Fourier Transform Infrared Spectroscopy Spectra Research Articles

Development of Mucoadhesive Chitosan-Iodoacetamide Buccal Tablets for Local Delivery of Dextromethorphan

Abstract This study aimed to synthesize a chitosan (CHI) derivative, chitosan-iodoacetamide (CHI-IA), with enhanced mucoadhesive properties and develop buccal mucoadhesive tablets of CHI-IA for local delivery of dextromethorphan (DXT). Mucoadhesive CHI-IA was synthesized by a chemical reaction between CHI and iodoacetic acid (IA) in different weight ratios. The synthesized CHI-IA was characterized by Fourier-transformed infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (NMR) to confirm the chemical structure and assure successful synthesis. DXT was selected as the model drug to be incorporated into the matrix tablet to develop mucoadhesive buccal cough relief tablets. The mucoadhesive strength of the CHI-IA tablets was determined by a texture analyzer. Moreover, the drug content and the release characteristics of DXT from the mucoadhesive tablets were evaluated. The FT-IR and NMR spectra of CHI-IA indicated the conjugation of IA on the structure of CHI. The CHI-IA tablets exhibited a 4-time increase in mucoadhesion force compared with that of unmodified CHI. Moreover, a gradual release of DXT from the tablets was observed, and the release kinetics best fit with the Higuchi model (R2 = 0.9912). Therefore, the CHI-IA could be applied as the mucoadhesive carrier system for drug delivery. Keywords: Chitosan, Iodoacetic acid, Mucoadhesive, Buccal tablets, Dextromethorphan

Differentiation between copal and amber by their structure and thermal behaviour

The relationships between the polymerization related to structure and the composition of different types of natural resins were determined. Analyses were carried out by Fourier transform infrared spectroscopy (FTIR), differential thermal analysis–thermogravimetry (DTA-TG) and hot stage microscopy (HSM). Copal specimens were collected from the Mai-Ndombe Lake, Democratic Republic of Congo, and amber pieces that came from Bitterfeld, Germany, and from Kaliningrad, Russia. FTIR spectra of copal show a vibrational band at 1643 cm−1 (C=O stretching) attributed to communic acids, while amber shows a band at 1735 cm−1 associated with ester-group vibrations and a shoulder at about 3340 cm−1, suggesting partial oxidization. DTA shows the main exothermic peak, related to the combustion, at 546–552 °C in amber and at 518 °C in copal. The derivative thermogravimetry (DTG) peaks vary in the different resin types; in amber, they occur at 333–335, 401–404 and 548–555 °C and are related to mass losses of 31, 26 and 39 mass%, respectively; copal peaks are at 394 and 507 °C, with mass losses of 71 and 27 mass%, respectively. In copal, hot stage microscopy (HSM) shows the start of sintering at 131 °C, followed by an expansion produced by the material decomposition and the generation of gases that cannot be released because of the material plastic behaviour. Finally, the increase in pressure produces an explosion that results in a lower viscosity of the liquid, which at this point can no longer support the internal pressure of gases. In amber samples, a smaller decrease in viscosity is observed and the start of sintering occurs at 150 °C with no significant change in their morphology.

Toward function starch nanogels by self-assembly of polysaccharide and protein: From synthesis to potential for polyphenol delivery

Nanogels formed by self-assembly of natural proteins and polysaccharides have attracted great interest as potential carriers of bioactive molecules. Herein, we reported that carboxymethyl starch-lysozyme nanogels (CMS-Ly NGs) were prepared using carboxymethyl starch and lysozyme by green and facile electrostatic self-assembly, and the nanogels served as epigallocatechin gallate (EGCG) delivery systems. The dimensions and structure of the prepared starch-based nanogels (i.e., CMS-Ly NGs) were characterized by dynamic light scattering (DLS), ζ-potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and thermal gravimetric analyzer (TGA). FT-IR and 1H NMR spectra together confirmed the formation of CMS; FT-IR spectra confirmed the formation of CMS-Ly NGs; XRD spectra confirmed the disruption of the crystal structure of lysozyme after electrostatic self-assembly with CMS, and further confirmed the formation of nanogels. TGA demonstrated the thermal stability of nanogels. More importantly, the nanogels showed a high EGCG encapsulation rate of 80.0 ± 1.4 %. The CMS-Ly NGs encapsulated with EGCG exhibited regular spherical structure and stable particle size. Under the simulated gastrointestinal environmental conditions, CMS-Ly NGs encapsulated with EGCG showed the controlled release potential, which increased its utilization. Additionally, anthocyanins can also be encapsulated in CMS-Ly NGs and showed slow-release properties during gastrointestinal digestion in the same way. Cytotoxicity assay also demonstrated good biocompatibility between CMS-Ly NGs and CMS-Ly NGs encapsulated with EGCG. The findings of this research suggested the potential application of protein and polysaccharides-based nanogels in the delivery system of bioactive compounds.

Shape, Microstructure, and Chemical Composition of Pearls from the Freshwater Clam Diplodon chilensis Native to South America.

The capability to produce pearls is widespread in the phylum Mollusca, including bivalves of the superfamily Unionoidea. Here, we identified and characterized natural pearls formed by Diplodon chilensis, a freshwater clam native to southern South America, using samples obtained from two lakes located in the Chilean Patagonia. Pearls were studied using light and scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Naturally formed pearls were found in both male and female D. chilensis specimens. Pearls are produced in different shapes, including spherical, ellipsoidal, buttoned, and bumpy, ranging in size from 200 µm to 1.9 mm. The internal microstructure is composed of irregular polygonal tablets, about 0.40 to 0.55 μm in thickness. EDX analysis showed that pearls are composed of calcium carbonate. FTIR and Raman spectra recorded several peaks attributable to the aragonite in pearls of this species, as has been shown in other mollusks. In addition to these results, pearls of different colors are illustrated.

Preparation of Al2O3 /PVA Nanocomposite Thin Films by a Plasma Jet Method

Alumina thin films have significant applications in the areas of optoelectronics, optics, electrical insulators, sensors and tribology. The novel aspect of this work is that the homogeneous alumina thin films were prepared in several stages to generate a plasma jet. In this paper, aluminium nanoparticles suspended in vinyl alcohol were prepared using exploding wire plasma. TEM analysis was used to determine the size and shape of particles in aluminium and vinyl alcohol suspensions; the TEM images showed that the particle size is 17.2 nm. Aluminium/poly vinyl alcohol (Al/PVA) thin films were prepared using this suspension on quartz substrate by plasma jet technique at room temperature with an argon gas flow rate of 1 L/min. The Al/PVA thin films were thermally converted to alumina films, where they were annealed at different temperatures (700, 800, or 900°C). X-ray diffraction (XRD), atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) techniques were used to characterise these thin films before and after annealing process. The diffraction patterns of the prepared thin films before subjecting them to the annealing process indicated the presence of peaks belonging to aluminium and PVA; however, the diffraction patterns and FTIR spectra obtained for these films after the annealing process showed peaks indicating the formation of alumina films of different phases. AFM and SEM investigations proved that the formed particles for all prepared films before and after the annealing process were similar in size and almost spherical; the diameter of the particles was on the order of a few nanometres. To control the properties of prepared thin films, the plasma which was used to produce thin films is diagnosed spectrophotometrically. The generated plasma was diagnosed using optical emission spectroscopy to estimate the electron temperature Te; the electron temperature was 1.925 eV.

Multilayer polycaprolactone - pullulan nanofiber mats incorporated with the antimicrobial palindromic peptide LfcinB (21-25)Pal as a potential application in active packaging

Food losses are generated by microbial contamination due to the lack of packaging that not only functions as a barrier but releases compounds against such organisms. Electrospinning was used to develop multilayer nanofiber mats using poly-(ε-caprolactone) (PCL) in the outer layer and encapsulating the peptide LfcinB (21-25)Pal in an inner pullulan (PUL) layer. The nanofiber mats were characterized by Fourier Transformed Infrared Spectroscopy (FTIR). FTIR spectra showed the presence of the peptide in PUL nanofiber mats, the presence of both polymers in multilayer nanofiber mats, and the absence of chemical changes. In addition, a High Performance Liquid Chromatography (HPLC) was performed for peptide quantification, where an encapsulation efficiency of 65 % in the nanofiber mat was observed, and a maximum load of 50 mg peptide / g PUL. The antioxidant capacity of the peptide, evaluated through the inhibition of radical DPPH, showed an antiradical activity of 5.21 × 10−4 mg ± 1.12 × 10−5 gallic acid/mg nanofiber mat. Finally, the antimicrobial activity showed a minimum inhibitory concentration of 15 ± 0.01 μM against Escherichia coli. In conclusion, the multilayer nanofiber mat can potentially be used as part of active packaging to prolong the shelf life of foodstuff susceptible to microbial contamination.

Physiochemical Characterization of Ethiopian Mined Kaolin Clay through Beneficiation Process

Kaolin mineral is a commercially solid powder with a comparatively low level of purity and is regularly used for a variety of applications, including filler, paints, ceramics, adsorbents, and paper. In Ethiopia, the kaolin clay mineral is significant for financial growth as the raw material used in the industry sector. However, slight consideration was given to the chemical, physical, mineralogical, and morphological properties of kaolin. In this study, the property of kaolin is investigated by using advanced instruments such as X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermogravimetric analysis (DTA). Based on the XRF test, the main component of kaolin clay contains SiO2 (58.73%), Al2O3 (24.35%), K2O (5.36%), and other impurities, including Fe2O3 (2.06%) and TiO2 (0.13%). The FTIR spectra displayed the functional groups Si-O, Al-OH, Al-O, and Si-O-Al. The XRD diffractogram identified kaolin clay as the main mineral phase in the existence of quartz, halloysite, and chlorite.

Microencapsulation of riboflavin-producing Lactiplantibacillus Plantarum MTCC 25,432 and Evaluation of its Survival in Simulated Gastric and Intestinal Fluid.

Microencapsulation is an optimistic method for the delivery of live microbial cells through different food products. In this study, riboflavin-producing probiotic strain Lactiplantibacillus plantarum MTCC 25,432 was encapsulated using a spray drying technique with different wall materials including Inulin, maltodextrin (MD), and MD + Inulin (1:1). The obtained spray dried powder was investigated for probiotic viability, encapsulation efficiency, particle size, water activity, moisture content, hygroscopicity, bulk and tapped densities, storage stabilities, Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Besides this, the viability of the free and encapsulated probiotic cells was tested under simulated gastric and intestinal fluid conditions. In the results, microcapsules produced with the combination of MD + Inulin showed higher dry powder yield (36.5%) and viability of L. plantarum MTCC 25,432 (7.4 log CFU / g) as compared with individual coating materials. Further characterization revealed that MD + Inulin microcapsules are spherical (3.50 ± 1.61μm in diameter) in shape with concavities, showed the highest encapsulation efficiency (82%), low water activity (0.307), moisture content (3.67%) and good survival ability at low pH (pH 2.0 and 3.0), high bile salt concentrations (1.0% and 2.0%), and long storage conditions. No differences in FTIR spectra were observed among the tested samples. However, TGA showed enhanced thermal stability of probiotic-loaded microcapsules when MD + Inulin was used together. In conclusion, MD + Inulin could be a potential encapsulation material for riboflavin-producing probiotic bacteria L. plantarum MTCC 25,432.

Employing alternative culture media in kefiran exopolysaccharide production: Impact on microbial diversity, physicochemical properties, and bioactivities

Kefiran is a biomaterial with potential application in developing novel materials for food technology. In this study, sugarcane sugar (REF), raw sugar (RAS), brown sugar (BRS), soy molasses (SOM), and sugarcane molasses (SCM) were evaluated for the production of kefiran from kefir biomass rather than cow's milk (CMK), the usual medium. The produced kefiran was purified and characterized by colorimetry, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis, and morphology. It was also assayed for antioxidant and antimicrobial activity. SCM had the highest average daily rate of kefir biomass production (29.17 %/day). The composition of the culture medium affected the microbial diversity of kefir grains, and the Lactobacillus genus was the most abundant (39.8 %, 40.0 %, and 83.9 % to SCM, SOM, and CMK, respectively) in the samples that presented the highest biomass production and kefiran extraction yields. FTIR spectra showed that the bands of kefiran produced in REF and RAS were narrower than those of the other samples. Kefiran grew in an alternative culture medium also exhibited higher thermal stability (Tonset and TMax was higher than 250 and 280 °C, respectively). Those grown in SOM and SCM displayed antimicrobial and antioxidant activities similar to those of kefiran produced in CMK. The results indicate that agro-industrial by-products (SCM and SOM) are potential alternatives for kefiran production from kefir biomass.

Superparamagnetic properties of iron oxide nanoparticles using vitex negundo leaf extract by green synthesis method and its antimicrobial activity against wound pathogen

Now-a-days green synthesis method is used to prepare the nanoparticles because of its non-toxicity and echo friendly nature. So we are focus the green synthesis method to make iron oxide nanoparticles from vitex negundo leaf extract. The prepared nanoparticles crystal structure, functional, morphology and elemental studies are analyzed by using X-ray Diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX). The occurrence of a single phase cubic spinel structure with excellent purity is clearly demonstrated by the XRD. To determine the average crystallite size, the Debye Scherrer formula is employed. The created nanoparticles are used in biomedical applications and feature a superparamagnetic characteristic. SEM gives the agglomerated image. EDX has confirmed the existence of Fe and O elemental composition. The phytochemical studies are carried out for the vitex negundo leaf extract, such as flavonoids and terpenoids are present. The strong peak between 582 cm−1 in FTIR spectra is seen and is related to the characteristics of magnetite nanoparticles. Investigations of the antibacterial properties of iron oxide nanoparticles against staphylococcus sp. utilising the well diffusion method. The highest zone of clearance was observed at 100 µg/mL (2 mm).

Fabrication and characterization of antimicrobial wound dressing nanofibrous materials by PVA-betel leaf extract

This present study involves the formation and investigation of the characteristics of a fabricated mat from a PVA-betel leaf mixture. Under ideal processing parameters, nanofibrous mat is synthesized from the PVA-betel leaf blended solution by using the electrospinning technique. Afterwards, the produced nanofibrous mat is assessed for its thermal, antibacterial, morphological, moisture management and chemical interaction behavior using thermogravimetric analysis (TGA), antibacterial assay, scanning electron microscope (SEM), moisture management tester (MMT) and Fourier-transform infrared spectroscopy (FTIR) respectively. The antibacterial action against Staphylococcus aureus and Escherichia coli bacteria has been assessed using the agar diffusion technique, which reveals the creation of zones of inhibition with a value of about 20 mm. Besides, the fabricated nanomat reveals an average diameter of 183.4 nm with improved moisture and thermal characteristics. Furthermore, the generated nanofibrous mat has all the necessary components, as evidenced by the distinctive peaks in the FTIR spectra. Hence, the recently developed nanofibrous mat exhibits promising potential as a suitable material for wound dressing applications.

Effect of Heating Time Variation in Green Synthesis of Copper Nanoparticles with Sweet Orange Juice (Citrus Sinensis) Bioreductor using Microwave Assisted Method

Inexpensive and environmentally friendly synthesis of copper oxide nanoparticles (CuO NPs) was produced using microwave-assisted green synthesis method. In this method, microwave (ME731K Solo with Ceramic enamel, 20 L) was used. the effect of time was examined to produce CuO NPs. Nanoparticles were produced when micro waves (800 watts) irradiated a solution of CuSO4.5H2O mixed with sweet orange extract (Citrus Sinensis). The fabricated CuO nanoparticles of C. Sinensis were further characterized by UV-Visible spectroscopy (UV-Vis). Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Time variation has been used in the preparation of CuO NPs. UV-Vis test showed the formation of CuO NPs at the absorbance peak around 270-300 nm. Time variation affects the wavelength shift and the absorbance level is an indication of the concentration of the amount of nanoparticles produced. FTIR spectra identified functional biomolecules from the nanoparticles at a wavelength of 618 nm. X-ray diffraction (XRD) analysis revealed the crystalline structure of the copper nanoparticles at 36°.

Characterization of functionalized multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) are functionalized to determine structural and chemical changes occurred due to oxidation at room temperature in presence of an aqueous solution of concentrated HNO3. The raw and processed (functionalized) MWCNTs were investigated with FTIR and FESEM spectroscopy methods. The surface morphology was examined by FESEM and presence of carboxylic group were identified with Fourier Transform Infrared Spectroscopy (FTIR). The multi walled carbon nanotube of 8 nm, 10–30 nm & 50 nm were taken for experimentation. The FTIR spectra revealed that the broad peak @3450 cm-1 corresponds to O–H bond and peak at @ 1630 cm-1 corresponds to C = O bond. The intensity of both raw and functionalized MWCNTs peak signifies presence of COOH group. Likewise, FESEM images shows, agglomeration of MWCNTs due to Van der Waals forces in raw MWCNTs but after functionalization, unbundled CNTs with reduction in length due to breakage of C = C bond and presence of carboxyl group at end of CNTs.

Methods to characterize the crystal polymorphs of polyvinylidene fluoride using Fourier transform infrared spectroscopy

AbstractPolyvinylidene fluoride (PVDF), a polymer with three common crystal polymorphs (α, β, γ), has several practically useful properties, including piezoelectric properties. Accurate measurement of its crystalline polymorphs is important since only the β phase has the desired piezo properties. PVDF was processed into isotropic samples having predominantly α, β, and γ crystalline phases. These samples were analyzed with Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and differential scanning calorimetry (DSC). FTIR spectra were fitted with the Gaussian peaks for quantitative analysis of the phases. Peaks exclusive to the amorphous phase were identified and used for the amorphous phase quantification, leading to the accurate determination of the crystalline fraction. IR absorption coefficients for their respective peaks were calculated to quantify individual crystalline polymorphs in the sample. Pure phase spectra were extracted, and a linear combination of the pure phase spectra was fitted to the spectrum of a sample with different phases to accurately obtain the values of the phase fraction and the thickness of the sample.

Modifying platinum microelectrodes with electrochemically reduced graphene oxide for application in electrochemical ascorbic acid sensor

Graphene oxide drop-casted on a platinum microelectrode was successfully changed to reduced graphene oxide by using a cyclic voltammetry method. The presence of an electrochemically reduced graphene oxide layer on the platinum electrode was proved by using scanning electron microscopy images, Raman and Fourier-transform infrared spectroscopy spectra. Cyclic voltammetry and linear sweep voltammetry results indicated that the platinum microelectrode modified with electrochemically reduced graphene oxide can be used as an electrochemical sensor for detection of ascorbic acid in aqueous solutions. In a cyclic voltammetry scan and a linear sweep voltammetry curve corresponding to the presence of ascorbic acid, a peak related to the direct oxidation of ascorbic acid appears. The electrochemical sensor based on the electrochemically reduced graphene oxide material works effectively with a detection limit of 0.04 mM, a detection linear range from 0.04 mM to 1.0 mM, a good repeatability, and especially, a rapid detection time thanks to a direct ascorbic acid detection based on the oxidation of ascorbic acid.

Multifunctional chromone-incorporated poly(hydroxybutyrate) luminescent film for active and intelligent food packaging

The major objective of present work was to fabricate poly(hydroxybutyrate) based luminescent films for genuine food packaging applications. These films were synthesized by incorporating varying Chromone (CH) concentrations (5, 10, 15, 20, and 25 wt%) into poly(hydroxybutyrate) (PHB) matrix through solvent-casting. Different characteristics of prepared films were examined using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), Mechanical testing, and Time-resolved photoluminescence (TRPL). UV-blocking properties and water vapor permeation were also examined. FTIR spectra indicated the occurrence of hydrogen bonding between PHB and CH. Among all prepared film samples, PHB/CH15 showed maximum tensile strength (22.5 MPa) with enhanced barrier ability against water vapor and UV rays, thermal stability, and luminescent performance. After overall analysis, PHB/CH15 film was selected to investigate its X-ray diffraction, release behavior, DPPH scavenging, and antimicrobial potential. Release kinetics revealed that the cumulative release percentage of CH was higher in fatty acid stimulant. Moreover, results suggested that this film demonstrated antioxidant activity (>55 %) and superior antimicrobial potential against Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Furthermore, packaging of bread samples using PHB/CH15 film demonstrated the complete inhibition of microbial growth in bread up to 10 days of storage and ensure the safety of genuine food products.

Design and characterization of functional TiO2–lignin fillers used in rotational molded polyethylene containers

In this study, new TiO2–lignin hybrid systems were synthesized and characterized by various methods, including non-invasive backscattering (NIBS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA) and zeta potential analysis (ZP). The weak hydrogen bonds between the components, as shown on FTIR spectra, proved the production of class I hybrid systems. TiO2–lignin systems were found to display good thermal stability and relatively good homogeneity. These newly designed hybrid materials were used to produce functional composites via rotational molding in a linear low-density polyethylene (LLDPE) matrix at 2.5 % and 5.0 % loading by weight of the fillers, namely, TiO2, TiO2–lignin (5:1 wt./wt.), TiO2–lignin (1:1 wt./wt.), TiO2–lignin (1:5 wt./wt.) and pristine lignin, creating rectangular specimens. The mechanical properties of the specimens were measured via compression testing and by low-energy impact damage testing (the drop test). The results showed that the system containing 5.0 % by weight of TiO2–lignin (1:1 wt./wt.) had the most positive effect on the container's compression strength, while the LLDPE filled with 5.0 % by weight of TiO2–lignin (5:1 wt./wt.) demonstrated the best impact resistance among all the tested composites.

Influence of Tinuvin 292 on Chlorinated Rubber Varnish/ Coating Properties under UV Radiation

This article presents the effect of Tinuvin 292 (a light stabilizer based on liquid hindered amine) on properties of chlorinated rubber varnish/coating under 100 UV-thermo-humidity complex cycles. The properties included relative hardness, adhesion, flexural strength, impact resistance, and gloss loss. The results showed that 2.5 weight percent (wt%) of Tinuvin 292 had much improved physical properties of varnish coating such as relative hardness, adhesion, flexural strength, impact resistance, and gloss loss. Fourier-transform infrared spectroscopy (FT-IR),Thermogravimetric analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM) were used to evaluate the changes of aged coatings in comparison to the initial ones. FT-IR spectrums also showed that intensities of CH2 and C=O (ester) groups changed strongly or slightly depending on the appearance of Tinuvin 292. SEM images indicated that the surface of aged coating with Tinuvin 292 was smoother than coating without Tinuvin 292. TGA also expressed that thermal oxidation stability of chlorinated rubber varnish/ coating had been enhanced with 2.5 wt% of Tinuvin 292.

Optimization of Adsorption Conditions Using Response Surface Methodology for Tetracycline Removal by MnFe2O4/Multi-Wall Carbon Nanotubes

In this study, the optimal conditions and effects of external factors on tetracycline adsorption by magnetic multi-walled carbon nanotubes (MMWCNTs) were established by a response surface methodology for the first time. Batch adsorption experiments showed that increasing the dosage and contact time effectively promoted the adsorption of tetracycline and maximum removal of 97.93–99.13% was achieved at pH 3–7. The pseudo-second-order model and Fourier-transform infrared spectroscopy spectra indicated that the mechanism of adsorption may be π–π electron interaction and cation–π electron bonding. Design Expert was utilized to develop a response surface methodology for the analysis and optimization of tetracycline adsorption by magnetic multi-walled carbon nanotubes. The Box–Behnken design (BBD) results showed that the optimization exhibited high significance and reliability. The main effect plots and Pareto chart indicated that pH exerted a significant individual effect on the regulation of adsorption, while 3D response surface plots and interaction effect plots exhibited a significant antagonistic interaction between pH and contact time. A maximum tetracycline removal of 99.16% was achieved under the optimal conditions of 12 mg adsorbent dosage at pH 5.43, with an adsorption time of 120 min. Mathematical and experimental results confirmed the accuracy of the established optimal conditions.

Synthesis of Daidzein and Thiophene Containing Benzoxazine Resin and Its Thermoset and Carbon Material.

In this work, a novel bio-based high-performance bisbenzoxazine resin was synthesized from daidzein, 2-thiophenemethylamine and paraformaldehyde. The chemical structure was confirmed using nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FT-IR). The polymerization process was systematically studied using differential scanning calorimetry (DSC) and in situ FT-IR spectra. It can be polymerized through multiple polymerization behaviors under the synergistic reaction of thiophene rings with benzopyrone rather than a single polymerization mechanism of traditional benzoxazines, as reported. In addition, thermogravimetric analysis (TGA) and a microscale combustion calorimeter (MCC) were used to study the thermal stability and flame retardancy of the resulting polybenzoxazine. The thermosetting material showed a high carbon residue rate of 62.8% and a low heat release capacity (HRC) value of 33 J/gK without adding any flame retardants. Based on its outstanding capability of carbon formation, this newly obtained benzoxazine resin was carbonized and activated to obtain a porous carbon material doped with both sulfur and nitrogen. The CO2 absorption of the carbon material at 0 °C and 25 °C at 1 bar was 3.64 mmol/g and 3.26 mmol/g, respectively. The above excellent comprehensive properties prove its potential applications in many advanced fields.