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Local cattle (lamb and camel) bones were used as a starting material to obtain pure nano‐hydroxyapatite n‐HAp. Extraction of nano‐HAp is done at 700 °C and 900 °C calcination temperatures, followed by some characterization technics such as FTIR spectroscopy, UV‐visible spectroscopy, XRD diffraction pattern, SEM and EDX analyzes. All the technics used have confirmed that calcination at these temperatures leads to a material in which pure hydroxyapatite is the only crystallographic phase. The heavy metals removal capacity of n‐HAp applied to Cu2+ and Co2+ from aqueous solutions was exanimated and compared. The obtained results were interpreted and compared based on; (i) the calcination temperature, (ii) the nature of the adsorbed cation on the nano‐hydroxyapatite surface and (iii) the nature of the adsorbent. [ABSTRACT FROM AUTHOR]

This study proposes an ultrasound-horn system for the extraction of a natural active compound “artemisinin” from Artemisia annua L. leaves as an alternative to hot maceration technique. Ultrasound leaching improves artemisinin recovery at all temperatures where only ten minutes is required to recover 70% (4.42 mg g −1 ) compared to 60 min of conventional hot leaching for the same yield. For instance, ultrasound treatment at 30 °C produced a higher yield than the one obtained by conventional maceration at 40 °C. Kinetic study suggests that the extraction pattern can be assimilated, during the first ten minutes, to a first order steady state, from which activation energy calculations revealed that each gram of artemisinin required 7.38 kJ in ultrasound versus 10.3 kJ in the conventional system. Modeling results indicate the presence of two extraction stages, a faster stage with a diffusion coefficient of 19 × 10 −5 cm 2 min −1 for ultrasound technique at 40 °C, seven times higher than the conventional one; and a second deceleration stage similar for both techniques with diffusion coefficient ranging from 1.7 to 3.1 × 10 −5 cm 2 min −1 . It is noted that the efficient ultrasound extraction potential implies extraction of higher amount of co-metabolites so low artemisinin crystal purity is engendered but a combination with a purification step using activated charcoal and celite adsorbents produced crystals with comparable purity for conventional and ultrasound samples. [ABSTRACT FROM AUTHOR]

Understanding phosphonates-CaHAp structure interaction and its role in the control of CaHAp particles properties is of interest for the development of biomaterials able for repairing the skeletal system. In this work, the direct synthesis by hydrothermal method of calcium hydroxyapatite (CaHAp)-phosphonic acids (PA) nanocomposites was carried out in the presence of increasing contents of methylphosphonic (MPA) and vinylphosphonic (VPA) acids in the solution. The new CaHAp-PA composite formation was confirmed by IR, Raman and NMR-MAS spectroscopy, and by chemical and thermal analyses. PA amount in composites increased with their added content and MPA showed a greater affinity for CaHAp. A part of PA substituted phosphate groups in CaHAp structure and another was grafted on its surface via Ca-OH sites. X-ray powder diffraction showed that the presence of the PA did not inhibit CaHAp nucleation, but reduced the growth of their crystals and affected their crystallinity. TEM observations revealed nanosized crystallites and confirmed the dimension reduction, which is in agreement with the increase of the surface area up to 250 m 2 g −1 . Taken together, the characteristics of the obtained CaHAp-PA nanocomposites suggest their usefulness for the preparation of biomaterials for bone replacement. [ABSTRACT FROM AUTHOR]

Highlights: [•] Our studies of apatite–etidronic acid hybrid compounds highlight the influence of apatitic surface in grafting process. [•] We showed that the apatitic surface possesses two different functional groups Ca OH and P OH acting as the active sites. [•] Synthesizing CaHAp-(ETD) composites offers a relevant tool as possible application as biomaterials to repair bone tissues. [ABSTRACT FROM AUTHOR]

Abstract: Mixed calcium–copper hydroxyapatite (Ca–CuHAp), with general formula Ca(10−x)Cu x (PO4)6(OH)2, where 0≤ x ≤0.75 was prepared in aqueous medium in the presence of different concentrations of poly-l-aspartic acid (PASP). XRD, IR, TG-DTA, TEM-EDX, AFM and chemical analyses were used to characterize the structure, morphology and composition of the products. All techniques show the formation of new hybrid compounds Ca–CuHAp–PASP. The presence of the grafting moiety on the apatitic material is more significant with increasing of copper amount and/or organic concentration in the starting solution. These increases lead to the affectation of apatite crystallinity. The IR spectroscopy shows the conservation of (Pof (HPO4)2− groups, suggesting that PASP acid was interacted only with metallic cations of hydroxyapatite. [Copyright &y& Elsevier]

Abstract: The nature of apatite–organic molecule interaction was the subject of many investigations. Grafting the organic molecule onto the inorganic support may precede through either formation of covalent bonds or ionic interaction between superficial hydroxyl on the apatite surface and organic functions. The hybrid materials obtained by functionalization of apatite surfaces with phosphonate moieties are of interest for their potential applications such in catalysis, chromatography and biomedical domain. In this scope, calcium hydroxyl and fluoroapatite (CaHAp and CaFAp) were prepared in the presence of the methyl phosphonic dichloride (MPO), by contact method in organic solvent at 25°C for 2 days. The products are rigorously characterized by chemical analysis, infrared (IR), MAS-NMR spectroscopies, powder X-ray diffraction (XRD), atomic force microscopy (AFM) and specific surface area (SSA). The X-ray powder analysis showed that the crystallinity was sensibly affected by the presence of organic moieties. The IR spectroscopy showed new vibration modes appearing related to phosphonate groups essentially at 2930, 1315, 945, 764 and 514cm−1. The 31P MAS NMR spectrum for hydroxy and fluoroapatite exhibits a single signal at 2.8ppm. After reaction with (MPO) the spectra show the presence of new signals, assigned to the formation of organic–inorganic bond between the superficial hydroxyl groups of the apatite ( (methyl phosphonic dichloride. The SSA decreases with increasing phosphonate amount especially for CaHAp modified by (MPO). AFM indicated that the texture surface was changed by grafting. [Copyright &y& Elsevier]

Abstract: The new hybrid inorganic–organic composites, Ca(10−x)Zn x (PO4)6(OH)2-lactic acid, at different amounts of zinc and lactic acid were prepared by dissolution of the organic compound in an hydroxyapatite suspension. They were characterized by XRD, IR, MAS NMR (13C and 1H) and chemical analysis. The crystallinity was slightly affected by the presence of organic fragments. IR and (13C and 1H) MAS NMR measurements indicate that the carboxylic groups of the acid interact with calcium and zinc ions of hydroxyapatite surface. Chemical analysis displays that zinc promotes the acid grafting. A mechanism of surface modification is proposed based on the obtained results. [Copyright &y& Elsevier]

Abstract: The reactivity of the surface of calcium hydroxyapatite (CaHAp) and fluorapatite (CaFAp) was tested and compared by grafting the 1-octylphosphonic dichloride (C8H17OPCl2) using a molar ratio x =2 or 4, x = n(organic)/n(apatite). Successful synthesis was confirmed by different characterisation techniques such as X-ray powder diffraction patterns, IR spectroscopy, MAS-NMR (1H and 31P) and chemical analysis. The difference between their specific surface area (SSA: 57.46 for HAp and 12.09m2/g for FAp), the percentage of carbon measured after treatment with (C8H17OPCl2) and the intensities of IR bands attributed to the grafted moiety suggests that the surface of hydroxyapatite is more reactive than that of fluorapatite. The 31P CP-MAS-NMR spectra of treated fluorapatite show a significant change in isotropic signal due to the protonation and deprotonation of superficial phosphate group. This can be explained by the difference in the nature of inorganic material. [Copyright &y& Elsevier]

Abstract: Cadmium substituted strontium hydroxy- and fluoro-apatites, Sr(10−x)Cd x (PO4)6Y2 (Y=OH and F), have been prepared as single phases in the 0≤ x ≤4 interval for the former and 0≤ x ≤6 for the latter compound, respectively. The refinements of the X-ray full powder patterns allowed the structure determination of nine samples, and showed a preference of cadmium atoms for the M(1) site in fluoroapatite samples. IR investigation gave information about the nature of the metal oxygen interactions. The obtained results are used for a comparative discussion about the factors which drive the mutual substitution of Ca, Sr, Cd and Pb in apatites. The important role of electronegativity and polarisability, as well as of ionic radii, is evidenced. [Copyright &y& Elsevier]

Abstract: The present article details the formation of lanthanum-modified apatites and the binding process of tartrate ions with these obtained apatites. Chemical analyses, FT-IR and 31P NMR spectroscopies, XRD powder, TGA, and TEM analyses were employed for studying the reaction between Ca10(PO4)6(OH)2 (HAp) or Ca10(PO4)6(F)2 (FAp) and LaCl3. The reaction was found to take place mainly through partial dissolution of the apatite followed by precipitation of a new phase containing lanthanum phosphate. When La3+ was introduced in the presence of L(+)-tartaric acid (TAH2), no fundamental changes were observed in the HAp or FAp structures. However, there did occur a formation of a new phase of Ca or/and La tartrate salt. [Copyright &y& Elsevier]

Abstract: The reaction between phenyl phosphonic dichloride (C6H5P(O)Cl2) and synthetic calcium hydroxy- and fluorapatite has been investigated. The presence of mono- or polymeric (C6H5PO) fragment bound to hydroxyapatite was evidenced by IR, and solid-state 31P NMR spectroscopy. X-ray powder analysis has shown that the apatitic structure remains unchanged during the reaction. In contrast, no reaction was found using fluorapatite. According to the results found for these two different apatites a mechanism was proposed for the formation of covalent P–O–P bonds as the result of a reaction between the C6H5P(O)Cl2 organic reagent and (HPO4)− and/or OH− ions of the hydroxyapatite. [Copyright &y& Elsevier]

Abstract: Solid solutions of cadmium and lead fluoroapatite [Pb(10− x )Cd x (PO4)6F2 (0⩽x⩽5)] were synthesized by a wet process in a basic medium. Replacement of lead by cadmium induces a linear variation of the crystallographic parameters “a” and “c” according to Végard''s law. The cadmium content, as obtained from the refinement, is in agreement with the chemical analysis. The distribution of the lead and cadmium ions between two non-equivalent crystallographic sites, M(1) and M(2), was determined by the Rietveld method. The site-occupancy factors of atoms clearly indicate a preference of cadmium for site M(1) in the apatite structure in agreement with its smaller ionic radii. A progressive shift of the F− ion toward the center of the triangles formed by the site M(2) metals has been observed with increasing cadmium content. [Copyright &y& Elsevier]

Abstract: Solid solutions in the system Pb(10− x )Sr x (PO4)6F2, 0⩽x⩽10, were obtained as apatitic phases from aqueous medium. They were investigated by X-ray diffraction, chemical analysis and infrared (IR) spectroscopy. The results of the structural refinements indicated that the substitution of lead by strontium induces a regular decrease of the lattice constant “a” and a preferential strontium distribution in site M(1). A progressive shift of the F− ion position along the apatitic channel was detected and confirmed by IR evidence. The different character of the M–F and M–O interactions was invoked to justify the structural differences observed as a function of composition. [Copyright &y& Elsevier]

Tetradenia riparia (commonly known as ginger bush) is frequently used in traditional African medicine to treat foodborne infections including diarrhoea, gastroenteritis, and stomach ache. The present study aims to identify in Tetradenia riparia the compounds active against foodborne pathogens. Dried Tetradenia riparia leaf powder was consecutively extracted with hexane, ethyl acetate, methanol and water. The hexane extract was counter-extracted with methanol:water (9:1), and after evaporation of the methanol, this phase was extracted with dichloromethane. The water extract was counter-extracted with butanol. All these fractions were tested against a panel of foodborne bacterial pathogens. A bioassay-guided purification was performed to isolate antimicrobial compounds using Staphylococcus aureus as a target organism. Further, antibiofilm activity was evaluated on S. aureus USA 300. The dichloromethane fraction and ethyl acetate extract were the most potent, and therefore subjected to silica gel chromatography. From the dichloromethane fraction, one active compound was crystalized and identified using NMR as 8(14),15-sandaracopimaradiene-7alpha, 18-diol (compound 1). Two active compounds were isolated from the ethyl acetate extract: deacetylumuravumbolide (compound 2) and umuravumbolide (compound 3). Using a microdilution method, their antimicrobial activity was tested against eight foodborne bacterial pathogens: Shigella sonnei , S. flexneri , Salmonella enterica subsp. enterica , Escherichia coli , Micrococcus luteus , S. aureus , Enterococcus faecalis , and Listeria innocua. Compound 1 had the strongest activity (IC 50 ranging from 11.2 to 212.5 μg/mL), and compounds 2 and 3 showed moderate activity (IC 50 from 212.9 to 637.7 μg/mL and from 176.1 to 521.4 μg/mL, respectively). Interestingly, 8(14),15-sandaracopimaradiene-7alpha, 18-diol is bactericidal, and also showed good antibiofilm activity with BIC 50 (8.8 ± 1.5 μg/mL) slightly lower than for planktonic cells (11.4 ± 2.8 μg/mL). These results support the traditional use of this plant to conserve foodstuffs and to treat gastrointestinal ailments, and open perspectives for its use in the prevention and treatment of foodborne diseases. [Display omitted] [ABSTRACT FROM AUTHOR]

The aim of this work is to study and identify the best conditions for peroxidase immobilization on chitosan (CS)–decorated Alumina–Zirconia–Titania composites (AZT) activated with glutaraldehyde. A statistical method such as response surface methodology was used to carry out the optimization investigation based on AZT composites, the concentration ranges (20–80 mg), glutaraldehyde concentrations (0.5–3.5%), enzyme (50–200 units), and pH (5.5–8.5). The system achieved a maximum immobilization efficiency of 91.3% against 91.92%, and maximum enzyme activity was 181.26 vs. 182.6 unit/g of the predicted and actual results, respectively. These values were obtained using 40 mg of AZT composites, 1.5% of glutaraldehyde, 200 units of enzyme, and pH 6.5. X-ray diffraction patterns were used to study the mineralogical structure of the prepared AZT and CS/AZT. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy were used to investigate and characterize the morphological/chemical properties of the immobilized peroxidase on CS/AZT. After 15 repetitions, the residual immobilized peroxidase activity was found to be 85%. The residual activity of immobilized and free enzymes after 12 weeks of storage at 4 °C was determined to be 81% and 32% of their initial activity, respectively. As a result of all the above-mentioned properties and values, it is possible to conclude that adopting technology for peroxidase immobilization is promising and plays a role in the field of industrial applications. [ABSTRACT FROM AUTHOR]

The correlation of the phase structure, dielectric, and ferroelectric properties of lead-free (1-x)(Na 0.5 Bi 0.5)TiO 3 –xK 0.5 Na 0.5 NbO 3 (NBTKNx) (0 = x ≤ 0.1) polycrystalline ceramics, fabricated via a solid state reaction technique, were investigated. The Rietveld refinement allowed identifying the crystallographic transformation from a rhombohedral to a coexisting rhombohedral-tetragonal or tetragonal long range-ordered ferroelectric (FE) phase. The dielectric investigations showed an increase of the dielectric diffuseness (1.53 = γ ≤ 1.73) and a clear shift of the depolarization temperature (T d) to a lower temperature while increasing substitution. More importantly, the lattice disorder also generated a plateau-like dielectric anomaly, leading to a thermally stable ϵ r ∼2859 ± 20% (120–500 °C) and ∼3112 ± 10% (120–420 °C) for x = 0.075 and 0.1 samples, respectively. At room temperature (RT) , Raman spectroscopy investigations revealed a downshift of the frequencies as a function of the composition with an inhomogeneous broadening of the Raman lines. On heating, Raman spectra showed changes in the region where the dielectric transitions are observed. Moreover, the composition dependence of the current peaks in the I-E loops confirmed the occurrence of a phase transition from a non-ergodic polar phase to an ergodic weakly polar after the applying of an electric field of 60 kV/cm−1. [ABSTRACT FROM AUTHOR]

Structural study of fluorapatite containing magnesium in substitution. The crystal structure refinement of a serial of solid solutions Ca10–xMgx(PO4)6F2, prepared with 2.5 ;5.0 ;10.0 ;15.0 ; 20.0 and 30.0 atom% of magnesium, was carried out by the Rietveld method. Chemical analysis showed that the total incorporated magnesium in each solid solution was 2.3, 4.7, 9.6, 14.4, and 18.5 atom%, respectively. Those obtained by structural refinement indicated that the limit substitution was 16.8 atom%. Occupancy factors showed that magnesium prefer to occupy the site S(II); for ratios higher then 10 atom%, repartition became quasi-statistical. The substitution limit and the cationic repartition were correlated to physicochemical properties of the ions. To cite this article: M. Hidouri et al., C. R. Chimie 7 (2004). [Copyright &y& Elsevier]

The online version of the original article can be found at https://doi.org/10.1007/s10562-022-04185-y. B Correction to: Catalysis Letters (2022) b https://doi.org/10.1007/s10562-022-04185-y The original version of this article unfortunately contained an error in the affiliation of the author Dr. Muhammad Bilal. [Extracted from the article]

Copper-substituted calcium in hydroxyapatite nanocrystals (CuHAp) were synthesized by co-precipitation method and characterized using various analyses. Structural and chemical characterizations indicate that copper was quantitatively incorporated into the HAp structure, replacing calcium up to 15 at.%. The presence of copper in the HAp structure affected clearly its crystallinity and reduced its crystallite sizes. Rietveld analysis showed a regular decrease of the CuHAp cell parameters a and c. Moreover, this substitution caused a shift in the infrared absorption bands and the nuclear magnetic resonance signals of phosphate groups and a decrease in the thermal stability. Morphological characterizations indicated that the prepared CuHAp consists of extremely thin needle-shaped nanocrystals with a greater aggregation, and confirmed the decrease in crystal size that was associated to the increasing in the surface area. The prepared CuHAp nanocrystals showed a high catalytic effect (up to 70%) in the discoloration of the Naphthol Blue Black solutions. [ABSTRACT FROM AUTHOR]