Ca Sites Research Articles

A Perspective on the Use of Hydroxyapatites to Improve the Dissolution Behavior of Poorly Water-Soluble Piretanide

Background/Objectives: Interest in drug delivery systems (DDS) based on inorganic substrates has increased in parallel with the increase in the number of poorly water-soluble drugs. Hydroxyapatite is one of the ideal matrices for DDS due to its biocompatibility, low cost, and ease of preparation. Methods: We propose two doped hydroxyapatites, one with Ba on Ca sites another with Si on P sites, with the aim of improving the dissolution rate of piretanide, a diuretic, poorly water-soluble drug. The hybrids were characterized by different physical–chemical techniques, and their formation was demonstrated by infrared spectroscopy, thermal analysis, and electron microanalysis, as well as by comparing the results with those obtained on physical mixtures of HAPs and properly prepared piretanide. Results: Both the hybrids improved the piretanide dissolution rate compared with the physical mixtures and the drug alone. The dose was completely solubilized from the Si-doped hybrid in about 5 min in the three fluids considered. This remarkable improvement can be explained by an increase in the wettability and solubility of the drug loaded in the drug-carrier systems. Conclusions: Different experimental techniques, in particular spectroscopy and electronic microanalysis, proved the successful loading of piretanide onto doped HAP. Pharmaceutical measurements demonstrated rapid drug release in different fluids simulating gastrointestinal conditions after oral administration. These hybrid systems could be a very promising platform for drug delivery.

Copper Versatility in Hydroxyapatite: Valence States, Clusters, and Optical Absorption Properties.

The solid-state reaction between a stoichiometric hydroxyapatite (HA) and CuO at temperatures above 1100 °C produces pure Cux-HA phases for x ≤ 0.7 with the general formula Ca10CuIx(PO4)6(OH)2-xOx. The Cu atoms are located at the center of the hexagonal tunnels between two hydroxyl ligands, as determined by Fourier analysis based on XRD data. During heat treatment, the reduction of Cu2+ ions into Cu+ is concomitant with the stabilization of copper in HA in the hexagonal tunnel. The incorporation of monovalent copper within the apatite, as revealed by XANES spectroscopy, explains the violet color of the samples. The incorporation of Cu+ ions, by substitution of a hydrogen atom by copper(I), results in the formation of linear O-Cu-O chains where the majority of which are isolated for x ≤ 0.3. In addition, the EXAFS investigation showed, thanks to the linear geometry of these clusters that results in multiple diffusion effects, the existence of [CuO]n chains with n ≥ 2, which only appear clearly for higher copper contents x ≥ 0.5. The strong covalency of the Cu-O bond in such a dumbbell configuration would lead to strong hybridization between the 3d and 4s orbitals of copper and the 2p orbitals of oxygen, as illustrated by ESR signals. In the case of Cu-doped HA prepared by coprecipitation and annealed at a lower temperature (T ≤ 600 °C), copper substitutes calcium according to the theoretical formula Ca10-xCux(PO4)6(OH)2, mainly at the Ca(2) site. This local environment is in line with the Jahn-Teller distortion induced by the Cu2+ ion (as evidenced by UV-vis-NIR, XPS, and XANES-EXAFS spectroscopy analyses) and also allows copper-copper interactions from one site to another, as observed by ESR spectroscopy. This versatility of copper in HA gives it optical properties that change from a violet color with near-IR absorption to a blue hue. In all cases, Cu-O-Cu interactions persist whatever the valence state, and heat treatment induces a redox phenomenon, with copper exchanging between two sites close to each other.

An environmentally friendly depressant for magnesite and calcite flotation separation: Selective depression and adsorption mechanism

The similar crystal structures and chemical properties of magnesite and calcite make their effective separation through flotation challenging. This study explores the use of Glutamic acid diacetic acid tetrasodium salt (GLDA), a novel environmentally friendly chelating reagent, to enhance the flotation separation of magnesite and calcite. Flotation test results indicate that in a sodium oleate (NaOL) system, GLDA selectively inhibits the flotation of calcite. Under optimal conditions (slurry pH=9.20, GLDA 15 mg/L, and NaOL 140 mg/L), a flotation concentrate with an MgO grade of 46.21 %, CaO grade of 1.39 %, and an MgO recovery rate of 73.17 % was achieved. GLDA minimally affects the hydrophobicity of magnesite but significantly reduces the hydrophobicity of calcite. The selective inhibition mechanism of GLDA was investigated using zeta potential measurements, FTIR, and XPS analyses. Results show that GLDA selectively reacts with Ca sites on the calcite surface, adsorbing and covering it, thereby preventing NaOL from adsorbing on the calcite. Conversely, GLDA has a minor impact on the Mg sites on the magnesite surface, resulting in a negligible effect on NaOL adsorption by magnesite. Consequently, GLDA enhances the flotation separation efficiency of magnesite and calcite. The research results have potential for application in the purification of low-grade magnesite ore.

Study on flotation separation of chlorite and kaolinite by modified fatty acid collector and its mechanism

The modified fatty acid collector α-bromododecanoic acid (α-BDDA) had a significant effect on the separation of chlorite and kaolinite. In this paper, the flotation separation of the independent lithium bearing mineral chlorite (cookeite) from the main gangue mineral kaolinite in clay-type lithium ore was studied. The results showed that when pH was 9, the concentration of CaCl2 was 1.64×10−4 mol/L, and the concentration of α-BDDA was 5.82×10−4 mol/L, the flotation separation effect of chlorite and kaolinite was the best, and the floating difference between them was 91.12 %. The flotation results of artificially mixed ore also proved that α-BDDA could realize the separation of chlorite and kaolinite. Adsorption amount analysis revealed that α-BDDA could adsorb both on chlorite and kaolinite, however, the amount of α-BDDA adsorbed on chlorite was much higher than that on kaolinite. Zeta potential analysis, FT-IR spectra analysis, and XPS analysis confirmed that α-BDDA could produce chemisorption on the surface of chlorite activated by CaCl2. The Al, Mg, Fe and Ca sites on chlorite could reacted with α-BDDA to form new chemical bonds. However, α-BDDA was adsorbed on kaolinite by weak physical adsorption, which was easily de-adsorbed by strong agitating or water washing.

Flotation of Li Pegmatite with a Soybean Oil-Based Collector: Fundamental Studies

ABSTRACT In this work, the effect of a soybean oil-based collector on the surface properties of spodumene, feldspar, quartz, and muscovite was characterized and evaluated. By means of gas chromatography, it was determined that the reagent was composed of a mixture of carboxylic acids: linoleic (48%), oleic (28%), palmitic (13.3%), stearic (3.6%), α-linolenic (3.4%), and elaidic (3.2%). The reagent contained ~14 ppm Ca (determined by inductively coupled plasma optical emission spectroscopy – ICP-OES) and a critical micellar concentration (CMC) of 100 mg/L. At pH 6, the spodumene recovery was 50–60% higher than the other mineral recoveries, ascribed to chemical adsorption of the collector ionic-molecular species, which has high hydrophobicity power, on Al3+ sites on the spodumene surface. For pH values >10, the recoveries of feldspar and quartz were higher than spodumene, due to their activation by hydroxyl and hydroxide of Ca and subsequent adsorption of ionic specimen of the collector. The electrokinetic potential curves of spodumene, feldspar, and muscovite with collector were shifted toward more negative values compared to their electrokinetic potential curves without reagent. Fourier transform infrared spectroscopy (FT-IR) showed chemical adsorption of the anionic species of the collector at pH 6 with the Al3+, Fe3+, and Ca sites on the surface of aluminosilicates and Ca for quartz.

The selective flotation separation of apatite from dolomite using carrageenan as an innovative bio-based inhibitor

The direct flotation is highly effective in enhancing the quality of concentrate products and removing the content of magnesium for the beneficiation of middle and low grade phosphate ore. This study introduces carrageenan (CG) as an innovative dolomite inhibitor and assesses its effectiveness through micro-flotation tests with sodium oleate (NaOL) as a collector. At pH 10, the combination of 40 mg/L CG and 4 × 10−4 M NaOL successfully separated dolomite from apatite, the artificially mixed ore tests produced a concentrate assaying 32.23 % P2O5 with 76.44 % P2O5 recovery. Results demonstrate CG's strong inhibition of dolomite while minimally affecting apatite. The interaction mechanisms of CG with apatite and dolomite were investigated through various analyses including ICP-OES tests, zeta potential measurements, FTIR tests, contact angle measurements, XPS analysis, AFM tests, and ToF-SIMS analysis. Findings suggest that CG adsorbs strongly to dolomite surfaces by chemisorption between carboxyl groups and Ca sites, whereas it adsorbs weakly to apatite surfaces by hydrogen bonds between carboxyl and hydroxyl groups with F sites. Thus, CG shows promise as an innovative bio-based inhibitor for separating apatite from dolomite using direct flotation.

The location of cationic substitutions in carbonated biomimetic apatites significantly affects crystal nanomechanics

Bone and teeth are comprised of carbonate-substituted apatites with cationic substitutions, like sodium and potassium. Cations substitute for calcium in the apatite lattice but it is unclear whether they substitute for Ca(1) or Ca(2). Additionally, although we know that anionic substitutions affect the mineral mechanics, it is unclear how cationic substitutions affect mineral stiffness. Here, a combined experimental and theoretical approach using in situ fluid-mediated hydrostatic loading with synchrotron Wide Angle X-ray Scattering (WAXS) and Density Functional Theory (DFT) is used to elucidate the role of CO32− and Na+ or K+ co-substitutions on the atomic structure and mechanics of biomimetic apatites. Comparison of WAXS and DFT results showed that preferential substitutions at the Ca(1) and Ca(2) sites depended on cationic type and concentration, with a preference for Ca(1) at higher levels of co-substitution. Substitution levels and location of the cationic substitution both significantly affected the modulus of the minerals. This presents a new paradigm for the development of biomimetic apatites with multi-property tunability by considering composition and atomic organization.

Research on the method of improving carbon storage capacity of a new low calcium CO2 storage binder: Based on the recycling of heavy metal Ba ions

The novel low calcium CO2 storage binder (LCCSB) containing α-CS, C3S2 and C2AS as the primary minerals shows promise as a carbon fixation material, but exhibits low carbonation activity. This study aims to enhance the carbonation activity of LCCSB through barium (Ba) doping, investigate the impact of Ba doping on its carbonation behavior, and elucidate its mechanism. Density functional theory (DFT) simulation, scanning electron microscope test and X-ray diffraction results indicate that Ba ions preferentially substitute Ca atoms within α-CS, followed by Ca sites in C3S2, with a maximum solid solubility of 1mol%. Following Ba ion solid solution into LCCSB, there is an increase in carbonation reaction products along with elevated levels of calcite and aragonite. Additionally, small particles are formed to fill mineral matrix and pores leading to increased porosity and enhanced hardening strength. DFT calculations reveal that Ba ion doping reduces the total bond sequence density TBOD of the LCCSB system while weakening the bond strength of Ca–O bonds thereby accelerating the dissolution of Ca ions. Furthermore, average bond length, volume and distortion index of Ca–O polyhedra increase after Ba ion doping indicating structural distortion resulting in more active sites for potential high carbonation reactivity. This study presents a new research approach for achieving high carbonation activity in LCCSB preparation while also offering insights into the potential for clarifying the carbonation mechanism based on ion-doped LCCSB which could lead to improved environmental and economic benefits for CO2 storage within the cement industry.

Application of waste gypsum as novel selective depressant in the flotation separation of apatite from dolomite

The accumulation of gypsum slag not only causes resource wastage, but also poses serious environmental hazards, therefore, utilizing the resources of the main components in gypsum slag is an imperative task. In this study, gypsum was used as an inorganic depressant for the flotation separation of apatite from dolomite through the selective adsorption of gypsum on the surface of dolomite. Micro-flotation experiments showed that sodium oleate exhibited a good ability to collect apatite and dolomite, but poor ability to collect gypsum. At pH 9.5, when 3.75 g/L gypsum was added to the slurry, the recovery of dolomite decreased from 76.77 % to 18.34 %, whereas that of apatite was 86.45 %. Atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to elucidate the adsorption characteristics of gypsum on the apatite and dolomite surfaces. The results showed that gypsum was selectively adsorbed on the raised particles on the dolomite surface and combined with the active sites of Ca and Mg metal ions. However, the adsorption of gypsum on the surface of apatite was weak and had little effect on the flotation performance. Density functional theory calculations showed that the O in gypsum reacted easily with Ca and Mg metal ions on the mineral surface. The adsorption energies of gypsum at the Ca and Mg sites on the dolomite surface were −81.97 and −86.18 kJ/mol, respectively, whereas the adsorption energy on the apatite surface was only −34.20 kJ/mol. Gypsum is the main component of gypsum slag, and this study provides a potential recycling method for gypsum slag resources.

Calcium single atoms stabilized by nitrogen coordination in metal–organic frameworks as efficient solid base catalysts

Considerable attention has been paid to the preparation of single-atom solid base catalysts (SASBCs) owing to their high activity and maximized utilization of basic sites. At present, the reported fabrication methods of SASBCs, such as two-step reduction strategy and sublimation capture strategy, require high temperature. Such a high activation temperature is easy to cause the sublimation loss of alkali or alkaline earth metal atoms and destructive to the support structure. Herein, a new SASBC, Ca1/UiO-67-BPY, is fabricated, in which the alkaline earth metal Ca sites are immobilized onto N-rich metal–organic framework UiO-67-BPY at room temperature. The results show that the atomic configuration of Ca single atoms is coordinated by two N atoms in the framework. The obtained Ca SASBC possesses ordered structure and exhibits high product yield of 87.2% in the Knoevenagel reaction between benzaldehyde and malononitrile. Furthermore, thanks to the Ca single atoms sites anchored on UiO-67-BPY, the Ca1/UiO-67-BPY catalyst also shows good stability during cycles. This work might offer new insight in designing SASBCs for different base-catalyzed reactions.

Adsorption behavior and selective regulation of tartaric acid at solid-liquid interface: For ilmenite flotation separation

Ilmenite and its main gangue minerals (titanaugite and forsterite) are challenging to separate due to their similar surface chemical properties. The flotation process is an effective method, and the use of surface modifiers is essential. There is an urgent need to develop more effective and environmentally friendly agents to address the shortcomings of existing surface modifiers and the lack of understanding of the inhibition mechanism. In this work, sodium oleate was used as a collector to investigate the inhibitory effect of tartaric acid (TA) on gangue minerals in ilmenite flotation. This was done through micro-flotation experiments, Zeta potential measurements, x-ray photoelectron spectroscopy (XPS) analysis, solution chemical simulations, molecular dynamics (MD) simulations, and density functional theory (DFT). The results demonstrated a significant decrease in the recovery rates of titanaugite and forsterite after the addition of 1 × 10^4 mol/L TA at pH = 8. TA chemically adsorbs onto the Ca and Mg sites on the surfaces of titanaugite and forsterite through carboxylic acid groups. This impedes the adsorption of anionic collectors due to electrostatic repulsion and steric hindrance, effectively inhibiting gangue minerals and achieving separation from ilmenite.

Abstract Mo059: Leucine-Rich Repeat-Containing Protein 10 Modulates Human Cardiac L-Type Ca 2+ Channels but not T-Type Ca 2+ Channels

Background: Leucine-rich repeat-containing protein 10 (LRRC10) is a novel regulator of the cardiac L-type Ca 2+ channel/current (LTCC/I Ca,L ). LRRC10 is crucial for cardiac regeneration in multiple species, and LRRC10 variants have been associated with dilated cardiomyopathy in humans. LRRC10 increases I Ca,L in HEK-293 cells expressing rabbit Ca V 1.2 subunit, and knockout of LRRC10 in zebrafish and mouse cardiomyocytes (CM) reduces I Ca,L . However, LRRC10-mediated regulation of human cardiac LTCC has not been demonstrated, and the mechanism by which LRRC10 modulates LTCC is not known. Moreover, the effect of LRRC10 on the T-type Ca 2+ channel/current (TTCC/I Ca,T ), which has been implicated in CM cell cycle regulation, has never been tested. Methods: LRRC10 knockout ( LRRC10 –/– ) human induced-pluripotent stem cells (hiPSC) were generated from wild-type (WT) DF19-9-11T hiPSCs using CRISPR-Cas9 techniques. LRRC10 –/– and WT hiPSCs were differentiated to CMs using the standard GiWi protocol. Whole-cell I Ca,L and I Ca,T were examined in LRRC10 –/– and WT hiPSC-CMs. Whole-cell I Ca,L was also assessed in HEK-293 cells expressing human cardiac LTCC subunits (Ca V 1.2, β 2 , and α 2 δ) with or without human LRRC10. To identify the LRRC10-interacting site of Ca V 1.2, GST-pulldown assays were performed using purified GST-fusion constructs of the intracellular domains of rabbit Ca V 1.2 and lysates from HEK-293 cells expressing human LRRC10. Ca V protein sequences were analyzed using the Clustal Omega program. Results: Genetic ablation of LRRC10 in hiPSC-CMs decreased peak I Ca,L (WT -29.4±2.2 pA/pF, LRRC10 –/– -15.0±1.8 pA/pF, p<0.01) but did not significantly affect I Ca,T magnitude (WT -3.9±0.5 pA/pF, LRRC10 –/– -4.0±0.7 pA/pF, p>0.05 [NS]). LRRC10 increased peak I Ca,L in HEK-293 cells expressing human LTCC (with LRRC10 -156.0±19.8 pA/pF, without LRRC10 -60.2±12.0 pA/pF, p<0.05). LRRC10 was pulled down by the GST-Ca V 1.2-N-terminus but not by other GST-Ca V 1.2 constructs. Sequence analyses revealed an invariant exon 2-encoded segment of the N-terminus (NT) that was present in both human and rabbit LTCC Ca V 1.2 but not in TTCC Ca V 3.1 and Ca V 3.2. Conclusions: The Ca 2+ influx-potentiating effect of LRRC10 is conserved in human LTCC and is specific to regulate I Ca,L , not I Ca,T . The invariant Ca V 1.2 NT segment is a potential LRRC10-interacting site. The LRRC10 –/– hiPSC line is a promising tool for future investigations into the roles of LRRC10-LTCC interaction in human cardiac biology and disease.

Flotation separation of brucite and calcite in dodecylamine system enhanced by regulator potassium dihydrogen phosphate

To achieve efficient flotation separation of brucite and calcite, flotation separation experiments were conducted on two minerals using dodecylamine (DDA) as the collector and potassium dihydrogen phosphate (PDP) as the regulator. The action mechanism of DDA and PDP was explored through contact angle measurement, zeta potential detection, solution chemistry calculation, FTIR analysis, and XPS detection. The flotation results showed that when DDA dosage was 35 mg/L and PDP dosage was 40 mg/L, the maximum floating difference between brucite and calcite was 79.81%, and the selectivity separation index was 6.46. The detection analysis showed that the main dissolved component HPO42− of PDP is selectively strongly adsorbed on the Ca site on the surface of calcite, promoting the adsorption of the main dissolved component RNH+ 3 of DDA on calcite surface, while brucite is basically not affected by PDP. Therefore, PDP is an effective regulator for the reverse flotation separation of brucite and calcite in DDA system.

Influence of carboxymethyl chitosan on selective flotation separation of smithsonite from calcite with sodium oleate

Addressing the persistent challenge of separating smithsonite from calcite using flotation method, this study explores the impact of carboxymethyl chitosan (CMCS) on selective separation using sodium oleate (NaOL) assisted flotation. Results indicated a substantial reduction in calcite recovery to 2.25 % with the addition of 40 mg/L CMCS at pH 9, while recovery of smithsonite remained essentially unchanged at 94.78 %. Moreover, we found that using CMCS as the depressant can effectively separate smithsonite from calcite, based on the flotation testing results with artificially mixed minerals. Contact angle tests results showed that CMCS can significantly lower the surface hydrophobicity of calcite without any negative effect on that of smithsonite when using NaOL as a collector. TOC, FTIR, AFM, and ToF-SIMS analyses demonstrated stronger adsorption of CMCS on the surface of calcite compared to smithsonite. XPS data, solution chemical analysis and DFT revealed interaction between –COO- in CMCS with Ca sites on the surface of calcite because of the electrostatic adsorption and chemical adsorption, forming −COOCa. It leaded to shielding effects on the NaOL adsorption stemming, which makes NaOL more adsorbed on smithsonite surface.

Substitution of europium (III) in hydroxyapatite lattice for luminescence applications: Integrating experimental and theoretical insights

Europium(III) (Eu3+/Eu(III)) substitution in the hydroxyapatite (HAp) lattice imparts luminescence properties, enabling its application in diagnostics and bioimaging. Despite numerous experimental studies, there has been a lack of comprehensive discussion on the substitution behavior and local structural stability of Eu3+ within HAp. In this study, experimental and first-principles investigations were integrated to explore and understand the substitution of Eu3+ in HAp. Optimization of various HAp models revealed the dependency of Eu3+ substitution site on the charge compensation mechanism. Eu3+ prefers the Ca(2) site when OH is converted to O and the Ca(1) site in the presence of a Ca vacancy. Phonon calculations showed that temperature influences charge compensation and site preference, favoring OH to O compensation and Eu3+ in Ca(2) at higher temperatures and Ca vacancy and Eu3+ in Ca(1) at lower temperatures. Electronic structure simulations explained that the luminescence in Eu(III)-substituted HAp primarily arises from charge transfer between Eu3+ and O atoms, supported by experimental photoluminescence measurements. Correspondence between simulations and experimental photoluminescence data emphasizes the reliability of the computational approach in this study. The integration of insights from experimental and simulation results enhances the understanding of substitution of Eu3+ in the HAp lattice, providing valuable guidance for designing and optimizing HAp-based luminescent and optical materials.

Single-crystal X-ray diffraction study of a largely Cs-exchanged natural Ca-chabazite: Crystal-chemical factors for its excellent Cs-exchange ability

A hydrated natural Ca-chabazite, (Ca1.86Na0.13K0.09)(Al3.98Si8.03)O24·12.38H2O, and its Cs-exchanged form, (Cs2.66Ca0.45Na0.04K0.10)(Al4.04Si8.04)O24·8.52H2O, have been studied by the structure analyses based on single-crystal X-ray diffraction data. In the hydrated natural Ca-chabazite, all of extraframework species were found at the essentially identical locations to those in previously reported room-temperature structure. On the other hand, we revealed that the Cs-exchanged form has the essentially ten occupied-sites in extraframework: four water sites (OW2′, OW3, OW4, OW5), essentially two Cs sites (Cs1/Cs1′, Cs2) and four Ca sites (Ca1, Ca2, Ca3, Ca4). The Cs+ ions more preferentially occupy the Cs1/Cs1′ site, located at/around the centers of the 8-membered ring windows of [4126286]-cavities, than the Cs2 site. The Cs1/Cs1’ and Cs2 sites are essentially identical to the OW2 and OW3 sites observed in the hydrated natural Ca-chabazite, respectively; thus, these Cs sites are produced by replacing water molecules in both OW sites with Cs+ ions. In terms of interatomic distances, the coordination environments of the extraframework species in the chabazite crystals before and after the Cs-exchange treatment are discussed. In particular, both samples have a common feature that possible hydrogen bonds are relatively weak between water molecules and framework O atoms, whereas those are relatively strong between water molecules. On the basis of the present findings, we discuss the crystal-chemical key factors for an excellent Cs-exchange ability of chabazite as a highly efficient radioactive-element remover.

Enhanced flotation separation of barite and fluorite using tetrasodium iminodisuccinate (IDS) as a biodegradable fluorite depressant: Experiments and DFT calculations

With the increasing of application fields and market demand of barite and fluorite, the research of flotation separation of barite and fluorite has attracted much attention. In this work, a novel biodegradable fluorite depressant, tetrasodium iminodisuccinate (IDS) was developed for the flotation separation of barite and fluorite in sodium dodecyl sulfonate (SDSN) system, and its interaction mechanism were revealed. The micro-flotation results proved IDS had a strong depressant on fluorite at pH 6–11. Under the best conditions (pH 8, IDS 30 mg/L, SDSN 1 × 10-4 mol/L), the BaSO4 grade and recovery in the concentrate reached 90.15 % and 92.00 %, and the CaF2 grade and recovery in the tailing reached 89.77 % and 95.32 %, which indicated that IDS could achieve the separation of barite and fluorite. Zeta potential, contact angle, Fourier Transform Infrared Spectrometer (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Density Functional Theory (DFT) calculation indicated that IDS was chemisorbed on the fluorite, forming a bidentate binuclear stable adsorption configuration through the coordination of O with Ca site of fluorite, while a weak physical adsorption occurred between IDS and barite. Furthermore, the pre-adsorption of IDS hindered the binding between SDSN and fluorite, while the effect on barite was negligible. Therefore, IDS as a biodegradable and high-selectivity depressant, has potential value in the separation of barite and fluorite.

Insights into Amorphous Metal‐Organic Framework as Carbonic Anhydrase Mimic

AbstractCarbonic anhydrase (CA) is an important enzyme which breaks the C−O bond and catalyzes the hydration of CO2 and developing artificial enzyme to mimic the function of CA is important for the related applications. Zeolitic imidazolate frameworks (ZIFs) with typical tetrahedral Zn−N coordination units which were similar to the catalytically active site of natural CA have been reported to displayed CA‐like activities. However, the activity of crystalline ZIFs remains unsatisfactory. Herein, amorphous zeolitic imidazolate framework (aZIF) was fabricated through a facile self‐assembly process and exhibited 2.2‐fold higher CA‐like hydrolytic activity than the corresponding crystalline ZIF‐8.This phenomenon can be ascribed to the unsaturated Zn−N coordination structure and mesopores inside aZIF. This work affords a new avenue for the rational design of nanozymes.

New insights into selective depression mechanism of Tamarindus indica kernel gum in flotation separation of fluorapatite and calcite

The similar floatability of fluorapatite (FAp) and calcite (Cal) lead to difficulty in their separation using fatty acid collectors alone. To effectively recover FAp from Cal, a biodegradable polysaccharide, called Tamarindus indica kernel gum (TIKG), was introduced as an efficient Cal depressant in this study, and its depression mechanisms were elucidated. Flotation tests suggested that in sodium oleate (NaOl) system, TIKG strongly depressed Cal but hardly affected FAp, significantly widening the difference in their floatability. Infrared spectroscopy (IR), zeta potential, and wettability analyses indicated that TIKG had strong adsorption interaction with Cal, hindered NaOl adsorption on Cal, and significantly weakened the hydrophobicity of Cal, while the opposite effect was observed for FAp. X-ray photoelectron spectroscopy (XPS) proved that intense interactions of TIKG with Ca sites of Cal enhanced its adsorption on Cal rather than FAp. Extended Derjaguin–Landau–Verwey–Overbeek (EDLVO) calculations confirmed that TIKG reduced the hydrophobic attraction between Cal and bubbles and enhanced the electrostatic repulsion between them, thereby weakening Cal adhesion to bubbles and depressing Cal flotation. Consequently, TIKG achieved effective separation of FAp and Cal, in which 90.21% of Cal was efficiently removed in addition to 83.58% of FAp recovered. Based on these findings, TIKG serves as a Cal depressant for the purification of Cal-bearing phosphate ores by flotation.

Electronic structure and resonant inelastic x-ray scattering in Ca3Ru2O7

We have investigated the electronic structure of the transition metal oxide Ca3Ru2O7 within density-functional theory using the generalized gradient approximation while considering strong Coulomb correlations in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band structure method. Ca3Ru2O7 can be classified as a Mott insulator since it was expected to be metallic from band structure calculations. We found that the magnetic ground state of Ca3Ru2O7 possesses an AFM−b magnetic structure with the Ru spin moments ordered antiferromagnetically along the b axis. We have investigated the resonant inelastic x-ray scattering (RIXS) spectra at the Ru and Ca K, L3, and M3 edges as well as at the OK edge. The experimentally measured RIXS spectrum of Ca3Ru2O7 at the Ru L3 edge possesses a sharp feature ≤2eV corresponding to transitions within the Ru t2g levels. The excitation located from 2 to 4 eV is due to t2g→ eg transitions. The third wide structure situated at 4.5−11eV appears due to transitions between the Ru 4dO states derived from the tails of oxygen 2p states and eg and t2g states. The RIXS spectra at the Ru L3 and M3 edges are quite similar. However, the corresponding RIXS spectra at the Ca site are quite different from each other due to the significant difference in the widths of core levels. The RIXS spectrum at the OK edge consists of three major inelastic excitations. We found that the first two low energy features ≤2.5eV are due to interband transitions between occupied and empty Ot2g states which appear due to the strong hybridization between oxygen 2p and Ru t2g states in close vicinity to the Fermi level. The next major peak between 2.5 and 8 eV reflects interband transitions from occupied O2p to empty Ot2g states. A wide energy interval between 4 and 11 eV is occupied by rather weak O2p→Oeg transitions. Published by the American Physical Society 2024