Calcium Phosphate Precipitation Research Articles

Impact of electrical polarization in the production of hydroxyapatite on ZnO substituted 45S5 bioglass

In the present investigation, we show the role of dielectric permittivity in the growth of hydroxyl carbonate apatite over ZnO-substituted 45S5 bioglass. ZnO is incorporated here in 45S5 bioglass because of its incipient dielectricity. Zinc is a necessary element for the formation, mineralization, development and maintenance of healthy bones. Here, the bioactive glass ZBG, having the general composition of 46.1 SiO2, 26.9 CaO, 2.6 P2O5, 24.4-X Na2O, and X ZnO (here X = 0 to 3 mole %), was synthesized using the traditional melting technique. The ZBG bioglass samples underwent electro-thermal poling with a voltage value of 10 kV at a temperature of 500 °C for 1 h. The impact of substituting Na2O with ZnO on the in-vitro bioactive property following submersion in simulated bodily fluid (SBF) was examined using the Fourier transform of infrared spectroscopy (FTIR) and x-ray diffraction (XRD). A comparison has been made between the dielectric constant (ε) and alternating current conductivity of unpolarized and polarized hydroxyl carbonate apatite (HCA) formed samples subjected to a 90 kV cm−1 polarisation field. Additionally, the influence of electrical poling on the ZBG samples that were created was examined via the use of XRD, scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDX), and atomic force microscopy (AFM) research. The dielectric characteristics of bioactive glasses were improved by substituting Na2O with ZnO, as seen in the study. The ZBG samples immersed in SBF solution enhance the hydroxyl calcium phosphate precipitation process due to electrical interaction with the polarized sample. This result shows us that N-poled samples are more suitable for orthopaedic applications. Thus, our main aim of the present investigation is to increase the bioactivity of 45S5 glasses substituted with ZnO after polarization, which will be more suitable for orthopaedic implants.

Ecofriendly solidification of sand using microbially induced calcium phosphate precipitation

This study introduces microbiologically induced calcium phosphate precipitation (MICPP) as a novel and environmentally sustainable method of soil stabilization. Using Limosilactobacillus sp., especially NBRC 14511 and fish bone solution (FBS) extracted from Tuna fish bones, the study was aimed at testing the feasibility of calcium phosphate compounds (CPCs) deposition and sand stabilization. Dynamic changes in pH and calcium ion (Ca2+) concentration during the precipitation experiments affected the precipitation and sequential conversion of dicalcium phosphate dihydrate (DCPD) to hydroxyapatite (HAp), which was confirmed by XRD and SEM analysis. Sand solidification experiments demonstrated improvements in unconfined compressive strength (UCS), especially at higher Urea/Ca2+ ratios. The UCS values obtained were 10.35 MPa at a ratio of 2.0, 3.34 MPa at a ratio of 1.0, and 0.43 MPa at a ratio of 0.5, highlighting the advantages of MICPP over traditional methods. Microstructural analysis further clarified the mineral composition, demonstrating the potential of MICPP in environmentally friendly soil engineering. The study highlights the promise of MICPP for sustainable soil stabilization, offering improved mechanical properties and reducing environmental impact, paving the way for novel geotechnical practices.

Electron Microscopy for the Stability Assessment of Parenteral Nutrition Admixtures: Focus on Precipitation.

(1) Background: parenteral nutrition (PN) is indispensable for patients unable to receive oral or enteral feeding. However, the complexity of PN solutions presents challenges regarding stability and compatibility. Precipitation reactions may occur. The most frequent is the formation of calcium phosphate (Ca-P). The different factors influencing these reactions must be considered to ensure patient safety. (2) Methods: eight paediatric PN solutions were prepared, following standard protocols. Samples were stored at room temperature and in a refrigerator. Electron microscopy, coupled with energy dispersive X-ray spectroscopy (EDS), was employed. Precipitates were analysed for composition and morphology. (3) Results: precipitates were observed in all samples, even at day 0. Crystalline structures, predominantly composed of calcium or magnesium, sometimes associated with chlorine or phosphorus, were detected. Additionally, amorphous precipitates, contained heterogeneous compositions, including unexpected elements, were identified. (4) Conclusions: various precipitates, primarily calcium- or magnesium-based, can form in PN solutions, although it is not expected that they can form under the real conditions of use. Calcium oxalate precipitation has been characterised, but the use of organic calcium and phosphate salts appears to mitigate calcium phosphate precipitation. Electron microscopy provides interesting results on NP precipitation, but sample preparation may present technical limitations that affect the interpretation of the results.

Biomineralization of Polyelectrolyte-Functionalized Electrospun Fibers: Optimization and In Vitro Validation for Bone Applications.

In recent years, polyelectrolytes have been successfully used as an alternative to non-collagenous proteins to promote interfibrillar biomineralization, to reproduce the spatial intercalation of mineral phases among collagen fibrils, and to design bioinspired scaffolds for hard tissue regeneration. Herein, hybrid nanofibers were fabricated via electrospinning, by using a mixture of Poly ɛ-caprolactone (PCL) and cationic cellulose derivatives, i.e., cellulose-bearing imidazolium tosylate (CIMD). The obtained fibers were self-assembled with Sodium Alginate (SA) by polyelectrolyte interactions with CIMD onto the fiber surface and, then, treated with simulated body fluid (SBF) to promote the precipitation of calcium phosphate (CaP) deposits. FTIR analysis confirmed the presence of SA and CaP, while SEM equipped with EDX analysis mapped the calcium phosphate constituent elements, estimating an average Ca/P ratio of about 1.33-falling in the range of biological apatites. Moreover, in vitro studies have confirmed the good response of mesenchymal cells (hMSCs) on biomineralized samples, since day 3, with a significant improvement in the presence of SA, due to the interaction of SA with CaP deposits. More interestingly, after a decay of metabolic activity on day 7, a relevant increase in cell proliferation can be recognized, in agreement with the beginning of the differentiation phase, confirmed by ALP results. Antibacterial tests performed by using different bacteria populations confirmed that nanofibers with an SA-CIMD complex show an optimal inhibitory response against S. mutans, S. aureus, and E. coli, with no significant decay due to the effect of CaP, in comparison with non-biomineralized controls. All these data suggest a promising use of these biomineralized fibers as bioinspired membranes with efficient antimicrobial and osteoconductive cues suitable to support bone healing/regeneration.

Calcium Phosphate Precipitation as an Unintended Consequence of Phosphate Dosing to High-pH Water

Calcium Phosphate Precipitation as an Unintended Consequence of Phosphate Dosing to High-pH Water

Pore graded borosilicate bioactive glass scaffolds: in vitro dissolution and cytocompatibility

3D borosilicate bioactive glass (1393B20 and B12.5MgSr) scaffolds were prepared by robocasting, with and without a dense layer at the top. Pore graded scaffolds are promising as they allow for membrane deposition and could limit the risk of soft tissue infiltration. In vitro dissolution was studied in tris(hydroxymethyl)aminomethane (TRIS) and Simulated Body Fluid (SBF). 1393B20 scaffolds dissolved faster than B12.5MgSr in TRIS whereas they dissolved slower in SBF. The difference in dissolution profiles, as a function of the medium used, is assigned to the different rates of precipitation of hydroxyapatite (HA). While the precipitation of calcium phosphate (CaP) in the form of HA, first sign of bioactivity, was confirmed by ICP, FTIR-ATR and SEM-EDX analysis for both compositions, 1393B20 was found to precipitate HA at a faster rate. The presence of a dense top layer did not significantly impact the dissolution rate and CaP precipitation. In vitro cell culture was performed using human adipose-derived stem cells (hADSCs). Prior to cell plating, a preincubation of 3 days was found optimum to prevent burst ion release. In direct contact, cells proliferate and spread on the scaffolds while maintaining characteristic spindle morphology. Cell plated on 1393B20 scaffolds showed increased viability when compared to cell plated on B12.5MgSr. The lower cell viability, when testing B12.5MgSr, was assigned to the depletion of Ca2+ ions from culture medium and higher pH. Static cell culture leads to believe that the scaffold produced from the 1393B20 glass composition are promising in bone regeneration applications.Graphical

Calcium ions have a detrimental impact on the boundary lubrication property of hyaluronic acid and lubricin (PRG-4) both alone and in combination

Cartilage demineralisation in Osteoarthritis (OA) patients can elevate calcium ion levels in synovial fluid, as evidenced by the prevalence of precipitated calcium phosphate crystals in OA synovial fluid. Although it has been reported that there is a potential connection between elevated concentrations of calcium ions and a deterioration in the lubrication and wear resistance of cartilage tissues, the mechanism behind the strong link between calcium ion concentration and decreased lubrication performance is unclear. In this work, the AFM friction, imaging, and normal force distance measurements were used to investigate the lubrication performances of hyaluronic acid (HA), Lubricin (LUB), and HA-LUB complex in the presence of calcium ions (5 mM, 15 mM, and 30 mM), to understand the possible mechanism behind the change of lubrication property. The results of AFM friction measurements suggest that introducing calcium ions to the environment effectively eliminated the lubrication ability of HA and HA-LUB, especially with relatively low loading applied. The AFM images indicate that it is unlikely that structural or morphological changes in the surface-bound layer upon calcium ions addition are primarily responsible for the friction results demonstrated. Further, the poor correlation between the effect of calcium ions on the adhesion forces and its impact on friction suggests that the decrease in the lubricating ability of both layers is likely a result of changes in the hydration of the HA-LUB surface bound layers than changes in intermolecular or intramolecular binding. This work provides the first experimental evidence lending towards the relationship between bone demineralisation and articular cartilage degradation at the onset of OA and the mechanism through which elevated calcium levels in the synovial fluid act on joint lubrication.

Optimized Calcium-Phosphate-Based Co-transfection of Tau and tdTomato into Human iPSC-Derived Neurons for the Study of Intracellular Distribution of Wild-type and Mutant Human Tau.

The study of Tau protein in disease-relevant neuronal cells in culture requires efficient delivery systems for transfection of exogenous Tau and also modulators and interactors of Tau. Transfection of cultivated cells using calcium phosphate precipitation is a simple and cost-effective approach, also for difficult-to-transfect and sensitive cells such as primary neurons. Because of its low cell toxicity and ease of use, the Ca2+-phosphate transfection method is one of the most widely used gene transfer procedures in neuroscience. However, Ca2+-phosphate transfection efficacy in neurons is poor, often in the range of 1-5%, limiting its use in functional investigations. Here, we outline our improved Ca2+-phosphate transfection methodology for human iPSC-derived neurons that yields a reasonable efficiency (20-30% for bright volume markers) without apparent effects on cell health. We have used it to introduce wild-type and mutant human Tau with and without co-transfection of a volume marker (used here: tdTomato). In sum, our procedure can deliver neuronal genes (e.g., MAPT) using typical eukaryotic expression vectors (e.g., using CMV promoter) and is optimized for transfection of human iPSC-derived neurons.

Pseudo-equilibrium equations for calcium phosphate precipitation with multi-unit particles.

The chemistry underlying bone mineral formation in vertebrates is the reaction of calcium phosphate precipitation. In a near-neutral solution, an amorphous phase and hydroxyapatite nanoparticles appear successively, and the reaction system containing either of the two kinds of precipitates is in a non-equilibrium state. Here, we propose a pseudo-equilibrium approach to the solution chemistry of the precipitation reactions. We employed two series of reaction systems, collected samples at various stages, and analyzed the solution chemistry data on the basis of a simplified model of reaction. We derived two types of pseudo-equilibrium equations from the two series, respectively. These equations reveal the existence of multiple structural units in a precipitate particle and correlate the ionic product with the surface proportion per structural unit (m). The surface proportion, in turn, is related to the whole particle through a particle-surface equation. Notably, the two types of pseudo-equilibrium constants have the common expression of "Kd = ionic product" if the number of the structural units (u) is large enough. Together, these findings have revealed some aspects of the non-equilibrium thermodynamics of precipitation reactions, indicating the solution chemistry route to the equilibrium state. The concept of the multi-unit particle may shed new light on the study of precipitation reactions of other slightly soluble electrolytes. And the relationship between the ionic product and the surface proportion of a structural unit is not only fundamental in chemistry, but may also apply to non-equilibrium systems in nature and biology, such as marine sedimentation, human vascular calcification, and bone mineral metabolism.

Surface treatment of magnetite nanoparticle thin films with potassium phosphate for calcium phosphate precipitation

The treatment of magnetite nanoparticle thin films with potassium phosphate and their surface reaction with simulated body fluid were in situ monitored by the QCM-D technique, which is suitable for the precipitation of calcium phosphate.

Baseline investigation on enzyme induced calcium phosphate precipitation for solidification of sand

Introduction: Bio-cementation processes [namely, microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP)] have recently become promising techniques for solidifying loose sands. However, these methods release gaseous ammonia to the atmosphere, which is not desirable for real-scale applications. This study aims to propose an enzyme induced calcium phosphate precipitation (EICPP) method as a sustainable direction for the solidification of sand.Methods: Precipitation of calcium phosphate compound (CPC) was driven through pH-dependent mechanism regulated by enzymatic hydrolysis of urea. The baseline study was designed to consist of a series of precipitation tests and sand column tests, evaluating the influence of various recipes of cementation media (CM) on treatment efficiency. The evaluation program consisted of Unconfined compression tests, precipitation content measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction.Results: The observations showed that the content of urea had an important role in proposed EICPP treatment, which determined the extent of the pH increase. This increase had a great influence on 1) utilization of soluble calcium, 2) precipitation content of calcium phosphate, and 3) the morphology of the precipitates. Results of sand column test suggested that injecting CM that consisted of acid-dissolved bone meal, urea and urease enzyme could result in the deposition of insoluble CPC that enabled the solidification of sand particles.Discussion: The precipitation quantity was found to increase with the increase in urea content; however, the treatment media with high urea content resulted amorphous-like crystals. The plate-like crystals were evidenced in CM with [Ca]/[urea] molar ratio between 1.5–2.0. X-ray Diffraction (XRD) analysis revealed that irrespective of the urea contents, the formed crystals were identified as brushite. Since the final pH of proposed EICPP method could be controllable within acidic-neutral conditions, the emission of ammonia gas would be eliminated.

Simultaneous removal of nitrate nitrogen and orthophosphate by electroreduction and electrochemical precipitation

Electrochemical methods can effectively remove nitrate nitrogen (NO3-N) and orthophosphate phosphorus (PO4-P) from wastewater. This work proposed a process for the simultaneous removal of NO3-N and PO4-P by combining electroreduction with electrochemically-induced calcium phosphate precipitation, and its performance and mechanisms were studied. For the treatment of 100 mg L–1 NO3-N and 5 mg L–1 PO4-P, NO3-N removal of 60–90% (per cathode area: 0.25–0.38 mg h–1 cm–2) and 80–90% (per cathode area: 0.33–0.38 mg h–1 cm–2) could be acquired within 3 h in single-chamber cell (SCC) and dual-chamber cell (DCC), while P removal was 80–98% (per cathode area: 0.10–0.12 mg h–1 cm–2) in SCC after 30 min and 98% (per cathode area: 0.37 mg h–1 cm–2) in DCC within 10 min. The faster P removal in DCC was due to the higher pH and more abundant Ca2+ in the cathode chamber of DCC, which was caused by the cation exchange membrane (CEM). Interestingly, NO3-N reduction enhanced P removal because more OH– can be produced by nitrate reduction than hydrogen evolution for an equal-charge reaction. For 10 mg L–1 PO4-P in SCC, when the initial NO3-N was 0, 20, 100, and 500 mg L–1, the P removal efficiencies after 1 h treatment were < 10%, 45–55%, 86–99%, and above 98% respectively. An increase in Ca2+ concentration also promoted P removal. However, Ca and P inhibited nitrate reduction in SCC at the relatively low initial Ca/P, as CaP on the cathode limited the charge or mass transfer process. The removal efficiency of NO3-N in SCC after 3 h reaction can reduce by about 17%, 40%, and 34% for Co3O4/Ti, Co/Ti, and TiO2/Ti. The degree of inhibition of P on NO3-N removal was related to the content and composition of CaP deposited on the cathode. On the cathode, the lower the deposited Ca and P, and the higher the deposited Ca/P molar ratio, the weaker the inhibition of P on NO3-N removal. Especially, P had little or even no inhibition on nitrate reduction when treated in DCC instead of SCC or under high initial Ca/P. It is speculated that under these conditions, a high local pH and local high concentration Ca2+ layer near the cathode led to a decrease in CaP deposition and an increase in Ca/P molar ratio on the cathode. High initial concentrations of NO3-N might also be beneficial in reducing the inhibition of P on nitrate reduction, as few CaP with high Ca/P molar ratios were deposited on the cathode. The evaluation of the real wastewater treatment was also conducted.

EU-compliant wastewater recycled phosphorus: How much national cereal demand can it meet?

Finding alternative phosphorus sources is imperative to address negative environmental and societal impacts caused by its current inefficient use. However, the direct use of phosphorus in sewage sludge in agriculture is controversial. This paper uses Denmark, Germany, and Spain as case examples to assess relevant legislation and boundary conditions in agricultural production to identify opportunities and barriers for the utilisation of recycled phosphorus from wastewater in agriculture on a regional level. Only five out of 22 phosphorus recycling technologies considered were in full compliance with legislation across all three countries, and these five were then assessed for their potential to supply phosphorus to major crops within countries. We considered the application of technologies across four scenarios: 1) struvite; 2) vivianite as iron supply; 3) vivianite for calcium phosphate precipitation; and 4) ashes for calcium phosphate precipitation. The most suitable scenario identified for Denmark was vivianite for calcium phosphate precipitation, whereas in Spain vivianite as iron supply was identified as most suitable, and ashes for calcium phosphate in Germany. We found that in 2018, the potential phosphorus supply from recycling technologies was on average 0.38, 0.29 and 0.05 kg of phosphorus per capita for Danish, German, and Spanish regions. These quantities could meet 9.1, 21.7, and 10.0 percent of the phosphorus required to produce major cereals in each country (specifically wheat, barley, and rye). Given current legal constraints, wastewater treatment plant connections and agronomic context, the potential contribution of recycled phosphorus is non-negligible in many sub-national regions. Still, to access the full potential of phosphorus circularity clear product specifications and transport and logistics among regions will be necessary.

Synergies of pH-induced calcium phosphate precipitation and magnetic separation for energy-efficient harvesting of freshwater microalgae

Energy- and time-consuming concentration steps currently limit the industrial application of microalgae. Compared to state-of-the-art technologies, magnetic separation shows a high potential for efficient harvesting of microalgae. This study presents a novel approach to combine pH-induced calcium phosphate precipitation with cheap natural magnetite microparticles for magnetic separation of the freshwater microalgae Chlorella vulgaris. Harvesting efficiencies up to 98% were achieved at moderate pH and low particle and calcium phosphate concentrations in a model medium. However, cultivation-dependent high loads of algogenic organic matter can severely inhibit flocculation and particle/algae interactions, requiring higher salt concentrations or pH. Harvesting efficiencies above 90% were still attainable at moderate pH with increased calcium phosphate concentrations of 10mM. Acidification of the suspension to pH 5 allows for simple and reversible particle recycling. The presented process provides a promising path to universal and cost-effective harvesting, advancing the utilization of microalgae as a sustainable bioresource.

Simultaneous phosphorus precipitation and sludge thickening by electrolysis with an anode covered by bivalve shells

A wastewater treatment plant with a large inflow of phosphorus (P) is a potential P source that can act as an alternative to phosphate rocks and a renewable source of P. During electrolysis with inert electrodes, hydroxide ions generated from the cathode cause calcium phosphate (CaP) precipitation, and oxygen and hydrogen generated from the electrodes cause thickening of the sludge by electroflotation in sludge treatment streams. However, these two effects have not been achieved simultaneously because the precipitation of CaP requires much more time than that required for thickening by electroflotation. In this study, an electrolysis system that used an anode covered with bivalve shells was used. Batch experiments were conducted and the results demonstrated that covering the anode with shells resulted in their dissolution and that the calcium ions provided by this process considerably enhanced P removal in the form of CaP, thereby shortening the time required for CaP precipitation. In continuous experiments with excess sludge, electrolysis with shells accomplished sludge thickening by electroflotation (the thickened sludge had 5.5 times the total solids in the original excess sludge) and low relative phosphate-P concentrations (0.0545–0.0812) in the effluent compared to the influent. This effect is attributed to CaP precipitation. Additional mixing of the CaP precipitates in the effluent enhanced their settleability. The results demonstrate that electrolysis using an anode covered with bivalve shells simultaneously achieved CaP precipitation and sludge thickening.

Enhanced electrochemically mediated calcium phosphate precipitation for phosphorus recovery simply by carbon felt barrier cathode

Phosphorus removal and recovery from wastewater is crucial for environmental pollution control and sustainable phosphorus fertilizer production. Electrochemical technologies are promising, but disadvantages like high energy consumption remain. Here, we improved the electrochemical system's performance by placing carbon felt in front of the cathode at a distance of 3 mm with a current density as low as 1 A/m2, which separated the reactor into two parts: near the cathode area and bulk solution. The phosphorus removal near the cathode can reach 75 % in 1 h, while it takes 8 h for the bulk solution to achieve 75 % removal efficiency. The main reason for the enhancement was the retention of OH− ions between the cathode and carbon felt with enriched calcium ions, providing an appropriate environment for calcium phosphate precipitation. The functional groups on the carbon felt surface were another reason for the retention of OH− ions. Furthermore, our results show that the carbon felt system has considerable stability under different mass transfer efficiencies. By adjusting the stirring rate, we could control the proportion of precipitation on the carbon felt or cathode, thereby reducing the scaling on the cathode and avoiding significantly reduced removal efficiency. A long-term continuous flow experiment also illustrated this. Interestingly, we observed that the phosphorus removal had a specific correlation with pH and fit an empirical formula. Therefore, we could estimate the removal efficiency by simply measuring the effluent pH of the solution after treatment. In treating real phosphorus-rich wastewater, the carbon felt system removed 63 %–87 % of 1500 mg/L P after 8 h to 48 h treatment at 20 A/m2, respectively, resulting in lower energy consumption (31 kWh/kg P, 8 h) compared to the system without carbon felt (48 kWh/kg P, 8 h). This study provides a simple yet efficient method for enhancing electrochemical phosphorus recovery.

Polycarboxy/Sulfo Betaine-Calcium Phosphate Hybrid Materials with a Remineralization Potential.

Biomacromolecules control mineral formation during the biomineralization process, but the effects of the organic components' functionality on the type of mineral phase is still unclear. The biomimetic precipitation of calcium phosphates in a physiological medium containing either polycarboxybetaine (PCB) or polysulfobetaine (PSB) was investigated in this study. Amorphous calcium phosphate (ACP) or a mixture of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) in different ratios were identified depending on the sequence of initial solution mixing and on the type of the negative functional group of the polymer used. The more acidic character of the sulfo group in PSB than the carboxy one in PCB determines the dominance of the acidic solid phases, namely, an acidic amorphous phase or DCPD. In the presence of PCB, the formation of ACP with acicular particles arranged in bundles with the same orientation was observed. A preliminary study on the remineralization potential of the hybrid material with the participation of PSB and a mixture of OCP and DCPD did not show an increase in enamel density, contrary to the materials based on PCB and ACP. Moreover, the latter showed the creation of a newly formed crystal layer similar to that of the underlying enamel. This defines PCB/ACP as a promising material for enamel remineralization.

Ultra-Short Laser-Assisted Micro-Structure Formations on Mg/Zn Double-Doped Calcium Phosphate Ceramics for Enhanced Antimicrobial Activity.

Bacterial infection is one of the most common and harmful medical issues following the implantation of materials and devices in the body leading to antibiotic resistance of diverse bacterial strains. In this work, a novel approach is presented combining adopted laser-based patterning method in addition to doping (Mg and Zn) metal ions to prepare calcium phosphate ceramic substrate, applicable in medicine, with enhanced surface antimicrobial characteristics. The preparation of tablets containing Mg (8.44 mol%) and Zn (2.63 mol%) β-tricalcium phosphate involved biomimetic precipitation of amorphous calcium phosphate in media of simulated body fluid enriched with Mg2+ and Zn2+ ions as well as the presence of valine as an organic additive, followed by step-wise calcination up to 1000 °C. The results from laser processing showed formation of deeper patterns with increased surface roughness (from 4.9 µm to 9.4 µm) as laser power and velocity increase, keeping constant the hatch sizes of 50 µm. The textured surfaces consist of peaks and valleys arrangement that change the morphology of Escherichia coli cells and decrease of cell viability. Our study reveals the possibilities of the application of ultra-short laser radiation as a potential alternative therapy for controlling the antimicrobial effect of the ceramic surface.

Leaching of phosphorus from phosphate tailings and extraction of calcium phosphates: Toward comprehensive utilization of tailing resources

Phosphate tailing is an extremely fine by-product during phosphate ore flotation. Due to the large quantities and relatively higher P2O5 content, the phosphate tailings have been considered as a potential P resource, compared to other P-bearing wastes. Besides, phosphate tailings also contain a large amount of available components, such as Ca, Mg, and Si. To explore a low-cost and efficient process for the utilization of phosphate tailings, the hydrochloric acid leaching-precipitation method was employed to recover phosphorus. The P in phosphate tailings can be selectively dissolved into leaching liquor, followed by the precipitation of calcium phosphates from the leaching liquor through pH adjustment. The results showed that P was predominantly concentrated in fluorapatite and its dissolution ratio increased with the decrease in pH. At pH 1.0, the P dissolution efficiency from phosphate tailings reached 96.3%, along with the majority of Mg and Ca. However, Si was hardly dissolved. It demonstrated that almost all the fluorapatite and dolomite were dissolved while the quartz was difficult to dissolve. Dolomite was more preferentially dissolved than fluorapatite. Increasing temperature contributed to the dissolution of dolomite while suppressing fluorapatite dissolution. The residue containing 87.9% SiO2 (quartz) and only 0.25% P2O5 has the potential as a building material. As the pH increased to 7.0, the collected precipitate consisted of 34.18% P2O5 and 56.10% CaO, which can serve as a source of a slow-released phosphate fertilizer. The highly efficient utilization of phosphate tailings was achieved via this process.

Biphasic NMR of Hyperpolarized Suspensions-Real-Time Monitoring of Solute-to-Solid Conversion to Watch Materials Grow.

Nuclear magnetic resonance (NMR) spectroscopy is a key method for the determination of molecular structures. Due to its intrinsically high (i.e., atomistic) resolution and versatility, it has found numerous applications for investigating gases, liquids, and solids. However, liquid-state NMR has found little application for suspensions of solid particles as the resonances of such systems are excessively broadened, typically beyond the detection threshold. Herein, we propose a route to overcoming this critical limitation by enhancing the signals of particle suspensions by >3.000-fold using dissolution dynamic nuclear polarization (d-DNP) coupled with rapid solid precipitation. For the proof-of-concept series of experiments, we employed calcium phosphate (CaP) as a model system. By d-DNP, we boosted the signals of phosphate 31P spins before rapid CaP precipitation inside the NMR spectrometer, leading to the inclusion of the hyperpolarized phosphate into CaP-nucleated solid particles within milliseconds. With our approach, within only 1 s of acquisition time, we obtained spectra of biphasic systems, i.e., micrometer-sized dilute solid CaP particles coexisting with their solution-state precursors. Thus, this work is a step toward real-time characterization of the solid-solution equilibrium. Finally, integrating the hyperpolarized data with molecular dynamics simulations and electron microscopy enabled us to shed light on the CaP formation mechanism in atomistic detail.