Volume 61, Issue 2

The surface activity, intermolecular interactions and thermodynamic parameters of a mixture of a nonionic surfactant (branched-chain alkyl glycoside (IG-10)) and an anionic surfactant (alcohol ether carboxylic acid (90H)) were investigated and the wetting, emulsifying and foaming properties of the mixed system were also evaluated. The results show that there is a mutual attraction at the mixed micelles and gas/liquid interfaces formed by the two surfactants. The thermodynamic parameters show that the formation of mixed micelles from two different surfactants is a non-ideal process. In terms of application performance, the wetting ability and foaming properties of the mixed system showed good synergistic effects, with the wetting time of the mixed system being shorter than that of the two single surfactant systems and the foam stability being weaker than that of the single system. The best emulsifying capacity was obtained when the mass fraction of 90H was 50 %.

This paper investigates the interactions and aggregation behavior of biosurfactants, sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous solutions of Emtricitabine and Lamivudine (anti-HIV drugs). The study uses conductometry and UV–visible spectroscopy techniques to evaluate the critical micelle concentration (CMC) at different temperatures ranging from 298.15 K to 313.15 K with a variation of 5 K. The temperature dependence of the CMC was examined, and the stability of micelles was analyzed in light of the hydrophobic-hydrophilic interactions involved in this system. The CMC obtained from both the methods are in agreement. Various thermodynamic parameters, such as ∆ H m 0 ${\increment}{H}_{m}^{0}$ , ∆ S m 0   ${\increment}{S}_{m}^{0\hspace{0.17em}}$ and ∆ G m 0 ${\increment}{G}_{m}^{0}$ have been estimated using a “pseudo-phase separation model” to understand the contribution of the chemical and de-solvation part in the micellization process. Furthermore, the enthalpy-entropy compensation plots validate the micellar stability of the studied systems.

In this paper, the lamellar liquid crystals formed in S1570-Brij97/isopropyl myristate/PEG400 aqueous system were prepared at 37 °C. The effects of PEG400 and curcumin on the S1570-Brij97 lyotropic liquid crystal systems were studied by phase diagram, polarized optical microscopy, small angle X-ray scattering, and rheology. The prepared lamellar liquid crystals show stable structures at 37 °C. The encapsulation of curcumin improves the structural stability of the lamellar liquid crystals, which can be confirmed by their higher η γ =0.013 and σ y values, suggesting that the S1570-Brij97 lamellar liquid crystals are good carriers for curcumin. In addition, the prepared lamellar liquid crystals can effectively protect curcumin from decomposition, and curcumin can be released slowly in the liquid crystals. Therefore, based on the structural stability, protective effect on curcumin, and slow-release behavior, the constructed S1570-Brij97 lamellar liquid crystals have good potential for drug delivery.

Six surface-active ionic liquids (SAILs) with herbicidal anions were synthetized (with a yield of ≥ 88 %) and their structure was confirmed by NMR spectra. Subsequently, their surface properties, phytotoxicity and bulk aggregation behavior in aqueous solution investigated. The compounds studied have an amphiphilic structure and, due to the presence of two long alkyl chains in the cation, they displayed surface activity (CMC values, ranging from 0.13 mmol L −1 to 1.36 mmol L −1 ). Our results provide explanations for the role of counterions in the physical and chemical properties of SAILs. Indeed, the aromatic anion affects the hydrophilic charge of the surface-active compounds. The SAILs containing the [MCPA] − and [MCPP] − anions were the most phytotoxic to representatives of dicotyledonous plants compared to the other compounds. By analysis of the structure of SAILs, we demonstrate that counterions play an important role in self-assembly and adsorption processes in aqueous solutions, and therefore, in the potential biological application of these compounds.

Foam has been widely used in drilling, well washing, and oil driving during the development of oil and gas fields. Although air foams have been successfully employed as an enhanced oil medium, the oxygen they contain can seriously corrode piping systems, which can have a negative influence on output. This work used a combination of sodium dodecyl sulfate (SDS), dodecyl aminopropyl betaine (LAB), sodium dodecylbenzene sulfonate (SDBS), and cosurfactants to solve the problem above. The corrosion inhibitor hydrazine hydrate (N₂H₄·H₂O) was added as corrosion inhibitor. The foaming (air)-corrosion inhibitor all-in-one (SLN) was obtained with the formulation of SDS: LAB: N₂H₄·H₂O = 8:2:4. The foam volume of 0.7 % SLN was measured to be 515 mL at room temperature with a half-life of 4.1 min using the stirring method. The initial foam height of this all-in-one agent was measured to be 15.6 cm at 30 °C using the Roche foaming method. The foam height was still maintained at 15.5 cm after 20 min with a foam height retention of 99.2 %. The foam height retention rate was 50.0 % at 70 °C. Moreover, the formulation had good salt resistance to common inorganic salts in oilfield water. It should be emphasized that the SLN all-in-one agent has strong corrosion inhibition performance, and the corrosion inhibition rate can reach up to 96.9 %. The surface tension of this SLN all-in-one agent was reduced to 27.8 mN m −1 at a concentration of 0.1 %. It indicated that the all-in-one agent might increase the stability of the foam by decreasing the surface tension, thus improving the persistence of the foam and the effect of the repelling oil.

The salt blockage layer formed in the wellbore during the development of high salinity oil and gas fields has a serious impact on the safety of oil and gas production of the oil and gas fields. CaCO 3 is the main component of scale in high salinity oil and gas fields. Herein, focusing on CaCO 3 as an example, the precipitation and scaling process as well as the change of crystalline form of CaCO 3 under different temperature and salinity conditions were studied. The effects of two addition methods of organic chelating agent on the solubilization and dislodgement of CaCO 3 under high salinity conditions were also explored. The optimal concentration of organic chelating agent is determined to be 1 % and 5 % for solubilization and dislodgement, respectively. It was found that the solubilization is achieved by inhibiting the stable and difficult to treat calcite crystal phase to generate more irregular and more dispersed aragonite CaCO 3 . Organic chelating agent contains a large number of carboxyl groups in its molecules, which can be adsorbed onto the surface of CaCO 3 crystals through electrostatic adsorption. By chelating Ca 2+ in stable and difficult to treat calcite CaCO 3 , the further ordered growth of the crystals is prevented, causing lattice distortion or large crystal rupture, thereby achieving dislodgement. This study will provide theoretical and technical support for the solubilization and dislodgement of salt blockage layer in wellbore at high salinity conditions.

In this paper, in order to study the effect of emulsification on the oil displacement of the system, several polymer, surfactant/polymer (S/P) and alkali/surfactant/polymer (A/S/P) systems were prepared for experiments. Firstly, the interfacial tension of each system was investigated. After the emulsion was prepared, the droplet size was observed by microscope and the intensity of the backscattered light during the destabilisation process of the emulsion was tested with the stability analyser. The TSI value was calculated to evaluate the stability of the emulsion. Finally, the Berea core displacement experiment (chemicals are used to displace oil from the core) was carried out to test the ability to enhance the oil recovery. The experimental results show that the emulsion formed by the A/S/P system with the simulation oil has the best stability. The chemical displacement recovery is the highest, which is 32.15 %. The emulsion stability of the S/P system is second, and the chemical displacement recoveries are 17.03 % and 20.76 %, respectively. The polymer system has no interfacial activity, does not form an emulsion, and has the lowest chemical displacement recovery of 8.02 %. This shows that the deeper the degree of emulsification of the system and the more stable the emulsion, the better the oil displacement effect of the oil displacement system.

Household detergents are a source of water pollu-tants that adversely affect crops. These pollutants not only reduce plant growth, but also have a negative impact on the environment. To investigate the effect of handwashing liquid on the germination characteristics of wheat, mung bean, and chickpea, a study was conducted using a completely randomized design with three replications. Water contaminated with different concentrations of handwashing liquid ((0, 0.01, 0.1, 1, 10) % of handwashing liquid) was used as treatment. The results showed that with increasing concentration of the contaminant, germination characteristics such as seed germination percentage, caulicle length, radicle length, and seed vigor decreased. Wheat was the most sensitive to detergent concentration compared to the other two plants, with the lowest detergent concentration causing a severe reduction in its germination traits. Therefore, farmers using water contaminated with household detergents need to be aware of its concentration to ensure healthy plant growth.

To improve the insufficient performance of anion on cationic surfactants and to further study the influence of anion on the surface properties, a cationic surfactant (cetyltrimethylammonium p -toluenesulfonate, CTATS) was prepared, and the relevant surface properties, including surface tension, critical micelle concentration, foaming ability and stability, corrosion inhibition and oil displacement efficiency were studied. Compared to cetyltrimethylammonium chloride (CTAC), CTATS exhibited higher surface activity, lower foaming volume, higher foam stability, higher corrosion inhibition performance and oil displacement efficiency. The results indicate that the CTATS has better performances as a surfactant type in oil and gas fields.