Attenuated Total Reflection Infrared Spectroscopy Research Articles

Heteroatoms Induce Localization of the Electric Field and Promote a Wide Potential-Window Selectivity Towards CO in the CO2 Electroreduction.

Carbon dioxide electroreduction (CO2 RR) is a sustainable way of producing carbon-neutral fuels. Product selectivity in CO2 RR is regulated by the adsorption energy of reaction-intermediates. Here, we employ differential phase contrast-scanning transmission electron microscopy (DPC-STEM) to demonstrate that Sn heteroatoms on a Ag catalyst generate very strong and atomically localized electric fields. In situ attenuated total reflection infrared spectroscopy (ATR-IR) results verified that the localized electric field enhances the adsorption of *COOH, thus favoring the production of CO during CO2 RR. The Ag/Sn catalyst exhibits an approximately 100 % CO selectivity at a very wide range of potentials (from -0.5 to -1.1 V, versus reversible hydrogen electrode), and with a remarkably high energy efficiency (EE) of 76.1 %.

Heteroatoms Induce Localization of the Electric Field and Promote a Wide Potential‐Window Selectivity Towards CO in the CO2 Electroreduction

AbstractCarbon dioxide electroreduction (CO2RR) is a sustainable way of producing carbon‐neutral fuels. Product selectivity in CO2RR is regulated by the adsorption energy of reaction‐intermediates. Here, we employ differential phase contrast‐scanning transmission electron microscopy (DPC‐STEM) to demonstrate that Sn heteroatoms on a Ag catalyst generate very strong and atomically localized electric fields. In situ attenuated total reflection infrared spectroscopy (ATR‐IR) results verified that the localized electric field enhances the adsorption of *COOH, thus favoring the production of CO during CO2RR. The Ag/Sn catalyst exhibits an approximately 100 % CO selectivity at a very wide range of potentials (from −0.5 to −1.1 V, versus reversible hydrogen electrode), and with a remarkably high energy efficiency (EE) of 76.1 %.

Tannic acid-aminopropyltriethoxysilane co-deposition modified polymer membrane for α-glucosidase immobilization

Mussel-inspired catechol-amine co-deposition is an effective modification strategy for various materials. In this work, polyvinylidene fluoride (PVDF) membrane was employed as the carrier for α-glucosidase immobilization. By virtue of the co-polymerization of tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES) and the hydrolysis of APTES, a hierarchical layer-colloidal nanospheres coating was decorated on the surface of PVDF membrane. Subsequently, α-glucosidase was covalently bound to the modified PVDF membrane through Schiff base reaction and Michael addition reaction between the residual quinine groups in the coating and the amino groups in enzyme molecules. Several parameters affecting the immobilization procedure were investigated thoroughly. The morphology and functional groups of the prepared composite were characterized by scanning electron microscopy (SEM), Fourier transform infrared-Attenuated total reflectance spectroscopy (FTIR-ATR), and X-ray photoelectron spectroscopy (XPS). Combined with capillary electrophoresis (CE) analysis, the performance, enzyme reaction kinetics and inhibition kinetics of PVDF-immobilized α-glucosidase were studied. The immobilized enzyme exhibited the enhanced tolerance to temperature and pH value. In addition, it possessed good reusability maintaining 77.1% of initial relative activity after 11 recycles, and batch-to-batch reproducibility with RSD of 4.3% (n = 10). The Michaelis-Menten constant (Km) of immobilized enzyme was calculated to be 4.16 mM, and IC50 value of acarbose was 0.10 µM. Finally, the PVDF-immobilized α-glucosidase was applied to screening potential inhibitors from 13 kinds of traditional Chinese medicines (TCMs), among which Sanguisorba Radix exhibited the strongest inhibitory activity. The positive results suggested that TA/APTES co-deposition was a simple and mild functionalization method for chemically inert polymer membrane and the proposed screening method was a reliable approach for discovering enzyme inhibitors from TCMs.

Further Evidence and Mechanisms for Improvement in Tracking and Erosion Resistance of ATH-Free Silicone Rubbers by Direct Fluorination

In order to provide further evidence for the improvement in tracking and erosion resistance of alumina trihydrate (ATH)-free silicone rubbers (SRs) by direct fluorination and to explore the improvement mechanisms, the ATH-free SR samples containing 15-parts per hundred parts of rubber by weight (phr) melamine cyanurate and 18-phr fumed silica were prepared, and then they were surface fluorinated using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}_{{2}}/\text{N}_{{2}}$ </tex-math></inline-formula> mixture at 0.1 MPa and 85 °C for 120 min. Inclined plane tracking and erosion tests indicate that at 4.5-kV rms ac, all 15 fluorinated samples passed the test, while 7 of the 15 unfluorinated samples failed the test due to combustion. Analyses of erosion depth, length, and area show that the fluorinated sample, compared to the unfluorinated sample, has a larger average erosion depth but a smaller average erosion length or area. Attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray photoelectron spectroscopy (XPS) analyses indicate that both the SR matrix and the fillers of melamine cyanurate and fumed silica in the surface layer were fluorinated, forming the Si–F, C–F, and N–F bonds. Scanning electron microscopy (SEM) observations show that the fluorinated layer has a thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.15~\mu \text{m}$ </tex-math></inline-formula> and a rough surface, and the fillers are uniformly dispersed in the matrix. The resistance improvement by the fluorination is attributed to these changes of the surface layer in composition, structure, and interface of the SR matrix and the fillers and is also influenced by the change in surface morphology.

Detecting CdSe Nanomaterials with a Fluorescent Schiff Base Ligand

We investigated the easily synthesized ligand H3L as a fluorescent chemosensor for the detection of CdSe nanoparticles (CdSe NPs) and L-cysteine-capped CdSe quantum dots (CdSe-Cys QDs) in ethanol–water samples. A drastic quenching of the fluorescence emission of H3L at 510 nm occurred, as a result of the addition of CdSe NPs and CdSe-Cys QDs. A solution of H3L (1.26 ppb) showed sensitive responses to both CdSe NPs and CdSe-Cys QDs, with limits of detection (LOD) as low as 40 and 62 ppb, respectively. Moreover, using a smartphone color recognizer application, the fluorescence intensity response of H3L-modified cellulose paper to CdSe-Cys QDs was recorded on a red channel (R), which allowed us to detect CdSe-Cys QDs with LOD = 15 ppb. Interference of some common metal nanomaterials (NMs), as well as metal ions, in the determination of CdSe NMs in solution was studied. The affinity of H3L to CdSe NPs and CdSe-Cys QDs was spectroscopically determined. Scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), micro-X-ray fluorescence (µ-XRF), 1H-NMR, attenuated total reflection infrared spectroscopy (ATR-IR), and density functional theory (DFT) were also used to investigate the interaction of H3L with CdSe NMs.

Equilibrium Isotherms, Kinetics, and Thermodynamic Mechanisms of a Novel Polyacrylamide-Strychnos potatorum Seed-Derived Activated Carbon Composite for Aqueous Hardness Removal

Hardness in water is responsible for both residential and industrial problems. Moreover, drinking hard water is suspected as the main cause of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. The major constituents that are responsible for water hardness are calcium and magnesium ions. In this study, a composite was synthesized using activated carbon of Strychnos potatorum seeds (ACSP) and acrylamide to remove hardness in drinking water. The synthesized composite was characterized using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and scanning electron microscope (SEM). According to this study, the process of removal of hardness depends on the contact time, adsorbent dosage, initial contents, and pH of the solution. The adsorption data were well fitted to the Freundlich isotherm and the pseudo-second-order kinetic models. Furthermore, environmental samples collected from Anuradhapura, Sri Lanka, which is well known for water with high hardness, were treated with an adsorbent, and hardness was reduced effectively. Moreover, the adsorption appeared to be spontaneous in nature. Finally, it can be concluded that this adsorbent can be used as an effective hardness-removing agent.

In-situ ATR-IR monitoring of hydrothermal carbonation of wollastonite

In-situ reaction monitoring allows for the development of reaction models for hydrothermal carbonation reactions, which have recently gained attention due to their importance in CO2 sequestration and utilization. Here, we measured the carbonation kinetics of wollastonite (β- CaSiO3) powder compacts under hydrothermal conditions (90 °C and 2.4 atm) with the help of optical fiber-based attenuated total reflectance infrared spectroscopy (ATR-IR). The fiber probe was positioned at the target area to study the reaction chemistry at the desired region of the powder compact. Absorbances of solid reactants and products were monitored throughout the entire reaction in the 1000–1600 cm−1 spectral range. ATR-IR enabled the detection of amorphous silica, which allowed all solid reactants (β-CaSiO3) and products (CaCO3 and SiO2) to be monitored independently and simultaneously. A linear proportionality constant between absorbance and CaCO3 phase concentration was determined and used to construct a reaction kinetics profile for carbonate formation, which revealed a rapid reaction onset, followed by two distinct slower decaying regimes.

Evaluation of Pb doped Poly(lactic acid) (PLA) / Poly(ethylene glycol) (PEG) blend composites regarding physicochemical and radiation shielding properties

In this study, composites of lead element, which is used to eliminate the harmful effects of radiation, were prepared with a polymer blend with shape memory properties. Poly(lactic acid) (PLA)/Poly(ethylene glycol) (PEG) blend films doped with different amounts of lead were obtained by solvent casting method. Polymer blend/Pb composites were characterized by Attenuated total reflectance infrared spectroscopy (ATR-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM). When the thermal analysis results were examined, it was observed that the thermal stability of the polymer blend decreased as the Pb percentage increased. It was concluded that the shape memory properties were the best in the polymer blend containing 4% Pb. X-ray diffraction (XRD) results showed that the 2Ɵ peaks at 31.2°, 36.3°, 52.3°, 62.1° and 65.2° represent Pb with a characteristic cubic shape. It was calculated from XRD that the polymer blend composite containing 16% Pb had the highest degree of crystallinity with 31.41%. Finally, in the study, the gamma irradiation of the obtained polymer blend/Pb composites were examined. It was seen that the linear absorption capacity increased with increasing Pb percentage, which can be interpreted as an increase in the shielding ability.

A synergetic approach based on infrared spectroscopy and ion mobility spectrometry for the analysis of seized blotters: Boosting performance

A synergetic strategy based on the combination of attenuated total reflection-infrared spectroscopy (ATR-FTIR) and ion mobility spectrometry (IMS) information have been proposed for the analysis of new psychoactive substances (NPS) in seized blotters. Firstly, the discriminating capability of each technique was separately studied and, secondly, the results obtained after combination of the information provided by both techniques were evaluated. It has been demonstrated that the discriminating power was remarkably improved after data combination, indicating a synergetic effect of the analytical approach. The proposed method allowed a first-class identification of NPS on blotter samples by ATR-FTIR by using a spectral library containing around 1000 compounds after paper matrix subtraction. The analysis of blotters after 2-propanol extraction by IMS allowed NPS identification by comparison of the reduced mobility constant with those of a database of NPS standards. The proposed strategy was evaluated with 11 blotter samples that contained DOC, 25I-NBOH, 25E-NBOH, DOM, and LSD, providing the same identity that high resolution mass spectrometry employed as reference methodology. Moreover, determination of NPS by IMS provided results statistically comparable to those obtained by ultra-performance liquid chromatography-tandem mass spectrometry. Therefore, the synergetic combination of ATR-FTIR and IMS allows a simple, fast, and portable identification and quantification of NPS in seized blotters useful for screening purposes in field analysis.

Carbon isotope fractionation and its tracer significance to carbon source during precipitation of calcium carbonate in the presence of Bacillus cereus LV-1

Microbial-induced carbonate precipitation (MICP) has the potential to immobilize carbon durably. The carbon source of carbonate minerals is the crucial issue for understanding the fixation mechanism of CO2 by MICP. However, the carbon source and its temporal changes in microbial-induced carbonate minerals remain little explored. In this study, calcium carbonate (CaCO3) biomineralization experiments have been carried out using Bacillus cereus in the medium without additional dissolved inorganic carbon (DIC). X-ray diffraction (XRD), attenuated total reflection-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM) indicated that the precipitate produced mainly consisted of rhombohedral and irregular calcite. The δ13C values of DIC, dissolved organic carbon (DOC), and calcite were the main parameters studied. Carbon isotope fractionation was characterized by carbon isotope offset (Δ13Ccalcite-DIC or Δ13Ccalcite-fluid). The Δ13Ccalcite-DIC values ranged from +8.2‰ to +21.5‰, indicating that strain LV-1 induced the accumulation of 13C in calcite. The Δ13Ccalcite-fluid values indicated that the calcite was up to +15.0‰ (on average) 13C-enriched relative to the fluid. Calculated chemical mass balance data showed that the proportion of CO2(g) derived from DOC on days 16 and 20 was negative, but it became positive after day 20. Meanwhile, the δ13CCO2(g) value calculated by isotope mass balance was −8.5‰, near to δ13C for air (−8.0‰) on day 16, and then shifted to −16.4‰, similar to δ13C for tryptone (−17.2‰) after day 20. These results suggested that the amount of CO2 arising from organic matter through bacterial respiration and the action of enzymes might determine whether the carbon in calcite was derived from organic carbon or atmospheric CO2. Our findings corroborate the potential utility of MICP for immobilization of CO2 to reduce net soil CO2 emissions and to mitigate the greenhouse effect. Microbial-driven carbon isotope fractionation can also cause great carbon isotope shifts in calcite. Thus, carbon isotope value might be used as a marker to identify whether carbonate minerals/rocks are of microbial origin.

Biosorption studies of methylene blue dye using NaOH-treated Aspergillus niger-filled sodium alginate microbeads

The effectiveness of NaOH-functionalized Aspergillus niger-filled sodium alginate microbeads on methylene blue (MB) removal was investigated in this study. First of all, Aspergillus niger biomass was obtained, then functionalized using sodium hydroxide (NaOH). Lastly, the composites were prepared by dispersing NaOH-treated-Aspergillus niger in sodium alginate gel. The cross-linked composite microbeads in a 3% CaCl2 solution were characterized by Fourier-transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy, atomic force microscope (AFM), and scanning electron microscope (SEM). FTIR-ATR results indicated that the hydroxyl, amine, and carboxyl groups on the surface of the composite beads acted as binding sites. It was determined that the biosorption of MB occurred via the electrostatic interactions, Van der Waals interactions, π-π interactions, and H-bonding between functional groups and dye molecules. SEM and AFM analyses proved the presence of adsorbed dye molecules on the surface. Besides, optimum conditions were determined by examining the effects of different physicochemical parameters on biosorption. The maximum biosorption capacity of microbeads was obtained as 322.6 mg/g in pH = 7 at 25 °C. Moreover, various isotherms were used, including Freundlich, Langmuir, Dubinin-Radushkevich, and Harkins-Jura. The Langmuir model was found to be the best feasible when the correlation coefficients were taken into account. Biosorption followed the pseudo-second-order kinetic and occurred exothermically and spontaneously. This study indicates that NaOH-treated Aspergillus niger-filled sodium alginate microbeads are promising material as a biosorbent.

Environmental behaviour of a pesticide metabolite, the AMPA. Sequestration of Ca2+, Mg2+, Cu2+, Zn2+ and Al3+

The chelating and sequestering ability of a glyphosate metabolite, the aminomethylphosphonic acid (AMPA) towards bi- and trivalent metal cations, such as Ca2+, Mg2+, Zn2+, Cu2+ and Al3+, were investigated in aqueous solutions of NaCl, in an ionic strength range of 0.1 ≤ I/mol dm−3 ≤ 1.0 and at constant temperature of T = 298.15 ± 0.15 K. The investigations on the acid-base properties and complexing ability were performed, by means of potentiometry, in conditions of different cM:cAMPA molar ratios and pH values. The formation of insoluble species was experimentally observed in the Mn+/AMPA2− systems, and the solid phases were characterized by means of X-Ray Diffractometry (XRD), Scanning Electron Microscopy (SEM) and InfraRed Attenuated Total Reflection spectroscopy (IR-ATR). The dependence on ionic strength of the stability constants of the Mn+/AMPA2− complexes species, determined at different ionic strengths, was modelled by the Debye-Hückel type equation. The sequestering ability of AMPA toward the investigated metal cations was evaluated by pL0.5 parameter.

Non-Destructive Analysis of Chlorpheniramine Maleate Tablets and Granules by Chemometrics-Assisted Attenuated Total Reflectance Infrared Spectroscopy.

Non-destructive analysis of chlorpheniramine maleate (CPM), pharmaceutical tablets, and granules was conducted by chemometrics-assisted attenuated total reflectance infrared spectroscopy (ATR-IR). For tablets, an optimum PLSR model with eight latent factors was obtained from area-normalized and standard normal variate (SNV) pretreated ATR-IR spectral data with correlation coefficients (R2) of calibration and cross-validation of 0.9716 and 0.9602, respectively. The model capability for the 42 test set samples was proven with R2 between the reference and model prediction values of 0.9632, and a root-mean-square error of prediction (RMSEP) of 1.7786. The successive PLSR model for granules was constructed from SNV and first derivative pretreated ATR-IR spectral data with two latent factors and correlation coefficients (R2) of calibration and cross-validation of 0.9577 and 0.9450, respectively.

Monitoring the infection of powdery mildew pathogen on strawberry leaves by ATR‐IR technique

AbstractPowdery mildew is one of the most common fungal diseases in plants. The disease mainly occurs in leaves, fruits, and petioles. As infection at an early stage cannot be observed with the naked eye, it causes severe economic losses to global agriculture. Here, we used attenuated total reflection–infrared spectroscopy (ATR‐IR) to identify the stage of powdery mildew infection in strawberry leaves. For naturally diseased strawberry leaves, the ATR‐IR spectra on the abaxial surface had an intense peak at 1690 cm−1, showing gradually increased intensity from early‐to‐late stages of infection. This peak was attributed to the acetyl and carboxyl C=O stretching vibrations of the pathogen. However, the spectra of the abaxial surface did not demonstrate a comparable change in 1690 cm−1 peak. When strawberry leaves were inoculated with powdery mildew, ATR‐IR successfully identified the stages of this anthropogenic infection. Moreover, the peak area ratio of 1690/2920 cm−1 on the abaxial surface of strawberry leaves was extracted to quantitatively evaluate the stages of infection, using the fitting curve equation of y = 0.0015x2‐0.0014x‐0.0021 (R2 = .9721). This study indicated potential application of ATR‐IR in monitoring fungal infections in plants. In particular, the stages of infection can be quickly and accurately monitored using the ATR‐IR technique.

Degradative impact of Alternaria multiformis on novel polymeric biocomposites with the fillers of industrial waste materials under different pH and temperature conditions

The impact of Alternaria multiformis on novel polymeric biocomposites formed from epoxidized linseed oil and various types of fillers: pine needles (PN), pine bark (PB), grain mill waste (GW), rapeseed cake (RC) and specimen without filler (WF) under different pH and temperature conditions has been studied. Identification of fungal strain A. multiformis 0065 isolated from synthetic polymer was based on molecular and morphological analysis. Tested fungal strain showed significant production of polyphenol oxidase and weak production of amylase, endoglucanase, xylanase, and lipase. Polymeric biocomposites PB, GW, RC, and WF exposed to A. multiformis for four weeks showed the greatest weight loss at pH 4 or pH 5 and at a temperature of 26 °C, suggesting the optimal conditions for biodegradation of polymeric biocomposites studied. The attenuated total reflectance infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM) analysis confirmed biodegradation of polymeric biocomposites after fungal attack. ATR-IR technique revealed changes in the intensities of the signals, demonstrating dependence of degradation on the type of the filler. SEM analysis showed significant alterations of the specimen surfaces, indicating degradative impact of A. multiformis. Identification of the most biodegraded constituents could help in the creation of more environmentally friendly biocomposites.

An identification method of herbal medicines superior to traditional spectroscopy: Two-dimensional correlation spectral images combined with deep learning

Traditional spectral analysis is prone to integration and signals overlap. It makes the extracted information unavailable or inaccurate, limiting its application in the detection of complex components. Therefore, two-dimensional correlation spectroscopy (2D-COS) that was superior to traditional spectral analysis has been established, by extracting useful information under certain chemical or physical stimulus from a series of spectra to improve the spectral resolution. In this study, with the identification of the different origins and parts of Panax notoginseng as an example. First, as a comparison, the attenuated total reflection infrared spectroscopy (ATR-FTIR) of P. notoginseng samples combined with chemometric methods was applied to identify it. Then, we generated synchronous and asynchronous 2D-COS spectral images from the fingerprint regions in the spectrum, and established a Residual convolutional neural network (ResNet) to identify the different origins and parts. Finally, the externally verified was applied to evaluate the accuracy of the model. By comparison, the 2D-COS was more suitable for the identification of the origins and parts of P. notoginseng than traditional spectroscopy. The identification accuracy of these samples of synchronous 2D-COS spectral images in the training set and test set were both greater than 99%. And the results of the externally verified indicated that synchronous 2D-COS spectral images were significantly outperforming asynchronous 2D-COS spectral images, and the sensitivity, specificity, and accuracy of the samples are both better than 0.99. Furthermore, when the sample number was relatively small or large differences in sample number were large, the synchronous 2D-COS spectral images could also successfully distinguish the different origins and parts well of P. notoginseng. In general, the ResNet model could provide a better discriminant model, and perform high-resolution processing.

Organic compositional analysis of ancient maya tooth sealants and fillings

One of the major unknowns regarding the ancient Maya practice of dental inlaying is the nature of the cement, used to affix small stones inside artificially drilled cavities on labial tooth surfaces. These cements endured the harsh buccal environment of a lifespan and secured the inlay firmly in the tooth even through centuries of subsequent postmortem decay. Beyond their adhesive properties, the sealant materials probably reduced cariogenic activity and periodontal infectious disease. Prior analysis of dental sealings was limited to the identification of inorganic components. Among the materials identified are hydroxyapatite and Portland cement-related compounds, materials that hardened and strengthened Maya dental adhesives. However, the substances that provided the agglutinant and resistance properties to the sealants and fillings remain unknown. The present study involved the analysis of the organic fraction of tooth sealants and fillings in samples from three Classic-period Maya archaeological sites, Holmul (Guatemala), Baking Pot (Belize), and the Copan Valley (Honduras). Attenuated total reflectance infrared spectroscopy (ATR-FTIR) and gas chromatography coupled to mass spectrometry (GC–MS) of eight dental specimens, revealed compositional variety and provide further clues as to the organic materials used in the sealing potions prepared by the ancient dental practitioners. Organic molecules suggest that vegetal resins from Pinaceae species, a probable Lamiaceae-derived essential oil, an Asteraceae preparation, and bitumen, were among the main ingredients. The results of these analyses further attest the chromatic properties of dental fillings and suggest the sealants may also have had antibacterial and anti-inflammatory properties. Overall, the results of this analysis highlight the high degree of sophistication of ancient Maya dental practice.

Gamma Irradiation and Ag and ZnO Nanoparticles Combined Treatment of Cotton Textile Materials.

In this work, cotton textile materials were impregnated by immersion with three different nanocomposites: Ag/chitosan, Ag/polyvinylpyrrolidone, and ZnO/polyvinylpyrrolidone and irradiated with a 60Co gamma source. After the nanoparticles impregnation, the cotton materials were irradiated in a dry and wet state at 5 and 20 kGy radiation doses. The following methods were used for the characterization of the obtained cotton materials to reveal the modification of the textile materials: Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR) and thermogravimetry (TG). The obtained materials have good antibacterial properties. The microbiological tests have shown the best material results for the gamma irradition and Ag nanoparticles combined treatment. The objective was to create a more environmentally friendly approach for textile functionalization by eliminating toxic chemicals-based technology and replacing it with the eco-friendlier gamma technology.

Fabrication of sodium alginate/graphene oxide/nanocrystalline cellulose scaffold for methylene blue adsorption: Kinetics and thermodynamics study

The development of environmentally friendly and highly efficient adsorbent materials is an important issue under study all the time all over the world. Herein, a robust 3D scaffold of sodium alginate/graphene oxide/nanocrystalline cellulose (SA/GO/NC) was fabricated for the potential adsorption of methylene blue (MB) dye. First, NC was extracted from palm sheath fibers and graphene oxide was synthesized from graphite. Then the scaffold was fabricated from a lyophilized SA/GO/NC bio-nanocomposite via cross-linking treatment. The impact of NC content (10, 15, and 20%) on the chemical, physical, thermal, and mechanical properties of fabricated scaffolds was studied too. The physical properties, chemical structure, and surface morphology of SA/GO/NCs scaffolds were investigated by Brunauer-Emmett-Teller (BET), Attenuated total reflection infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) instruments. The effect of pH, adsorbent dose, contact time, pseudo-first-order models, pseudo-second-order models, and thermodynamics on MB uptake was also studied. The obtained thermodynamic values (ΔH°, ΔS°, and ΔG°) indicate that the process is exothermic and spontaneous with physisorption mechanism directly dependent on the amount of NC used.

Photoinduced evolution of optical properties and compositions of methoxyphenols by Fe(III)-carboxylates complexes in atmospheric aqueous phase

The changes in optical properties and chemical compositions of methoxyphenols, which acted as an important aromatic compound from the biomass burning, were investigated in the presence of Fe(III)-carboxylates under aqueous phase conditions. The light was confirmed to be a key factor for stimulating the reaction of methoxyphenols and Fe(III)-carboxylates. The photoinduced evolution of optical properties of methoxyphenols was dependent on various factors, including irradiation intensity, types of carboxylates, dissolved oxygen and pH. The changes in the mass absorption efficiency at 306 nm (MAE306) positively relied on irradiation intensity and dissolved oxygen. The acceleration effects of carboxylates on the decreases in MAE306 of methoxyphenols followed the order of oxalate > citrate > malonate. The change amplitude of MAE306 decreased with an increasing pH (3.5–9), while that of the mass absorption efficiency at 364 nm (MAE364) increased with pH ranging from 3.5 to 7. The compositional evolutions of methoxyphenols by the photochemical aging were analyzed with the attenuated total reflection infrared spectroscopy (ATR-IR), confirming the decrease of CO groups and the increase of O–H and C–O groups. The photochemical reaction pathways of methoxyphenols with Fe(III)-carboxylates were proposed according to optical properties and compositions measurements.