Systematic changes of bone hydroxyapatite along a charring temperature gradient: An integrative study with dissolution behavior

Partha Pratim Biswas; Biqing Liang; Gordon Turner-Walker; Jagat Rathod; Yao-Chang Lee; Chun-Chieh Wang; Chung-Kai Chang

doi:10.1016/j.scitotenv.2020.142601

Systematic changes of bone hydroxyapatite along a charring temperature gradient: An integrative study with dissolution behavior

Sci Total Environ. 2021 Apr 20:766:142601. doi: 10.1016/j.scitotenv.2020.142601. Epub 2020 Oct 3.

Authors

Partha Pratim Biswas¹, Biqing Liang², Gordon Turner-Walker³, Jagat Rathod¹, Yao-Chang Lee⁴, Chun-Chieh Wang⁵, Chung-Kai Chang⁶

Affiliations

¹ Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan.
² Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan. Electronic address: liangbq@gs.ncku.edu.tw.
³ Department of Cultural Heritage Conservation, National Yunlin University of Science & Technology, Douliu, Taiwan.
⁴ Life Science Group, National Synchrotron Radiation Research Center, Hsinchu, Taiwan; Department of Optics and Photonics, National Central University, Chung-Li, Taiwan; Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan.
⁵ X-ray Imaging Group, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
⁶ Material Science Group, National Synchrotron Radiation Research Center, Hsinchu, Taiwan.

PMID: 33071118
DOI: 10.1016/j.scitotenv.2020.142601

Abstract

The applicability of bone char as a long-term phosphorus nutrient source was assessed by integrating their mineral transformation and physicochemical properties with their dissolution behavior. We have explored synchrotron-based spectroscopic and imaging techniques (FTIR, XRD, and TXM) to investigate the physicochemical changes of bone and bone char along a charring temperature gradient (300-1200 °C) and used a lab incubation experiment to study their dissolution behaviors in solutions of different pH (4, 6, and 6.9). The thermal decomposition of inorganic carbonate (CO₃^2-) and the loss of organic components rendered a crystallographic rearrangement (blueshift of the PO₄^3- peak) and mineral transformation with increasing temperatures. The mineral transformation from B-type to AB- and A-type carbonate substitution occurred mainly at <700 °C, while the transformation from carbonated hydroxyapatite (CHAp) to more mineralogically and chemically stable HAp occurred at >800 °C. The loss of inorganic carbonate and the increase of structural OH^- with increasing temperatures explained the change of pH buffering capacity and increase of pH and their dissolution behaviors. The higher peak area ratios of phosphate to carbonate and phosphate to amide I band with increasing temperatures corroborated the higher stability and resistivity to acidic dissolution by bone chars made at higher temperatures. Our findings suggest that bone char made at low to intermediate temperatures can be a substantial source of phosphorus for soil fertility via waste management and recycling. The bone char made at 500 °C exhibited a high pH buffering capacity in acidic and near-neutral solutions. The 700 °C bone char was proposed as a suitable liming agent for raising the soil pH and abating soil acidity. Our study has underpinned the systematic changes of bone char and interlinked the charring effect with their dissolution behavior, providing a scientific base for understanding the applicability of different bone chars as suitable P-fertilizers.

Keywords: Bone char; Bone hydroxyapatite (HAp); Carbonated hydroxyapatite (CHAp); Mineral transformation; Phosphorus dissolution; Soil fertility.

MeSH terms

Bone and Bones*
Durapatite*
Fertilizers
Solubility
Temperature

Substances

Fertilizers
Durapatite