Phosphorus recovery from phosphate tailings through a two-stage leaching-precipitation process: Toward the harmless and reduction treatment of P-bearing wastes.

To achieve highly efficient extraction of phosphorus (P) and comprehensive utilization of phosphate tailings, a two-stage leaching-precipitation method was proposed. Phosphate tailings primarily consisted of dolomite, fluorapatite, and quartz. During the first-stage leaching, the large majority of dolomite was selectively dissolved and the leaching efficiency of Mg reached 93.1 % at pH 2.0 and 60 °C. The subsequent second-stage leaching of fluorapatite was performed and the P leaching efficiency was 98.8 % at pH 1.5 and 20 °C, while the quartz remained in the residue. Through two-stage leaching, a stepwise leaching of dolomite and fluorapatite was achieved. After chemical precipitation, calcium phosphate with a high purity of 97.9 % was obtained; and the total recovery efficiency of P exceeded 98 %. The obtained calcium phosphate can be a raw material in the phosphorus chemical industry, while the Mg-rich leachate and the final quartz-rich residue have the potential for Mg extraction and the production of mortars or geopolymers, respectively. The two-stage leaching-precipitation process could significantly reduce the leaching costs, and enhance the reaction rates. It is expected to realize a volume reduction and efficient resource utilization of the phosphate tailings by using this sustainable and promising solution.

Study on anaerobic phosphorus release from pig manure and phosphorus recovery by vivianite method.

In this study, pig manure rich in phosphorus was used as the recovery object, In order to realize the maximum recovery of phosphorus resources in pig manure, this study established a phosphorus recovery route combining the electrochemical method with the Vivianite method using sacrificial iron anode. And in order to obtain phosphorus rich supernatant, pig manure was treated with different pH values, and the changes in phosphorus components and metal content in the liquid phase were mainly investigated; Graded phosphorus components and microbial communities in the solid phase; Finally, the effect of electrolytic recovery of phosphorus from fermentation supernatant was studied. The results showed that the highest total phosphorus (TP) content in the liquid phase follows a trend of acidity > control > alkalinity; The analysis of the results of solid-phase phosphorus fractionation extraction shows that acidic conditions are more conducive to the release of Non-apatite inorganic phosphorus (NAIP) and Apatite inorganic phosphorus (AP); The microbial community promotes the release of phosphorus by participating in the decomposition of fermentation substrates; The analysis of the change of metal content in the liquid phase before and after electrolysis showed that the two chamber electrolytic cell can not remove other metal components while recovering the vivianite; More than 90% of the phosphorus in the supernatant after fermentation was recovered by electrolysis. The characterization results showed that 84.66% of the precipitate was Vivianite.

The effect of different concentrations of fluoride in toothpastes with or without bioactive glass on artificial root caries.

OBJECTIVE: To investigate the effect of different toothpastes either containing 5,000ppm-F, 1,450ppm-F or bioactive glass (BG) with 540ppm-F on artificial root carious lesions (ARCLs). METHOD: The crowns of 23 extracted sound teeth were removed leaving their roots only. Subsequently, each root was divided into four parts. A total of 15 sound root dentine (SRD) was left untreated as baseline. The ARCLs were developed for the remaining roots using demineralisation solution (pH-4.8). 15-ARCLs samples were then left untreated. The rest of samples were divided into four groups (n = 15 each) and treated with Group-1(BG with 540ppm-F); Group-2(5000ppm-F); Group-3(1450ppm-F) and Group-4(deionised water). 13-day pH-cycling included using demineralisation solution for 6 h, then placing samples into remineralisation solution (pH-7) for 16 h. Each sample was brushed with the assigned toothpaste twice a day during pH-cycling. Fluoride concentrations at each time point were measured using F-ISE, whilst calcium (Ca2+) and phosphorus (P) ion release was determined using ICP-OES, KHN, XRD, 19F-MAS-NMR analyses. RESULTS: KHN showed significant surface changes for each group (p<0.001). The uptake of Ca2+ occurred at days 1-2, phosphorus ion loss was high when compared to the uptake in all groups. XRD showed presence of sharp diffraction lines evidencing apatite formation for Groups 1-3. 19F-MAS-NMR confirmed fluorapatite presence in Groups 1-3. CONCLUSION: All toothpastes were promising in fluorapatite formation. BG with 540ppm-F toothpaste released more ions (Ca2+and P) and reharden the artificial root carious lesions when compared to other groups. However, 1450ppm-F toothpaste showed more fluoride-substituted apatite formation whilst 5000ppm-F toothpaste had more fluorapatite formation. CLINICAL SIGNIFICANCE: Toothpaste containing BG with 540ppm-F, 5000ppm-F and 1450ppm-F toothpastes are likely to have a significant impact in reversing and arresting root caries. However, randomised controlled double-blinded clinical trials are required to translate these results into clinical practice.

Fabrication of Multifunctional Drug Loaded Magnetic Phase Supported Calcium Phosphate Nanoparticle for Local Hyperthermia Combined Drug Delivery and Antibacterial Activity.

Magnetic calcium phosphate nanoparticles are biocompatible and have attracted much attention as biomaterials for bone tissue engineering and theranostic applications. In this study, we report the fabrication of a biocompatible magnetic nickel ferrite supported fluorapatite nanoparticle as a bone substitute material with hyperthermia potential using a facile wet precipitation approach. The composition and magnetic properties of the sample were analyzed using X-ray diffraction (XRD) and a vibrating sample magnetometer (VSM). The presence of both magnetic (NiFe2O4 and γ-Fe2O3) and fluorapatite phases was identified, and the sample exhibited ferromagnetic behavior with saturation magnetization and coercivity of 3.08 emu/g and 109 Oe, respectively. The fabricated sample achieved the hyperthermia temperature of ∼43 °C under tumor mimic conditions (neglecting Brownian relaxation) in 2.67 min, and the specific loss power (SLP) was estimated to be 898 W/g(Ni+Fe) which is sufficient to prompt irreversible cell apoptosis. Biocompatibility of the synthesized nanoparticle was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tetrazolium (MTT) assay with fibroblast NIH 3T3 and L929 cells. An in vitro drug release experiment was conducted at pH 5 (tumor mimic) and 7.4 (physiological), which revealed a release of 49.8% in the former and 11.6% in the latter pH for 11 days. The prepared sample showed antibacterial activity against S. aureus.

High performance self-assembled nano-chlorapatite in the presence of lactonic sophorolipid for the immobilization of cadmium in polluted sediment.

A novel lactonic sophorolipid (LS) self-assembled nano-chlorapatite (LS-nClAP) was prepared for the immobilization of severe cadmium (Cd) in sediment. The experimental results indicated that the introduction of LS not only improved the dispersed performance of chlorapatite, but also brought massive hydroxyl and carboxyl groups, which significantly improved the immobilization efficiency of Cd and reduced its eco-toxicity in sediment. LS can significantly increase the effective utilization rate of phosphorus in chlorapatite, and reduce the content of available phosphorus (AP) by half after remediation compared with ClAP. Additionally, the participation of LS possessed a significant impact on the enzyme activities in the sediment, especially for urease, which was closely related to the effective stability of Cd and the introduction of LS. All experimental results of this study provided new insights into the possible effects of Cd immobilization by chlorapatite in contaminated sediments, demonstrating great application potential for sediment remediation in the future.

Calcareous Materials Effectively Reduce the Accumulation of Cd in Potatoes in Acidic Cadmium-Contaminated Farmland Soils in Mining Areas.

The in situ chemical immobilization method reduces the activity of heavy metals in soil by adding chemical amendments. It is widely used in farmland soil with moderate and mild heavy metal pollution due to its high efficiency and economy. However, the effects of different materials depend heavily on environmental factors such as soil texture, properties, and pollution levels. Under the influence of lead-zinc ore smelting and soil acidification, Cd is enriched and highly activated in the soils of northwestern Guizhou, China. Potato is an important economic crop in this region, and its absorption of Cd depends on the availability of Cd in the soil and the distribution of Cd within the plant. In this study, pot experiments were used to compare the effects of lime (LM), apatite (AP), calcite (CA), sepiolite (SP), bentonite (BN), and biochar (BC) on Cd accumulation in potatoes. The results showed that the application of LM (0.4%), AP (1.4%), and CA (0.4%) had a positive effect on soil pH and cations, and that they effectively reduced the availability of Cd in the soil. In contrast, the application of SP, BN, and BC had no significant effect on the soil properties and Cd availability. LM, AP, and CA treatment strongly reduced Cd accumulation in the potato tubers by controlling the total 'flux' of Cd into the potato plants. In contrast, the application of SP and BN promoted the migration of Cd from the root to the shoot, while the effect of BC varied by potato genotype. Overall, calcareous materials (LM, CA, and AP) were more applicable in the remediation of Cd-contaminated soils in the study area.

Thiourea-Capped Nanoapatites Amplify Osmotic Stress Tolerance in Zea mays L. by Conserving Photosynthetic Pigments, Osmolytes Biosynthesis and Antioxidant Biosystems.

Salinity is one of the most prevalent abiotic stresses which not only limits plant growth and yield, but also limits the quality of food products. This study was conducted on the surface functionalization of phosphorus-rich mineral apatite nanoparticles (ANPs), with thiourea as a source of nitrogen (TU-ANPs) and through a co-precipitation technique for inducing osmotic stress tolerance in Zea mays. The resulting thiourea-capped apatite nanostructure (TU-ANP) was characterized using complementary analytical techniques, such as EDX, SEM, XRD and IR spectroscopy. The pre-sowing of soaked seeds of Zea mays in 1.00 µg/mL, 5.00 µg/mL and 10 µg/mL of TU-ANPs yielded growth under 0 mM, 60 mM and 100 mM osmotic stress of NaCl. The results show that Ca and P salt acted as precursors for the synthesis of ANPs at an alkaline pH of 10-11. Thiourea as a source of nitrogen stabilized the ANPs' suspension medium, leading to the synthesis of TU-ANPs. XRD diffraction analysis validated the crystalline nature of TU-ANPs with lattice dimensions of 29 nm, calculated from FWHM using the Sherrer equation. SEM revealed spherical morphology with polydispersion in size distribution. EDS confirmed the presence of Ca and P at a characteristic KeV, whereas IR spectroscopy showed certain stretches of binding functional groups associated with TU-ANPs. Seed priming with TU-ANPs standardized germination indices (T50, MGT, GI and GP) which were significantly declined by NaCl-based osmotic stress. Maximum values for biochemical parameters, such as sugar (39.8 mg/g at 10 µg/mL), protein (139.8 mg/g at 10 µg/mL) and proline (74.1 mg/g at 10 µg/mL) were recorded at different applied doses of TU-ANP. Antioxidant biosystems in the form of EC 1.11.1.6 catalase (11.34 IU/g FW at 10 µg/mL), EC 1.11.1.11 APX (0.95 IU/G FW at 10 µg/mL), EC 1.15.1.1 SOD (1.42 IU/g FW at 5 µg/mL), EC 1.11.1.7 POD (0.43 IU/g FW at 5 µg/mL) were significantly restored under osmotic stress. Moreover, photosynthetic pigments, such as chlorophyll A (2.33 mg/g at 5 µg/mL), chlorophyll B (1.99 mg/g at 5 µg/mL) and carotenoids (2.52 mg/g at 10 µg/mL), were significantly amplified under osmotic stress via the application of TU-ANPs. Hence, the application of TU-ANPs restores the growth performance of plants subjected to induced osmotic stress.

Effect of Sandblasting with Fluorapatite Glass-ceramic Powder and Chemical Primers/Adhesives on Shear Bond Strength of Indirect Repairing Composite to Zirconia.

OBJECTIVE: To investigate the effect of sandblasting with fluorapatite glass-ceramic (FGC) powder on zirconia surface roughness, crystallinity, and shear bond strength (SBS) of indirect repairing composite to zirconia using different primers/adhesives. METHODS: Zirconia blocks were treated as follows: no treatment (control group), blasting with 30-µm silica-coated alumina (CoJet group), and blasting with FGC powder (FGC group). The surface topography, silica content, roughness, and crystallinity of treated zirconia surfaces were analyzed by a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), an optical profilometer, and X-ray diffraction (XRD), respectively. Four primers/adhesives (Monobond Plus, Calibra Silane, Futurabond M+, and Scotchbond Universal) were compared to bond precured resin composite to zirconia groups using Multilink Automix resin cement. Bonded specimens were thermocycled for 10,000 cycles and tested in SBS and the modes of failure were recorded. The effect of different surface treatments and primers/adhesives on SBS results were statistically analyzed using two-way ANOVA and Bonferroni post-hoc tests (α=0.05). RESULTS: Both CoJet and FGC groups showed rough surfaces with a higher content of silica in FGC, but less monoclinic crystals, compared to the CoJet group. The highest mean SBS was found in the FGC group treated with Monobond Plus compared to CoJet and Control groups. Adhesive failure was predominant in control groups, while combined failure was found in the CoJet and FGC groups regardless of the primers/adhesives employed. CONCLUSION: Sandblasting zirconia with FGC powder increased SBS of resin composite to zirconia with lower monoclinic phase transformation compared to CoJet sand. Monobond Plus reported the highest means of SBS values compared to other primers/adhesives.

A novel route to enhance the dissolution of apatite: Structural incorporation of hydrogen phosphate.

Potential use of hydroxyapatite nanoparticles (HANPs) [Ca10(PO4)6(OH)2] as slow P-release fertilizer (SRF) has recently attracted wider attention. However, commercially available HANP (with Ca/P ratio = 1.667) is the least soluble calcium phosphate and thus limits its full potential as an SRF in agronomic applications. In this research, we sought to enhance the dissolution rate of HANPs by enriching hydrogen phosphate (HPO42-) species in the phosphate (PO43-) structural sites. Seven different types of pure crystalline HANPs were synthesized at a range of Ca/P ratio from 1.46 (at pH 6.0) to 2.10 (at pH 12.0). Complementary results from FTIR and solid-state 31P MAS NMR spectroscopies showed that HPO42- species is most abundant in HANPs crystallized at pH 6.0 and gradually depleted at higher pH products. The rate of depletion of HPO42- species is proportional to the increase in carbonate incorporation into the HANP lattice, which preferentially forms B-type carbonated HANPs. The enhanced dissolution rate of HANPs due to hydrogen phosphate incorporation was tested using a flow-through macro-dialysis system that limits the partial transition of HANPs to other solid phases, which otherwise interfere with dissolution. The results show that the dissolution rate of HANPs increased with decreasing pH of synthesis and was highest in HANPs at pH 6.0. The dissolution rate differed by ten times between HANPs synthesized at pH 7.0 and 10.0. Overall, the atom-efficient synthetic route developed and the ability to tune the dissolution rate of HANPs are significant steps forward in improving the P-release efficiency of a potent SRF and is expected to contribute to efforts toward enhancing agricultural sustainability.

Fabrication of strontium carbonate-based composite bioceramics as potential bone regenerative biomaterials.

Strontium carbonate (SrC) bioceramics are proposed as potential biomaterials to efficaciously repair the bone defects. However, the development of SrC bioceramics is restricted by their intrinsic low mechanical strength. In this study, SrC-based composite bioceramics (SrC-SrP) were fabricated by incorporating strontium-containing phosphate glass (SrP). The results indicated that aside from the main crystalline phase SrC, new compounds were generated in the SrC-SrP bioceramics. Incorporating 10 wt% SrP promoted densification, thus dramatically improving compressive strength of SrC-SrP bioceramics. The SrC-SrP bioceramics facilitated apatite precipitation on their surface, and sustainedly released strontium, phosphorus and sodium ions. Compared with the well-known ß-tricalcium phosphate bioceramics, the SrC-SrP bioceramics with certain amounts of SrP enhanced proliferation, alkaline phosphatase activity and osteogenesis-related gene expressions of mouse bone mesenchymal stem cells. The SrC-SrP bioceramics with appropriate constituent can serve as novel bone regenerative biomaterials.

Combined apatite, biochar, and organic fertilizer application for heavy metal co-contaminated soil remediation reduces heavy metal transport and alters soil microbial community structure.

Soil amendments are used extensively to remediate soils contaminated with heavy metals. However, the effects of soil amendments on heavy metal bioavailability, plant yield, and bacterial community structure in tropical farmland soils remain largely unknown. In the present study, seaweed organic fertilizer (S), apatite (A), biochar (B), and seaweed organic fertilizer-apatite-biochar mixtures (SAB) were applied at different rates to assess their influence on cadmium (Cd), lead (Pb), and chromium (Cr) bioavailability in contaminated farmland soils, using different component ratios and doses in maize field plots, and maize yield. Effects on soil bacterial community structure were also evaluated based on high-throughput sequencing. Following addition of 2 % S + A + B combined amendment at a ratio of 1:0.5:1.5 (2%S1A0.5B1.5), soil pH and electrical conductivity (EC) were elevated, and bioavailable Cd, Pb, and Cr concentrations were reduced in potted soils, leading to higher heavy metal immobilization. Under field conditions, soil pH, EC, organic matter, ammonium­nitrogen, available phosphorus, available potassium, and crop productivity were all increased considerably, whereas soil Cd and Cr bioavailability were lower in the combined amendment treatments than in the control treatments. Particularly, application of a 2.49 t·ha-1 combined amendment (0.83 t·ha-1 S + 0.41 t·ha-1A + 1.25 t·ha-1B,1:0.5:1.5) decreased Cd, Pb, and Cr concentrations in maize grain by 68.9 %, 68.9 %, and 65.7 %, respectively. Species abundance and evenness in bacterial communities increased in field soils subjected to combined amendments, with shifts in community structure and function mostly driven by changes in soil pH, organic matter content, and nutrient availability. Overall, the results suggest that 1.5%S1A0.5B1.5 is the optimal treatment for remediating heavy metal co-contaminated soil, and thereby, improving maize yield and quality. Combined organic and inorganic amendments achieve high remediation efficiency, mainly by improving chemical properties, reducing heavy metal bioavailability, and altering bacterial community structure and function in heavy metal contaminated farmland soils.

Fabrication and in vitro evaluation of 3D printed porous silicate substituted calcium phosphate scaffolds for bone tissue engineering.

Silicate-substituted calcium phosphate (Si-CaP) ceramics, alternative materials for autogenous bone grafting, exhibit excellent osteoinductivity, osteoconductivity, biocompatibility, and biodegradability; thus, they have been widely used for treating bone defects. However, the limited control over the spatial structure and weak mechanical properties of conventional Si-CaP ceramics hinder their wide application. Here, we used digital light processing (DLP) printing technology to fabricate a novel porous 3D printed Si-CaP scaffold to enhance the scaffold properties. Scanning electron microscopy, compression tests, and computational fluid dynamics simulations of the 3D printed Si-CaP scaffolds revealed a uniform spatial structure, appropriate mechanical properties, and effective interior permeability. Furthermore, compared to Si-CaP groups, 3D printed Si-CaP groups exhibited sustained release of silicon (Si), calcium (Ca), and phosphorus (P) ions. Furthermore, 3D printed Si-CaP groups had more comprehensive and persistent osteogenic effects due to increased osteogenic factor expression and calcium deposition. Our results show that the 3D printed Si-CaP scaffold successfully improved bone marrow mesenchymal stem cells (BMSCs) adhesion, proliferation, and osteogenic differentiation and possessed a distinct apatite mineralization ability. Overall, with the help of DLP printing technology, Si-CaP ceramic materials facilitate the fabrication of ideal bone tissue engineering scaffolds with essential elements, providing a promising approach for bone regeneration.

Identifying spatial influence of urban elements on road-deposited sediment and the associated phosphorus by coupling Geodetector and Bayesian Networks.

Elevated particles and phosphorus washed from road-deposited sediment (RDS) are noteworthy causes of eutrophication in urban water bodies. Identifying how urban elements (e.g., dwellings, roads) spatially influence RDS and the associated phosphorus can help pinpoint the primary management areas for RDS pollution and therefore effectively mitigate this problem. This study investigated spatial influence of urban elements on RDS build-up load and phosphorus load in Hanyang district of Wuhan city in central China. Bayesian Networks (BNs), combined with geographical detector (Geodetector) and correlation analysis, were applied to quantify spatial association between kernel density of urban elements, RDS build-up load and phosphorus load in RDS. Results showed that (1) areas with higher density of factories related elements usually had elevated level of RDS build-up load, aluminum-bound phosphorus (Al-P), occluded phosphorus (Oc-P), organophosphorus (Or-P). Higher load of RDS associated iron-bound phosphorus (Fe-P) and apatite phosphorus (Ca-P) usually occurred where dwellings, catering, and entertainment related elements were concentrated. (2) Urban elements mainly showed positive correlation with RDS build-up load, Fe-P, Ca-P, De-P (detrital apatite phosphorus), while they chiefly showed negative correlation with Ex-P (exchangeable phosphorus), Al-P, Oc-P, and Or-P. Bus stations, dwellings, and factories related elements had relatively strong determinant power over spatial stratified heterogeneity of RDS and RDS-associated phosphorus. (3) Geodetector and correlation analysis could boost factors filtering and construction of network structures in the process of developing BNs models. The developed BNs resulted in sound prediction of <150 µm RDS build-up load and phosphorus load, given that the prediction accuracy of models ranged from 0.532 to 0.657. These findings demonstrate that urban elements are useful spatial predictors of RDS pollution, and coupling Geodetector and BNs is promising in RDS pollution prediction and supporting urban nonpoint source pollution management.

Functional role of inorganic trace elements in dentin apatite tissue-part III: Se, F, Ag, and B.

Dentin hydroxyapatite possesses a unique versatile structure which allows it to undergo ionic substitutions. Trace elements play pivotal roles within the oral cavity, especially in dentin apatite tissue. Therefore, it is critical to explore the role of these elements in dentin apatite structure. The roles of other inorganic elements in dentin apatite were discussed in part I (Mg, Sr, Zn, and Fe) and part II (Cu, Mn, Si, and Li) of these series. In the last part of the review series, the role of selenium, fluorine, silver, and boron in the regulation of dentin apatite structure and function was discussed. We evaluated how these elements affect the overall size, morphology, and crystallinity of dentin apatite crystals. Moreover, we investigated the importance of these elements in regulating the solubility of dentin apatite. An electronic search was performed on the role of these trace elements in dentin apatite from January 2010 to January 2022. The concentration of selenium in teeth has been explored only recently, particularly its incorporation into dentin apatite. Silver nanomaterials inhibit the growth of cariogenic microorganisms as well as arrest the degradation of collagen. Fluorine was found to have important roles in dentin remineralization and dentinal tubule occlusion, making it widely used for hydroxyapatite doping. Boron is critical for mineralized tissues like bone, dentin, and enamel, but its exact role in dentin apatite is unknown. Therefore, understanding the impact of these elements on dentin apatite is potentially transformative, as it may help to fill a significant knowledge gap in teeth mechanics.

Effect of application mode (capping and amendment) on the control of cadmium release from sediment by apatite/calcite mixture and its phosphorus release risk.

In this research, the influence of application mode (capping and amendment) on the control of cadmium (Cd) liberation from sediment by apatite/calcite mixture and its phosphorus release risk were investigated. The results showed that calcite addition had a limited effect on the speciation of Cd in sediment, but apatite addition had a significant impact on the fractionation of Cd in sediment. Apatite amendment could effectively immobilize the most readily mobilized Cd by transferring the acid-soluble fraction to the reducible and residual fractions. Apatite addition also could effectively reduce the concentration of toxicity characteristic leaching procedure (TCLP)-leachable Cd in sediment, and apatite had a much higher reduction efficiency of TCLP-leachable Cd than calcite. Apatite/calcite mixture capping could reduce the risk of Cd liberation from sediment into the overlying water, and the controlling efficiency of apatite/calcite mixture capping was higher than that of apatite/calcite mixture amendment. The effect of apatite/calcite mixture addition on the concentration of reactive soluble phosphorus (SRP) in the overlying water was limited. The introduction of calcite into the apatite capping layer could lower the risk of phosphorus release from apatite to the overlying water as compared to single apatite capping. However, the apatite/calcite mixture capping layer still had a relatively high risk of phosphorus liberation into the overlying water. Results of this work suggest that apatite/calcite mixture has a high potential to be used as a capping material to control Cd release from sediment from the perspective of controlling efficiency and application convenience.

Solvothermally-derived nanoglass as a highly bioactive material.

A highly bioactive glass solvBG76 in a binary system 76SiO2-24CaO (wt%) was prepared following a solvothermal path of the synthesis. The facile synthesis, in terms of the steps and reagents needed, enabled the achievement of a mesoporous material. Many factors such as nano-size (<50 nm), different morphology (non-spherical), use of an unconventional network modifier (calcium hydroxide) during the synthesis, a structure free of crystalline impurities, and textural properties greatly enhanced the kinetic deposition process of hydroxyapatite (HA) when contacting with physiological fluids. The formation of a HA layer on the glass was analyzed by various techniques, namely XRD, IR-ATR, Raman, XPS, EDS analyses, SEM, and HR-TEM imaging. The results obtained were compared to the 45S5 glass tested as a reference biomaterial as well as 70S30C-a glass with similar size and composition to reported solvBG76 but obtained by the conventional sol-gel method. For the first time, superior apatite-mineralization ability in less than 1 h in a physiological-like buffer was achieved. This unique bioactivity is accompanied by biocompatibility and hemocompatibility, which was indicated by a set of various assays in human dermal fibroblasts and MC3T3 mouse osteoblast precursor cells, as well as hemolytic activity determination.

Phosphorus transformation during the carbonaceous skeleton assisted thermal hydrolysis of sludge.

On the basis of the carbonaceous skeleton assisted thermal hydrolysis that we proposed to achieve efficient sludge dewatering, this work further explored phosphorus (P) transformation in the process. The results showed that during independent thermal hydrolysis in the temperature range of 120-240 °C, organic-P was first decomposed into soluble-P and particulate-P in liquid, and then combined with Ca, Fe, and Al to form more apatite-P (AP) and less non-apatite inorganic-P (NAIP). When the skeleton assisted the sludge thermal hydrolysis, the turning point of the hydrolysis temperature would reduce from 180 °C to 150 °C, at which the liquid-P began to decrease and the organic-P generally decomposed. Moreover, the increment in the content of AP halved while that of NAIP doubled compared to that in the process without the carbonaceous skeleton. These effects come from the exogenous components introduced by adding the skeleton, which were different from the sludge. Compared with the P-rich compound and metal elements that tend to bond with phosphate introduced by the skeleton, hemicellulose as a main organic component played a leading role in the different P transformations of AP and NAIP. The hemicellulose slightly increased the acidity of sludge products, thereby inhibiting AP production and promoting the production of recyclable NAIP. Overall, the carbonaceous skeleton assisted thermal hydrolysis was beneficial for P recovery with a very low filtrate loss rate.

Tunable Enzyme-Assisted Mineralization of Apatitic Calcium Phosphate by Homogeneous Catalysis.

While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO32- and F-, in the HAP lattice at different positions.

Sustainable phosphorus management in soil using bone apatite.

Soil fertility and phosphorus management by bone apatite amendment are receiving increasing attention, yet further research is needed to integrate the physicochemical and mineralogical transformation of bone apatite and their impact on the supply and storage of phosphorus in soil. This study has examined bone transformation in the field over a span of 10-years using a set of synchrotron-based microscopic and spectroscopic techniques. Transmission X-ray microscopy (TXM) observations reveal the in-situ deterioration of bone osteocyte-canaliculi system and sub-micron microbial tunneling within a year. Extensive organic decomposition, secondary mineral formation and re-mineralization of apatite are evident from the 3rd year. The relative ratio of (v1 + v3) PO43- to v3 CO32- and to amide I increase, and the v3c PO43- peak exhibits a blue-shift in less than 3 years. The carbonate substitution of bone hydroxyapatite (HAp) to AB-type CHAp, and phosphate crystallographic rearrangement become apparent after 10 years' aging. The overall CO32- peak absorbance increases over time, contributing to a higher acid susceptibility in the aged bone. The X-ray Photoelectron Spectroscopy (XPS) binding energies for Ca (2p), P (2p) and O (1s) exhibit a red-shift after 1 year because of organo-mineral interplay and a blue-shift starting from the 3rd year as a result of the de-coupling of mineral and organic components. Nutrient supply to soil occurs within months via organo-mineral decoupling and demineralization. More phosphorus has been released from the bones and enriched in the associated and adjacent soils over time. Lab incubation studies reveal prominent secondary mineral formation via re-precipitation at a pH similar to that in soil, which are highly amorphous and carbonate substituted and prone to further dissolution in an acidic environment. Our high-resolution observations reveal a stage-dependent microbial decomposition, phosphorus dissolution and immobilization via secondary mineral formation over time. The active cycling of phosphorus within the bone and its interplay with adjacent soil account for a sustainable supply and storage of phosphorus nutrients.

Multi-Wall Carbon Nanotubes, Metal Oxide and Hydroxy-Apatite Nanoparticles Enhanced Plant Growth Promoting Capabilities of Root Endosymbionts of Cowpea (Vigna unguiculata (L.) Walp.).

The present study was aimed to evaluate the effect of three different nanomaterials (NMs) on the growth, physiology and protein profile of the endosymbiotic bacteria isolated from the root nodules of vegetable cowpea. The alterations in growth and viability of the bacterial cells, their indole-acetic acid (IAA) and siderophore production abilities, phosphate solubilization potential and total protein content were assessed. Further, the isolates were also analyzed for changes in their exopolysaccharide (EPS) production and secretion behavior with exposure to different concentrations of the NMs. The NM supplementation of the broth improved the growth, viable cell count, IAA content, siderophore production and potential to solubilize tri-calcium phosphate (TCP) as sole phosphorus (P)-source. The NMs also improved the total protein content of the bacterial cells indicating the improved physiology and biochemistry of the treated bacterial cells. The treated cells produced significantly high EPS compared to untreated control cultures. The present investigation revealed that the NMs improved plant growth abilities of cowpea root endosymbiotic bacteria, though the impact varied across various isolates as well as NM concentrations.