Pure Reagents Research Articles

Reduction Kinetics of Compact Hematite with Hydrogen from 600 to 1050 °C

Reduction of iron ores with hydrogen is a solution to replace fossil fuels. For this reason, it is important to discuss previous discrepancies. Some previous studies suggest a rate minimum with respect to temperature. Our research work indicates that a rate minimum can be avoided. Thermogravimetric isothermal reduction experiments were carried out from 600 to 1050 °C with pure reagent ferric oxide and hydrogen using a tubular furnace. The morphology and chemical composition of the initial sample, consisting of particulate hematite (Fe2O3), and the final product, consisting of metallic iron (Fe°), was defined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The reduction rate for the conversion from hematite to magnetite (Fe2O3 to Fe3O4) was the highest, around 5 %/min, decreasing to around 2–5%/min for the second stage of conversion from magnetite to wüstite (Fe3O4 to FeO). This reduction rate remains almost constant from about 20–80% reduction, decreasing to 0.3–1%/min for the completion of reduction from wüstite to metallic iron (FeO to Fe°). The reduction controlling mechanism was evaluated based on the calculated apparent activation energy and fitting the experimental data to one gas-solid reaction equation. Under the experimental conditions in this work, the reduction rate of pure hematite with hydrogen linearly increased with temperatures from 600 to 1000 °C, without a rate minimum in this temperature range. Above 1000 °C, the reduction rate decreased due to sintering phenomena. This result suggests a maximum reduction temperature of 1000 °C using pure hematite and hydrogen as the reducing gas. The reduction controlling mechanisms identified using hydrogen as a reducing gas were chemical reaction for the conversion from hematite to wüstite and diffusion control for the final reduction from wüstite to metallic iron. Since the reduction rate from wüstite to metallic iron is the one that affects the overall rate of reduction, overall changes in porosity were also evaluated. Finally, the reduction of wüstite is schematically described.

A Toolbox of Reagents for Trifluoromethylthiolation: From Serendipitous Findings to Rational Design.

Two types of electrophilic trifluoromethylthiolating reagents were developed in the past 10 years in our laboratory. The development of the first type of reagent, trifluoromethanesulfenate I, which is highly reactive toward a variety of nucleophiles, was based on an unexpected discovery in the initial design for the development of an electrophilic trifluoromethylthiolating reagent with a hypervalent iodine skeleton. A structure-activity study disclosed that α-cumyl trifluoromethanesulfenate (reagent II) without the iodo substituent is equally effective. Subsequent derivatization let us develop an α-cumyl bromodifluoromethanesulfenate III that could be used for the preparation of [18F]ArSCF3. To remediate the low reactivity of the type I electrophilic trifluoromethylthiolating reagent for Friedel-Crafts trifluoromethylthiolation of electron-rich (hetero)arenes, we designed and prepared N-trifluoromethylthiosaccharin IV, which exhibits broad reactivity toward various nucleophiles, including electron-rich arenes. A comparison of the structure of N-trifluoromethylthiosaccharin IV with that of N-trifluoromethylthiophthalimide showed that the replacement of one carbonyl group in N-trifluoromethylthiophthalimide with a sulfonyl group made N-trifluoromethylthiosaccharin IV much more electrophilic. Thus, the replacement of both carbonyls with two sulfonyl groups would further increase the electrophilicity. Such a rationale prompted us to design and develop the current most electrophilic trifluoromethylthiolating reagent, N-trifluoromethylthiodibenzenesulfonimide V, and its reactivity was much higher than that of N-trifluoromethylthiosaccharin IV. We further developed an optically pure electrophilic trifluoromethylthiolating reagent, (1S)-(-)-N-trifluoromethylthio-2,10-camphorsultam VI, for the preparation of optically active trifluoromethylthio-substituted carbon stereogenic centers. Reagents I-VI now constitute a powerful toolbox for the introduction of the trifluoromethylthio group into the target molecules.

Mechanical and Hydration Characteristics of Stabilized Gold Mine Tailings Using a Sustainable Industrial Waste-Based Binder.

Sustainable resource utilization of tailings is a long-term challenge. Therefore, a novel waste-based binder is proposed in this study to stabilize/solidify gold mine tailings (GMTs). This binder is composed of fly ash (FA), ground blast furnace slag (GBFS), and metakaolin (MK) activated with mixed calcium carbide residue (CCR) as well as pure reagent grade chemical, sodium hydroxide (SH, NaOH), and plaster gypsum (PG, CaSO4·2H2O). The mechanical properties and hydration of stabilized tailings with curing period were investigated. Tests included triaxial compression test and nitrogen adsorption to evaluate the strength of the stabilized tailings and microstructure. The results show that the addition of the waste-based binder yields significant improvement in shear strength. Strain softening occurred for all cured samples, and a local shear band can be observed in all failed stabilized samples. Based on the relationship between strength and curing period, it can be speculated that the hydration reaction of the sample ends after around 40 days of curing. A bimodal pore-size distribution was observed in all solidified/stabilized samples. FTIR and 27Al MAS-NMR were used to analyze hydration products. The strength improvement of stabilized tailings was mainly attributed to the formation of ettringite and C-S-H gels after various polymerization reactions. These new hydrates bind tailings particles and fill the pores to form a more stable structure, which supplied superior mechanical properties. This paper can provide a theoretical basis for exploring the application of the industrial waste-based binder to modify the mechanical properties of gold tailings.

Characterization and mechanical properties of one-part geopolymer based on a pure metakaolin

Geopolymers are amorphous silicate polymers that have been extensively studied due to their applications, scientific and technical relevance, and their potential as cement in substitution to Portland. Much of the focus has been in the use of precursors and aggregates that are rarely pure and homogeneous with the use of tailings being very common. The presence of these impurities complicates the interpretation of some spectral methods, mainly infrared spectrometry. Therefore, this research focuses on the use of a nearly pure kaolin main precursor, having only a trace of iron and titanium, along with other almost pure reagents, to achieve an ideal geopolymer. It was possible to produce metakaolinite, resulting in a material with a good size particle (8.24µm) and surface specific area (6.57m2/g). The XRD result shows that the calcination process resulted in 100% of amorphous material. FTIR data revealed the presence of H2O and NaCO3 in the geopolymer. More important, the Si-Al-O various bands located between 1100 and 500cm-1 validate the polymerization reaction effectiveness. SEM-EDS analyses have demonstrated that the reaction with Na2SiO3 and NaOH were nearly complete, concerning the finer metakaolinite particles that comprised the material’s matrix. However, the coarser metakaolinite lamellae, in the 15-35µm range, did not react completely; a thin border layer was enriched with sodium and most of the interior material maintained its Si-Al-O composition. The presence of traces of iron and titanium did not influence in the polymerization reaction. Compressive strength values of the geopolymer have presented good values in the range of 25 to 35 MPa.

Effect of Iron Phase on the Formation of Barium Calcium Sulphoaluminate Clinker

In this paper, analytically pure chemical reagents, as raw materials, were fired in barium calcium sulfoaluminate cement clinker. The effect of the iron phase on the calcination of barium calcium sulfoaluminate cement clinker was studied. The content of f-CaO in the sample was determined using the ethylene glycol method. The raw meal’s heat absorption and heat release were tested with an integrated thermal analyzer TG-DSC, and XRD and SEM measurements were used to characterize the composition and microstructure of the clinker. The results showed that the iron phase could lower the decomposition temperature of the calcium carbonate. When the calcination temperature increased, the lattice spacing of the mineral changed. The XRD pattern showed that a substitution reaction had occurred. Ba2+ replaced Ca2+ and formed a sulfoaluminate barium calcium mineral. The SEM images showed hexagonal plates or dodecahedral barium calcium sulfoaluminate minerals.

Electrochemical oxidation of meglumine in a pharmaceutical formulation using a nanocomposite anode

The electrocatalytic oxidation of meglumine and gadoterate meglumine (Gd-DOTA) on a TiO2-Ni(SO4)0.3(OH)1.4 composite anode was investigated in alkaline medium (5 M KOH) using cyclic voltammetry and chronoamperometry. The composite was prepared by hydrothermal method and the morphology and structure of the produced nanoparticles were studied by scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy, BET surface area analysis and Fourier transform infrared spectroscopy. The characterization revealed the formation of Ni(SO4)0.3(OH)1.4 nanobelts dispersed on TiO2 nanoaggregates. The composite was coated onto a porous graphite rod, showing good adherence without requiring any binder (according to their anodic and cathodic charges). The supported composite was electrocatalytic, allowing the oxidation of meglumine, either as pure reagent or contained in gadoterate meglumine solutions. Electrochemical methods allowed determining the kinetic parameters, such as the electron transfer coefficient α, the total number of electrons n and the standard heterogeneous rate constant k0 for the reaction of meglumine. The chronoamperometric tests informed about the good stability of the composite anode upon meglumine oxidation at +0.6 V for 10 h. The electrochemical oxidation of meglumine in a commercial pharmaceutical formulation (Dotarem®) was corroborated via ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry.

CO2 high-temperature sorbent (Al, Fe, Ti) CO-doped Li4SiO4 from fly ash-derived SiO2 aerogel: In-situ synthesis, enhanced capture ability and long cycle stability

Lithium silicate (Li4SiO4), an efficient CO2 high-temperature sorbent, has become the research hotspot in CO2 capture due to its large theoretical adsorption capacity and fast rate. How to further reduce production cost while ensuring the adsorption performance has become the key to industrial application. In this work, using Al, Fe, Ti co-doped SiO2 aerogel synthesized from fly ash as silicon source, Li4SiO4 sorbents were achieved through solid-state calcination method. The influences of preparing conditions on the microstructure and CO2 capture property were systematically investigated. Under the optimum conditions, the as-prepared Li4SiO4 demonstrated the best CO2 adsorption capacity of 33.24 wt% within 7.0 min. Particularly, the CO2 capture capacity remained 23.38 wt% (>70% of the first value) after 35 cycles, indicative of long cycle stability. Moreover, the kinetic characteristics of CO2 adsorption process could be well simulated by the double exponential model, and the diffusion process of Li+/O2− ions was the decisive step of the whole adsorption reaction. Compared with Li4SiO4 by pure reagents, the sorbent from fly ash-based aerogel exhibited competitive adsorption capacity, which provides a new cost-effective way to synthesize CO2 high-temperature sorbent with super capture performance and good cycle stability.

A study of the solidification and stability mechanisms of heavy metals in electrolytic manganese slag-based glass-ceramics.

To better solve the waste pollution problem generated by the electrolytic manganese industry, electrolytic manganese slag as the main raw material, chromium iron slag, and pure chemical reagents containing heavy metal elements mixed with electrolytic manganese slag doping. A parent glass was formed by melting the slag mixture at 1,250°C, which was, thereafter, heat-treated at 900°C to obtain the glass-ceramic. The results from characterizations showed that the heavy metal elements in the glass-ceramic system were well solidified and isolated, with a leakage concentration at a relatively low level. After crystallization, the curing rates of harmful heavy metals all exceed 99.9%. The mechanisms of heavy metal migration, transformation, and solidification/isolation in glass-ceramic curing bodies were investigated by using characterization methods such as chemical elemental morphological analysis, transmission electron microscopy, and electron microprobe. The most toxic Cr and Mn elements were found to be mainly kept in their residual state in the glass-ceramic system. It was concluded that the curing mechanism of the heavy metals in a glass-ceramic can either be explained by the chemical curing induced by bonding (or interaction) during phase formation, or by physical encapsulation. Characterization by using both Transmission electron microscopy and EPMA confirmed that Cr and Mn were mainly present in the newly formed spinel phase, while the diopside phase contained a small amount of Mn. Zn, Cd, and Pb are not found to be concentrated and uniformly dispersed in the system, which is speculated to be physical coating and curing.

Is K-Struvite Precipitation a Plausible Nutrient Recovery Method from Potassium-Containing Wastes?—A Review

The definition of technologies capable of removing and recovering nutrients from polluting effluents is a key environmental challenge. Through these technologies, it would be possible to protect aquatic systems and prevent the consumption of natural resources for the production of commercial fertilizers. In this regard, the application of the precipitation processes of struvite-type compounds is an attractive approach. Indeed, these processes are potentially able to remove nutrients from many effluents and produce a precipitate reusable as a slow-release fertilizer. The scientific community has largely focused on the precipitation of magnesium ammonium phosphate (MgNH4PO4·6H2O, MAP), while the recovery of the analogous magnesium potassium phosphate (MgKPO4·6H2O, MPP) has received extensive attention in the last decade. Research on this topic is continuously progressing to improve the precipitation process in different aspects (working conditions, reaction units, interference elimination, etc.). Until now, there has been no paper that comprehensively reviewed the applicability of MPP precipitation for the removal and recovery of nutrients from aqueous waste. To fill this gap, the present paper aimed to provide an exhaustive analysis of the literature reports on MPP processes to help researchers understand the theoretical and applicative aspects, the main problems, and the need for further research. In this regard, the applications in the treatment of various aqueous wastes were considered. The theoretical concepts, the main process parameters, and the effects of inhibiting substances and impurities are presented. Moreover, the development of reactor configurations and their working conditions are evaluated. Finally, the potential use of MPP as a fertilizer and some economic evaluations are reported. On the basis of the conducted analysis, it emerged that the recovery of MPP was mainly affected by the pH, dose, and nature of reagents, as well as the presence of competitive ions. The optimal pH values were reported to be between 9 and 11. Reagent overdoses with respect to the theoretical values improved the process and the use of pure reagents guaranteed superior performance. The stirred-tank reactors and fluidized bed reactors were the most used units with high process yields. The applicability of MPP in agronomic practices appears to be a suitable option.

Synthesis of Mg-Al LDH and its calcined form with natural materials for efficient Cr(VI) removal

Layered double hydroxide (LDH) has been extensively studied due to its excellent capacity of heavy metal adsorption. However, the synthesis of LDH is always complex and requiring pure chemical reagents. In this study, two solid minerals, MgO and metakaolin (MK), derived from abundant natural resources, were used as raw materials to synthesize Mg-Al LDH via a facile one-pot method. The compositions and morphologies of synthetic products and its calcined form(C-LDH) were characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Cr(VI) adsorption by the LDH and C-LDH was systematically studied including the effect of contact time, initial pH value, temperature, liquid/solid ratio, and initial Cr(VI) concentration. The adsorption kinetics and isotherms were modelled, and thermodynamic parameters were determined. Results showed that the LDH and C-LDH exhibited high adsorption capacities (23.5–33.2 mg/g and 33.2–38.9 mg/g, respectively) within a wide pH range of 1.75–6.0, and maintained a higher adsorption capacity in all cases afterwards. The pseudo-second-order kinetic model fitted the kinetic data well in which the Langmuir model described the adsorption isotherms the best. The adsorption process was endothermic and spontaneous. The adsorption mechanisms may include anion exchange, redox reaction, and electrostatic adsorption. Moreover, the effect of the synthesis conditions (i.e., alkali concentration, temperature and liquid/solid ratio) on the adsorption characteristics were discussed. And XPS, UV-Vis Spectrophotometer (UV-Vis) and FTIR analysis confirmed Cr(VI) adsorption on the LDH and C-LDH surface, followed by its subsequent reduction to Cr(III). It has been revealed that the LDH/C-LDH synthesized in this work exhibited higher Cr(VI) removal capacities compared to the ones reported in the literature, demonstrating the significant potential of synthesizing high performance absorbents by low-cost natural materials.

Investigation on the oxygen-carrying performance and reaction kinetics of CaMnxFe1−xO3−δ perovskites prepared from red mud

In this study, two Ca/Mn/Fe perovskite oxygen carriers (i.e., CaMn0.5Fe0.5O3−δ and CaMn0.75Fe0.25O3−δ, respectively) were prepared using red mud and two pure reagents to recycle the red mud for the chemical looping combustion of biomass. The oxygen uncoupling (OU) capacity and redox cycle characteristics of perovskites were examined by thermogravimetric analysis (TGA) under a gaseous (H2, O2, N2) environment. With the same Mn/Fe mole ratio, reagent-based perovskites exhibited a higher total oxygen transport capacity, while perovskites derived from red mud exhibited a better cycling stability. The addition of red mud did not affect the reactivity of perovskites. The curves of conversion level vs time revealed that two control mechanisms are involved in the reaction between oxygen carriers and gaseous compounds. That is, the oxidation kinetics of perovskite oxygen carriers were mainly controlled by a chemical reaction, while the reduction kinetics were controlled by a chemical reaction at a low conversion level, and with the increase in the reduction degree, gas diffusion through the solid product layer was enhanced. In addition, kinetic parameters of OU and redox were obtained, and the grain model was considered to be suitable to describe reduction and oxidation reactions.

Absolute Quantification of Pure Free Radical Reagents by Combination of the Effective Magnetic Moment Method and Quantitative Electron Paramagnetic Resonance Method.

An absolute quantitative analysis of free radicals by combining the effective magnetic moment method and the quantitative electron paramagnetic resonance [qEPR] method is proposed. This combined method utilizes the advantages of both the analytical methods and compensates for their disadvantages. In the effective magnetic moment method, the magnetic moment under a constant magnetic field is measured accurately using a superconducting quantum interference device. The qEPR method compares a "primary standard sample" and "secondary standard sample". The effective magnetic moment method was used to determine the purity of the primary standard sample. The qEPR method realizes a simple purity analysis of free-radical reagents with traceability to the International System of Units (SI). The purity of the free radicals by the qEPR method for pure 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl benzoate [4HTB], 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine [TEMPOL], and di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium [DPPH] reagents was obtained with a relative expanded uncertainty of 0.7% for 4HTB to 1.5% for the DPPH. These small uncertainties were almost equal to those of the purity of the primary standard samples and were achieved by adopting in-plane positioning of the measured sample perpendicular to the cylindrical axis of the sample space of the superconducting quantum interference device. Some purity values of the free radicals for these reagents differed from those stated by the manufacturers. This combined method enables short-time quality control of pure radical reagents, instead of quality control by separation analytical methods or titrations.

Anisotropic Thermal Expansion and Electronic Structure of LiInSe2.

Optical quality cm-sized LiInSe2 crystals were grown using the Bridgman–Stockbarger method, starting from pure element reagents, under the conditions of a low temperature gradient of 5–6 degrees/cm and a slight melt overheating. The phase purity of the grown crystal was verified by the powder XRD analysis. The thermophysical characteristics of LiInSe2 were determined by the XRD measurements in the temperature range of 303–703 K and strong anisotropy of the thermal expansion coefficients was established. The following values of thermal expansion coefficients were determined in LiInSe2: αa = 8.1 (1), αb = 16.1 (2) and αc = 5.64 (6) MK−1. The electronic structure of LiInSe2 was measured by X-ray photoelectron spectroscopy. The band structure of LiInSe2 was calculated by ab initio methods.

Review on impact of pegylation on biopharmaceuticals

Covalent conjugation of polyethylene glycol (PEG) molecules to biopharmaceutical molecules is known to increase the pharmacological and medicinal characteristics of proteins and other big molecules and has been utilized effectively in 12 authorized medications. PEG reagents with straight and branched chains up to 40 kDa were utilized with a variety of PEG derivatives with varied linker chemistries. This article discusses the characteristics of PEG, the history and evolution of PEGylation chemistry, and examples of PEGylated pharmaceuticals with a proven track record. They prefer to employ bigger PEG polymers and complicated PEG structures, although they use extremely pure and well-characterized PEG reagents. The preclinical toxicity data for PEG in PEGylated biologics that have been authorized are summarised. Microscopically detected cell vacuolization in phagocytes, which is connected to the biological function of absorption and elimination of particles and macromolecules from blood and tissues. It's possible. Side effects in toxicity tests typically relate to the active moiety of the medicine, not the PEG moiety, according to experience with commercially available PEGylated pharmaceuticals.

Solvent-free preparation of α-Fe2O3 nanoparticles from metallurgical iron sludge for the treatment of Cr(VI)-contaminated wastewater

Metallurgical iron sludge (MIS) is an industrial by-product that needs high value-added utilization without harmless to the environment. Here, α-Fe2O3 nanoparticles were successfully prepared from MIS via a novel solvent-free method (SN-α-Fe2O3) and applied to Cr(VI) ions removal. Compared to conventional methods using pure reagents, the as-prepared SN-α-Fe2O3 aggregated into uniform cake-like mesoporous structures with a higher specific surface area (115.03 m2/g) and smaller crystal size (32.87 nm), thus providing a large number of active adsorption sites. Therefore, SN-α-Fe2O3 exhibited superior Cr(VI) removal performance (removal efficiency 98.21%) in Cr(VI)-contaminated wastewater compared to previous studies. Furthermore, Cr(VI)-saturated SN-α-Fe2O3 exhibited great stability under acidic conditions and maintained excellent adsorption performance after five cycles. The proposed SN-α-Fe2O3 preparation process forwent the use of water solvent or organic solvents, thus improving reactor efficiency and avoiding wastewater generation. Particularly, the growth mechanism of SN-α-Fe2O3 crystal followed the solid-phase transition mechanism, whereby small amounts of crystal water contained in pretreated MIS was sufficient for SN-α-Fe2O3 crystallization. Furthermore, SN-α-Fe2O3-mediated Cr(VI) adsorption was attributed to the electrostatic interaction and reduction of hydroxyl group on the surface of SN-α-Fe2O3. This study thus provides a win-win strategy for the conversion of industrial by-products into valuable nanoparticles for the cost-efficient treatment of heavy metal-polluted wastewater.

Preparation and Use of Cellular Reagents: A Low-resource Molecular Biology Reagent Platform.

Protein reagents are indispensable for most molecular and synthetic biology procedures. Most conventional protocols rely on highly purified protein reagents that require considerable expertise, time, and infrastructure to produce. In consequence, most proteins are acquired from commercial sources, reagent expense is often high, and accessibility may be hampered by shipping delays, customs barriers, geopolitical constraints, and the need for a constant cold chain. Such limitations to the widespread availability of protein reagents, in turn, limit the expansion and adoption of molecular biology methods in research, education, and technology development and application. Here, we describe protocols for producing a low-resource and locally sustainable reagent delivery system, termed "cellular reagents," in which bacteria engineered to overexpress proteins of interest are dried and can then be used directly as reagent packets in numerous molecular biology reactions, without the need for protein purification or a constant cold chain. As an example of their application, we describe the execution of polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP) using cellular reagents, detailing how to replace pure protein reagents with optimal amounts of rehydrated cellular reagents. We additionally describe a do-it-yourself fluorescence visualization device for using these cellular reagents in common molecular biology applications. The methods presented in this article can be used for low-cost, on-site production of commonly used molecular biology reagents (including DNA and RNA polymerases, reverse transcriptases, and ligases) with minimal instrumentation and expertise, and without the need for protein purification. Consequently, these methods should generally make molecular biology reagents more affordable and accessible. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Preparation of cellular reagents Alternate Protocol 1: Preparation of lyophilized cellular reagents Alternate Protocol 2: Evaluation of bacterial culture growth via comparison to McFarland turbidity standards Support Protocol 1: SDS-PAGE for protein expression analysis of cellular reagents Basic Protocol 2: Using Taq DNA polymerase cellular reagents for PCR Basic Protocol 3: Using Br512 DNA polymerase cellular reagents for loop-mediated isothermal amplification (LAMP) Support Protocol 2: Building a fluorescence visualization device.

Regeneration of well-performed anode material for sodium ion battery from waste lithium cobalt oxide via a facile sulfuration process

More attentions have been paid to the increasing expired spent lithium ion batteries due to the contained precious metals, especially Li and Co. However, the recycling systems at present have their limitations, such as unsatisfied recovery rate for pyrometallurgical process. In this study, a facile and efficient recovery method is proposed to simultaneously achieve the selective separation of metals and material regeneration. Based on the thermodynamic equilibrium diagrams and practical experiments, the product of recovery process, as expected, consists of soluble lithium salt and insoluble cobalt sulfide. Almost all of Co is recycled and transformed into regenerated material, while 89.76% Li is recycled separately. Moreover, the regenerated material exhibits excellent sodium storage performance (500 mAh/g at the current density of 2 A/g in 500 cycles), which is on a par with the similar reported materials synthesized by pure reagents. This study may provide a different perspective with potential values for the future large-scale recycling of spent lithium ion batteries.

Component spectra extraction and quantitative analysis for preservative mixtures by combining terahertz spectroscopy and machine learning

Preservatives are universally used in synergistic combination to enhance antimicrobial effect. Identify compositions and quantify components of preservatives are crucial steps in quality monitoring to guarantee merchandise safety. In the work, three most common preservatives, sorbic acid, potassium sorbate and sodium benzoate, are deliberately mixed in pairs with different mass ratios, which aresupposedto be the “unknown” multicomponent systems and measured by terahertz (THz) time-domain spectroscopy. Subsequently, three major challenges have been accomplished by machine learning methods in this work. The singular value decomposition (SVD) effectively obtains the number of components in mixed preservatives. Then, the component spectra are successfully extracted by non-negative matrix factorization (NMF) and self-modeling mixture analysis (SMMA), which match well with the measured THz spectra of pure reagents. Moreover, the support vector machine for regression (SVR) designed an underlying model to the target components and simultaneously identify contents of each individual component in validation mixtures with decision coefficient R2 = 0.989. By taking advantages of the fingerprint-based THz technique and machine learning methods, our approach has been demonstrated the great potential to be served as a useful strategy for detecting preservative mixtures in practical applications.

'Ab Ovo' Chiral Phases and Chiral Reagents for Liquid Chromatographic Separation and Isolation of Enantiomers.

The de-novo approach of mixing chirally pure reagents or Cu(II)-L-amino acid complexes in the slurry of silica gel for preparing TLC plates was reported from author's laboratory and was successful for separation and isolation of enantiomers. Using high molar absorptivity molecules, e. g., 1,5-difluoro-2,4-dinitrobenzene and cyanuric chloride, more than 38 new chiral derivatizing reagents were synthesized in our laboratory by straightforward nucleophilic substitution with simple chiral auxiliaries. Besides, (S)-naproxen, (S)-ketoprofen, and (S)-levofloxacin were used as chiral platforms. A conceptual approach using both achiral phases in chromatography for enantioseparation was also adopted. 1 H NMR and DFT based software were used to explain structures of non-covalent and covalent diastereomeric pairs and determination of configuration and separation mechanism. The methods can be easily used to determine and control enantiomeric purity with advantages over a variety of commercial chiral phases.

Features and mechanisms of self-sintering of molybdenite during oxidative roasting

Roasting experiments were carried out with pure reagents as raw materials. The self-sintering behaviors of molybdenite (MoS2) during oxidation were investigated by thermodynamic calculation, XRD, SEM-EDS and high-temperature in situ analysis. The results indicate that the desulfurization efficiency of MoS2 pellet decreases with the increase of roasting temperature from 600 to 700°C, owing to the expansion of sintered area. At the very beginning of roasting, sintered layer can be rapidly formed and cover the pellet surface on the windward side, and meanwhile, MoO2 and Mo4O11 intensively appear and constitute the sintered layer together with MoO3. Moreover, it is proven that MoO3-rich products containing low-valence molybdenum oxides have low melting points, thus easy to be melted during the occurrence of exothermic reaction between MoS2 and O2, which leads to the sintering of materials.