Crystal Purity Research Articles

Rapid formation of imidazolium glutarate (IMGA) compound and investigation of its single crystal growth by modified vertical Bridgman technique for optical limiting applications

In this paper, we have examined the formation of the imidazole glutarate adduct by protonation-deprotonation between imidazole and glutaric acid using a direct precipitation method within a short period. Following that, we have succeeded in growing imidazolium glutarate (IMGA) single crystaldirectly from synthesized material and we have also grown IMGA single crystal from the melt methodusing the vertical Bridgman technique for the first time in literature. A special Bridgman furnace was constructed with a slight modification in the winding section for this crystal growth. Crystal structure, phase purity, and growth plane were analyzed for the grown crystal from both single and powder XRD analysis. Functional groups were verified after the growth using FTIR transmittance analysis. The optical homogeneity and growth mechanism were scrutinized by birefringence interferogram and chemical etching studies, respectively. The grown IMGA has 80 % transparency in the entire visible region. The cut-off wavelength of the grown crystal is 235 nm, and the optical band gap energy of IMGA was found to be 5.26 eV. The photocurrent study reveals that IMGA has a negative photoconductivity nature. Third-order nonlinear parameters were found by the Z-scan technique. IMGA has a self-defocusing nature, negative non-linearity, and saturated absorption properties. The calculated χ(3) value is 2.045 x 10-8 esu.

Growth and characterization of perovskite TbMnO3 single crystal: Structural, vibrational and magnetic properties

In this study, we have successfully grown a high-quality single crystal of perovskite TbMnO3 utilizing an optical floating zone furnace under an air atmosphere. To ensure the crystal purity and orientation, we probed X-ray diffractometer (XRD) and X-ray Laue photographic analysis, respectively. The XRD analysis confirmed that TbMnO3 ceramics possess a distorted orthorhombic perovskite structure (Pbnm). By analyzing the X-ray absorption and vibrational modes via Raman spectroscopy, we not only confirmed the pure phase of the TbMnO3 sample but also gained valuable insights. In terms of magnetic properties, we conducted measurements in two different orientations: H||a and H||c. Notably, there were no successive transitions observed along the H||a direction, but along H||c, we observed three successive transitions with decreasing temperature at TN = 41 K, TS = 28 K, and TNTb = 7 K. Below TN (41 K), there is an unusual softening observed in one of the first order phonon modes, indicating a robust connection between spin and phonon interactions. The magnetic phase transition along both axes validates the presence of magnetic anisotropy in the prepared single crystal, as indicated by magnetic susceptibility. The negative θcw value along the a-axis and the positive θcw value along the c-axis suggest a competition between antiferromagnetic and ferromagnetic interactions in the ac-plane.

Effect of Heating Rate on Melting Point of HMX, RDX, TNT and PETN

Melting point of HMX, RDX, TNT and PETN are measured for judging crystal purity. The heating rate when doing this has a significant effect on the melting point reading. This work gives an insight on how heating rate affects the melting point reading for these high explosives using Differential Scanning Calorimetry (DSC). With increase in heating rates (from 1 to 20°C min-1) the different behaviours of the DSC curves for HMX, RDX, TNT and PETN are analysed. It is also observed from this study that heating rate causes a shift in the temperatures for onset and the peak for HMX, RDX, TNT and PETN. This study reflects that in some cases the decomposition of the explosives is influencing the melting graphs. Hence a conclusion has been drawn on the adequate heating rate that should be chosen for determining the melting point of these high explosives.

Hybrid nanogels and their roles in eliminating soot stains from historical paper manuscripts

Soot stain from diverse sources is the most common stain that stains historical paper documents found in libraries, museums, and storage facilities. It is believed to be one of the types of deterioration that arises from the contact between stains and paper sheets. Therefore, in the present work, the effectiveness of the synthesized hybrid nanogel consisting of carbopol and nanoparticles (NPs) of ZnO, TiO2, or Fe3O4, in low and high-viscosity forms, for eliminating soot stains from historical paper manuscripts was conducted. The prepared hybrid nanogels were characterized utilizing the TEM, AFM, XRD, DLS, and Zeta Potential techniques. Following preparation, the soot-stained paper samples were heated to 105 °C for 6 days, a process known as accelerated thermal aging. Surface morphology, mechanical properties and the color change of the paper samples were investigated. The prepared hybrid nanogel had a spherical shape with well-defined edges and uniform size, with an average particle diameter ranging from 30 to 35 nm. There was no significant NPs agglomeration seen, suggesting uniform dispersion in the carbopol matrix. Additionally, the prepared gels' crystal structure and phase purity were revealed by the XRD analysis results. Paper fibers were visible in some parts of the treated sample with TiO2/carbopol hybrid nanogel at high-viscosity before aging. Cleaning soot-stained paper samples using high-viscosity Fe3O4/carbopol hybrid nanogel is more successful than using low-viscosity nanogel. the sample treated with high-viscosity ZnONPs/carbopol hybrid nanogel produced the highest total color differences (ΔE) (26.17). The paper sample treated with high-viscosity ZnO/carbopol hybrid nanogel exhibited the maximum tensile strength (61.8 N/mm2) and elongation at break (1.174%). The evaluation of the paper samples both before and after the cleaning process revealed that, the treatment with high-viscosity ZnO/carbopol hybrid nanogel gave the best results in removing soot stains from stained paper samples.

Lanthanoid(Ⅲ) complexes containing bipyridinedicarboxylic acid ligand: Synthesis, spectroscopic characterization, thermal analysis, and crystal structures

The present report deals with the synthesis of the two complexes of respective formula {[Ce(bpydcb)(HCOO)(H2O)]·H2O}n (1) and [Eu2(bpydcb)3(H2O)2(DMF)]·3H2O·0.5DMF (2) the structure of both of them elucidated by single-crystal X-ray diffraction and powder X-ray diffraction to demonstrated that complexes 1 and 2 crystallize in a similar space group P21/c as a monoclinic system with high crystal purity. X-ray Single crystal diffraction analysis demonstrates, nine-coordinate environment of Ce (Ⅲ) in the complex 1 and octa-coordinate environment of Eu (Ⅲ) in the complex 2. And discovered the tricapped trigonal prism of cerium complex and the triangular dodecahedron of europium complex. Meanwhile, the complexes were characterized by elemental, infrared, ultraviolet, fluorescence and thermal analysis. Fluorescence testing shows that complex 1 emits ligand fluorescence, while complex 2 emits fluorescence from the ligand to the central ion, emitting characteristic fluorescence of europium ion, both complexes can emit strong fluorescence. The thermogravimetric analysis results show that the thermal stability of complex 1 is better than that of complex 2, and its organic framework only begins to collapse after 375 ℃.

Effects of Assisting Solvents on Purification Efficiency in the Layer Melt Crystallization of Glycerol.

The efficiency of layer melt crystallization for the selective separation of glycerol from a glycerol-diethylene glycol mixture containing 4 wt % of diethylene glycol was evaluated using solvent-free and solvent-aided approaches. The effect of 1-butanol and the binary solvent of 1-butanol and acetone with a total molar composition of 25 mol % on the crystal growth kinetics and the purity of the final product was studied at different undercooling degrees and crystallization yields. The melting point temperature of the mixtures was predicted by using the modified UNIFAC Dortmund model. The addition of both a single and binary solvents significantly increased the crystal growth rate and purity of the final product compared to crystallization from the solvent-free mixture. Additionally, higher crystal growth rates and product purity were observed in the binary solvent system compared to those in the single solvent system at the same degree of undercooling. The second stage of solvent-aided crystallization resulted in glycerol with a purity above 99.5 wt %, depending on the type of solvent used and the rate of crystal growth.

Efficient performance of InP and InP/ZnS quantum dots for photocatalytic degradation of toxic aquatic pollutants.

In recent years, the growing concern over the presence of toxic aquatic pollutants has prompted intensive research into effective and environmentally friendly remediation methods. Photocatalysis using semiconductor quantum dots (QDs) has developed as a promising technology for pollutant degradation. Among various QD materials, indium phosphide (InP) and its hybrid with zinc sulfide (ZnS) have gained considerable attention due to their unique optical and photocatalytic properties. Herein, InP and InP/ZnS QDs were employed for the removal of dyes (crystal violet, and congo red), polyaromatic hydrocarbons (pyrene, naphthalene, and phenanthrene), and pesticides (deltamethrin) in the presence of visible light. The degradation efficiencies of crystal violet (CV) and congo red (CR) were 74.54% and 88.12% with InP, and 84.53% and 91.78% with InP/ZnS, respectively, within 50min of reaction. The InP/ZnS showed efficient performance for the removal of polyaromatic hydrocarbons (PAHs). For example, the removal percentage for naphthalene, phenanthrene, and pyrene was 99.8%, 99.6%, and 88.97% after the photocatalytic reaction. However, the removal percentage of InP/ZnS for pesticide deltamethrin was 90.2% after 90 min light irradiation. Additionally, advanced characterization techniques including UV-visible spectrophotometer (UV-Vis), photoluminescence (PL), X-ray diffractometer (XRD), energy-dispersive spectrometer (EDS) elemental mapping, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) were used to analyze the crystal structure, morphology, and purity of the fabricated materials in detail. The particle size results obtained from TEM are in the range of 2.28-4.60nm. Both materials (InP and InP/ZnS) exhibited a spherical morphology, displaying distinct lattice fringes. XRD results of InP depicted lattice planes (111), (220), and (311) in good agreement with cubic geometry. Furthermore, the addition of dopants was discovered to enhance the thermal stability of the fabricated material. In addition, QDs exhibited efficacy in the breakdown of PAHs. The analysis of their fragmentation suggests that the primary mechanism for PAHs degradation is the phthalic acid pathway.

Investigating Influential Parameters for High-Purity Germanium Crystal Growth

This paper focuses on the research and development of high-purity germanium (HPGe) crystals for detector fabrication, specifically targeting applications in rare-event physics searches. The primary objective was to produce large-scale germanium crystals weighing >1 kg with a controlled diameter of ∼10 cm and an impurity range of approximately 1010/cm 3. Ensuring structural integrity and excellent crystalline quality requires a thorough assessment of dislocation density, a critical aspect of the crystal development process. Dislocation density measurements play a crucial role in maximizing the sensitivity of HPGe detectors, and our findings confirmed that the dislocation density fell within acceptable ranges for detector fabrication. Additionally, this paper examines the segregation coefficient of various contaminants during the crystal development process. Comprehensive analysis of impurity segregation is essential for reducing contaminant quantities in the crystal lattice and customizing purification processes. This, in turn, minimizes undesired background noise, enhancing signal-to-noise ratios for rare-event physics searches and overall detector performance. The investigation included the segregation coefficients of three major acceptors and one donor in crystals grown at the University of South Dakota, providing valuable insights for optimizing crystal purity and detector efficiency.

Bio‐fabrication of Zinc oxide nanoparticles using Strobilanthes cordifolia: Characterization and evaluation of antioxidant, anti‐cholinergic, anti‐inflammatory and wound healing activities

AbstractStrobilanthes cordifolia has emerged as a promising material in traditional medicine. In this study, we have made an attempt to synthesize zinc oxide nanoparticles derived from S. cordifolia leaf. The team employed a wide range of techniques including UV, FT‐IR, XRD, FE‐SEM with EDAX, HR‐TEM with SAED, DLS, Zeta potential, BET and PZC analysis to thoroughly examine the properties of the NPs. FTIR analysis provided evidence of various functional groups within the NPs. XRD analysis demonstrated the crystal nature and phase purity of the NPs. SEM analysis showcased the spherical shape of the particles, while TEM revealed their rod‐like shape with sizes averaging at approximately 10 nm. DLS analysis indicated the average particle size, and the high zeta potential value confirmed the stability and BET analysis deciphered the specific surface area of the biosynthesized NPs. The NPs confirmed strong antioxidant properties with DPPH, ABTS, and hydroxyl radicals. Enzyme studies confirmed good anti‐cholinergic activity and anti‐inflammatory efficacy, highlighting their potential therapeutic benefits. The NPs demonstrated promising wound healing properties. Overall, this research study sheds light on the medicinal aspects of zinc oxide nanoparticles from S. cordifolia leaf extract and it offers exciting prospects for future exploration and development in this field.

Study on the control of flow field by resonance acoustic mixing technology for purification of high performance spherical HATO crystals

As an innovative energetic material, dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (HATO) surpasses conventional nitro energetic materials in many aspects. However, the inherent presence of edges and corners in HATO crystals poses limitations on its widespread application. Spheroidization emerges as a transformative solution, enhancing the overall performance of HATO. To achieve spheroidization of HATO, spheroidization process utilized resonance acoustic mixing-assisted solvent erosion, employing water as the erosion solvent to ensure environmentally friendly production. Then, based on thermodynamic stability and dynamic equilibrium of crystal dissolution and precipitation, spherical HATO with various particle sizes were prepared. The characterization results of spherical HATO indicate that spheroidization does not alter the crystal form of HATO. Compared with the raw HATO, the thermal decomposition activation energy of spherical HATO has been increased by at least 16.72 kJ∙mol−1, furthermore, the ultimate impact energy has been increased by at least 2.5 J, and the ultimate friction load has been increased by at least 8 N. In addition, the performance testing results of pressed explosives columns and cast explosive columns indicate that spheroidization can improve the charging performance and mechanical properties of HATO explosive columns. Therefore, spheroidization effectively improves the thermal performance, safety performance, and charging performance of HATO.

Investigation of X-ray excited optical luminescence properties of Er, Nd-doped YVO4 phosphors using a hard X-ray beam

Scintillators based on YVO4:Er3+ and YVO4:Er3+, Nd3+, synthesized through glucose-assisted sol-gel method and calcined under different temperatures were studied via X-ray excited optical luminescence (XEOL). The samples' crystalline structure was studied via X-ray powder diffraction and the crystallite size estimated by Scherrer's method. The results indicated the crystal purity phase in all samples, indexed as YVO4, and crystallite size in nanometric order, which is in accordance with Transmission Electron Microscopy results that indicate the formation of nanoparticles with spherical shape tendency. The spectroscopic studies taken by XEOL demonstrated typical Er3+ and Nd3+ transitions were dominant on the emission spectra. An unusual host emission was also identified c.a. 340 and 600 nm and ascribed as an intrinsic host vanadate emission related with the material optical band gap (c.a. 3.5 eV) and/or associated with VO43− to rare earth ions energy transfer. The scintillators kept the emission stability even exposed to ∼1010 photon/sec, which demonstrated their radiation hardness, which is an important feature to the application of YVO4 based-materials as scintillators. Independently of the calcination temperature, glucose-assisted sol-gel method was reliable to produce YVO4-based scintillators nanopowders with stable optical properties with potential to be applied in biological imaging and/or in theranostics.

From sulfite liquor to vanillin: effect of crystallization process on the yield, purity, and polymorphic form of crystals

ABSTRACT Different approaches for vanillin crystallization were performed using an aqueous solution, with low concentrations of this potential food and pharmaceutical phenolic compound, obtained from adsorption/desorption experiments applied to an oxidized solution of lignin isolated from softwood sulfite liquor. The process yield and purity of the vanillin crystals were determined, and the thermal stability of the two resulting polymorphic forms was analyzed by DSC. Crystallization processes by swift cooling and evaporation with heat favor the nucleation of metastable vanillin crystals (Form II) with lower yields than slow evaporative and cooling processes that crystallize vanillin into the stable polymorph (Form I) with yields around 80%. Moreover, the polymorphic form of vanillin, yield, and purity were found to be highly dependent on the conditions of the crystallization process, mainly the temperature and the range of temperature variation. The melting points of polymorphic Form I and II were found to be 82.6 and 81.0°C, respectively, proving that Form I is the most thermodynamically stable vanillin crystal form. In conclusion, the process conditions for vanillin crystallization strongly affect the polymorphic form, the process yield, the contents, and the type of impurities in the final product, consequently, influencing its potential industrial applications.

Fluorescence properties of novel deep-red phosphor LiMg4SbO7:Mn4+ with excellent quantum efficiency and color purity for warm white LEDs.

Red fluorescent materials have important application value in the background light and LED lighting fields of displays. In this work, a novel type of rare earth free deep-red phosphor LiMg4SbO7:Mn4+ was prepared successfully, and its crystal structure, microstructure, fluorescence spectrum, quantum yield, thermal stability, fluorescence lifetime, color coordinates and color purity were studied in detail. The excitation spectra of LiMg4SbO7:Mn4+ phosphors are located at 200-600 nm, which can be matched with ultraviolet, near-ultraviolet, and blue-light chips. The exciting result is that the LiMg4SbO7:0.002Mn4+ phosphor exhibits astonishing quantum efficiency, thermal stability and color purity. Finally, the developed LiMg4SbO7:Mn4+ and the yellow phosphor Y3Al5O12:Ce3+ (YAG:Ce3+) were mixed and coated on a blue light chip (460 nm) to produce a w-LED, which exhibited warm white luminescence with color coordinates of (0.3575, 0.3809), correlated colour temperature (CCT) of 4687 K, and color rendering index (CRI) of 83.6. It is reasonable to consider that LiMg4SbO7:Mn4+ phosphors with excellent photoluminescence performance have great application value in LED lighting fields.

Characterization of Sm3+-activated carbonated calcium chlorapatite phosphors for theranostic applications: a comparative study of co-precipitation and hydrothermal methods.

Continuous efforts are ongoing to discover new luminescent materials with appropriate properties for applications in medicine, serving as theranostic agents for healing and bioimaging. In this paper, novel single-phase carbonated calcium chlorapatite (Ca10(PO4)5(CO3)Cl2, abbreviated as CaClAp-CO3) phosphors activated with varying concentrations of Sm3+ ions were successfully fabricated using both co-precipitation and hydrothermal methods to investigate the influence of the synthesis techniques on the physicochemical properties of these materials. The effects of doping concentration of Sm3+ ions and synthesis techniques on the structure, photoluminescence (PL), energy transfer, substitute sites, fluorescence lifetime and luminescence colour of phosphors were investigated. The synthesized phosphors were characterized by X-ray diffraction (XRD) to confirm their crystal phase structure and purity. Vibrational features and the incorporation of carbonate ions were verified using Fourier-transform infrared (FTIR) spectroscopy. The obtained materials emit reddish-orange light, primarily from the most intense 4G5/2 → 6H7/2 transition. The electric dipole to magnetic dipole transition ratio (ED/MD), CIE colour coordinates and colour purity were determined to provide additional insights into the spectroscopic attributes of the obtained phosphors. In addition, the concentration quenching was also observed, and its mechanism was proposed based on theoretical calculations showing the multipolar interactions.

Performance of membrane distillation assisted crystallization and crystal characteristics for resource recovery from desalination brine

Membrane distillation crystallization (MDC) has been widely studied in recent year for its potential for resource recovery from desalination brine with high concentrations. In this study, crystal samples produced from a bench-scale MDC system have been analysed for crystal morphology, crystal purity and crystal size distribution (CSD). In addition, orthogonal fractional factorial (OFF) experimental design has been introduced to evaluate the influence of various operating conditions on the crystal size and CSD. Feed temperature (40 to 60 °C), crystallization time (60 to 180 min) and the feed composition have been used as the control factors. The results show that the MD in the MDC system maintains a consistent flux of 1.32 to 4.2 kg/m2·h across various feed compositions; higher feed temperatures led to the formation of larger crystal clusters, while longer crystallization time yielded more cubic-shaped crystals; an overall NaCl purity exceeding 99.08 % has been achieved throughout all the experiments; and the increased feed temperature and prolonged crystallization time results in a narrower CSD. The result of OFF experimental design identifies feed temperature as the dominant factor affecting crystal size and CSD. However, the presence of impurities in the feed water could pose challenge to the thermal stability and longevity of the membrane.

Investigating carrier mobility in hollow and mesoporous ZnSe/ZnTe heterostructures: Microscopic observations of swift charge transfer and visible-light-driven dye decomposition

We report herein a one-pot hydrothermal approach to synthesize zinc selenide (ZnSe)/zinc telluride (ZnTe) heterostructures - a set of common cation-based photocatalysts. The crystal structure and phase purity of the heterostructures were verified by powder X-ray diffraction (PXRD) analysis, while field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques were employed to study their morphology, microstructures, and surface electronic states, respectively. Notably, a detailed XPS analysis was conducted to discern the chemical species present on the surface of the photocatalyst, providing valuable insights into the compound's stability in an aqueous medium. Furthermore, the synthesized hybrid structures were utilized to fabricate Schottky barrier diodes, enabling a study of their electrical and dielectric properties using the Spatial-charge-limited conduction (SCLC) mechanism. The key charge transport parameters for all the photocatalysts, namely, carriers' mobility and transit time, influencing the photo response and consequently, dye degradation were estimated. Notably, the ZnSe/ZnTe heterostructure, comprising 50 % ZnSe and 50 % ZnTe, exhibited the highest mobility (3.36 × 10-6 S/m in the dark, increasing to 1.70 × 10-5 S/m in light) and proved to be the most effective photocatalyst for degrading Rhodamine B (with up to ∼ 78 % degradation over 60 min of solar light irradiation) - underscoring the pivotal role of carriers' mobility in governing the photocatalytic activity. Moreover, the ZnSe/ZnTe heterostructure demonstrated a remarkable reduction in the photo-corrosion process, a key challenge affecting the photocatalytic activity of numerous materials. Our discussion highlighted the efficient separation of photoinduced electron-hole pairs in the ZnSe/ZnTe heterostructure, facilitated by the synergistic effects of ZnSe and ZnTe, leading to the achievement of the highest photocatalytic performance.

Synthesis of Bi3+ and Eu3+ co-doped Na4CaSi3O9 blue-red light tunable emission phosphors for inducing plant growth

Sunlight is an important factor in plant growth. In this regard, both blue and red lights provide significant contributions. Blue–red light dual-emission phosphors, which can be achieved by regulating energy transfer between two independent luminous centers, have recently been investigated extensively. In this study, Bi3+ and Eu3+ co-doped Na4CaSi3O9 (NCSO: Bi3+, Eu3+) phosphors are successfully synthesized via a high-temperature solid-phase method at approximately 900 °C for a few hours. X-ray powder diffraction is used to verify the crystal structure, phase purity, and structural refinement of the NCSO-based phosphors. Upon light excitation at 299 nm, the phosphors show blue–red dual emission. The blue emission (300–500 nm) may have originated from the 3P1 → 1S0 transition of Bi3+, whereas the red emission (575–725 nm) is attributable to the 5D0 → 7FJ (J = 1, 2, 3 and 4) transition of Eu3+ ions. Energy transfer from Bi3+ to Eu3+ is systematically investigated and the thermal stability of the phosphors is analyzed using temperature-dependent spectroscopy. The emission spectra of NCSO: Bi3+, Eu3+ are consistent with the absorption spectra of chlorophyll a, chlorophyll b, phytochrome PR, and phytochrome PFR. These results indicate that the obtained phosphors exhibit significant potential for inducing plant growth.

Effect of phase transformation on the electrochemical supercapacitive behavior of thermally exfoliated zirconia

Amorphous and crystalline zirconia (ZrO2) are successfully synthesized through a rapid thermal exfoliation process. The crystal structure and phase purity of exfoliated materials are examined using XRD. Crystalline ZrO2 reveals the formation of a tetragonal phase. Amorphous zirconia possesses a specific surface area of 45 m2/g. As synthesized, amorphous zirconia provides a specific capacity of 1406C/g at 2 A/g (3-electrode measurements). A two-electrode asymmetric supercapacitor of activated carbon, amorphous zirconia (ZrO2//AC), exhibits a better electrochemical performance than its crystalline phase. The amorphous ZrO2-based asymmetric supercapacitor gives a specific capacitance of 160 F/g at 3 A/g. The device delivered an energy density of 47.6 Wh/kg at a power density of 2.2 kW/kg. These high energy and power density values of asymmetric amorphous ZrO2 supercapacitors outperform most of the reported ZrO2-based electrode materials. Amorphous ZrO2 is a promising electrode material in terms of its capacitance retention of ∼75 % over 10,000 cycles. The as-developed device has a rate capability of 35 % at a current density of 25 A/g and a self-discharge current of 2.6 mA.

Recovery of tungsten from spent selective catalytic reduction catalyst by sulfuric acid precipitation and evaporation crystallization method

AbstractBACKGROUNDSelective catalytic reduction (SCR) can effectively handle NOx from flue gas in coal‐fired power plants. However, as the core part of the SCR method, V2O5–WO3/TiO2 catalyst has a limited operational life in the complex flue gas environment. The recovery of rare metals from spent catalyst would not only bring economic benefits but also solve environmental problems. The process of reducing acid leaching and further roasting‐water leaching could realize the efficient recycling of vanadium, tungsten and titanium.RESULTSAfter reducing acid leaching and roasting‐water leaching to treat spent SCR catalyst, the obtained solution containing tungsten was used as the raw material in this study. The optimal pH value of solution for removal of silicon and aluminum impurities was 9.2–9.5. The best tungsten precipitation conditions were shown as follows: a tungsten concentration of 30 g L−1, a sulfuric acid concentration of 8 mol L−1, reaction temperature of 70 °C and reaction time of 2 h. Under the optimal tungsten precipitation conditions, the tungsten precipitation efficiency can reach 92.53%. Finally, in order to further improve the purity of the crude H2WO4, the crude H2WO4 was fully dissolved in ammonia, followed by filtration and evaporation crystallization to obtain 5(NH4)2O.12WO3.5H2O (APT) crystals with a purity of 93.05 wt%. The crystallization efficiency of APT was 73.37% at 60 °C for 2 h with a rotor speed of 400 rpm.CONCLUSIONThese results indicated that a higher purity of APT crystals can be obtained by the steps of removing silicon and aluminum, precipitation of tungsten by sulfuric acid, ammonia dissolution and evaporation crystallization. © 2023 Society of Chemical Industry (SCI).

An effective method for the direct crystallization of xylonic acid from fermentation broth of agricultural residue hydrolysate

Xylose is the second most abundant sugar in nature and conversion of xylose to xylonic acid (XA) has become a research hotspot in recent years. Xylonic acid can be applied in the equivalent market niche of gluconic acid, due to their similar physical properties. XA bioproduction and application presents certainly a promising approach for xylose valorization in lignocellulose biorefinery, while the XA crystallization is so far still an unattainable goal. In this paper, an original method was proposed and experimentally investigated for the first time to get XA crystals from fermentation broth. In the XA crystallization, methanol was introduced as buffer-cum-solvent. The H2SO4 was dropwise added into the methanol solution dissolving potassium xylonate that is beforehand produced by fermentation. During H2SO4 blending with methanol, the strong and polar H2SO4 leads to XA diffusion and aggregation. Overall, 2.21 g of xylonic acid crystals was obtained per gram of 98% H2SO4 acidification. NMR detection showed that over 99% purity of XA crystals was finally obtained at the yields of 67.2% from xylonate. The integrated process could provide a practicable and effective technology for the high-qualify XA preparation from xylose derivations and lignocellulose biomass biorefinery.