Fourier Transform Infrared Experiments Research Articles

Accounting for spatial variations during photopolymerization of 1,6‐hexane‐diol diacrylate in the presence of oxygen

AbstractA dynamic model is proposed for photopolymerization of 1,6‐hexane‐diol diacrylate (HDDA) with bifunctional initiator bis‐acylphosphine oxide (BAPO) in the presence of oxygen. This partial‐differential‐equation model predicts time and spatially varying vinyl‐group conversion as well as concentrations of monomer, initiator, oxygen, and seven types of radicals. Experiments to obtain diffusivities of oxygen, BAPO and HDDA are reported. Oxygen‐related parameters are estimated using real‐time Fourier‐transform infrared (FTIR) conversion data. FTIR experiments were conducted using a range of film thicknesses (), BAPO levels () and light intensities (). The model predicts qualitative trends. Conversion predictions for runs with high intensities () and high BAPO () are accurate with a root‐mean‐squared error (RMSE) of 0.04. Larger RMSE (0.13) for runs with lower intensities and BAPO indicates that improved parameter estimates are required. Parameter estimates will be updated in future using a model that accounts for shrinkage during polymerization.

Non-destructive three-dimensional imaging of artificially degraded CdS paints by pump-probe microscopy

Cadmium sulfide (CdS) pigments have degraded in several well-known artworks, but the influence of pigment properties and environmental conditions on the degradation process have yet to be fully understood. Traditional non-destructive analysis techniques primarily focus on macroscopic degradation, whereas microscopic information is typically obtained with invasive techniques that require sample removal. Here, we demonstrate the use of pump-probe microscopy to nondestructively visualize the three-dimensional structure and degradation progress of CdS pigments in oil paints. CdS pigments, reproduced following historical synthesis methods, were reproduced as oil paints and artificially aged by exposure to high relative humidity and light. The degradation of CdS to CdSO4·xH2O was confirmed by both FTIR (Fourier-transform infrared) and XPS (x-ray photoelectron spectroscopy) experiments. During the degradation process, optical pump-probe microscopy was applied to track the degradation progress in single grains, and volumetric imaging revealed early CdS degradation of small particles and on the surface of large particles. This indicates that the particle dimension influences the extent and evolution of degradation of historical CdS. In addition, the pump-probe signal decrease in degraded CdS is observable before visible changes to the eye, demonstrating that pump-probe microscopy is a promising tool to detect early-stage degradation in artworks.

Co-combustion characteristics and kinetics of sludge/coal blends in 21%–50% oxygen-enriched O2/CO2 atmospheres

This research investigated the thermogravimetric analysis (TGA) and combustion kinetics of sewage sludge and Australian sub-bituminous coal and their blends with different mixing ratios (sludge/coal = 100/0, 80/20, 50/50, 20/80, 0/100 by weight) under air atmosphere (O2/N2 = 21/79 by volume), oxy-fuel combustion (O2/CO2 = 21/79, 25/75, 35/65, and 50/50 by volume), and pyrolysis (pure N2 atmospheres). The gaseous products that evolved from the TGA experiments were also analyzed using a Fourier transform infrared (FTIR) spectrometer under pyrolysis conditions. Results showed that the mixed fuel with higher coal blending ratio had higher ignition temperature, lower burnout temperature and larger combustion characteristic index. Furthermore, TGA–FTIR experiments of the 20 % sludge + 80 % coal blended fuel under nitrogen atmospheres showed more gasification components in pure coal than in sludge. The combustion kinetics analytical results via the Flynn–Wall–Ozawa method indicated that the larger the conversion degree, the smaller the obtained activation energy value. Under the oxy-fuel combustion conditions, when the oxygen concentration increased from 21 % to 50 % for the 20 % sludge + 80 % coal blended fuel, the ignition and burnout temperatures decreased, and the combustion characteristic index increased nearly three times. Oxygen enrichment can clearly improve combustion characteristics and flammability.

Crystal growth, structural, vibrational, spectroscopic studies of novelly synthesized NLO active melaminium sulfamate single crystal: Experimental and theoretical approach

Semi-organic nonlinear optical (NLO) melaminium sulfamate (MASA) single crystals were synthesized by slow evaporation method and analyzed by using X-ray diffraction, UV–vis, FT-IR and FT-Raman experiments. Single crystal X-ray diffraction (SXRD) analysis confirms that MASA crystal belongs to triclinic system with centrosymmetric space group P-1. The quantum chemical calculation were carried out using density functional theory (DFT) with B3LYP/6-31+G(d) basis set. The intermolecular interactions were deeply analyzed by NBO analysis. The molecule with intermolecular N-H⋯N and N-H⋯O hydrogen bonds show notable vibrational effect. The optical property of MASA was evaluated by UV–vis optical transmittance spectrum. Thermal stability of the grown crystal was performed by using TG-DTA analysis. The frontier molecular orbital analysis illustrates the charge transferred from sulfamate anion to melaminium cation. Hirshfeld and 2D fingerprint plot reveals the intermolecular N-H⋯O and N-H⋯N contacts of MASA molecule. The existence of various functional groups and vibrational modes are affirmed by Fourier transform infrared (FT-IR) and FT-Raman spectral analysis. Additionally, the molecular electrostatic potential (MESP) and topological analysis such as electron localization function (ELF), reduced density gradient(RDG), localized orbital locator(LOL) and atoms in molecule(AIM) have been used to predict the intermolecular interaction, especially the hydrogen bonds. The hydrogen atom from sulphamic acid was transferred to the melamine molecule giving the singly protonated melaminium cation. The outcome of SXRD, UV–visible, TG/DTA, HOMO–LUMO, NLO and Z-Scan values were compared with earlier reported compounds and amongst the analyzed compound MASA shows good NLO activity. The NLO activity of MASA was analyzed theoretically and experimentally by DFT and Z-scan method.

Towards a heat‐ and mass‐balanced kinetic model of TATB decomposition

AbstractTATB (1,3,5‐triamino‐2,4,6‐trinitrobenzene) was thermally degraded by two small‐scale analytical methods – simultaneous differential scanning calorimetry and thermogravimetric analysis (SDT) and a hot‐stage microscope with Fourier Transform Infrared (FTIR) analysis capabilities. SDT used ramped heating, isothermal soaking, and thermal pretreatment at various conditions. The heat flow and mass loss were monitored during various treatment conditions to derive chemical decomposition kinetics and Arrhenius parameters. FTIR experiments used isothermal heating, and changes were monitored spectroscopically. Solid samples generated at specific conditions were collected from both methods and were analyzed by DMSO extraction followed by chemical speciation by optical and mass spectrometric methods. Characterization provided the following reaction insights:1. TATB decreases in a sigmoidal pattern in isothermally heated samples. Other soluble products gradually increase in concentration and then abruptly decline in concentration during the second exotherm, such as diamino‐dinitro‐benzofurazan and amino‐nitro‐benzodifurazan.2. FTIR showed gradual changes in the amino and nitro functionality, shifting positions and decreasing intensity for the first 40 min. Then the solid gradually appeared more like an amorphous C with N incorporated, similar to previous studies on thermally degraded TATB‐type materials.3. Extracted residues (DMSO‐soluble components removed) examined by FTIR showed an abrupt change in chemical composition between 40‐ and 45‐min isothermal treatment, indicating early forming solids are different than later forming residues.4. A reliable mass‐ and energy‐balanced global reaction network must include at least two autocatalytic reactions, either in parallel or series, and at least one must have an explicit initiation reaction having a low activation energy.

Research on surface morphology characteristics and micro-damage mechanism of asphalt mastic based on charge transfer principle

Asphalt mastic damage is a major element influencing the mechanical qualities of the asphalt mixture. Based on electrochemistry theory, the idea of charge transfer of moisture between asphalt-asphalt and asphalt-mineral powder is proposed in this study to explore the damage mechanism of asphalt mastic under the operation of freeze–thaw cycles.On this basis, the damage mechanism of asphalt mastic was analyzed at multiple scales using relevant experimental means (Scanning electron microscopy-Energy dispersion spectrum(SEM-EDS) experiment, Fourier Transform Infrared(FT-IR) experiment and Atomic Force Microscope(AFM) experiment). FT-IR and AFM experiments results showed that: Water molecules in asphalt mastic might compete for asphaltene electrons in the asphalt mastic, causing the carboxyl dimer formed between asphaltenes to be disrupted. This causes asphaltene dispersion and a reduction in asphaltene concentration. Asphalt colloid structure changes from gel to sol, causing asphalt mastic degradation. Furthermore, freeze–thaw cycles accelerate the damage. On the other hand, the results of FT-IR and SEM-EDS experiments showed that: Freeze-thaw processes in asphalt mastics can also result in varying pore sizes and higher carbon concentration. Water molecules can create structural water on the subsurface of mineral powder crystals as well as physical water on the surface of mineral powder. This affects the adsorption of structural asphalt on the subsurface of the mineral powder crystals, resulting in the dissociation of the adsorbed asphalt from the mineral powder crystals' surface. The results of the study have some theoretical value to further explore the damage mechanism of asphalt mastic.

Experimental and Theoretical Characterization of Rh Single Atoms Supported on γ-Al2O3 with Varying Hydroxyl Contents during NO Reduction by CO

Oxide-supported Rh catalysts are important components of commercial three-way catalysts for pollution abatement. Despite their universal application, many mysteries remain about the active structure of Rh on oxide supports as these materials often contain a mixture of nanoparticles and single-atom Rh species on the same support, even after aging. Probe molecule Fourier transform infrared (FTIR) spectroscopy in this work shows that atomically dispersed Rh on γ-Al2O3 prefer to strongly bind CO when exposed to NO and CO mixtures and that light-off of NO reduction occurs at temperatures similar to CO desorption, suggesting that the first and rate-determining step in NO–CO reactions may be the desorption of CO from single-atom Rh dicarbonyl complexes, Rh(CO)2. Two sets of symmetric and asymmetric stretching frequencies associated with distinct Rh(CO)2 species are observed in FTIR spectra at 2084/2010 and 2094/2020 cm–1. During temperature ramps, the latter pair of bands at 2094/2020 cm–1 converts to the 2084/2010 cm–1 bands at 463 K before all symmetric and asymmetric bands disappear at 573 K. Bands then appear in the range of 1975–1985 cm–1 associated with Rh monocarbonyl, Rh(CO), species upon the disappearance of the 2084/2010 cm–1 bands, suggesting that CO desorbs sequentially from Rh(CO)2 by forming Rh(CO) intermediates. Combined DFT and FTIR experiments suggest that local OH coverage on the γ-Al2O3 surface distinguishes the two Rh(CO)2 species: the higher frequency species resides on a less hydroxylated region and migrates to a more hydroxylated region at higher temperatures, causing the CO vibrational frequency to decrease by ∼10 cm–1. CO desorption occurs from this Rh(CO)2 structure with high local OH coverage, consistent with the DFT predicted trend of CO binding energies. Because of the coincidence of CO desorption with the light-off of NO reduction, local support hydroxylation of atomically dispersed Rh1/γ-Al2O3 catalysts likely affects both the Rh structure after CO desorption and the kinetics of NO reduction, studies of which are enabled by the Rh(CO)2 model developed here.

Monitoring and investigating reactive extraction of (di–)carboxylic acids using online FTIR – Part II: Reaction equilibria, reaction kinetics and competition within the complex formation between itaconic acid and several amine extractants

The downstream processing of biocatalytically produced (di–)carboxylic acids still is a challenging task. One innovative approach, demonstrating industrial applicability, applies an initial reactive extraction (RE) using hydrophobic amine extractants into an organic solvent, followed by a subsequent back-extraction (BE) using water soluble amine extractants into a (fresh) aqueous solution. Although showing promising results in terms of yield and selectivity, state-of-the-art amine extractant selection is only based on trial-and-error screening approaches. Thus, to enable an optimized process design and thereby optimized downstream processing, a deeper understanding of RE and BE on a molecular level is crucial.Within this work, we successfully applied an experimental setup incorporating online Fourier Transform Infrared (FTIR) spectroscopy to elucidate influencing factors on RE and BE as well as to provide a guideline for an optimized selection of amine extractants. Investigations on the kinetics of complex formation between itaconic acid (IA) and tri-n-octylamine (TNOA) in 1-decanol revealed the reaction order to be zero in TNOA, indicating that mass transfer is the rate limiting step in RE. Reaction equilibrium investigations revealed that for all IA - amine extractants combinations in 1-decanol reaction equilibrium was almost completely on the product (complex) side. The strength of the acid-extractant complexes was evaluated using FTIR experiments, providing a novel approach / methodology to efficiently select an optimal combination of amine extractants for RE and BE. Applying the novel online FTIR spectroscopy setup allowed to monitor a complete process sequence of RE and BE of IA with selected amine extractants, validating the proposed guidelines for an optimized selection of amine extractants. The results of this work will facilitate the definition of appropriate RE and BE systems for biocatalytically produced (di–)carboxylic acids.

A molecular tuner: Substituent controlled π/π···hole induced selective colorimetric intramolecular push-pull fluoride sensor

Controlling the anion selectivity of synthetic anion receptors towards a particular anion is challenging task for researcher. In the case of bipodal receptors this become trickier since anion can approach the recognition elements of receptors from any direction. In order to overcome this problem, we adopted the new strategy in which the receptor molecules are functionalized with electron donating and/or withdrawing group. In the way of hunting such a receptors, herein Thio-semicarbazide based chemosensors 1-(2,4-dinitrophenyl)-4-(4-nitrophenyl) thiosemicarbazide L1, and 1-(2,4-dimethylphenyl)-4-(4-nitrophenyl) thiosemicarbazide L2 with electron withdrawing (EW) and donating (ED) groups have been synthesized for selective colorimetric anion sensing. Substituent effects on the strength of those receptors L1 and L2 have been studied by naked-eye colorimetric experiments, Ultraviolet-Visible (UV-Vis) spectrometric titration studies, Fourier-Transform Infrared experiments (FT-IR), 1H-NMR, 19F-NMR spectroscopic studies and Molecular Electrostatic Potential (MEP) surface analysis. When we have nitro substitution on both end of the thio-semicarbazide receptor L1, there were no selectivity was found with anions and receptor L1 shows visible color change with the all the tested anions. On the other hand, instead of nitro, when we have methyl substitution on one end and nitro substitution at an another end of the thio-semicarbazide receptor L2, then the receptor L2 show excellent selectivity towards fluoride ion with high association constant. Additionally, for azide considerable bathochromic shift of 70 nm also observed with reference to absorption values of cyanide and fluoride anion which will clearly distinguish the presence of azide ion from cyanide and fluoride. The observed bathochromic shift is mainly attributed due to the intramolecular charge transfer (ICT). In this work, we have successfully tuned the selectivity of synthesized receptors via generating a push-pull effect originated by electron withdrawing and donation substitutions on both end of the receptor L2. The enhanced selectivity of L2 is achieved by altering the acidity of -NHs of thio-semicarbazide derivative L2 by substituting EW and ED groups. In this present work, we have tuned the selectivity of receptor is via intramolecular push-pull effect by electron withdrawing and donating substituent.

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Surface Coordination Decouples Hydrogenation Catalysis on Supported Metal Catalysts

Influence mechanism of Na2O on the network structure depolymerization of ZD coal ash silicate under high temperature

Na2O is the basic alkali metal oxide in Zhundong (ZD) coal, the content of Na2O directly affects the ash fusion temperatures (AFTs) of coal ash. Fourier transform infrared (FTIR) spectroscopy and molecular dynamics (MD) simulation were used to study the structural characteristics of synthetic coal ash under Na2O concentration of 1–13 mol%. Both FTIR experiments and MD simulation show that Na+ attacks the tri-coordinate oxygen (Ot) and the bridge oxygen (Ob) formed by [SiO4]4− and [AlO4]5− tetrahedron structure, generates more non-bridge oxygen (Onb), the shelf-like network structure(Q4) in fused coal ash is depolymerized to form layered silicate structure (Q3), chain or cyclic silicate structure (Q2, Q1). O(Al, Al, Si) and O(Al, Al, Al) in Ot decreased their trend by 3% each, Si–O–Si was reduced from 12% to 7%. Al–O–Si was reduced from 36% to 29%. The intricate structures are gradually depolymerized into plain structures, which leads to the decrease of AFTs.

Probing How Various Metal Ions Interact with the Surface of QDs: Implication of the Interaction Event on the Photophysics of QDs.

With an aim to understand the mechanism of interaction between quantum dots (QDs) and various metal ions, fluorescence response of less-toxic and water-soluble glutathione-capped Zn-Ag-In-S (GSH@ZAIS) QDs in the presence of different metal ions has been investigated at both ensemble and single-molecule level. Fourier transform infrared (FT-IR) spectroscopy has also been performed to obtain a molecular level understanding of the interaction event. The steady-state data reveal no significant change in QD emission for alkali and alkaline earth metal ions, while there is a decrease in fluorescence intensity for transition metal (TM) and some heavy transition metal (HTM) ions. Interestingly, a significant fluorescent enhancement (FE) (19-96%) of QDs is found for Cd2+ ions. Time-resolved fluorescence studies reveal that all the three decay components of QDs decrease in the presence of first-row TM ions. However, in the case of Cd2+, the shorter component is found to increase while the longer one decreases. The analysis of data reveals that photoinduced electron transfer is responsible for fluorescence quenching of QDs in the presence of first-row TM ions and destruction/removal of trap/defect states in the case of Cd2+ causes the FE. In FT-IR experiments, a prominent peak at 670 cm-1, corresponding to Cd-S stretching vibrations, indicates strong ground-state interactions between the -SH of GSH and Cd2+ ions. Moreover, a decrease in the diffusion coefficient of QDs in the presence of Cd2+ ions during fluorescence correlation spectroscopy (FCS) studies further substantiates the removal of GSH by Cd2+ from the surface of QDs. The optical output of this study demonstrates that ZAIS can be used for fluorescence signaling of various metal ions and in particular selective detection of Cd2+. More importantly, these results also suggest that Cd2+ can effectively be used for enhancing the fluorescence quantum yield of thiol-capped QDs such as GSH@ZAIS.

Effect of Basicity on the Structure, Viscosity and Crystallization of CaO-SiO2-B2O3 Based Mold Fluxes

In this study, the structure, viscosity characteristics, and crystallization behavior of CaO-SiO2-B2O3 based melts were studied combining molecular dynamics (MD) simulation, Fourier transform infrared (FTIR) spectroscopy, rotating viscometer test, and FactSage thermodynamic calculation. The results showed that, in the ternary CaO-SiO2-B2O3 glass system, stable structural units of [SiO4]4− tetrahedral, [BO3]3− trihedral and [BO4]5− tetrahedral were formed, and the Si-O and B-O structure depolymerize with the basicity increase from 1.15 to 1.25, then the B-O structure become complex with the basicity further increase to 1.35. In fluorine-free mold fluxes, with the basicity increases, the viscosity at 1300 °C increases, the liquidus temperature decreases and then increases, the network structure polymerizes, it indicates that the structural complexity rather than the melting property change plays a predominant role in increasing the viscosity at 1300 °C. Moreover, due to the changes in crystallization phase and solid solution ratio, the viscosity-temperature curve of fluorine-free slag shows the characteristics of alkaline slag and the break temperature increase with the basicity increase. The MD simulation, FTIR experiment, viscosity test, and FactSage calculation results are verified and complemented each other.

Biosynthesis of selenium nanoparticles mediated by fungus Mariannaea sp. HJ and their characterization

The biosynthesis of selenium nanoparticles (SeNPs) by Mariannaea sp. HJ was reported for the first time. Different cultural conditions, including SeO2 concentrations and pH were studied, 2 mM SeO2 and pH 10 were favorable for the removal of Se(IV), and extracellular SeNPs were observed at alkaline pH values. UV–vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to characterize SeNPs. The results showed that removal of Se(IV) ions occurred during the late exponential phase of strain HJ. TEM and SEM images revealed that spherical nanoparticles were deposited on the cell wall and in the cytoplasmic region of strain HJ with a uniform size distribution. XRD pattern suggested the standard hexagonal phase of selenium crystals. FTIR, XPS and selective passivation experiments implicated that lipid and amide groups were involved in the formation process and Se(-I) or Se(-II) species were demonstrated to be functioned in this process. Based on the SDS-PAGE analysis, the up-regulated proteins of MW ∼91.6 and ∼37.4–57.2 kDa might promote SeNP formation, and a number of proteins adsorbed on the surface of nanoparticles, which may act as a natural stabilizing agent.

Molecular Origin of the Induction Period in Photoinitiated Cationic Polymerization of Epoxies and Oxetanes

We investigated how the reactivity of epoxide and oxetane monomers in photoinitiated cationic polymerization is strongly influenced by their ability to form intramolecular hydrogen-bonding complexes with the Brønsted acids produced by the photoinitiator. In this paper, we highlight the importance of the thermal stability of the hydrogen-bonded complexes of the protonated monomers. We observed that the glycidyl ether structural motif (and its oxetane analog) is key for the formation of the complexes. Using temperature-controlled Fourier transform infrared (FTIR) with in situ ultraviolet irradiation, we performed a series of real-time FTIR experiments which support the hypothesis that the induction period is due to the thermal stability of the hydrogen-bonded complex. In particular, we focused on the photoinitiated cationic polymerization of bis(1-ethyl(3-oxetanil)methyl) ether (“di-oxetane”, DOX) for the thermal stability study because it exhibits a prolonged induction period. Furthermore, it was possible to delay the cationic polymerization of DOX without causing autocatalytic polymerization if the temperature is kept lower than 30 °C. This is because the protonated monomer is stable and propagates very slowly at temperatures below 30 °C. On subsequent heating, the hydrogen-bonded complex of DOX loses its thermal stability, and the autocatalytic cationic polymerization of DOX occurs.

Hydrochlorothiazide binding to human serum albumin induces some compactness in the molecular structure of the protein: A multi-spectroscopic and computational study

The interaction between hydrochlorothiazide (HCTZ), a diuretic drug, with human serum albumin (HSA) was investigated by different biophysical approaches such as UV absorption, circular dichroism (CD), Fourier transform infrared (FT-IR), and fluorescence spectroscopy in 50 mM sodium phosphate buffer, pH 7.4. The results of fluorescence titration experiments revealed that HCTZ strongly quenches the intrinsic fluorescence of HSA through a static quenching mechanism. Binding constants and the number of binding sites were calculated using Stern–Volmer plots. Thermodynamic analysis of the binding data elucidated that hydrogen bonding and van der Waals interactions played the major role in the binding process. Computation of the protein surface hydrophobicity (PSH) index using 1-anilinonaphtalene-8-sulfonate indicated that considerable decrement in PSH value of the protein happened upon drug binding. The binding site of HCTZ in HSA was identified using warfarin and ibuprofen as site markers, a result confirmed by molecular docking study. The results of CD experiments showed that some alterations occurred in the structure of the protein upon ligation. Also, the results of FT-IR experiments were in good agreement with CD experiments. It looks like that both secondary and tertiary structures of HSA have been affected upon HCTZ binding.

Combined use of infrared and hard X-ray microprobes for spectroscopy-based neuroanatomy

Understanding the pathological triggers that affect the structural and physiological integrity of biochemical milieu of neurons is crucial to extend our knowledge on brain disorders, that are in many circumstances hardly treatable. Over recently, by using sophisticated hyperspectral micro-imaging modalities, it has been placed within our reach to get an insight into high fidelity histological details along with corresponding biochemical information in a label-free fashion, without using any additional chemical fixatives. However, in order to push forwards extensive application of these methods in the clinical arena, it is viable to make further iterations in novel data analysis protocols in order to boost their sensitivity. Therefore, in our study we proposed a new combined approach utilizing both benchtop Fourier transform infrared (FTIR) and synchrotron X-ray fluorescence (SR-XRF) micro-spectroscopies coupled with multivariate data clustering using the K-means algorithm for combined molecular and elemental micro-imaging, so that these complimentary analytical tools could be used for delineating between various brain structures based on their biochemical composition. By utilizing mid-IR transmission FTIR experiments, the biochemical composition in terms of lipids, proteins and phosphodiesters became accessible. In turn, the SR-XRF experiment was carried out at the advanced IAEA X-ray spectrometry station at Elettra Sincrotrone Trieste. By measuring in vacuum and by using the primary exciting X-ray beam, monochromatized to 10.5 keV, we took advantage of accessing the characteristic X-ray lines of a variety of elements ranging from carbon to zinc. Herein, we can report that the developed methodology has high specificity for label-free discriminating between lipid- and protein-rich brain tissue areas.

Sorption mechanism of zinc on reed, lignin, and reed- and lignin-derived biochars: kinetics, equilibrium, and spectroscopic studies

Biochar is considered as a substitute for stabilizing heavy metals, yet systematic studies regarding the stabilization mechanism of Zn on biochars from different biomass sources under different pyrolysis temperatures are still lacking. This study was endeavored to assess the sorption behavior and mechanism of Zn on pristine reed, lignin, and reed- and lignin-derived biochars at different pyrolysis temperatures (350, 450, and 550 °C). Batch experiments were performed to investigate the Zn sorption on pristine reed, lignin, and their derived biochars. Major functional groups on the surface of samples were measured using Fourier transform infrared (FTIR) spectroscopy and Boehm titration method, while the speciation and binding mechanisms were elucidated using X-ray absorption near-edge structure (XANES). The FTIR results showed an abrupt decline in the oxygen-containing functional groups with elevating pyrolysis temperature. The total amount of three acidic functional groups (carboxyl, lactone, phenol) was highest (2.39 mmol/g) in lignin, and it significantly decreased in reed- and lignin-derived biochars (0.05–0.94 mmol/g). Lignin exhibited the highest sorption capacity to Zn (qe = 3360 mg/kg) in the batch sorption experiments, while the sorption capacities for biochars were reduced with increasing pyrolysis temperature, irrespective of biomass sources. The XANES results indicated that soil organic matter (SOM), iron, and phosphate mineral components in the tested sorbents played an indispensable role in Zn immobilization. A large fraction of Zn-OM complex was observed in lignin due to its highest abundance of acidic functional group, leading to the highest sorption capacity for lignin toward Zn. The combination of XANES with FTIR, Boehm titration, batch sorption, and kinetic experiments altogether revealed that the decline in sorption capacity of Zn on reed- and lignin-derived biochars with elevating pyrolysis temperature was attributed to the loss in O-containing functional groups. The complexation of Zn with surface functional groups contributed to the Zn sorption on reed, lignin, and their derived biochars. The projected results will not only provide the detailed stabilization mechanism of Zn on lignin and reed- and lignin-derived biochars but also develop a novel and effective material (lignin) for heavy metal remediation.

Experimental Study of High Temperature Combustion for Enhanced Shale Gas Recovery

As an alternative to hydraulic fracture for shale gas recovery, high temperature treatments such as combustion and pyrolysis are being used to remove organic matters and decompose minerals from shale to increase shale rock permeability for gas recovery. In this study, shales obtained from Shang Gu Basin, Shangxi, China, were burned in an air environment at a temperature of 800 °C for 45 min to oxidize the organic matters to improve shale physical properties. Energy dispersive spectrometer (EDS), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) tests were conducted to identify minerals and functional group inside the shale samples. The shale samples were also tested in a thermogravimetric analysis FTIR (TGA-FTIR) experiment to study the combustion characteristics and gas emission. The TGA curve shows that two weight loss peaks existed in the combustion process. The first peak occurring between 400 and 500 °C was found to be caused by oxidization of organic matter, and the second pe...

Ground-based remote sensing of O<sub>3</sub> by high- and medium-resolution FTIR spectrometers over the Mexico City basin

Abstract. We present atmospheric ozone (O3) profiles measured over central Mexico between November 2012 and February 2014 from two different ground-based FTIR (Fourier transform infrared) solar absorption experiments. The first instrument offers very high-resolution spectra and contributes to NDACC (Network for the Detection of Atmospheric Composition Change). It is located at a mountain observatory about 1700 m above the Mexico City basin. The second instrument has a medium spectral resolution and is located inside Mexico City at a horizontal distance of about 60 km from the mountain observatory. It is documented that the retrieval with the high- and medium-resolution experiments provides O3 variations for four and three independent atmospheric altitude ranges, respectively, and the theoretically estimated errors of these profile data are mostly within 10 %. The good quality of the data is empirically demonstrated above the tropopause by intercomparing the two FTIR O3 data, and for the boundary layer by comparing the Mexico City FTIR O3 data with in situ O3 surface data. Furthermore, we develop a combined boundary layer O3 remote sensing product that uses the retrieval results of both FTIR experiments, and we use theoretical and empirical evaluations to document the improvements that can be achieved by such a combination.