Formulation of Novel Composite (Activated Nanoclay/Hydrocolloid of Nostoc sphaericum) and Its Application in the Removal of Heavy Metals from Wastewater.

The removal of heavy metals from wastewater is an environmental challenge which demands the use of environmentally friendly materials that promote a circular economy. This study aimed to apply a novel composite of an activated nanoclay/hydrocolloid in the removal of heavy metals from wastewater. A composite blended under pressure was prepared with spray-dried hydrocolloid derived from Nostoc sphaericum algae and activated nanoclay in an acid medium and 1M NaCl. The composite and components were analyzed through infrared (IR), X-ray (XR), ζ potential, cation exchange capacity (CEC), particle size, and SEM images. The composite was subjected to the adsorption of heavy metals (Pb, As, Zn, and Cd) at pH 4.5 and the removal percentage, kinetics, and adsorption isotherms were evaluated. It was observed that the activated nanoclay and the composite that presented a particle size of around 400 nm significantly increased (p-value < 0.05) the CEC, ζ potential, the functional groups, and chelating components, removing heavy metals above 99% for Pb, As 33%, Cd 15%, and Zn 10%. Adsorption kinetics was adjusted to the pseudo second-order model (R2 > 0.98), and the Langmuir and Freundlich models better represented the sorption isotherm at 20 °C. The formulated composite presents a good ability to remove heavy metals in wastewater.

Hidroxiapatita sintetizada a partir de la cáscara de huevo como potencial sustituto óseo en defectos periodontales y periimplantarios / Hydroxyapatite synthesized from the eggshell as a potential bone substitute in periodontal and peri-implant defects

La hidroxiapatita sintética es un biomaterial ampliamente utilizado en los procedimien-tos de regeneración ósea guiada. Objetivo: Sintetizar hidroxiapatita sintética a partir de la cáscara de huevo bajo distintos precipitados de ácido nítrico. Métodos: Estudio expe-rimental que obtuvo CaCO3 a partir de la pulverización de la cáscara de huevo (Gallus gallus). El carbonato fue titulado con tres concentraciones de ácido nítrico (5, 10 y 15%) y fosfato de amonio. De las mezclas se realizaron pruebas a distintas temperaturas de cal-cinación (150, 600, 700, 800 y 900 °C) y tiempos de calcinación (2, 4, 8 y 12 h). Se utili-zó el análisis de difracción de rayos X para caracterizar la presencia de carbonato de calcio e hidroxiapatita. Resultados: De las distintas rutas de síntesis, la vía de precipitación de ácido nítrico por exceso al 15% más el carbonato de calcio calcinado a 700 °C durante 8 h ofreció los resultados más similares a la hidroxiapatita sintética al ser comparado con el patrón estándar comercial. Los picos de intensidad correspondieron a los ángulos 2�: 20, 26, 33, 34, 40, 48 y 50 Conclusiones: El método de síntesis por precipitación utilizando como sustrato el carbonato de calcio proveniente de la cáscara de huevo más nitrato de calcio y ácido nítrico, evidenció ser adecuado y práctico para la síntesis de hidroxiapatita. Su uso puede ser replicado para los estudios de caracterización y respuesta toxicológica en modelos experimentales pre clínicos. Palabras clave: Cáscara de huevo; Difracción de rayos X; Hidroxiapatita; Precipitación química; Regeneración ósea

Synthetic hydroxyapatite is a biomaterial widely used in guided bone regeneration pro-cedures. Objective: Synthesize synthetic hydroxyapatite from eggshells under different precipitates of nitric acid. Methods: Experimental study, which obtained CaCO3 from the pulverization of eggshells (Gallus gallus). The carbonate was titrated with three con-centrations of nitric acid (5, 10 and 15%) and ammonium phosphate. The mixtures were tested at different calcination temperatures (150, 600, 700, 800 and 900 °C) and calcination times (2, 4, 8 and 12 h). X-ray diffraction analysis was used to characterize the presence of calcium carbonate and hydroxyapatite. Results: Of the different routes of synthesis, the route of precipitation of nitric acid by excess to 15% plus calcined calcium carbonate at 700 °C during 8h offered more equivalent results to the synthetic hydroxyapatite when compared with the commercial standard. The peaks of intensity corresponded to the angles 2�: 20, 26, 33, 34, 40, 48 and 50. Conclusions: The method f synthesis by precipitation, using calcium carbonate from eggshells as substrate plus calcium nitrate and nitric acid; proved to be adequate and practical for the synthesis of hydroxyapatite. Its use can be replicated for toxicological characterization and response studies in pre-clinical experimental models. Keywords: Bone regeneration; Chemical precipitation; Egg shell; Hydroxyapatite; X-Ray diffraction