Tetrahedral Morphology Research Articles

Impact of the biogas impurities on the quality of the precipitated calcium carbonate in the regenaration stage of a chemical absorption biogas upgrading unit

Combining Carbon Capture and Storage (CCS) with producing competitive secondary raw materials is key to decarbonizing industry and reducing resource extraction. Biogas upgrading to biomethane stand out as an alternative, but a significant gap remains in integrating this process within a circular economy framework. This issue has been recently addressed by a process that integrates biogas upgrading via caustic absorption with the production of Precipitated Calcium Carbonate (PCC) and the recovery of sodium hydroxide from waste brine solution using membrane technologies. The profitability of this approach depends on the quality of the PCC, a critical factor that this work addresses. By characterizing PCC is determined whether trace compounds in biogas contaminate the PCC and potentially affect its commercial value. It also examines the CO2 absorption process and analyzes the aqueous samples from the filtration phase of the PCC slurry. Results confirm the high purity of PCC obtained from biogas treatment using Raman spectroscopy, X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The analyses show that the PCC is pure calcium carbonate, mainly in the stable calcite form, with a typical tetrahedral morphology and no detectable impurities. Characterization of aqueous solutions revealed organic trace compounds from biogas, with TOC concentrations of 9.7 (± 6.4) and 16.0 (± 8) mg C/l. Silicon measurements showed similar concentrations in the absorbent solution and filtrated PCC slurry. Additionally, ammonia escapes as gas, and hydrogen sulfide in the biogas likely contributed to sulfate salt formation. Analysis of the CO₂ absorption shows a first-order reaction with OH-, where the amount of CO₂ absorbed (46.3–50.0 g) closely matches the theoretical value of 48 g. The study reveals that most of the biogas impurities dissolve into the aqueous solution, being crucial for future studies and downstream membrane treatments, and the PCC is unaffected by these impurities with a purity suitable for commercial applications.

A novel magnetic porous organic cage adsorbent for high-efficient removal of endocrine disrupting chemicals from environmental water

Endocrine disrupting chemicals (EDCs) are pervasive emerging pollutants found in environmental water, stemming from their widespread use in personal consumer products. This study presents a novel magnetic Porous organic cage (POC) material, Fe3O4-COOH@CC3R-OH, which has been proven to be highly effective in eco-friendly eliminating EDCs. Featuring a tetrahedral morphology with core–shell structure, the new magnetic adsorbent boasts a substantial Brunauer-Emmett-Teller surface area of 94.02 m2/g and a particle pore size of 1.14 nm. Rigorous optimization of adsorption conditions for eight specific EDCs was conducted, complemented by insightful molecular docking simulations shedding light on the adsorption mechanisms. Furthermore, the developed Fe3O4-COOH@CC3R-OH magnetic solid phase extraction-assisted high performance liquid chromatography-tandem mass spectrometry (MSPE-HPLC-MS/MS) method exhibits good sensitivity and precision in the quantitative detection of EDCs in environmental water samples. This integrated approach provides a robust platform for both efficient removal and accurate detection of EDCs, advancing water quality control and safeguarding human health.

An Electrically Conducting Three-Dimensional Iron-Catecholate Porous Framework.

We report the synthesis of a unique cubic metal–organic framework (MOF), Fe‐HHTP‐MOF, comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and FeIII ions, arranged in a diamond topology. The MOF is synthesized under solvothermal conditions, yielding a highly crystalline, deep black powder, with crystallites of 300–500 nm size and tetrahedral morphology. Nitrogen sorption analysis indicates a highly porous material with a surface area exceeding 1400 m2 g−1. Furthermore, Fe‐HHTP‐MOF shows broadband absorption from 475 up to 1900 nm with excellent absorption capability of 98.5 % of the incoming light over the visible spectral region. Electrical conductivity measurements of pressed pellets reveal a high intrinsic electrical conductivity of up to 10−3 S cm−1. Quantum mechanical calculations predict Fe‐HHTP‐MOF to be an efficient electron conductor, exhibiting continuous charge‐carrier pathways throughout the structure.

An Electrically Conducting Three‐Dimensional Iron–Catecholate Porous Framework

AbstractWe report the synthesis of a unique cubic metal–organic framework (MOF), Fe‐HHTP‐MOF, comprising hexahydroxytriphenylene (HHTP) supertetrahedral units and FeIII ions, arranged in a diamond topology. The MOF is synthesized under solvothermal conditions, yielding a highly crystalline, deep black powder, with crystallites of 300–500 nm size and tetrahedral morphology. Nitrogen sorption analysis indicates a highly porous material with a surface area exceeding 1400 m2 g−1. Furthermore, Fe‐HHTP‐MOF shows broadband absorption from 475 up to 1900 nm with excellent absorption capability of 98.5 % of the incoming light over the visible spectral region. Electrical conductivity measurements of pressed pellets reveal a high intrinsic electrical conductivity of up to 10−3 S cm−1. Quantum mechanical calculations predict Fe‐HHTP‐MOF to be an efficient electron conductor, exhibiting continuous charge‐carrier pathways throughout the structure.

Controlled synthesis of photoactive gallium based sillenite single crystal and its application in environmental remediation

Among the numerous photocatalytic materials studied for potential application in degradation of organic effluents and antibiotic wastes, sillenite materials emerge as important candidates. In the present work, Ga based sillenite has been used to degrade aqueous persistent organic pollutants such as bisphenol (BPA) and Norfloxacin (NF) in presence of natural solar irradiation. Sillenite based oxides have exhibited various physico chemical applications due to their photocatalytic nature. Here, gallium based sillenite, Bi24Ga2O39, has been successfully synthesized through two different techniques, hydrothermal route (HY) and solid state reaction (SS) method. X-Ray Diffraction patterns and Rietveld refinement of same revealed the occurrence of sillenite single phase. Morphological investigation by Scanning Electron Microscopy revealed regular tetrahedral morphology of HY sample. X-ray photoelectron and Raman spectroscopy were performed to analyze the chemical composition and its environment. UV–Visible spectroscopy on sillenites was used to analyze and calculate the effective optical band gap energy ~2.55 eV (HY) and ~2.76 eV (SS) respectively. Photoelectrochemical measurements performed on the samples showed appreciable photocurrent response (~1.9 μA/cm2 for HY sample). The photoactivity of samples have been utilized for degradation of aqueous persistent organic pollutants, such as methylene blue, norfloxacin and bisphenol A in presence of visible light degrading upto 92%, 82% and 84% (HY) respectively.

Bi metal/oxygen-deficient BiO2−x with tetrahedral morphology and high photocatalytic activity

Vacancy-rich materials with high photocatalytic activity are of great interest for pollutants removal and play a significant role in green chemistry. Herein, we successfully synthesized Bi/BiO2−x composite through hydrothermal route. In this case, the surface plasmon resonance effect of Bi and oxygen vacancies of BiO2−x collectively increase the removal rate of pollutants. More importantly, the Bi/BiO2−x composites have enhanced activity in the degradation of RhB, MO, BPA and CIP, and the reduction of Cr(VI) and PNA. Besides, an enhanced photocatalytic activity is due to the main reactive species of · and h+ that is confirmed by trapping experiments and ESR analyses. The electronic structure and visible light harvesting of photocatalysts were measured and also theoretically calculated by using density functional theory and finite difference time domain calculations, DRS, VB x-ray photoelectron spectroscopy and Mott–Schottky plots, which allowed to propose a possible photocatalytic mechanism for the degradation process.

The effect of electrodeposition time on CuCl anodes from waste copper etchant

As one common industrial waste liquid, waste copper (Cu) etchant can seriously pollute the environment if it is unreasonably managed. Herein, tetrahedron-like copper (I) chloride (CuCl) crystals were extracted from waste copper etchant by way of facile electrodeposition, and the effect of the electrodeposition time on the lithium (Li)-storage capacity of the copper (I) chloride crystal was further investigated. The results showed that the copper (I) chloride crystal had a regular tetrahedral morphology, and the density of the regular tetrahedral particles gradually increased with the extension of the electrodeposition time from 5 to 15, 20 and 25 s. Correspondingly, the reversible lithium-storage capacity of the copper (I) chloride anode experienced an initial increase and a subsequent decrease. In detail, when cycling at 2 C for 250 cycles, the reversible discharge capacity of the copper (I) chloride anode increased from 187·3 mAh/g at 5 s to 284·5 mAh/g at 15 s and then decreased to 191·9 mAh/g at 20 s and to 125·3 mAh/g at 25 s, indicating that 15 s may be the most optimal electrodeposition time. Excessive copper (I) chloride particles may result in poor performance due to the poor inherent conductivity of copper (I) chloride. Such efforts would alleviate environmental pollution and facilitate the circular economy of wastes.

Continuous and Rapid Synthesis of UiO-67 by Electrochemical Methods for the Electrochemical Detection of Hydroquinone.

Continuous and rapid synthesis of UiO-67 under mild conditions has been achieved by electrochemical methods for the first time. In the reaction system, a zirconium sheet was utilized as electrodes and a metal source for the assembly of UiO-67. High-crystalline UiO-67 with a regular tetrahedral morphology of around 1 μm was obtained within 1.5 h under the optimized solvent composition, voltage, and temperature conditions. This electrochemical synthetic method of UiO-67 in our work overcomes the shortcomings of high temperature and pressure of a traditional solvothermal method, which proposes new ideas for the large-scale and rapid synthesis of UiO-67. The UiO-67 synthesized by an electrochemical method was prepared as a UiO-67-carbon paste electrode (CPE), which exhibited a linear response to hydroquinone (HQ) in the range of 5-300 μM with a detection limit of 3.6 × 10-9 M (S/N = 3), for the electrochemical detection of HQ. It was confirmed that UiO-67-CPE possessed excellent reusability and antiinterference ability for the detection of HQ, and its detection ability even did not change after standing for 3 months. We further tried to apply UiO-67-CPE to the practical determination of HQ in tap water and river water samples, and the results proved that the recovery rate is 97.9-104.7% in real samples.

Controllable hydrothermal synthesis and morphology evolution of Zn4B6O13:Tb/Eu phosphors with tunable luminescent properties

A series of Tb, Eu single or co-doped Zn4B6O13 phosphors with tetrahedral morphology were synthesized by facile hydrothermal method. The influences of reaction temperature and the pH value of the reaction system on the structures and compositions of product were also investigated, in which four kinds of zinc borates with different structures and compositions (Zn4B2O7·H2O, Zn4B6O13, Zn(H2O)B2O4·0.12H2O, and H(Zn6O2(BO3)3)) were obtained. A possible growth mechanism of tetrahedral morphology of Zn4B6O13 has been proposed according to reaction time. The obtained samples were characterized by XRD, EDS, SEM, TEM, XPS, BET, DR, PL and QY. XPS results indicate that Eu2+ and Tb4+ are present in Tb/Eu co-doped Zn4B6O13, which might be generated from charge transfer between Tb3+ and Eu3+. The PL results shows that Eu3+, Tb3+ ion single-doped Zn4B6O13 microstructure exhibit orange and green emission under ultraviolet excitation, respectively. Compared to Eu3+ and Tb3+ single doped Zn4B6O13 phosphors, the Eu/Tb co-doped Zn4B6O13 phosphors showed stronger blue emission of Eu2+. These results imply that the tetrahedral morphology of Eu3+, Tb3+ ion single-doped and Eu2+/3+/Tb3+/4+ co-doped Zn4B6O13 phosphors have the promise application for nano/micro-optical functional devices.

A formaldehyde gas sensor with improved gas response and sub-ppm level detection limit based on NiO/NiFe2O4 composite nanotetrahedrons

Formaldehyde is a hazardous indoor volatile organic pollutant, thus selective and precise detection at a low concentration level is crucial. In this paper, NiO/NiFe2O4 nanocomposites were prepared through a simple two-step hydrothermal route and their gas sensing performances were investigated. SEM and TEM results showed that the composite products were NiO nanotetrahedrons decorated with numerous separated NiFe2O4 nanoparticles on the outer layer surface. XPS characterization confirmed that the as formed NiFe2O4 exhibited a p-type conductivity due to the hole transfer between Ni3+ and Ni2+ and therefore p-p isotype heterojunctions formed in the composite products. The element ratio of Fe to Ni was optimized to gain higher gas-sensing performance through adjusting the feeding amount of Fe3+ in the synthesis process. As a consequence, the gas sensor based on the sample NiFe-0.008 showed the highest response of 33.3–200 ppm formaldehyde vapor at 240 °C and a low detection limit of 200 ppb. The composite sensor also showed short response/recovery time and good long term stability. The enhanced gas sensing properties to formaldehyde can be attributed to the unique tetrahedral morphology and p-p heterojunction structure, which can provide more active sites and significantly enlarge resistance variation. This work will provide a new perspective of p-p heterojunction for the practical application in formaldehyde gas sensor.

Pd@tetrahedral hollow magnetic nanoparticles coated with N‐doped porous carbon as an efficient catalyst for hydrogenation of nitroarenes

Hollow magnetic nanoparticles (MNPs) with tetrahedral morphology were synthesized and then covered by a shell prepared by coating with melamine–formaldehyde followed by the introduction of glucose‐derived carbon. Subsequently, Pd nanoparticles were immobilized and the core–shell nanocomposite was carbonized. The obtained magnetic catalyst was successfully applied for the hydrogenation of nitroarenes in aqueous media. To investigate the effects of the morphology of MNPs, the nature of carbon shell, and the order of incorporation of Pd nanoparticles, several control catalysts, including the MNPs with different morphologies (disc‐like and cylinder); MNPs coated with different shells (sole glucose‐derived carbon or melamine–formaldehyde carbon shell); and a nanocomposite, in which Pd was immobilized after carbonization, were prepared and examined as catalyst for the model reaction. To justify the observed different catalytic activities of the catalysts, their Pd loadings, leaching, and specific surface areas were compared. The results confirmed that tetrahedral MNPs coated with porous N‐rich carbon shell exhibited the best catalytic activity. The high catalytic activity of this catalyst was attributed to its high surface area and the interaction of N‐rich shell with Pd nanoparticles that led to the higher Pd loading and suppressed Pd leaching.

Ordered stacking faults within nanosized silicon precipitates in aluminum alloy

A considerable amount of superfine Si precipitates with the sizes ranging from 5 to 15nm were found uniformly dispersed in the Al matrix of an Al-1Si (wt.%) alloy after electropulsing treatment. Through high resolution transmission electron microscopy (HRTEM), an unusual 9R (ABCBCACAB…) ordered stacking faults were identified within the Si precipitates with a truncated tetrahedral morphology that hold a (111)Si//(111)Al &[101‾]Si//[11‾0]Al orientation relationship with the Al matrix. An atomistic model was established to preform image simulations and explain that the existence of these nanosized Si precipitates is attributable to increment of coincidence lattice sites between Si and Al.

Facile synthesis of tetrahedral Ag3PO4 mesocrystals and its enhanced photocatalytic activity

A novel and rapid strategy has been developed to synthesize tetrahedral Ag3PO4 mesocrystals with the help of surfactant oleic acid. Homogeneous Ag3PO4 tetrahedron with average apex-to-apex length of 1.1μm could be synthesized under optimized conditions. Oleic acid is considered to be essential for the formation of this homogeneous tetrahedral morphology. The as-prepared tetrahedral Ag3PO4 mesocrystals could be formed through the close-packed assembly of Ag3PO4 nanoparticles, thus the formation of tetrahedral Ag3PO4 mesocrystals is explained by the oriented aggregation mechanism based on time-dependent experiments. Furthermore, the obtained tetrahedral Ag3PO4 mesocrystals exhibit enhanced visible-light photocatalytic degradation of methylene blue (MB) and methyl orange (MO) solutions compared to the reported micro-sized spherical Ag3PO4 particles with high photocatalytic performance.

Size- and support-dependent evolution of the oxidation state and structure by oxidation of subnanometer cobalt clusters.

Size-selected subnanometer cobalt clusters with 4, 7, and 27 cobalt atoms supported on amorphous alumina and ultrananocrystalline diamond (UNCD) surfaces were oxidized after exposure to ambient air. Grazing incidence X-ray absorption near-edge spectroscopy (GIXANES) and near-edge X-ray absorption fine structure (NEXAFS) were used to characterize the clusters revealed a strong dependency of the oxidation state and structure of the clusters on the surface. A dominant Co(2+) phase was identified in all samples. However, XANES analysis of cobalt clusters on UNCD showed that ∼10% fraction of a Co(0) phase was identified for all three cluster sizes and about 30 and 12% fraction of a Co(3+) phase in 4, 7, and 27 atom clusters, respectively. In the alumina-supported clusters, the dominating Co(2+) component was attributed to a cobalt aluminate, indicative of a very strong binding to the support. NEXAFS showed that in addition to strong binding of the clusters to alumina, their structure to a great extent follows the tetrahedral morphology of the support. All supported clusters were found to be resistant to agglomeration when exposed to reactive gases at elevated temperatures and atmospheric pressure.

SYNTHESIS OF STRUCTURALLY NOVEL CARBON MICRO/ NANOSPHERES BY LOW TEMPERATURE-HYDROTHERMAL PROCESS

ABSTRACT Carbon spheres with two to four attached lobes having axial, trigonal and tetrahedral morphology were synthesized at considerably low temperature of 200 °C by a hydrothermal reaction. The source of carbon used was sucrose in sulfuric acid medium. The product obtained was characterized by X-ray diffraction, Fourier transforms infrared and Raman spectroscopy, which have inferred us the graphitic nature of the product. Further Scanning and Transmission electron microscopic studies have revealed the spheres having attractive morphology with attached lobes and nodes like structures. The carbon spheres are having the size ranging from 200 nm to 4 µm. The spheres are solid balls exhibiting metallic luster. They possess surface area and pore volume of 2.956 m 2 g -1 and 0.616 x 10 -2 cm 3 g -1 respectively as obtained from Brunauer-Emmett-Teller method. The yield product obtained was about 70-80 %. Keywords: Hydrothermal Process, Carbon Spheres, Spheres with lobes, Low Temperature Synthesis, Microscopic Techniques.

Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour.

Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S-26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms involved in the origin of economically important species of Arachis, either by triploid bridge or bilateral sexual polyploidization.

Morphologie, fonction et évolution de quelques grains de pollen normapolles du Crétacé supérieur

Upper Cretaceous pollen grains with a thick wall (exine) and sometimes protruding apertures, included in the Normapolles Pflug, are considered from a functional point of view. Because of the high development of compression-resistance features correlative with a high protection of the gametophyte, an entomophilic phase is supposed in the dissemination of some types, but anemophily appears to have been a developmental trend of apertural specialization for others. As these functional features are characteristic of the outer part of the wall (the sexine), the tetrahedral morphology of the inner part (the nexine) and the lack of evidence that it influenced the whole adaptive system suggest that angiospermic constraints have acted first at a pteridophytic stage.

Facile Synthesis of Single-Crystalline γ-CuI Nanotetrahedrons and Their Induced Transformation to Tetrahedral CuO Nanocages

We report a high-yield facile synthesis of uniform single-crystalline γ-CuI nanocrystals with tetrahedral morphology from the reaction between Cun and KI under ambient conditions. In our method, I- perform the roles of reactant and surface stabilizing agent, thereby reducing the complexity of the reaction by eliminating the need for an external capping agent. Nanotetrahedrons grow from single-crystalline seeds whose growth has been promoted by iodide-induced oxidative etching of twinned seeds. These nanocrystals have Td symmetry in which three triangular faces meet at each corner, and thus may be classified as platonic solids. Removal of excess free I- in solution initiates the dissolution of CuI nanotetrahedrons and simultaneous oxidation to CuO nanocages. Transmission electron microscopy was used to trace the hollowing process, and the nanoscale Kirkendall effect and other possible mechanisms were discussed for the formation of void interiors.

X-ray topography of a natural twinned diamond of unusual pseudo-tetrahedral morphology

The internal morphology of a natural twinned diamond was investigated using X-ray section topography. The diamond consisted of two crystals joined along a {1 1 1} plane whose remote ends were triangular {1 1 1} faces with sizes approximately 4 mm on the edge. A coating of fibrous growth obscured the morphology of the good quality diamond inside. Although the coat displayed re-entrant surfaces near the twin plane along three edges of the crystal, X-ray topography showed the inner crystal to protrude outwards along these same edges. The good quality inner core displayed the classical “spinel law” twinned octahedral morphology whereas the fibrous rim showed a typical sphalerite-like twinned tetrahedral morphology. A possible growth mechanism which could account for this is discussed.

Room temperature solution synthesis of alkyl-capped tetrahedral shaped silicon nanocrystals.

We report the room temperature solution synthesis of alkyl protected silicon nanocrystals. The nanocrystals are of unusually uniform tetrahedral morphology and of a limited size distribution. The nanocrystals were characterized by transmission and scanning electron microscopy as well as atomic force microscopy.