The surface charge/surface potential of the air/water interface plays a key role in many natural and industrial processes. Since the first decade of the 20th century, there are many theoretical proposals to describe the surface charge in the presence of different moieties. However, a complete and consistent description of the interfacial layer remains elusive. More recently, the theoretical frameworks and experimental data get complementary support from the simulation at a molecular level. This paper reviews the recent developments from the theoretical, experimental and simulation aspects. The combined results indicated that the interaction between hydration shells of adsorbed ions and the H-bonds network of surface water plays a critical role in the ionic adsorption. The factor should be incorporated into the conventional theories to correctly predict the ion distribution near the air/water surface.
In this review, we report controlled self-assembly systems of amphiphilic random copolymers in aqueous or organic media and the solid state to produce folded micelles, related nanoaggregates, vesicles, and microphase separation materials. The key features of random copolymer self-assemblies are 1) self-folding of polymer chains, 2) precision self-assembly of side chains, and 3) dynamic self-sorting and selective recognition. Typically, random copolymers bearing hydrophilic poly(ethylene glycol) and hydrophobic alkyl groups folded into small unimer micelles (~10 nm) via the association of the hydrophobic groups in water. Importantly, those random copolymers afforded precision intermolecular self-assembly into multichain micelles; the size, aggregation number, and thermoresponsive properties can be controlled as desired by tuning their molecular weight, composition, and side chains. The binary mixture of different random copolymers further self-sorted via chain exchange in water to simultaneously form discrete micelles. Namely, amphiphilic random copolymers can dynamically recognize themselves in complex media like natural biomolecules and proteins. Amphiphilic random copolymers opened new ways to create self-assembled materials with well-defined nanostructures and compartments, dynamic recognition properties, and functions.
Highly efficient nanocomposite electrolytes were prepared by mixing the montmorillonite (MMT) clay nanofillers and iodide poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) gel electrolytes for the purpose of measuring the performance of quasi-solid-state dye-sensitized solar cells (QS-DSSCs). The impacts of different amounts of MMT nanofillers on the ion diffusivity, conductivity of the polymer gel electrolytes (PGEs), and the photovoltaic performance of the cells using the PGEs were evaluated. The results indicated that the use of 5 wt.% MMT markedly increase the ion diffusivity and conductivity of the PVDF-HFP PGE. The introduction of 5 wt.% nanofillers considerably reduced the Warburg diffusion resistance, which made to the high performance of the QS-DSSCs. Cells utilizing 5 wt.% MMT nanofillers were shown to obtain a power conversion efficiency (PCE) (6.77%) higher than that obtained for cells using pure PGEs and identical to that obtained using liquid electrolytes (LEs) (6.77%). The high PCE was a result of an enhance in the current density in the presence of the 5 wt.% MMT nanofillers. The DSSC efficiency was found to maintain 99.9% of its initial value after 194 h of testing at 60℃ under dark environments. The stability of the DSSC using PGEs with the optimal amount of MMT nanofillers was higher than that for the cells using liquid electrolyte and pure PGE.
Foam separation can selectively remove a target substance from a solution via adsorption of the substance with the surfactant at the surface of the bubble. A cationic dye, methylene blue, and an anionic dye, Fast Green FCF, were prepared as substances to be removed via foam separation. Anionic (sodium dodecyl sulfate, SDS), cationic (dodecyltrimethylammonium chloride, DTAC), and amphoteric (3-(dodecyldimethylammonio)propane-1-sulfonate, SB-12) surfactants were used in the foam separation process. The effectiveness of the surfactants for removing the cationic methylene blue increased as follows: DTAC < SB-12 < SDS. On the other hand, the effectiveness of the surfactants for removing the anionic Fast Green FCF was in the opposite order. The dyes were effectively adsorbed by the foams via electrostatic interactions between the oppositely charged surfactant and the dye molecules. Since amphoteric surfactants have both anionic and cationic charges in a molecule, they could effectively remove both dyes in the foam separation process. Therefore, it was found that the amphoteric surfactant was highly versatile. Analysis of the kinetics of the removal rate showed that the aqueous solutions of monomers could remove the dyes more effectively than micellar solutions in foam separation.
The solubilization of poorly water-soluble progesterone derivatives into micelles of a gemini surfactant was investigated in an aqueous medium. The aqueous solubility at different temperatures was determined spectroscopically using an ultraviolet visible light spectrophotometer. Thermodynamic parameters for the solubilization were calculated under the basis of the solubility change against temperature. The solubility of progesterone was quite low and remained constant below the critical micelle concentration (cmc) of the surfactant. On the other hand, the solubility increased considerably with increasing surfactant concentration above the cmc. It was suggested that the solubilizates were located in the vicinity of polar regions of micelles.
Foam separation promotes the removal of dissolved materials from solutions by adsorbing the molecules onto a surfactant. The zwitterion of rhodamine B was removed by using both anionic (sodium dodecyl sulfate: SDS) and cationic (dodecyltrimethylammonium chloride: DTAC) surfactants through foam separation. However, rhodamine B could not be removed from a strongly acidic DTAC solution (pH 2), because the molecular form changes from the zwitterion to cation. Moreover, the cationic dye of rhodamine 6G could not be removed from the DTAC solution. Therefore, these results demonstrate that the electrostatic interaction between a surfactant and target ion is an important factor in foam separation.
The effect of solvent species and quantity of solvent used for spreading on the morphology of Langmuir monolayer composed of palmitic and lignoceric acids was investigated based on atomic force microscopy observations. The variation in domain size depending on the evaporation time of the spreading solution indicated that the mixed monolayer was in a non-equilibrium phase-separated state.
For the controversy still existed about the oxidation stability of the high oleic oils compared with palm oil (PO), this study was aimed to explore the possible reason causing the controversies. Total polar compounds (TPC) was used to evaluate the oxidation stability of oils. Results showed there exist two kinds of lineal changes about the content of total polar compounds (TPC) in each oil, which were closely linked with the fatty acid composition and the tocochromanols content. The possible influence of the initial quality of oils also should be considered. The TPC of high oleic peanut oil (HOPO), high oleic sunflower oil (HOSO), high oleic rapeseed oil (HORO) and PO increased slowly at the initial period mainly owing to the antioxidation of tocochromanols, then sharply after 24, 48, 36 and 72 h respectively, when tocochromanols in each oil almost reduced below the detection limit. After that, the major factor would be fatty acids, particularly PUFA. It showed that the major tocochromanols in different oils (e.g. α, γ-tocotrienols in PO, α, γ-tocopherols in HORO and HOPO, and α-tocopherols in HOSO), could impose the main effects of inhibiting the TPC generation in the initial thermal treatment. The TPC in HORO significantly increased after 84 hours of heat process, which might be caused by the higher content of the polyunsaturated fatty acids (PUFA) (i.e. C18:2 and C18:3). However, the content of the saturated fatty acid (SFA) did not show statistically significant change during the thermal treatment.
The extraction of peanut oil was investigated using the combination of ultrasound and heat application, which is known as a novel technology called thermosonication. The study was set up using the Box–Behnken design and the models based on quadratic equations were established. The effects of extraction time (4-12 min), extraction temperature (40-60°C), solvent–to–solid ratio (SSR) (3:1-9:1)(v/w) and ultrasound power (60-100%) on the extraction yield and the oleic acid concentration of extracted oils were investigated. Results showed that the extraction yield was primarily affected by the extraction temperature and SSR. The average maximum yield of 39.93% was achieved when variables were set to 12 min of time, 50°C of temperature, 9:1(v/w) of SSR and 80% of ultrasound power. Thermosonication did not significantly affect the fatty acid composition. Since it was targeted to determine an optimum point where the maximum extraction yield and oleic acid concentration were obtained, a multiobjective optimization was performed. The optimum thermosonication conditions were determined as 4 min of time, 60°C of temperature, 9:1(v/w) of SSR and 100% of power with a maximum extraction yield of 39.86%. Also, the oleic acid concentration was determined as 63.51% in this optimum condition.
The aim of the present research is to investigate the effect of three harvest date on the composition of apricot seed. Indeed, triacylglycerols (TAGs) content and composition were studied in developing Tunisian apricot varieties bitter (Bargoug), semi-sweet (Oud Rhayem) and sweet (Chechi Bazza) cultivars at intervals of early (14 DAP), mid phase (28 DAP) and full phase (55 DAP) of oil accumulation by UHPLC-ESI-MS method. Eleven molecular species of triacylglycerols were detected and identified as LLL, LLO, LLP, LOO, LLS/LOP, LPP, OOO, LOS, OOP, POP and OOS. At 14 DAP, LLO was the major TAGs molecular species with 35.4-52.6% (maximum reached in semi-sweet apricot). Others major TAGs were founded at lower content as LOO (17.5-40.3%) and OOO (5.7-12.7%). However, among maturity, three distinct profiles of TAGs molecular species were observed: bitter apricot was significantly richer in OOO molecular species than cultivars ones. However, semi-sweet and sweet cultivars were richer in LLO and LOO molecular species at different time-dates. These latter may provide a schedule for harvesting Tunisian apricot seeds with high quality of oil content.
The main objective of this study was to differentiate twenty-three monovarietal olive oils produced in China (Azappa, Thiaki, Leucocarpa ovoid, manzanillo de labata, etc.) by studying their physicochemical properties, fatty acid profiles and oxidative stability. The majority of analytical indicators had statistically significant differences (p < 0.05). The tested cultivars produced excellent olive oils with an appreciable amount of natural antioxidants and chemical composition within the legal range. Our results demonstrate that Leucocarpa ovoid oil was characterized by high mean levels of total phenols (401.8 mg/kg), oleic acid (79.62%) and oxidative stability (18.64 h). Additionally, five types of olive oil were selected due to their high overall quality. Investigation of virgin olive oils indicates that the differences in the fatty acid profiles, phenols, sterols and tocopherols may be caused by genetic factors. The principal components analysis (PCA) results showed a strong differentiation between various cultivars in regard to their fatty acid composition and phenol, sterol and tocopherol levels. These components can be effective tools for efficient comparison and differentiation of these cultivars. To the best of our knowledge, this is the first work on the differentiation of the chemical constituents of virgin olive oils.
This study investigated the effect of papain on the demulsification of peanut oil body emulsion extracted using an aqueous enzymatic method and the associated mechanism. The highest free oil yield using papain (92.39%) was obtained under the following conditions: an enzymatic hydrolysis temperature of 55°C, sample-to-water ratio of 1:3, enzyme concentration of 1400 U/g, and an enzymatic hydrolysis time of 3 h. Papain degraded the peanut oil body protein to small-molecular-weight peptides (≤ 14.4 kDa). Compared to the emulsion before enzymatic hydrolysis, the amino acid content in the aqueous phase was higher after enzymatic hydrolysis, the viscosity of the oil body emulsion was lower, and the particle diameter of the emulsion was significantly larger. The following demulsification mechanism was derived. Papain degrades the protein on the peanut oil body and dissolves it in water. The outer side of the oil body loses the protection of electrostatic repulsion and steric hindrance provided by the membrane protein. This causes the viscosity of the emulsion system and the molecular steric hindrance to decrease. As a result, the oil droplets gather and eventually demulsify. The results of this study provide the theoretical basis for the instability in oil body emulsions and are expected to promote the application of enzymatic demulsification in industry.
Present study has successfully synthesized melamine-based covalent organic polymers (MCOPs) and applied it as lipase carrier for recyclable esters hydrolysis and transesterification. The synthesized MCOPs are composed of dense nanosheet structures having a thickness of 3.5 nm. Three immobilization methods namely physical adsorption, cross-linking and carrier activation were employed to prepare the MCOPs-immobilized CRL. Cross-linked MCOPs-immobilized CRL (41.30 mg protein/g MCOPs) and carrier activated MCOPs-immobilized CRL (33.20 mg protein/g MCOPs) had higher enzyme loading as compared to physical absorb MCOPs-immobilized CRL (29.30 mg protein/g MCOPs). Nevertheless, physical absorb MCOPs-immobilized CRL demonstrated the highest esters hydrolysis (49.85 U) and transesterification (1.04 U) activities. Despite having the highest enzymatic activity, physical absorb MCOPs-immobilized CRL were not able to maintain its catalytic stability with more than 30% decreased in enzymatic activity during consecutive hydrolysis and transesterification activities. Meanwhile, cross-linked MCOPs-immobilized CRL demonstrated highest catalytic stability with highest enzymatic activities at the end of consecutive reactions. All the MCOPs-immobilized CRL can be easily recovered and reused through centrifugation with more than 85% of recovery rate.
In this study, we provide a method for obtaining essential oil from Mentha arvensis L. in large quantities. Three types of polysaccharide-degrading enzymes were investigated, namely cellulase A “Amano” 3, cellulase T “Amano” 4, and hemicellulase “Amano” 90. The optimum extraction conditions were the combined use of 2 wt% cellulase T and 2 wt% hemicellulase 90, and 3 h of incubation. Enzymeassisted extraction increased the amount of the essential oil from 2.2 mL to 3.0 mL, compared with the amount extracted without an enzyme.
Sour citrus are prized for their flavor and fragrance. This work identified the components of the peel oil of Hetsuka-daidai (Citrus sp. hetsukadaidai), a special sour citrus that is native to the southern part of the Osumi peninsula, Kagoshima, Japan. These compounds were compared to those identified from the peels of six other major sour citrus: lime (Citrus latifolia), lemon (Citrus limon), Yuzu (Citrus junos), Kabusu (Citrus aurantium), Kabosu (Citrus sphaerocarpa), and Sudachi (Citrus sudachi). Peel oil contents were analyzed for the duration of four months during harvest season to investigate the differences in peel oil/fragrance during ripening. These results could facilitate the development of preferred flavor and scent profiles using local species.
Microwave is an alternative method which can rapidly pyrolyze biomass by thermal treating, and produce clean syngas and bio-oil products. In this research, the wood particles microwave pyrolysis process was proposed for preparing bio-oil and syngas production. The wood particles were first pyrolyzed by microwave reactor in the process, and then the bio-oil products were separated by cyclone separator and multi-phase separator, syngas products were prepared by steam reforming reactor and absorption tower. Kinetics for larch microwave thermogravimetry reactions were proposed and correlated with lab-scale experiments; the microwave pyrolysis process was simulated in Aspen HYSYS, and the results showed that when pyrolysis reaction temperature and microwave power were 900℃ and 2.0 kW respectively, the maximum bio-oil and syngas production can be achieved. The H2/CO and CO2 content in syngas which can be used in chemical processes such as Fischer-Tropsch synthesis, can be controlled by the molar ratio function of steam and pyrolysis gas.