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Hydroxyapatite was obtained by bone calcinations. To study the calcination process, bovine and porcine bones were first autoclaved to remove fat and other non-bone tissues. They were then heated in an alumina pan in an oxidizing atmosphere of air, where simultaneous thermal analysis curves were recorded. To prepare the hydroxyapatites, bone samples were calcined at 850 °C and 1000 °C using a muffle furnace for 1 h. The obtained materials were powdered using mortar and pestle, and sifted in a sieve (60 mesh) without any additional purification or chemical treatment. The materials obtained were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy. The antimicrobial properties of these materials were determined through direct contact tests against Staphylococcus aureus. The natural hydroxyapatites obtained by bone calcination inhibited S. aureus growth, with the material obtained by calcination of bovine bones at 1000 °C, showing the best antimicrobial activity. These results indicated that bone wastes can be used to obtain hydroxyapatites with antimicrobial activity.

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Magnetic iron oxides are of great scientific and technological relevance. Therefore, herein, we report the research on developing methodologies for their sustainable and reproducible preparation. We discuss the synthesis of iron oxides involving citrus pectin as a source of energy (42 MJ kg-1) to promote the formation of the magnetic phases. The method involved two simple steps: gelation of the pectin (80 °C, 4 h) with iron nitrate nonahydrate [Fe(NO 3) 3 .9H 2 O], and calcination (600 °C, 1 h). X-ray diffraction indicated the major formation of hematite (α-Fe 2 O 3) and ferrite phases. Microscopy images show materials with an average size below 50 nm. Textural properties indicated pore sizes of 7-30 nm while magnetic measurements indicated the formation of soft and hard oxides (coercivity between 90 and 400 Oe) and high magnetization saturation (50 emu g-1).

RESUMOSais de níquel (acetato, cloreto e nitrato) são de uso corriqueiro nos laboratórios de síntese inorgânica e orgâ-nica. No processo de obtenção de óxidos, hidróxidos e oxi-hidróxidos de níquel para as mais diversas aplicações (baterias, pigmentos, sensores e eletrocatálise, por exemplo) se faz necessário compreender as características, as propriedades estruturais e eletrônicas, que cada sal precursor pode conferir ao produto final. Como premissa, foi realizado uma avaliação do comportamento estrutural, espectroscópico e térmico de sais de ní-quel. O perfil de difração de raios X (DRX) possibilitou identificar a rede cristalina e seus parâmetros. Dados espectroscópicos (UV-Vis) mostram a similaridade de absorção em solução e as bandas atribuídas de acordo com as transições permitidas e proibidas para o íon hexa(aquo)níquel(II). Porém, os espectros se diferenciam quando se avalia os sólidos por refletância difusa. Fato que possibilita calcular as energias de band gap para cada sal; acetato 2,85 eV, cloreto 2,46 eV e nitrato 2,61 eV. Dados colorimétricos (L*a*b) permitem prever que a intensidade de tom verde diminui na sequência: nitrato > cloreto > acetato. Curvas térmicas (TG/DTA) inferem grau de pureza e quantificam o número de moléculas de água de hidratação, compatíveis com os dados do fornecedor. A análise morfológica (MEV) e estrutural (DRX) das partículas geradas nas curvas térmi-cas permitiram determinar a composição estimada de NiO residual, com maior precisão para o derivado do nitrato de níquel (NiO 1,1 ), com tamanho de partícula da ordem de 0,1 µm, o menor entre os resíduos.Palavras-chave: Sais de níquel, caracterização, espectroscopia, colorimetria. ABSTRACTNickel salts (acetate, chloride and nitrate) are of everyday use in laboratories of inorganic and organic syntheses. In the process of obtaining oxides, hydroxides and oxy-hydroxides of nickel for the most diverse applications (batteries, pigments, sensors and electrocatalysis for example) it is necessary to understand the characteristics, the structural and electronic properties, that each precursor salt can confer to the final product. Premised carry out an assessment of the structural, spectroscopic and thermal behavior of nickel salts. Profile X-ray diffraction (XRD) enabled the identification of the crystal lattice and its parameters. Spectroscopic data (UV-Vis) show the similarity of solution absorption bands assigned in accordance with the permitted and prohibited transitions to hexa(aqua)nickel(II) ion. However, the spectra differ when evaluating the solids by diffuse reflectance. Fact that enables to calculate the band gap energies for each salt; value of 2.85 eV for acetate, 2.46 eV for chloride and 2.61 eV for nitrate. Color data (L*a*b*) can predict the green ton of intensity decreases in the sequence: nitrate> chloride> acetate. Curves thermal (TG-DTA) infer purity and quantify the number of hydration water molecules, consistent with the supplier information. Morphological analysis (SEM) and structural (XRD) of the particles gene...