PLGA-NPs by MPM was found to decrease markedly compared to PLGA-NPs. The experimental results showed that PEG-PLGA-NPs were potential nano drug delivery carriers for ATO.展开更多
基金the funding from National Natural Science Foundation of China(Grant No.52474105).
文摘Natural surfactants that are present in complex crude oil may induce spontaneous emulsification in the oil and brine phases that co-exist in rock pores.This process is known to be affected by the salinity of brine.However,the role of salinity in water-oil micro-emulsification is not fully understood.In this paper,we report on our experimental studies of the effect of salinity on spontaneous emulsification in a“mixture”of dodecane and brine.The dodecane contains SPAN 80 surfactant and brine with different salinity values,varying from 0.2%to 20%(by weight).For our observations,we use dynamic light scattering(DLS)technique to capture nano-scale emulsion formation and pendant drop method to observe micro-scale emulsion dynamics.The DLS experiments show that small(2.2 nm)and medium-sized emulsions(100 nm)are formed at low salinities,while at higher salinities only smaller droplets are formed and emulsification is reduced.In pendant drop experiments,dodecane and heptane systems were tested over 13 h.Heptane exhibited faster emulsification at water-oil interfaces in the cases with pure water and low salinity brine(0.2%),where the changes at interfacial area occurring within two hours and significant droplet shrinkage by 13 h.Lower salinity enhances micelle activity and emulsification,while higher salinities(2%,5%,and 20%)stabilize the oil-water interface and suppress emulsion formation.Dodecane exhibits a similar trend in emulsification but forms more stable emulsions and maintains a more stable water-oil interface compared to heptane.Additionally,we present the theory of reverse micelle exclusion through a theoretical derivation,providing a deeper understanding of the emulsification mechanism.Four distinct scenarios are schematically presented to explain the influence of salinity on spontaneous emulsification,illustrating how varying salinity levels affect micelle formation and emulsion behaviour.This study provides valuable insights into optimizing salinity levels in enhanced oil recovery.
基金Supported by the Special Funds for Major State Basic Research Program of China (973 Program, No.2007CB935800)theNational High Technology Research and Development Program of China (863 Program, No.2004AA215162).
文摘The aim of this study was to prepare arsenic trioxide （ATO）-loaded stealth PEGylated PLGA nanoparticles （PEG-PLGA-NPs） and to assess the merits of PEG-PLGA-NPs as drug carriers for ATO delivery. PEG-PLGA copolymer was synthesized with methoxypolyethyleneglycol （Mw=5000）, D, L-lactide, and glycolide by the ring-opening polymerization method. Amorphous ATO was transformed into cubic crystal form to increase its solu-bility in the organic solvent. ATO-loaded PEG-PLGA-NPs were prepared by the modified spontaneous emulsification solvent diffusion （SESD） method, and the main experimental factors influencing the characteristics of nanopar- ticles were investigated, to optimize the preparation. To confirm the escape of PEG-PLGA-NPs from phagocytosis by phagocytes, PEG-PLGA-NPs labeled rhodamine B uptake by murine peritoneal macrophages （MPM） were analyzed by flow cytometry. The results showed that the physicochemical characteristics of PEG-PLGA-NPs were affected by the type and concentration of the emulsifiers, polymer concentration, and drug concentration. ATO-loaded PEG-PLGA-NPs, with particle size of 120.8nm, zeta potential of-10.73mV, encapsulation efficiency of 73.6%, and drug loading of 1.36%, were prepared under optimal conditions. The images of transmission electron micros-copy （TEM） indicated that the optimized nanoparticles were near spherical and without aggregation or adhesion. The release experiments in vitro showed the ATO release from PEG-PLGA-NPs exhibited consequently sustained release for more than 26d, which was in accordance with Higuchi equation. The uptake of PEG-PLGA-NPs by MPM was found to decrease markedly compared to PLGA-NPs. The experimental results showed that PEG-PLGA-NPs were potential nano drug delivery carriers for ATO.
