Sol-Gel Synthesis of Calcium-Deficient Hydroxyapatite: Influence of the pH Behavior during Synthesis on the Structural, Chemical Composition and Physical Properties

Abstract

This work analyzes the influence of the pH on the physical-chemical properties of calciumdeficient hydroxyapatite synthesized by the sol-gel method. The pH evolution in the course of the synthesis was followed during the drop-by-drop adding of the calcium source to the phosphorus source, for different drip rates. The structural, morphological, and textural characterizations demonstrate that increasing the drip rate up to values of 10 μl•s À1 increases the crystallite size and the specific surface area, while the chemical and optical characterizations show that higher drip rates also increase the calcium and oxygen vacancies, related to an increase in the energy of the optical band gap. However, for the sample synthesized at a drip rate of 17 μl•s À1 , the conjunction of higher calcium and oxygen vacancies has an opposite effect in the optical properties, in comparison to the observations in the synthesized samples at lower drip rates. Finally, the thermal characterization shows that, for all cases, the thermal diffusivity values agree with the reported values elsewhere.

Estudio de eliminación de iones fluoruro en agua sintética en un sistema de columna usando como adsorbente un material híbrido

“…La hidroxiapatita deficiente en calcio se preparó utilizando un método sol-gel modificado del método Rojas-Trigos et al, (2018) bajo los principios de la química verde, de acuerdo con el siguiente procedimiento: Se prepararon soluciones 0.1 M de NaOH, Ca(NO3)2 y Na3PO4. La solución de Ca(NO3)2 debió permanecer en agitación en todo momento, mientras que las soluciones NaOH y Na3PO4 se mezclaron y se colocaron en un baño ultrasónico Bransonic Modelo:2510, durante 5 minutos con la finalidad de obtener la fuente precursora de calcio, posteriormente la mezcla se colocó en la jeringa del inyector automático y se incorporó a la solución de Ca(NO3)2 a una tasa de 40 ml/h.…”