Adsorption Zone Research Articles

Molecular heterostructured interlayer for fabrication of high-performance thin film composite reverse osmosis membranes

To solve the scarcity of fresh water, reverse osmosis (RO) technology for seawater desalination and wastewater reuse has been developed rapidly. However, the performance of RO is limited by poor selectivity towards certain harmful small molecule constituents (e.g., boron in seawater and N-nitrosodimethylamine in wastewater) and the permeability-selectivity trade-off. Herein, a metal polyphenol network interlayer including both hydrophobic zone and monomer adsorption zone is proposed to optimize interfacial polymerization (IP) process for fabrication of RO membrane. This heterogeneous characteristic is endowed by well-chosen phenol (i.e. TTSBI) and metal (Ni). The physicochemical properties of the substrate are also optimized. An ultra-selective RO membrane with thinner separation layer, higher crosslinking degree and larger surface area is obtained. The RO membranes exhibit separation performance beyond the upper selectivity limit for NaCl and hazardous small molecules. The membrane water permeance is 3.50 L m−2h−1bar−1while the NaCl rejection is 99.5 %. Meanwhile, the mechanism of the interlayer influencing IP process is investigated by combining molecular simulation and experimental methods. Our work provides a novel design direction of substrate used for fabricating RO membrane with outstanding performance.

РАЗРАБОТКА МЕТОДА ИДЕНТИФИКАЦИИ И ОЦЕНКА КОЛИЧЕСТВЕННОГО СОДЕРЖАНИЯ ЭФИРНОГО МАСЛА В ХВОЕ МОЖЖЕВЕЛЬНИКА ОБЫКНОВЕННОГО

The aim of the study is to develop methods for the identification of terpenoids and to assess the quantitative content of essential oil in the conifers of juniper, fresh and dried by air-shade drying. The object of the study were samples of needles of juniper. The raw materials were used fresh and dried. To carry out qualitative reactions, well-known methods were selected, which are most often used in the analysis of essential oil raw materials. The identification of essential oil components was carried out by TLC method on Silufol plates. A-pinene solution was used as a standard. The quantitative content of essential oil in the raw material was determined by steam distillation in accordance with the OFS method.1.5.3.00010.15. Determination of the essential oil content in medicinal plant raw materials and medicinal herbal preparations. The authors proposed qualitative reactions for the identification of terpenoids in raw materials, which can be used to form the "Authenticity" section for a new type of raw material-needles of juniper. A-pinene was identified by the TLC method. A quantitative assessment of the essential oil content in fresh and dried raw materials was carried out. A decrease in the content of essential oil during drying of raw materials was revealed. Qualitative reactions were selected experimentally to confirm the presence of terpenoids in alcoholic extracts from juniper needles, as well as unsaturated compounds in essential oil obtained by steam distillation. The TLC method identified a-pinene in the analyzed samples. The presence of additional 11 adsorption zones in the samples of essential oil obtained from fresh raw materials and 9 in samples from dried raw materials was also revealed. The results obtained indicate changes in the composition of the terpenoid fraction occurring during the drying process and actualize further research in this direction. Assessment of the quantitative content of essential oil in the raw material, carried out according to the method 2 of the OFS.1.5.3.00010.15 "Determination of the essential oil content in medicinal plant raw materials and medicinal plant preparations", showed a decrease in the essential oil content in all dried samples compared with fresh raw materials. The data obtained during the experiment allow us to recommend the inclusion of an essential oil content of at least 1% in the quality indicators of juniper needles, as well as optimize the drying mode to better ensure the preservation of essential oil in raw materials.

Determination of GaN nanosensor for scavenging of toxic heavy metal ions (Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+) from water: Application of green sustainable materials by molecular modeling approach

Gallium nitride nanocage (GaN_NC) can select toxic heavy metals from water. Therefore, it has been found a selective competition for metal cations in the GaN_NC. The electromagnetic and thermodynamic attributes of heavy metals cations-trapped gallium nitride nanocage (GaN_NC) was depicted by material modeling. The data display that heavy metals cations-trapped in the GaN_NC system are resistant materials, with the firm adsorption zone in the center of the cage. Furthermore, charge transfer from GaN_NC to the heavy metals cations demonstrates clear n-type adsorbing manner. The encapsulation of heavy metals cations occurs via chemisorption. In this article, the behavior of trapping of heavy metal ions of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ by gallium nitride nanocone for sensing the water metal cations was observed. The nature of covalent features for these complexes has represented the analogous energy amount and vision of the PDOS for the p states of N and d states of heavy metal cations of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through water treatment. The partial density of states (PDOS) can also evaluate an appointed charge group between Mn2+, Zn2+, Ag+, Au3+, Al3+, Sn2+ and GaN_NC which indicate the most stable complex of metallic visage and a certain degree of covalent specifications between heavy metals cations and gallium nitride nanocage. Furthermore, the NMR analysis indicated the notable peaks surrounding metal elements of Mn2+, Zn2+, Ag+, Au3+, Al3+ and Sn2+ through the trapping in the GaN_NC during ion detection and removal from water; however, it can be seen some fluctuations in the chemical shielding treatment of isotropic and anisotropy tensors. Based on the results in this research, the selectivity of metal ion adsorption by gallium nitride nanocage (ion sensor) has been approved as: Ag+ ˃ Au3+ ˃ Mn2+ ≫ Zn2+ ˃ Sn2+ ˃ Al3+. Using quantum theory of atoms in molecules (QTAIMs) method, intermolecular interactions and corresponding parameters at critical bonding points were also investigated.

РАЗРАБОТКА МЕТОДА ИДЕНТИФИКАЦИИ И ОПРЕДЕЛЕНИЕ ЭФИРНОГО МАСЛА В ПОБЕГАХ ТУИ ЗАПАДНОЙ (THUJA OCCIDENTALIS)

The purpose of the study is to develop methods for identifying terpenoids and assessing the quantitative content of essential oil in the shoots of western thuja (Thuja occidentalis). The object of the study was samples of thuja occidentalis shoots. The raw materials were used fresh. To carry out qualitative reactions, well-known methods were selected that are most often used in the analysis of essential oil raw materials. Identification of essential oil components was carried out by TLC on Silufol plates. A solution of α-pinene was used as a standard. The quantitative content of essential oil in the raw materials was determined by steam distillation in accordance with the GPM method 1.5.3.00010.15 Determination of the content of essential oil in medicinal plant raw materials and medicinal herbal preparations. The authors proposed qualitative reactions for identifying terpenoids in raw materials, which can be used to form the “Authenticity” section for a new type of raw material - thuja occidentalis shoots. α-pinene was identified by TLC. A quantitative assessment of the essential oil content in raw materials was carried out. Qualitative reactions were experimentally selected to confirm the presence of terpenoids in alcoholic extracts from thuja occidentalis shoots, as well as for unsaturated compounds in essential oil obtained by steam distillation. Using TLC, α-pinene was identified in the analyzed samples. The presence of additional 8 adsorption zones in the essential oil samples was also revealed. Assessment of the quantitative content of essential oil in raw materials, carried out according to method 2 OFS.1.5.3.00010.15 “Determination of the content of essential oil in medicinal plant raw materials and medicinal herbal preparations.” The data obtained during the experiment allows us to recommend the inclusion of an essential oil content of at least 2.84% in the quality indicators of western thuja shoots.

Desulfurization of Zawia Refinery Diesel Using Adsorption Fixed Bed Process

The study focuses on the dynamic modeling of a fixed-bed adsorber for the adsorption of sulfur compounds in diesel fuel. The model considers non-ideal plug flow behavior and velocity variation along the column, providing a more realistic representation of the adsorption process. Additionally, internal mass-transfer resistances due to pore diffusion mechanisms are incorporated into the model. The study investigates adsorption performance by examining different flow rates (5 cc/min, 10 cc/min, 15 cc/min, and 20 cc/min) and inlet concentrations ranging from 586 to 100 ppm. The bed height is constant at 30 cm. The behavior of various parameters, such as bed utilization, breakpoint time, film mass transfer coefficient, and height of the adsorption zone, is analyzed. The results indicate that a sharp front of the breakthrough curve is observed, followed by the broadening of the tail of the breakthrough curve. The breakthrough curve represents the adsorbate concentration in the effluent stream over time. The investigation reveals that a high flow rate of 20 cc/min and a high inlet concentration yield better overall bed capacity utilization for the adsorption system. This means that the bed is more effectively utilized at higher flow rates and higher inlet concentrations, leading to improved adsorption performance. In conclusion, high flow rates and high inlet concentrations are favorable for enhancing the adsorption system's performance in terms of bed utilization. These results provide valuable insights for optimizing the design and operation of fixed-bed adsorbers that remove sulfur compounds from diesel fuel.

Research on column adsorption of Zn<sup>2+</sup> by hydroxyapatite granules

Hydroxyapatite (HAp) granules were fabricated successfully from HAp powder and polyvinyl alcohol (PVA) additive by sintering method. The characterization of material was analyzed by color, durability in the water, XRD, EDX, SEM and BET. The obtained HAp granules were white, single phase of HAp, with specific surface area of 73 m2/g, size of granule about (2 × 10) mm. HAp granules were used for the removal of Zn2+ ions from aqueous solution. The effect of factors on the Zn2+ adsorption property was investigated. The adsorption efficiency and capacity obtained 77.15 % and 2.57 mg/g, respectively at suitable batch adsorption condition: HAp granule mass of 0.5 g/ 50mL solution, initial concentration of 20 mg/L Zn2+, contact time 40 minutes and pH0 5.7 at 30 oC. The adsorption efficiency reached about 99.55 % at suitable column adsorption condition: contact time of 3,5 min, flow rate of 14 mL/min, adsorption zone height of 4Ф (Ф = 2.5 cm), initial concentration of 20 mg/L Zn2+, HAp granule mass of 11.9 g/ 2L solution, pH0 5.7 at 30 oC.

Developing lateral-flow devices for the fast and cheap detection of SARS-cov-2 in wastewater: a potential tool to monitoring local virus outbreaks by wastewater based epidemiology

The SARS-CoV-2 virus generates severe respiratory tract complications such as pneumonia and bronchitis and mild symptoms such as common colds or asymptomatic conditions. The SARS-CoV-2 presence in human feces and in treated/untreated wastewater suggests a transmission way that could generate local outbreaks, in addition to other type of diseases or disorders. Based on the above, in this work it was proposed the assembly of a lateral flow device (LFD) to determine the SARS-CoV-2 presence in wastewater samples. In the LFD a wastewater sample capillary flowed through four membranes: sample zone, conjugate delivery zone, reaction zone and the reactive adsorption zone. The virus amplification was achieved by the novel reverse transcription loop-mediated isothermal amplification (RT-LAMP) at the sampling point. The membranes preconditioning processes and the use of membranes with 5-20 nm porous size increased the capillary flow rate and it was promoted the interaction of the gen of SARS-CoV-2 with the capture agents in the reactive adsorption zone. Additionally, the sensibility of the detection was improved using several methods for the immobilization of the capture agents on the reaction zone membrane. The RT-LAMP method combined with the assembled LFD allowed an efficient SARS-CoV-2 detection at the sampling point in a simple way, cheap and fast compared to conventional and expensive RT-PCR.

Long-Term Bearing Capacity of Concrete Pile Composite Foundation under Composite Salt Erosion

In order to study the long-term bearing capacity of concrete pile composite foundation in the Salt Lake area, based on the Tehran Isfahan high-speed railway project in Iran, the full (semi) immersion drying test and rapid freeze-thaw test was carried out, and the specimens were scanned by electron microscope. Numerical calculations were used to study the effects of different pile strengths and design parameters on the long-term bearing capacity of the composite foundation. The main conclusions were as follows: The concrete specimens in the adsorption zone deteriorated earlier and faster. In the rapid freeze-thaw tests, the strength attenuation of high-strength (C40, C50) specimens was smaller than that of low-strength specimens (C20). Within 20 years after construction, the additional settlement of low-strength (C20) piles was 12.21 mm, while high-strength concrete was less affected by deterioration. With pile spacing ranging from 1.8 m to 4.5 m, the maximum increase in additional settlement under the C20 condition was about 20 mm. The pile-soil stress ratio under the three conditions increased by 2.42, 6.59, and 8.63. As the pile length and diameter increased, the peak stress of the pile body moved towards the pile end, and the changes in the pile-soil stress ratio under the three conditions were similar.

Simulation on the Breakthrough Curve During CO2 Adsorption from Biogas in a Fixed Bed Column

Separation of CO2 gas from the biogas can be accomplished by adsorption process. An adsorbent has a maximum capacity, so the adsorbent will eventually be saturated at a certain time. Therefore, it is necessary to simulate the adsorption mass transfer to produce a breakthrough curve. The breakthrough curve from the simulation of adsorption mass transfer was validated with the experimental data. The research was conducted using variations in temperature and pressure. The mass transfer simulation was solved using the finite difference method. The adsorbent used in this research was 13X zeolite and the biogas was obtained from cow dung waste. Convergent curves can be obtained in numerical simulations as breakthrough curves. This research shows that adsorption should occur at low temperatures and high pressure. Column height and flow velocity also influence the breakthrough time. The comparison of the simulated breakthrough time with experimental data is not much different with R2 0.9969. The striking difference is in the adsorption zone with average relative error (ARE) values ranging from 9.57% to 20.49%. From the results of entropy, enthalpy, and Gibbs free energy calculations, the biogas adsorption research on the 13x zeolite column is an exothermic and spontaneous process

Analysis of colloidal activated carbon alternatives for in situ remediation of a large PFAS plume and source area

AbstractThis study evaluated optimal locations for in situ remediation of per‐ and poly‐fluoroalkyl substances (PFAS) in groundwater with colloidal activated carbon (CAC). New Freundlich isotherms for PFAS adsorption to CAC were estimated to illustrate the effect of competitive adsorption with dissolved organic carbon and other PFAS in a groundwater sample. A hypothetical model scenario was constructed based on source area characteristics similar to a site impacted by aqueous film forming foam in South Dakota. Modeling indicates that, even with high PFAS concentrations, CAC would still be capable of maintaining concentrations below proposed maximum contaminant levels in the adsorption zone for at least 30–40 years. Two‐dimensional areal modeling indicates that the future breakthrough of PFAS is likely to occur in the localized core of the plume, and that the corresponding future reinjection of CAC will only need to be conducted over a smaller portion of the original injection footprint. The benefits of implementing a phased remedial approach at PFAS sites are discussed. Source area and mid‐plume CAC treatments are shown to be ineffective at attenuating PFAS concentrations at the downgradient property boundary within a reasonable timeframe when PFAS travel time is relatively slow. Among the CAC alternatives evaluated here, a downgradient CAC permeable reactive barrier has the best performance with respect to protecting downgradient receptors.

Trapping of toxic heavy metals from water by GN–nanocage: Application of nanomaterials for contaminant removal technique

Gallium nitride nanocage (GaN_NC) can select toxic heavy metals from water. Therefore, it has been found a selective competition for metal cations in the GaN_NC. The electromagnetic and thermodynamic attributes of heavy metals cations trapped GaN_NC was depicted by material modeling. The data displays those heavy metals cations-trapped in the GaN_NC system are resistant materials, with the most firm adsorption zone in the center of the cage. Furthermore, charge transfer from GaN_NC to the heavy metals cations demonstrates clear n-type adsorbing manner. The encapsulation of heavy metals cations occurs via chemisorption. In this article, it was observed the behavior of trapping of main group cations of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ by GaN_NC for sensing the water metal cations. The nature of covalent features for these complexes has represented the analogous energy amount and vision of the partial density of states (PDOS) for the p states of N and d states of heavy metal cations of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ through water treatment. The PDOS can also evaluate an appointed charge group between Cr3+, Co2+, Cu2+, Ni2+, Pb2+, As3+ and GaN_NC which indicate the most stable complex of metallic visage and a certain degree of covalent specifications between heavy metals cations and GaN_NC. Furthermore, the nuclear magnetic resonance (NMR) analysis indicated the notable peaks surrounding metal elements of Cr3+, Co2+, Cu2+, Ni2+, Pb2+ and As3+ through the trapping in the GaN_NC during ion detection and removal from water; however, it can be seen some fluctuations in the chemical shielding treatment of isotropic and anisotropy tensors. Based on the results in this research, the selectivity of metal ion adsorption by GaN_NC (ion sensor) has been approved as: Ni2+˃˃˃ Cu2+ ˃Co2+˃ Cr3+˃˃ Pb2+ ˃ As3+.

Migration behavior of water molecules and chloride ions at the nanopore scale based on molecular properties under temperature effect

The durability of cement-based materials is closely related to the transmission characteristics of water and chloride ions in the pores of calcium silicate hydrate (C-S-H) gel, especially in the climate conditions with significant temperature difference. The local structure and transport process of water molecules and chloride ions in gel pores are affected by interfacial effects. The unsaturated transport model of sodium chloride solution in C-S-H gel pores is established on the molecular scale, under different temperature and pore size conditions. Divide the regions in the C-S-H gel pore model into internal adsorption zone, external adsorption zone, and free zone. Taking into account the intrinsic mechanisms and molecular properties of water molecules and ions during transport in the C-S-H gel pores, the local structures and dynamic properties of water molecules and ions in the gel pores are quantitatively described. The electrical double layer and the double-layer water film overlap in the 1.5 nm gel pore, the water molecule and the chloride ion are closely arranged. Thus the diffusion coefficient is far lower than others, and is rarely affected by temperature. Considering the changes in the molecule properties of water and ion in different zones in molecular simulation results, a theoretical model of nanopore water and ion migration was established, revealing the migration behavior of water and ions. The results indicate that the steady-state diffusion fluxes of water and chloride ions are positively correlated with the effects of temperature and pore size, and the increasing amplitude of their diffusion fluxes is characterised by a similar phenomenon with that. This research provides a theoretical basis for the mechanism and durability of cement-based materials corroded by water and chloride ions in marine environments.

Effects of Charged Surfactants on Interfacial Water Structure and Macroscopic Properties of the Air-Water Interface.

Surfactants are used to control the macroscopic properties of air-water interfaces. However, the link between the molecular structure of surfactant adsorption and macroscopic properties is poorly understood. Using sum-frequency generation spectroscopy and molecular dynamics simulation, we show that two ionic surfactants (dodecyl trimethylammonium bromide and sodium dodecyl sulphate) with the same carbon chain lengths and head group charge magnitude (but different signs) can interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br- counterions compared to smaller Na+ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H+ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H+ point down to water. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature.

Modeling and application of continuous ion exchanges process for lithium recovery from salt lake brine

A composite model has been developed to simulate and optimize the continuous multi-column lithium adsorption based on the continuous adsorption of lithium from high Mg/Li ratio brines. The model not only simulates all the adsorption columns of the adsorption process, but also the auxiliary equipment connected to the adsorption columns such as pumps and valves, to describe the multi-column continuous lithium extraction process in detail. To improve the efficiency of lithium extraction, a 4-zone, 20-column carousel-type continuous lithium extraction process was proposed and optimized using the composite model. When the feed flow rate was set to 25 mL/min in the adsorption zone, 8 mL/min in the washing zone and 15 mL/min in the product zone, the Li+ extraction rate in the adsorption zone was 98.26%, the lithium loss in the washing zone was 16.12%, the magnesium removal rate in the washing process was 98.77%, the concentration of lithium solution obtained in the product zone was 488.55 mg/L, and the magnesium-lithium ratio was 6.45, with a lithium recovery of 79.68% for the whole continuous lithium extraction process. Overall, the continuous carousel lithium extraction process achieved the expected magnesium separation and continuous lithium extraction from the brine of the Qarhan Salt Lake.

A Thin-Layer Chromatography Method for the Determination of Essential Oil Components in Anise and Fennel Fruits

Scientific relevance. The State Pharmacopoeia of the Russian Federation, edition XIV, requires the identification of aniseed and fennel fruits by the same thin-layer chromatography (TLC) procedure using Sudan III and menthol. These markers are neither specific nor related to the therapeutic effects of these herbal drug products. The visual interpretation of chromatograms is complicated because of the low intensity of adsorption zones. Moreover, the corresponding compendial monographs do not characterise the adsorption zones specific to each of the plants. The most abundant component in aniseed and fennel essential oils, trans-anethole, would make a better reference standard from a methodological point of view.Aim. This study aimed to optimise the TLC procedure for essential oil determination in herbal drugs and herbal medicinal products of aniseed and fennel fruits and subsequently recommend it for inclusion in the relevant compendial monographs.Materials and methods. The study examined samples from several batches of herbal drugs, including aniseed and common fennel fruits, sourced from Russian manufacturers. The reference standards comprised commercial reagents, including trans-anethole, anise oil, and linalool, as well as fresh essential oils that had been steam distilled from the test samples in a Clevenger apparatus. The study was conducted by TLC. Sample preparation involved using Merck aluminium TLC plates, an IKA KS-501 digital orbital shaker, and a CAMAG Linomat 5 semi-automatic sample application system. The authors heated the plates in either a Binder ED53 drying oven or a CAMAG TLC plate heater. For visualisation, the authors selected a CAMAG TLC VISUALIZER 2 UV imaging and documentation system.Results. The informational and experimental research showed the feasibility of using trans-anethole as an identification reference standard for common anise and fennel fruits. The authors selected the optimal solvent for extracting active substances from the test products (hexane) and a detection reagent for improving visual evaluation of the chromatograms (1% sulfovanillin). The authors established characteristic adsorption zones for differentiating between aniseed and fennel fruits.Conclusions. The optimised procedure identifies the main components in the essential oils of aniseed and fennel fruits with a specific reference standard. This procedure may be recommended for inclusion in draft monographs for the corresponding herbal medicinal products.

Boron continuous recovery from brines by the multicolumn simulated moving bed process with boron chelating resin

The objective of this work is to develop an advanced adsorption process to continuously recover and remove boron from brines. Firstly, the adsorption and desorption performances of boron on the commercially available N-methylglucamine resin (D403 resin) are evaluated, then, the cyclic adsorption and desorption process is investigated experimentally in the fixed bed adsorber for boron recovery from brine. It is confirmed that the cyclic process involves five steps, such as boron recovery from brine, water washing 1 to remove the retained brine, boron desorption to obtain boron-rich solution, water washing 2 to recover the retained HCl solution, and resin regeneration for the reuse. Furthermore, the seven-column simulated moving bed (SMB) process with four zones is designed and investigated experimentally. Experimental results demonstrate that boron can be recovered continuously from brine in adsorption zone, and boron-rich solution is obtained continuously in desorption zone. When the inlet brine contains a low boron content (for example 296.5 mg/L), most boron in brine can be recovered by the seven-column SMB unit with 96.8 % boron adsorption efficiency, and the discharged brine contains 8.77 mg/L boron, approximately meeting the environmental protection requirement for the limitation of boron emission. Therefore, the simultaneous recovery and removal of boron from brine can be achieved by the proposed multicolumn SMB process.

Design of frontal chromatography separation of 1-phenylethanol and acetophenone using a hydrophobic resin

Adsorption and chromatographic processes havegood potential in the purification of natural aromas produced via biocatalytic routes. This work deals with the recovery of 1-phenylethanol (PE) from mixtures containing different amounts of acetophenone (AP). Amberlite FPX68, an industrial adsorbent with high selectivity with respect to acetophenone, was chosen for the separation of PE and AP by frontal chromatography. Small-scale experiments were performed for two different feed compositions and various flow rates and bed lengths. Using the target purity of 99 %, promising yields close to 90 % were obtained. The breakthrough curves were fitted with the equilibrium dispersive model, which provided HETP values under the different conditions. The obtained dependences of HETP on flow velocity complied with the Van Deemter equation. The contributions of individual phenomena responsible for adsorption zone broadening were analyzed. The experimental and modelling results obtained for the small-scale column became the basis for the scale-up of frontal chromatography separation of PE with an annual capacity up to 500 kg.

COMBINATION OF METHODS FOR DETERMINE THE AUTHENTICITY OF HERBS THYMUS SERPYLLUM AND THYMUS MARSHALLIANUS

Relevance. Authentication of crushed medicinal plant raw materials (RM) is an actual issue because there are species similar in morphology or there is a possibility of interspecific hybridization. The characteristics of the absorption spectra of extracts and their chromatographic profile are significant indicators of the authenticity of RS. The aim of the study was a comparative analysis by TLC and spectrophotometry of water-alcohol extracts from the herb Thymus marshallianus Willd. (TM) and Thymus serpyllum L. (TP). Material and methods. Water-alcohol extracts were obtained from 1.0 g of RS (exact suspension) in two ways (extractant – 70% ethanol, heating in a boiling water bath; extractant – 50% ethanol, 20–22 °C). Absorption spectra were recorded in the range of 200–500 nm. Eluent – ethyl acetate : formic acid anhydrous : water (70:15:15) was used for chromatography. Detection of adsorption zones was carried out after treatment with a 5% alcohol solution of AlCl3 at 365 nm. Rutin, quercetin and cinaroside were used as standard samples. Results. Microscopic analysis revealed diagnostic signs of the TM and TP leaf – trichomes of various types. The absorption spectra of water-alcohol extracts from TM and TP (obtained with 50% and 70% ethanol) have two pronounced maxima. When AlCl3 is added, a bathochromic shift of the long-wavelength absorption bands is observed. The chromatograms of these extracts revealed a yellow zone at the level of cinaroside, and differences in the number and color of the adsorption zones of TM and TP extracts. Conclusion. The absorption spectra of water-alcohol extracts have two pronounced maxima for TP of the same intensity, for TM – different. The intensity of differential absorption spectra of water-alcohol extracts of TM is higher, which indicates a higher content of flavonoids in its extracts. Cinaroside was detected in TM and TP extracts by TLC, while 11 adsorption zones are distinguishable on the chromatogram of extracts from TM herb, and 9 from TP.

Current aspects of qualitative and quantitative analysis of common yarrow (<i>Achillea Millefolium</i> L.)

Aim to develop a methodology for qualitative and quantitative analysis of flavonoids in the herb of Achillea millefolium L.
 Material and methods. The material of the study was the yarrow herb harvested in 2020 and 2021, and an industrial sample from JSC "Krasnogorskleksredstva". Additionally, we used the reference samples of flavonoids: rutin, quercetin, kaempferol, cynaroside, and luteolin, received previously during our studies of the raw materials containing the flavonoids and described using the NMR, UV and mass spectroscopy. The authenticity was determined by the thin layer chromatography (qualitative analysis). For the quantitative analysis of the total flavonoids, we used the differential spectrophotometry, conducted in accordance with Pharmacopoeial monograph 1.2.1.1.0003.15 "Spectrophotometry in ultraviolet and visible spectra". The spectral characteristics of the water-ethanolic extractions were marked using the spectrophotometer "Specord 40" (Analytik Jena AG, Germany), in cuvettes with layer thickness of 10 mm.
 Results. Based on the results of the authenticity determination, we revealed three adsorption zones with bright yellow glow in UV light at a wavelength of 365 nm (reagent AlCl3), one of which was at the level of the adsorption zone in the chromatogram of the solution of standard sample of cinaroside with a value of Rf 0.7. The dominant adsorption zone with a value of Rs 1.3 in respect to the reference sample of cynaroside was presumably attributed to cosmosiin, while the adsorption zone with a value of Rf 0.8 was detected at the level of standard sample of kaempferol. The obtained data confirmed the presence of cynaroside in the herb of common yarrow, and also the possibility to conduct the qualitative and quantitative analysis of the given raw material with the use of cynaroside as a reference sample. We developed the method of quantitative determination of the total flavonoids in yarrow herb using a reference sample of cynaroside and differential spectrophotometry at an analytical wave length of 400 nm. The content of the total flavonoids for the common yarrow herb varied from 0.410.02% to 0.740.03% (equivalent to cynaroside). The error of single determination with 95% confidence interval was 6.70%.

Water transport in calcium silicate hydrate nanoscale pores by molecular dynamics: Unsaturated steady-state diffusion and suction

Water transfer in calcium silicate hydrate (CSH) nanoscale pores is an important factor affecting the durability of cement-based materials. Using molecular dynamics, the transport behaviour of nanoscale water in unsaturated CSH gel pores can be simulated to explore the transport law and mechanism of unsaturated water in the gel pores. In this paper, two kinds of transport models were established: an unsaturated steady-state diffusion model and a suction model. The effects of pore size and saturation level on the steady-state density distribution, dipole orientation, dipole moment and diffusion coefficient of water in each region were studied. Then, the influence of temperature, pore diameter, initial saturation level and tortuosity on the water absorption rate in the suction process was analysed, and the CSH molecular formula for the saturation state was calculated. The results showed that the distribution of water in the CSH gel pore was mainly related to the saturation level and wall position, and the percolation effect was triggered when the saturation of the gel pore reached 53 %. Water molecules located in the interlayer zone, adsorption zone and free zone exhibit the laws of the free zone > adsorption zone > interlayer zone due to the differences in geometric constraints and bonding. With the increase in the saturation level of water in the gel pore, the overall diffusion coefficient of water presents a change law of first rising and then falling. A higher temperature will magnify the effect on the promotion of transport. The pore size of the gel pore is positively correlated with the diffusion capacity of water, while higher initial saturation level and tortuosity will both inhibit the absorption rate of the gel pore. The CSH formula in the saturated stable state is (CaO)1.65SiO2(H2O)2.1. For cement-based materials with a high proportion of large gel pores (above 2 nm), limiting the saturation level in the gel pores below the percolation threshold (preferably below 45 %) as far as possible can effectively inhibit the water transport capacity. The simulation results are in good agreement with the data in the literature.