Dados do Trabalho

Título

ECO-FRIENDLY NANOFERTILIZER FROM BIOGENIC HYDROXYAPATITE

Resumo

Nanostructured hydroxyapatites (nHP) have been shown to be more efficient than conventional fertilizers in gradually supply phosphorus (P) to plants growing in acidic soils. However, nHP used as fertilizers are produced with expensive chemicals such as phosphoric acid, ammonium, and/or nitrates. In this study, we investigated the effects of calcination and high-energy milling on the citric acid-extractable P content in bones of slaughtered animals. For this, bovine femurs were sliced and sterilized in an autoclave (120°C, 1 kfg/cm2, 3h). A portion of the sterilized material was crushed with a mortar, passed through a 300-µm sieve, and analyzed by thermogravimetry. This revealed four stages of mass loss, three of which occurred before 550°C and accounted for over 97% of the total weight loss. Another portion of the sterilized material was calcined at 600°C for 1 hour at a heating rate of 15°C/min, resulting in a total yield of 25% (m/m). Subsequently, 25 g of the ash was milled in a Servitech ball mill (model CT -242) at 380 rpm for 1 hour, using alumina balls of different diameters at a ratio of 10:1 (w/w). The ground material was analyzed by Scanning Electron Microscopy (SEM) and Dynamic Light Scattering (DLS). The SEM micrographs showed nano-sized particles with a mean diameter of 49 ± 3 nm. In addition, DLS revealed a mean surface potential of -13.9 mV, indicating a net negative charge occuring due to the partial replacement of PO43− by CO32− and/or HPO42− in the biomineral structure, which results in higher solubility than stoichiometric hydroxyapatite (1.67/1). Finally, the P soluble in 2% (w/v) citric acid was determined and found to be 7.2% (w/w) for the sterilized non-calcined samples, 10.3% (w/w) for the sterilized calcined ash, and 13.8% (w/w) for the calcined milled samples (n=4). These results highlight the potential of using biogenic nHP as an enhanced-efficiency fertilizer to address both the scarcity of easily mineable P and the low efficiency of fertilizations. 

Palavras-chave

bioresources; smart-fertilizers; nutrient recycling.

Instituição financiadora

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Agradecimentos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).