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Phosphorus (P) adsorption from aqueous solutions is usually evaluated by monitoring the P concentration and employed kinetic models. In this work, three adsorbents obtained from eggshell (ES) and eggshell mixed with palm mesocarp fiber (ESF-1:1 and ESF-1:10) at different Ca(OH) 2 /CaCO 3 compositions were evaluated, and the Ca-P species formed monitored as a function of time deconvoluting Fourier Transform Infrared (FTIR) spectra. At 0.25 h the ESF-1:10 (Ca(OH) 2 : 26.2 wt%) exhibited better adsorption performance of 35 mgg -1 while ESF-1:1 and ES (Ca(OH) 2 : 2.8 and 3.0 wt%) showed 26 and 4 mgg -1 , respectively. Characteristic PO 4 3- bands in apatite were corroborated by XRD and FTIR. It was found that the role of Ca(OH) 2 in the adsorption ends before 0.25 h, and thereafter CaCO 3 becomes the phase responsible for the removal of orthophosphate H 2 PO 4 - /HPO 4 2- /PO 4 3- ions. The results indicate a direct ligand exchange of CO 3 2- for PO 4 3- that takes place while increasing the apatite crystallinity. On the other hand, the P adsorption process is also dependent on P concentration. At low P concentrations, characteristic bands of PO 4 3- in apatite were observed in FTIR, while at high concentrations, characteristic bands for adsorbed HPO 4 2- were obtained. The obtained results give a relevant role to CaCO 3 in P adsorption. Kinetic analysis for Ca-based biocomposites showed that the Avrami order kinetic model fits better for the adsorbents. For P adsorption isotherm process the Langmuir's isotherms showed a good fit, with a maximum adsorption capacity of 90.8, 134.0, and 67.9 mgg -1 for ES, ESF-1:1, and ESF-1:10, respectively., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

We report a comprehensive comparative study of ferroelectric and piezoelectric properties of BNT-BKT-BT ceramics through the MPB (morphotropic phase boundary) zone, from the rhombohedral to the tetragonal phases in the system (97.5- x )(Bi 0.5 Na 0.5 )TiO₃ + x (Bi 0.5 K 0.5 )TiO₃ + 2.5(BaTiO₃), where x = 0 to 24.5 mol %. The structural transitions were studied by XRD patterns and Raman spectra. The MPB was confirmed between x = 10 and 12.5 mol % BKT. The dielectric/ferroelectric/piezoelectric properties of the BNT-BKT-BT system are maximized in the MPB region exhibiting a dielectric constant of 1506, a remanent polarization of 34.4 μC/cm², a coercive field = 36.9 kV/cm, and piezoelectric values of d 33 = 109 pC/N, k t = 0.52, and k p = 0.24. Changes in microstructure as a function of BKT content are also presented and discussed., Competing Interests: Authors confirm that the content of this article has no conflict of interest.

The physicochemical properties and biological behavior of sintered-bovine-derived hydroxyapatite (BHAp) are here reported and compared to commercial synthetic-HAp (CHAp). Dense ceramics were sintered for 2 h and 4 h at 1200 °C to investigate their microstructure-structure-in-vitro behavior relationship for both HAp ceramics. Densification was directly proportional to sintering time, showing a grain coarsening behavior with a greater effect on BHAp. Lattice parameters, crystallite size, cell volume and Ca / P ratio were determined by Rietveld refinement of X-ray diffraction (XRD) patterns using GSAS ® . Ionic substitutions (Na⁺, Mg 2+ , CO₃ 2- ) related to BHAp structure were associated with their position changes in the vibrational modes and correlated with the structural parameters obtained from the XRD analysis. Variations in the structural parameters and surface morphology were also evaluated after different soaking periods in simulated body fluid, which is associated with the formation of bone-like apatite layer and thus bioactivity. Mitochondrial activity (MTS) and lactate dehydrogenase (LDH) assays showed that the material released by the ceramics does not induce toxicity after exposure in human fetal osteoblastic (hFOB) cells. Furthermore, no statistically significant differences were found between the HAp obtained from different sources. These results show that BHAp can be used with no restrictions for the same biomedical applications as CHAp., Competing Interests: The authors declare no conflict of interest.