Evaluation of adsorption of nonionic surfactants blend at water/oil interfaces

The inherent biocompatibility of Span and Tween surfactants makes them an important class of nonionic emulsifiers that are employed extensively in emulsion and foam stabilization. The adsorption of Span-Tween blend at water/oil surface of emulsion has been investigated using a population balance model for the first time. Destability of emulsion was modeled by considering sedimentation, coalescence and interfacial coalescence terms in population balance equation (PBE). The terms of coalescence efficiency and interfacial coalescence time were considered as a function of surface coverage of droplets by surfactant molecules. The surface coverage at different surfactant concentrations was determined by minimization of difference between the model predictions and experimental average droplet sizes. After optimization, the surface coverage outputs were fitted with different adsorption isotherms to evaluate the adsorption behavior of Span-Tween surfactants blend at water/oil surface. The results show that Freundlich isotherm can predict the adsorption behavior of closer to the experimental observation. Moreover, fitted parameters imply the favorable adsorption of Span-Tween blend at water/oil interface

Improved Polymer Flooding in Harsh Environments by Free-Radical Polymerization and the Use of Nanomaterials

High temperature and high salinity (HTHS) and extreme pH conditions can significantly affect the stability of polymers and deteriorate the performance of polymers in enhanced oil recovery (EOR). This work advances polymer flooding in harsh environments on two fronts: engineering polymers with improved temperature tolerance and dispersing suitable nanoparticles in the synthesized polymers to further improve their capabilities to withstand temperature, salinity, and different pH conditions. Different modified acrylamide copolymers (polymers synthesized from two different monomers) and terpolymers (polymers synthesized from three different monomers) are produced via free-radical polymerization, and multiwall carbon nanotubes (MWCNTs) were introduced to obtain aqueous polymer dispersions with unique properties. The conversion, molecular weight, and polydispersity of the co/terpolymers were evaluated by 1 H-NMR and GPC analysis. The interfacial, rheological behavior and stability of the dispersions were investigated under HTHS conditions at various pH values to identify the suitable candidates for EOR applications. The oil recovery performance is examined in a core flooding setup at 85 °C and American Petroleum Institute (API) brine conditions. The polyampholytic terpolymer and polyelectrolyte copolymer containing negative sulfonate groups showed improved viscosity and stability in the presence of MWCNTs in alkaline and saline conditions, respectively. Compared to the pure polymer dispersions, the addition of MWCNTs to polymers improves the oil recovery efficiency at high temperature (85 °C) in the presence of both alkaline pH and API brine conditions yet with a lower pressure drop. This shows great promise for future EOR applications

Rheological Properties of Partially Hydrolyzed Polyacrylamide Seeded by Nanoparticles

This work aims to improve the rheological properties of partially hydrolyzed polyacrylamide (HPAM) for enhanced oil recovery by using silica (or silicon dioxide, SiO₂) nanoparticles (NPs). Novel aqueous HPAM-based SiO₂ nanocomposites were formulated, and their rheological properties were investigated under different salinities, temperatures, and aging times. The results show that the inclusion of silica NPs significantly improved the viscosity and viscoelastic properties of HPAM especially under high temperature and high salinities. The NP/HPAM hybrid showed an impressive thermal stability at T = 80 °C after 12 days, and the viscosity reached ∼5 times that of HPAM at 0.8 wt % NP loading. The Fourier transform infrared spectral data confirmed that the formation of a hydrogen bond between the carbonyl groups in HPAM and the silanol functionalities on the surface of silica NPs contributed to the improved performance. The oscillation test indicated that seeding SiO₂ remarkably facilitated the cross-links among polymer molecules and made the hybrids more elastically dominant. For a given HPAM concentration, it was observed that there was a critical nanoparticle concentration, which may indicate the absorption status of SiO₂ NPs onto HPAM, and the salinity also affected the viscosity value

Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media

Carbon nanoparticles (CNPs) are becoming promising candidates for oil/gas applications due to their biocompatibility and size-dependent optical and electronic properties. Their applications, however, are always associated with the flow of nanoparticles inside a reservoir, i.e., a porous medium, where insufficient studies have been conducted. In this work, we synthesized CNPs with two different size categories in 200 nm carbon balls (CNP-200) and 5 nm carbon dots (CNP-5), via a hydrothermal carbonation process. Comprehensive experiments in packed glass bead columns, as well as mathematical simulations, were conducted to understand the transport and deposition of CNPs under various ionic strength, particle sizes and concentration conditions. Our results show that the retention of CNP-200 is highly sensitive to the salinity and particle concentrations, while both of them are unaffected in the transport of small CNP-5. Supplemented with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the clean bed filtration theory with blocking effect can successfully fit the experimental breakthrough curves of CNP-200. However, the high breakthrough ability for CNP-5 regardless of ionic strength change is in conflict with the energy interactions predicted by traditional DLVO theory

Controlled delivery and release of surfactant for enhanced oil recovery by nanodroplets

Chemical-based oil recovery method has promising applications but suffers the problem of large quantity of chemical loss inside the reservoir. This work proposes an innovative concept of using nanodroplets as carriers for surfactants/polymers and control their release inside porous media to increase oil recovery in water-wet reservoirs. Comparing to conventional surfactant flooding, the proposed concept could not only reduce the adsorption of surfactant on rock surface, but also ease the problem of unstable surfactant slug injection and release surfactant slowly inside a reservoir. The oil recovery efficiency was evaluated for micelles and nanodroplet forms of surfactants blend in a customized core flooding system and differential pressures were monitored to evaluate the injection stability of flooding fluids. The retention of surfactants was analyzed by high-performance liquid chromatography after the core flooding tests. The experiments confirm the advantages of nanodroplets as surfactant carriers. The results show that the new approach promoted tertiary oil recovery around ∼8%, while reducing the adsorption of surfactants almost half on the surface of sandstone rock comparing to the micelle form

Formulation optimization of reverse microemulsions using design of experiments for nanoparticle synthesis

The present work investigates the development of water/mixed nonionic surfactant/co-surfactant/cyclohexane reverse microemulsions (RM)suitable for nanoparticles synthesis. The mixture of Span 80 (oil soluble) and Tween 80 (water soluble) was selected as the surfactants. Optimum formulation of RM was obtained by using the Box-Behnken (33) experimental design method to evaluate the effect of three independent process variables, i.e., pH, Span 80 wt% in surfactant mixture, and propyl alcohol wt% in mixture of cyclohexane and propyl alcohol, on the preferred responses: average droplet size (ADS) and polydispersity index (PDI) of droplets. The model was validated experimentally based on an ANOVA table, and was optimized to reach the optimum formulation to yield the ADS and PDI for RMs.The determination coefficient (R2) values of 0.991for ADS and 0.975 for PDI show that Box-Behnken design is a useful platform for the optimization of RMs formulation. Finally, iron oxide nanoparticles were synthesized under the optimum RM conditions and the uniform nanoparticle distribution with an average particle size of 2.1 ± 0.49 nanometer and a polydispersity of 0.06 ± 0.011 were obtained

Correction: Hu, Z.; et al. Transport and Deposition of Carbon Nanoparticles in Saturated Porous Media. Energies 2017, 10, 1151

The author wishes to correct Figure 1b in this paper [1][...

Synthesis of stable nanoparticles at harsh environment using the synergistic effect of surfactants blend

Synthesis of nanoparticles (NPs) that can withstand high temperature and high salinity (HT-HS) is a big challenge in the research community. A novel strategy to synthesize stable nanoparticles under harsh environment (HT-HS) is proposed in this work by using the synergistic effect of a surfactant mixture. Long-term stable iron oxide nanoparticles at HT-HS conditions were produced and stabilized by two different surfactant classes, i.e. sulfonate surfactant for high temperature resistance and ethoxylated alcohol surfactant for high salinity resistance. The results prove that the new strategy could be used for production of stable NPs which is suitable for enhanced oil recovery application

Anion exchange HPLC monitoring of mRNA in vitro transcription reactions to support mRNA manufacturing process development

mRNA technology has recently demonstrated the ability to significantly change the timeline for developing and delivering a new vaccine from years to months. The potential of mRNA technology for rapid vaccine development has recently been highlighted by the successful development and approval of two mRNA vaccines for COVID-19. Importantly, this RNA-based approach holds promise for treatments beyond vaccines and infectious diseases, e.g., treatments for cancer, metabolic disorders, cardiovascular conditions, and autoimmune diseases. There is currently significant demand for the development of improved manufacturing processes for the production of mRNA therapeutics in an effort to increase their yield and quality. The development of suitable analytical methods for the analysis of mRNA therapeutics is critical to underpin manufacturing development and the characterisation of the drug product and drug substance. In this study we have developed a high-throughput, high-performance liquid chromatography (HPLC) workflow for the rapid analysis of mRNA generated using in vitro transcription (IVT). We have optimised anion exchange (AEX) HPLC for the analysis of mRNA directly from IVT. Chromatography was performed in under 6 min enabling separation of all of the key components in the IVT, including nucleoside triphosphates (NTPs), Cap analogue, plasmid DNA and mRNA product. Moreover, baseline separation of the NTPs was achieved, which facilitates accurate quantification of each NTP such that their consumption may be determined during IVT reactions. Furthermore, the HPLC method was used to rapidly assess the purification of the mRNA product, including removal of NTPs/Cap analogue and other contaminants after downstream purification, including solid phase extraction (SPE), oligo deoxythymidine (oligo-dT) affinity chromatography and tangential flow filtration (TFF). Using the developed method excellent precision was obtained with calibration curves for an external mRNA standard and NTPs giving correlation coefficients of 0.98 and 1.0 respectively. Intra- and inter-day studies on retention time stability of NTPs, showed a relative standard deviation ≤ 0.3% and ≤1.5% respectively. The mRNA retention time variability was ≤0.13%. This method was then utilised to monitor the progress of an IVT reaction for the production of Covid spike protein (C-Spike) mRNA to measure the increasing yield of mRNA alongside the consumption of NTPs during the reaction

Nanomaterials for subsurface application: study of particles retention in porous media

The ability to transport nanoparticles through porous media has interesting engineering applications, notably in reservoir capacity exploration and soil remediation. A series of core-flooding experiments were conducted for quantitative analysis of functionalized TiO2 nanoparticles transport through various porous media including calcite, dolomite, silica, and limestone rocks. The adsorption of surfactants on the rock surface and nanoparticle retention in pore walls were evaluated by chemical oxygen demand (COD) and UV–Vis spectroscopy. By applying TiO2 nanoparticles, 49.3 and 68.0 wt.% of surfactant adsorption reduction were observed in pore walls of dolomite and silica rock, respectively. Not surprisingly, the value of nanoparticle deposition for dolomite and silica rocks was near zero, implying that surfactant adsorption is proportional to nanoparticle deposition. On the other hand, surfactant adsorption was increased for other types of rock in presence of nanoparticles. 5.5, 13.5, and 22.4 wt.% of nanoparticle deposition was estimated for calcite, black and red limestone, respectively. By making a connection between physicochemical rock properties and nanoparticle deposition rates, we concluded that the surface roughness of rock has a significant influence on mechanical trapping and deposition of nanoparticles in pore-throats