Characterization of phosphate structures in biochar from swine bones

Abstract

-The objective of this work was to develop an alternative methodology to study and characterize the phosphate crystalline properties, directly associated with solubility and plant availability, in biochar from swine bones. Some phosphate symmetry properties of pyrolyzed swine bones were established, using solid state nuclear magnetic resonance spectroscopy, principal component analysis, and multivariate curve resolution analysis, on four pyrolyzed samples at different carbonization intensities. Increasing carbonization parameters (temperature or residence time) generates diverse phosphate structures, increasing their symmetry and decreasing the crossed polarizability of the pair 1 H-31 P, producing phosphates with, probably, lower solubility than the ones produced at lower carbonization intensity. Additionally, a new methodology is being developed to study and characterize phosphate crystalline properties directly associated with phosphate solubility and availability to plants.Index terms: bone phosphate, phosphate availability, principal component analysis, pyrolysis, multivariedade curve resolution analysis, soil fertility. Caracterização da estrutura de fosfatos em "biochar" de ossos suínosResumo -O objetivo deste trabalho foi desenvolver uma metodologia alternativa para o estudo e a caracterização de propriedades cristalinas de fosfatos, diretamente associadas à sua solubilidade e disponibilidade para as plantas, em "biochar" de ossos de suínos. Foram estabelecidas algumas propriedades de simetria dos fosfatos de ossos pirolisados de suínos, por meio de espectroscopia de ressonância magnética nuclear no estado sólido, análise de componentes principais e análise multivariada de resolução de curvas, em quatro amostras pirolisadas em diferentes intensidades de carbonização. O aumento nos parâmetros de carbonização (temperatura ou tempo de residência) geram diferentes estruturas de fosfatos, com aumento de sua simetria e diminuição da polarizabilidade cruzada do par 1 H-31 P, o que resultou na síntese de fosfatos, provavelmente com menor solubilidade do que os produzidos com menor intensidade de carbonização. Além disso, uma nova metodologia está sendo desenvolvida para estudar e caracterizar as propriedades cristalinas de fosfatos diretamente relacionadas à sua solubilidade e disponibilidade para as plantas.Termos para indexação: fosfato de ossos, disponibilidade de fósforo, análise de componentes principais, pirólise, análise de resolução de curvas multivariadas, fertilidade do solo.

Response to Referees

“…The predominance of Ca hydroxyapatite in BCs as evidenced by P K-edge XANES analysis is consistent with findings reported by previous studies (Warren et al, 2009;. The mineral phase of bone consists mainly of hydroxyapatite, and its contribution to bone and bone char compositions depends on species, the age of animals (Wu et al, 2003), carbonization temperature and residence time (Novotny et al, 2012). Bone crystallinity might be improved through structural modifications on poorly crystalline fresh bone samples (such as mineral maturity over periods of time or intensive carbonization), which can also result in increased proportions of hydroxyapatite and accordingly a decrease in P solubility (Novotny et al, 2012).…”

Bone char effects on soil: sequential fractionations and XANES spectroscopy

“…The mineral phase of bone consists mainly of hydroxyapatite, and its contribution to bone and bone char compositions depends on species, the age of animals (Wu et al, 2003), carbonization temperature and residence time (Novotny et al, 2012). Bone crystallinity might be improved through structural modifications on poorly crystalline fresh bone samples (such as mineral maturity over periods of time or intensive carbonization), which can also result in increased proportions of hydroxyapatite and accordingly a decrease in P solubility (Novotny et al, 2012).…”

“…The mineral phase of bone consists mainly of hydroxyapatite, and its contribution to bone and bone char compositions depends on species, the age of animals (Wu et al, 2003), carbonization temperature and residence time (Novotny et al, 2012). Bone crystallinity might be improved through structural modifications on poorly crystalline fresh bone samples (such as mineral maturity over periods of time or intensive carbonization), which can also result in increased proportions of hydroxyapatite and accordingly a decrease in P solubility (Novotny et al, 2012). Based on LC fittings, the second major component of BC-BC plus particles was CaHPO 4 , in good agreement with the results of Rajendran et al (2013) who indicated that heated bones at 400 • C contained some more soluble phosphates, such as CaHPO 4 and CaH 2 PO 4 , in addition to the hydroxyapatite fraction.…”

Biochar: Pyrogenic Carbon for Agricultural Use - A Critical Review

“…The focus of this growing interest recently shifted from C sequestration and climate change mitigation to: soil fertility improvement and crop growth; water retention and movement in the soil; and soil pollution control, as indicated as a new tendency in a recent article in the journal Nature (Cernansky, 2015). It is however noteworthy that this discourse change, from Terra Preta de Índios and climate change to biochar technology, mainly towards "soil fertility improvement" and "improving crop residue management", had already been preconized by the Brazilian Research Network of Biochar since 2006 (Maia et al, 2011;Madari et al, 2012;Novotny et al, 2012;Paiva et al, 2012;Rittl et al, 2015a).…”