OH Peak Research Articles

Numerical simulation of flame propagation characteristics of NH3/Air flames assisted by non-equilibrium plasma discharge

Nanosecond non-equilibrium plasma-assisted combustion technology emerges as a reliable novel approach to enhance the flame propagation speed of NH3. In this study, we developed a zero-dimensional + one-dimensional (0-D+1-D) non-equilibrium plasma-assisted combustion model to investigate the impact of nanosecond pulse discharge on the freely propagating flame speed of NH3/Air mixture. The results reveal that due to the plasma discharge, abundant intermediate species (N2H4, N2H3, NO, H2O2) are formed at the inlet and are subsequently transported downstream, facilitating flame propagation. As a result, the speed of the 1-D freely propagating flame increases, and the flame front is closer to the inlet compared to the non-plasma condition. The transport effect of H2 is also evident, with high concentrations of H2 from the inlet providing the basis for reactions at the flame front that promote combustion. Furthermore, after the initial mixture flows into the flame front, a slight increase in heat release is observed, but this increase occurs within a very limited distance. Notably, in the case of plasma, a stronger heat release is evident at the flame front. Moreover, with plasma, the peaks of OH, H, O, NH2, and HO2 are higher and earlier than those of the non-plasma case due to the transport and kinetic effects of plasma. Pathway flux analyses reflect significant changes in the production and consumption paths of the three components OH, H, and O, which are most important for consuming NH3 due to plasma addition. The higher OH mass fraction promotes the chain reactions that consume NH3, effectively enhancing the flame propagation speed. Novelty and significance statementThis study introduces a novel 0-D+1-D nanosecond non-equilibrium plasma-assisted combustion model to examine the impact of nanosecond pulse discharge on NH3/Air flame propagation. It uniquely analyzes the interaction between species at the inlet and flame front, highlighting the transport effects of plasma-generated intermediates (N2H4, N2H3, NO, H2O2, H2) that enhance flame speed, with a detailed pathway analysis of key species (O, OH, H).

Effect of low degree succinylation on properties of enzyme-induced casein hydrogel

This study examines the impact of succinic anhydride (SA) modification (0–9 %) on the gel properties of casein. Upon succinylation, the surface hydrophobicity (H0) of casein initially increased before decreasing, achieving its peak at a degree of succinylation of 5.22 ± 0.16 %. The α-helix content rose to 14.13 ± 2.60 %, and the -OH peak shifted towards lower wavenumbers, suggesting enhanced hydrogen bonding within intra/intermolecular structures. The storage modulus in the rheological test escalated from 2160.11 Pa to 5047.60 Pa, and SEM analysis revealed that the optimally succinylated casein gel formed a denser and more stable gel network structure. Moreover, succinylated casein hydrogels demonstrated superior texture properties, swelling ability, and thermal stability. Molecular dynamics simulation (MD) results suggest that SA preferentially binds to LYS27 and LYS28 of β-casein via hydrogen bonds and amide bonds, respectively. The interaction between modified proteins is primarily governed by hydrogen bonds, aligning with FT-IR findings. PCA analysis identified a positive correlation between the ordered structure and gel performance. This research offers theoretical insights and reference data for modulating casein hydrogel properties through succinylation.

Low-energy argon ion beam irradiation for the surface modification and reduction of graphene oxide: Insights from XPS

Developing environmentally friendly methods for reducing graphene oxide (GO) is essential. This study investigates the surface modification and reduction of GO films using 200 eV argon ion (Ar+) beam irradiation. X-ray Photoelectron Spectroscopy (XPS) analysis reveals significant chemical changes on the GO surface. GO was irradiated with a 200 eV Ar+beam for varying times (0–80 s). XPS survey spectra showed the presence of carbon and oxygen, with an increasing carbon atomic percentage over time. High-resolution XPS spectra of C 1s revealed peaks corresponding to sp2, C–OH, O–C–O, CO, and O–CO bonds. In the O 1s spectra, CO, O–C–O, and C–OH groups were observed. Upon irradiation, the CO peak consistently decreased, the O–C–O peak fluctuated, and the C–OH peak increased, indicating effective reduction of CO groups, dynamic changes in O–C–O functionalities, and the formation of additional C–OH groups. The C/O ratio increased from ∼2.4 to 2.7, underscoring the reduction process and enhanced carbon content. This method proves to be an efficient approach for producing reduced graphene oxide (rGO) with improved properties for advanced applications.

Continuum and spectral-line observations of the OH megamaser galaxy IRAS 01298−0744

We present Very Long Baseline Array observations of radio continuum and OH line emission toward the OH megamaser (OHM) galaxy IRAS 01298−0744. We recover over 82% of the OH line emission seen in single-dish observations, including multiple strong OH line components and the broad shallow line profile spanning over 1000 km s−1. The OH emission spatially has four compact components, as well as diffuse emission, and the 3σ signals are distributed in a rectangular region with size of ∼40 × 30 mas. The spatial-velocity structure is complex and is consistent with that from HCN and HCO+ lines in the literature, indicating that the nuclear region of this source is likely still in the merging process characterized by intense nuclear activities. The multiple strong OH peaks are blue-shifted compared to dense millimetre-wave molecular gas tracers, but similar to optical Na I absorption. This suggests that the compact masers might be in an outflow driven by an active galactic nucleus or starburst. We have detected compact radio continuum emissions adjacent to the maser positions with a brightness temperature of around 3 × 106 K, similar to other OHM galaxies with very-long-baseline interferometry observations in the literature, which is consistent with a starburst origin.

Partially Bio-Based Benzoxazine Monomers Derived from Thymol: Photoluminescent Properties, Polymerization Characteristics, Hydrophobic Coating Investigations, and Anticorrosion Studies.

In this work, four thymol-based benzoxazines were synthesized using four primary amines with different chain lengths, namely methylamine, ethylamine, 1-propylamine, and 1-butylamine, which are then named T-m, T-e, T-p, and T-b, respectively. The optical properties of the synthesized thymol-based benzoxazines were examined via the photoluminescent study of their solutions in acetone. The results show that all the prepared benzoxazines emitted blue light with the maximum wavelengths from 425 to 450 nm when irradiated by the excitation wavelengths from 275 to 315 nm. The maximum excitation wavelengths are found to be 275 nm. The polymerization of the thymol-based benzoxazines is triggered by heat treatments with different conditions (160, 180, and 200 °C for 1 h). According to the FTIR results, the heat-curing process introduces a presence of the OH peak, of which intensity increases as the curing temperature increases. Thermal decompositions of thymol-based benzoxazines regarding TGA analyses reveal the enhancement of thermal stability of the benzoxazines with respect to the N-substituent chain length, as significantly observed the change in the first thermal decomposition at temperature ranged from 253 to 260 °C. Synthesized benzoxazine derivatives are further employed to coat the substrate, e.g., the glass slides. The investigation of the water contact angle shows that the coating of the benzoxazines onto the surface improves the hydrophobicity of the substrate, resulting in the enlargement of the contact angle from 25.5° to 93.3°. Moreover, the anticorrosion performance of the polybenzoxazine coatings is examined using potentiodynamic polarization techniques. The results illustrate the anticorrosion efficiency of the thymol-based polybenzoxazine up to 99.99%. Both hydrophobic and electrochemical studies suggest the feasibility for employing benzoxazines in anticorrosion coating applications.

Effects of H2/CO ratio and CO2 dilution on the explosion behavior and flame evolution of syngas/air mixtures

Syngas, which is used as both a fuel and a raw material, presents numerous safety risks during its utilization. In this paper, the effects of H2/CO ratio (R = 0%, 30%, 50%, 70% and 100%) and CO2 dilution ([CO2] = 0%–20%) on the explosion behaviors of syngas/air mixtures with different equivalence ratios (φ = 0.8, 1.0, 1.6, and 2.5) are examined via experiments and numerical calculations. The results show that the peaks of explosion pressure and OH* spectral intensity are significantly influenced by the H2 percentage in the syngas. The introduction of CO2 notably decreases these parameters in oxygen-rich and severe oxygen-poor states. Additionally, the flame propagation speed noticeably increases with increasing H2 proportion in the syngas. The influence of CO2 on the buoyancy instability of the spherical flame of syngas is considered negligible when compared to that of other combustible gases, such as CH4. Nevertheless, the presence of CO2 decreases the density ratio between the unburned gas and burned gas and increases the flame thickness of syngas/air mixtures. This trend reduces the cellular instability of the spherical flame, particularly in severe oxygen-poor states. Notably, there is a definite correlation between the formation of cellular flames and the rise rate of explosion pressure. The cellular structure on the flame surface becomes more pronounced when the rise rate of explosion pressure increases. Conversely, it develops later or is noticeably inhibited. Furthermore, the main reaction pathways are H2 → ∙OH → H2O2 → H2O and H2 → ∙OH → CO → CO2 during the syngas explosion process. ∙OH is critical in the entire chain reaction because it promotes the conversion of H2 to H2O and acts as a vital connection between the reactants H2 and CO in the explosion process.

Coherent anti-Stokes Raman scattering spectroscopy system for observation of water molecules in anion exchange membrane

Anion exchange membrane fuel cells (AEMFCs) provide one of the most feasible remedies to fuel cells’ dependency on the dwindling Pt group catalysts. Nevertheless, AEMFCs still suffer reduced durability, which requires an in-depth understanding of their membranes. The low thermal endurance of the anion exchange membranes (AEMs) usually limits the direct application of powerful techniques, such as Raman spectroscopy. We sought to establish a system for coherent anti-Stokes Raman scattering (CARS) spectroscopy capable of taking measurements inside an AEM rapidly and accurately without photodamage. A 785 nm CARS system was newly developed to study the water species in an AEM (QPAF-4) located vertically in a fuel cell. From the results of water measurement in a QPAF-4 membrane, the OH-related region was deconvoluted into nine Gaussian peaks: Five H-bonded OH peaks, non-H-bonded OH, OH–, and two CH peaks. The H-bonded species increased with increasing relative humidity, but the other species remained constant. These results open unlimited possibilities for studying and comparing different AEMFCs, enabling more rapid technology optimization.

Chemical States of Water in Anion Exchange Membrane for Fuel Cells Using Raman and Coherent Anti-Stokes Raman Spectroscopies

Purpose Low membrane durability remains a major challenge in anion exchange membrane fuel cells (AEMFCs). This is despite the AEMFCs’ proven potential to eliminate the dependency of Fuel cells on Pt catalysts and bring about the mass commercialization of the technology. This problem can be effectively addressed through combined optimization of the AEMFCs’ operating conditions during evaluation, followed by finetuning of the membrane chemistry to address any observed weaknesses. After synthesis, water distribution is the primary operation condition determining a given AEM’s performance and lifespan [1]. This is partly because water affects the ionic conductivity and, thus, maximum current density, which is known to play a significant role in the longevity of membranes. Therefore, establishing the water distribution during power generation for any given membrane is highly desirable. For this to happen, suitable and reliable techniques must exist to measure and compare the water distribution in situ and operando. In this paper, we used in-house assembled Raman spectroscopy and coherent anti-Stokes Raman scattering spectroscopy (CARS) systems to measure the water in an operational AEMFC for the first time. CARS comes with a high time resolution of 0.1 s, which is essential in the transient response study of FCs. Experimental Method QPAF-4 membrane film (Fig. 1) of the thickness of 30 µm and IEC of 2.0 meq g-1 was solution cast as reported [2]. The cell was then assembled, as reported [3]. An airtight transparent quartz window 200 μm thick was mounted at the cathode endplate for optical access to the QPAF-4 membrane through a 500 mm pinhole in the GDE. A thin Pt disk was placed on the opposite side of the membrane to reflect the signal to the spectrometer through the ×50 objective lens used. For Raman spectroscopy, a 632 nm, 1 mW laser with 5.5 min total exposure was used. For CARS, an 11 mW 785nm pump laser and 16 mW Stokes laser with 200 ms total exposure were used. The flow rate was 100 ml min-1 for all gases. The cell temperature was maintained at 60 °C. The relative humidity of the gas varied from 30% to 100% in steps of 10% RH. The system was allowed to stabilize for 3 hours at each humidity level before measurement. Results and discussion Figures 2 and 3 show the normalized in situ spectra recorded at the center of the membrane at different relative humidity values using CARS and Raman, respectively. The peak positions are comparable. However, the OH peak in CARS is taller relative to C=C than in Raman. CARS signal intensity is generally stronger than Raman [3]. Within the CARS peak, the purely OH portion of the signal is more prominent relative to the rest of the peak than in Raman. This is attributed to the fact that the Infrared laser associated with the stokes light (817-1144nm) of CARS is known to be more sensitive to OH vibration than the lower wavelength laser (632nm) used in Raman [4]. Conclusion We successfully developed a 785nm CARS system capable of operando water measurement in AEMFCs. The results from this technique are comparable to those from micro-Raman spectroscopy but with better signal intensity and time resolution. This increases the number of practical methods available to researchers interested in measuring water content in AEMFCs allowing for faster development of the technology. The water distribution results during power generation will be discussed at the conference. With CARS, higher temporal/time resolution is achieved, which is advantageous when cell response needs to be studied.

Wound Healing Improvement by Polymer Surgical Suture Coated with Tannic Acid

A surgical suture is a vital medical device to uphold wounded tissue during surgery. However, the application to improve tissue healing must still be developed. This study offered to solve this problem by incorporating tannic acid (TA) into polydioxanone (PDS) sutures. The PDS suture was immersed in TA complexing with iron (III) solutions in pH 8.0 solution. The engineered suture was successful, as revealed by the OH peak of TA in FTIR spectra. Furthermore, it was confirmed by TA particle appearance under Scanning Electron Microscopy. Contact angle measurement showed better wettability in biological mimicking solutions, such as water, serum, and saline solution. Thereby, it improved in vitro wound healing activity. Moreover, our bioinformatics data showed that TA enhanced the wound healing process by addressing multiple targets in the early phase of inflammation. For instance, it induced platelets to reduce bleeding at the early wound healing stage, activated T cells at the inflammation stage, accelerated epidermis cell proliferation, and activated fibroblast as a key player in wound healing. Due to multiple wound healing targets, our suture system was expected to be emphasized in clinical applications. HIGHLIGHTS The engineered surgical suture was fabricated by modifying the surface of surgical suture with tannic acid (TA) through iron (III) complex formation in basic condition The modified PDS suture had a high wettability degree of water, saline, and serum, representing the biological fluid, which was expected to have better biocompatibility Based on bioinformatics analysis, TA revealed multiple targets to stop bleeding by activating platelet through FYN, CD4, and CD8 T cells, induced epithelial cells proliferation through Epidermal Growth Factor Receptor (EGFR), and activated many transcription and migration factors of fibroblast GRAPHICAL ABSTRACT

Numerical analysis of the enrichment of CH4/H2 in ammonia combustion in a hot co-flow environment

A numerical investigation is conducted using OpenFOAM to study the characteristics of ammonia flames enriched with methane and hydrogen, influenced by a diluted co-flow (exhaust gas). The study aims to explore various flame characteristics, including fuel consumption, ignition delay time, lift-off height and position, temperature, and CO and NO emissions while maintaining a constant energy input of 5 kW. Non-stabilized flames are identified by analyzing the OH peak in the computational domain among ammonia flames enriched with CH4/H2 for different dilutions of O2 (6 %, 9 %, and 12 %). The study is structured into three stages of numerical simulations corresponding to stabilized flames: (1) no reaction, (2) reaction in the absence of O2, and (3) reaction with O2 to see the sole impact of the hot co-flow and local turbulence mixing on the primary cracking of ammonia. Furthermore, the rates of H2 and N2 formation resulting from the utilization of ammonia in the presence of hot co-flow are thoroughly examined. Additionally, the behavior of ammonia flames and CH4/H2-enriched ammonia flames under preheated air conditions (23 % O2) is analysed. Stable flames are observed in the co-flow at 12 % O2, displaying characteristics of Moderate or Intense Low-oxygen Dilution (MILD) combustion. Conversely, ammonia flames under preheated air conditions exhibit conventional flame behavior. Pure ammonia flames exhibit stronger temperature gradients and higher levels of CO and NO emissions. As the enrichment of NH3 with CH4/H2 increases, peak temperatures decrease while lift-off heights increase, indicating a transition towards more distributed flame structures. Notably, the instance with 40 % H2 enrichment exhibits lower NO emissions and a higher rate of ammonia consumption along with more distributive flame characteristics.

High Swelling Carboxymethyl Cellulose Synthesized from Coconut Fibers

ABSTRACT To attain the zero waste and green chemistry goals, much emphasis has shifted toward the use of cellulose derived from agricultural biomass. In this study, carboxymethylation of microcrystalline cellulose from coconut fiber by use of monochloroacetic acid in the presence of an alcohol medium under alkaline conditions was suitable for the synthesis of carboxymethyl cellulose. The carboxymethyl cellulose was prepared, and the physical properties, degree of substitution, swelling capacity, and characterization were investigated. The results indicated that the yield of carboxymethyl cellulose, degree of substitution, and swelling capacity were 9.45 ± 0.76 g, 1.82 ± 0.12, and 11.23 ± 0.28 g, respectively. The Fourier Transform Infrared spectra of carboxymethyl cellulose displayed a broad OH peak at 3352 cm−1 and a sharp peak at 1600 cm−1 attributed to -COO. Thermal behavior was investigated by Thermal gravimetric analysis, and the phase transition was determined by Differential Scanning Calorimetry, which revealed that alkalization and esterification of cellulose lead to a decrease in the thermal stability of the polymer. In conclusion, zero waste can be achieved in the coconut industry as it is rich in cellulose that can be converted to carboxymethyl cellulose, which can be utilized to produce emulsifiers and superabsorbent polymers.

Polycaprolactone/Cellulose Acetate Loaded Psidium guajava Essential Oil Electrospun Nanofibrous Mat Dressing for Healing Wounds

Natural products and essential oils of medicinal plants are extensively employed in wound healing, particularly in the pharmaceutical industry. Essential oils obtained from Psidium guajava were utilised as an antibacterial agent against Bacillus subtilis, Staphylococcus aureus, and Enterococcus faecalis, and to control drug-resistant strains. In this study, electrospinning for applications in antimicrobial activity and drug delivery systems was used to develop biocomposite nanofibers of Polycaprolactone (PCL)/Cellulose Acetate (CA) and Psidium guajava essential oil (PGEO). Images from the FESEM revealed that the mean fire diameters were 120 nm for the PCL/CA and 223 nm for PCL/CA/PGEO biocomposite nanofibers. The diameters of the nanofibers were increased following the addition of PGEO into PCL/CA nanofibers. Furthermore, FTIR studies revealed the -OH peak in pure electrospun PCL/CA and PCL/CA/PGEO, lacking pure PGEO nanofibrous mats. These findings reflect that Psidium guajava essential oil/PCL/CA electrospun nanofibers are promising candidates for presenting bioactive compounds in wound management or other approaches for wound healing and bacterial infections.

Unravelling hydrogen bond network in methanol-propanol mixtures via molecular dynamics simulation and experimental techniques

ABSTRACT Hydrogen-bonded networks in 1-propanol-methanol binary mixture are studied using molecular dynamics simulation along with experimental techniques (FTIR, dielectric spectroscopy and refractive index measurements) for the entire concentration range. The structure of hydrogen-bonded networks is studied through radial distribution function, hydrogen bond statistics and graph theoretical analysis from molecular dynamics. It is observed that the probability of hydrogen bonding is maximum in methanol molecules followed by hydrogen bonding between methanol and 1-propanol molecules and minimum among 1-propanol molecules, as the concentration changes. The graph theory results show the formation of linear chain hydrogen bond networks, with no caged structures, which is validated from the experimental results. Further, the deconvolution of the FTIR OH peak suggests the presence of linear multimers in all concentrations of the binary system. Average degree of the hydrogen-bonded networks from graph theory indicates a complex networks among pure alcohols and dimers between methanol and 1-propanol in their binary mixtures at all concentrations. The negative values of excess permittivity indicate that the components of the mixture interact in a manner such that the net dipole polarisation decreases.

Inferring the diurnal variability of OH radical concentrations over the Amazon from BVOC measurements

The atmospheric oxidation of biogenic volatile organic compounds (BVOC) by OH radicals over tropical rainforests impacts local particle production and the lifetime of globally distributed chemically and radiatively active gases. For the pristine Amazon rainforest during the dry season, we empirically determined the diurnal OH radical variability at the forest-atmosphere interface region between 80 and 325 m from 07:00 to 15:00 LT using BVOC measurements. A dynamic time warping approach was applied showing that median averaged mixing times between 80 to 325 m decrease from 105 to 15 min over this time period. The inferred OH concentrations show evidence for an early morning OH peak (07:00–08:00 LT) and an OH maximum (14:00 LT) reaching 2.2 (0.2, 3.8) × 106 molecules cm−3 controlled by the coupling between BVOC emission fluxes, nocturnal NOx accumulation, convective turbulence, air chemistry and photolysis rates. The results were evaluated with a turbulence resolving transport (DALES), a regional scale (WRF-Chem) and a global (EMAC) atmospheric chemistry model.

Developing a model-ready highly resolved HONO emission inventory in Guangdong using domestic measured emission factors

Nitrous acid (HONO) plays an important role in the budget of hydroxyl radical (OH) in the atmosphere. However, current chemical transport models (CTMs) typically underestimate ambient concentrations of HONO due to a dearth of high resolution primary HONO emission inventories. To address this issue, we have established a highly resolved bottom-up HONO emission inventory for CTMs in Guangdong province, utilizing the best available domestic measured emission factors and newly obtained activity data. Our results indicate that emissions from various sources in 2020, including soil, on-road traffic, non-road traffic, biomass burning, and stationary combustion, were estimated at 21.5, 10.0, 8.2, 2.5, and 0.7 kt, respectively. Notably, the HONO emissions structure differed between the Pearl River Delta (PRD) and the non-PRD regions. Specifically, traffic sources were the dominant contributors (62 %) to HONO emissions in the PRD, whereas soil sources accounted for the majority (65 %) of those in the non-PRD. Among on-road traffic sources, diesel vehicles played a significant role, contributing 99.7 %. Comparisons with previous methods suggest that HONO emissions from diesel vehicles are underestimated by approximately 2.5 times. Higher HONO emissions, dominated by soil emissions, were observed in summer months, particularly in August. Furthermore, diesel vehicle emissions were pronounced at night, likely contributing to the nighttime accumulation of HONO and the morning peak of OH. The emission inventories developed in this study can be directly applied to widely used CTMs, such as CMAQ, CAMx, WRF-Chem, and NAQPMS, to support the simulation of OH formation and secondary air pollution.

Industrial Wastewater Purification Using Cow Bone and Saw Dust Filters

Poorly treated wastewater can adversely affect the existence of plants and animals. There is a need to look for low-cost filters to address the scarcity of water in rural areas surrounded by industrial wastewater. The present study investigates the use of low-cost filter for purification of industrial wastewater. Filters made from cow bone (CBF) and saw dust (SDF) were used to remove some impurities in wastewater. Wastewater from Ore Industrial Estate, Ondo State, Nigeria, are collected and ran through the filter, the physicochemical parameters were determined using standard method while metal content were determined using Atomic Absorption Spectrophotometer. The filter content before and after use were analyzed using Fourier Transformed Infrared (FTIR) Spectrometer. CBF reduces Electrical Conductivity (EC), Chloride and chemical oxygen demand COD of the wastewater appreciably. It removed 74 %, 70 %, 65 %, 68 % and 81 % of Mn, Ni, Cd, Pb, and Zn respectively while SDF removed 8 %, 14 %, 26 %, 17 % and 28 % of the same elements respectively. The C = O stretch was recorded at wavelength of 1646.31cm-1 before filtration and broad at 1640.19 cm-1 after filtration in CBF. Broad OH peak was recorded at 3750.84 cm−1 before filtration and 3674.41 cm−1 after filtration for saw dust filter (SDF). It was concluded that the spectral showed that some materials are removed from the water. The cow bone filter is more efficient than the saw dust filter.

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver-graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm-1 of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe2+) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10-100 mg L-1 towards purification of groundwater for safe drinking water.

Influence of environmental pH on the interaction properties of WP-EGCG non-covalent nanocomplexes.

Whey protein-epigallocatechin gallate (WP-EGCG) covalent conjugates and non-covalent nanocomplexes were prepared and compared using Fourier-transform infrared spectra. The effect of pH (at 2.6, 6.2, 7.1, and 8.2) on the non-covalent nanocomplexes' functional properties and the WP-EGCG interactions were investigated by studying antioxidant activity, emulsification, fluorescence quenching, and molecular docking, respectively. With the formation of non-covalent and covalent complexes, the amide band decreased; the -OH peak disappeared; the antioxidant activity of WP-EGCG non-covalent complexes was 2.59- and 2.61-times stronger than WP-EGCG covalent conjugates for 1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing ability of plasma(FRAP), respectively (particle size: 137 versus 370 nm). The antioxidant activity (DPPH 27.48-44.32%, FRAP 0.47-0.63) was stronger at pH 6.2-7.1 than at pH 2.6 and pH 8.2 (DPPH 19.50% and 26.36%, FRAP 0.39 and 0.41). Emulsification was highest (emulsifying activity index 181 m2 g-1 , emulsifying stability index 107%) at pH 7.1. The interaction between whey protein (WP) and EGCG was stronger under neutral and weakly acidic conditions: KSV (5.11-8.95 × 102 L mol-1 ) and Kq (5.11-8.95 × 1010 L mol s-1 ) at pH 6.2-7.1. Binding constants (pH 6.2 and pH 7.1) increased with increasing temperature. Molecular docking suggested that hydrophobic interactions played key roles at pH 6.2 and pH 7.1 (∆H > 0, ∆S > 0). Hydrogen bonding was the dominant force at pH 2.6 and pH 8.2 (∆H < 0, ∆S < 0). Environmental pH impacted the binding forces of WP-EGCG nanocomplexes. The interaction between WP and EGCG was stronger under neutral and weakly acidic conditions. Neutral and weakly acidic conditions are preferable for WP-EGCG non-covalent nanocomplex formation. © 2023 Society of Chemical Industry.

Comparative Physicochemical Properties of Isolated Pectin from Various Tropical Fruit Peel Wastes

Pectin is widely used as the main polymer in cosmetics, pharmaceuticals, and biomedical applications. The pectin utilization in diverse fields can contribute to fruit waste processing since waste such as fruit peel serves as a pectin source. This study is aimed to analyze the extraction temperature effect on the physicochemical properties of extracted pectin from various tropical fruit peel waste. In this study, we determined the extracted pectin’s physicochemical properties from peel wastes of tropical fruits like papaya, lime, lemon, and dragon fruit using 3% citric acid at 65 and 90°C. A higher pectin yield resulted from a higher extraction temperature of 90oC (8.78 to 27.03 %) than that obtained at 65oC (5.78 to 17.71 %). The spectra of Fourier transform infrared (FT-IR) mainly showed the degradation of pectin, specifically in the cases of papaya, lime, and lemon, indicated by the higher OH peak intensity. All samples extracted were high methoxyl pectin (HM), with degrees of esterification (DE) ranging from 56.98 to 89.63%. Among the fruit peels studied, only the lemon peel pectin extracted at 90°C, with anhydrouronic acid (AUA) content of 77.35%, meets the criteria for food additives and pharmaceutical purposes.

Protein Determination and Soluble Amino Acids Prediction in Various Solvents Extracted Solutions of Indigenous Red Lentil and Moong Pulse through Direct UV- Visible Spectrophotometer Technique: A Comparative Study

In this comparative study, direct protein determination have been done for indigenous Red lentil (Lens culinaris) and Moong pulse (Vigna radiata) (obtained from Muzaffarpur, Bihar) by UV-visible spectroscopy in three different solvents viz. double distilled water(ddH 2 O), ethyl alcohol (C 2 H 5 OH), and methyl alcohol (CH 3 OH). A few amino acids insolutions have also been predicted (not characterized) based on their peaks observed in UV-region by comparing them with the reported range of wavelengths. Protein concentrations in red lentils for ddH 2 O, C 2 H 5 OH, and CH 3 OH extracted solution were 7.480, 1.205, and 0.835mg/mL, respectively. While, in case of moong pulse, protein concentrations in ddH 2 O,C 2 H 5 OH, and CH 3 OHextractedparts were 6.415, 1.150, and 3.485 mg/mL, respectively. Inboth cases, ddH 2 O extracted part showed the highest concentration of proteins while red lentil showed higher concentration in C 2 H 5 OH followed by CH 3 OH and moong pulse showed higher concentration in CH 3 OH followed by C 2 H 5 OH. During comparison with known wavelength ranges for amino acids peaks, red lentil in ddH 2 O showed peaks for cysteine, phenylalanine, tryptophan, and tyrosine; in C 2 H 5 OH peaks were only for cysteine and traces of phenylalanine; while in CH 3 OH, peaks were for cysteine, phenylalanine, tryptophan, and tyrosine. Whereas, moong pulse in ddH 2 O showed peaks for cysteine, phenylalanine, tryptophan, and tyrosine; in C 2 H 5 OH and CH 3 OH peaks were observed only for cysteine and phenylalanine. This method concludes that local pulses are rich in protein and amino acids and aqueous solutions showed highest protein concentration in each case. This direct method of protein quantitation is effective in the determination of protein at wavelength 280 nm as well as prediction of a few amino acids based on their specific peaks in UV-region. The main purpose of this work was to perform a comparative analysis of the protein concentrations in three different solvent-extracted solutions of two indigenous pulses by the direct UV-Visible spectroscopic technique without using any chemical. It is well known that pulses are rich in 3 protein but in best of authors knowledge there is no report on this type of work for these local pulses using this direct and fast quantitation method. As alcohols are not the very suitable solvents for the protein extraction, however, this study was performed using methanol and ethanol along with ddH 2 O in order to assess the experimental results in these two alcohols also and compare them to each other.