First principal observation documenting the three-dimensional uptake of cadmium and spatial distribution of cadmium hydroxyapatite mineral in bone char

Partha Pratim Biswas; Jagat Rathod; Ching-Yu Chiang; Biqing Liang; Chun-Chieh Wang; Yao-Chang Lee; Yu-Chun Chuang; Prakash C Loni; Wei-Hsin Chen; Shan-Li Wang

doi:10.1016/j.chemosphere.2023.139357

First principal observation documenting the three-dimensional uptake of cadmium and spatial distribution of cadmium hydroxyapatite mineral in bone char

Chemosphere. 2023 Oct:337:139357. doi: 10.1016/j.chemosphere.2023.139357. Epub 2023 Jun 29.

Authors

Affiliations

¹ Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan; Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, 407, Taiwan; College of Engineering, Tunghai University, Taichung, 407, Taiwan.
² Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan; Department of Environmental Biotechnology, Gujarat Biotechnology University, Gandhinagar, 382355, India.
³ National Synchrotron Radiation Research Center, Hsinchu, Taiwan.
⁴ Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan. Electronic address: liangbq@gs.ncku.edu.tw.
⁵ 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.
⁶ Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan.
⁷ Research Center for Smart Sustainable Circular Economy, Tunghai University, Taichung, 407, Taiwan; Department of Aeronautics and Astronautics, National Cheng Kung University, Tainan, 701, Taiwan; Department of Mechanical Engineering, National Chin-Yi University of Technology, Taichung, 411, Taiwan.
⁸ Department of Agricultural Chemistry, National Taiwan University, Taipei, Taiwan.

PMID: 37392801
DOI: 10.1016/j.chemosphere.2023.139357

Abstract

The 3-D matrix scale ion-exchange mechanism was explored for high-capacity cadmium (Cd) removal using bone chars (BC) chunks (1-2 mm) made at 500 °C (500BC) and 700 °C (700BC) in aqueous solutions. The Cd incorporation into the carbonated hydroxyapatite (CHAp) mineral of BC was examined using a set of synchrotron-based techniques. The Cd removal from solution and incorporation into mineral lattice were higher in 500BC than 700BC, and the diffusion depth was modulated by the initial Cd concentration and charring temperature. A higher carbonate level of BC, more pre-leached Ca sites, and external phosphorus input enhanced Cd removal. The 500BC showed a higher CO₃^2-/PO₄^3- ratio and specific surface area (SSA) than the 700BC, providing more vacant sites by dissolution of Ca²⁺. In situ observations revealed the refilling of sub-micron pore space in the mineral matrix because of Cd incorporation.The X-ray nanodiffraction (XND) analyses revealed that Cd was mainly removed from water by incorporation into the mineral lattice of 500BC via ion exchange, rather than surface sorption and precipitation, and the mineral phase was transformed from hydroxyapatite (HAp) to cadmium hydroxyapatite (Cd-HAp). The Rietveld's refinement of X-ray diffraction (XRD) data resolved up to 91% of the crystal displacement of Ca²⁺ by Cd²⁺. The specific phase and stoichiometry of the new Cd-HAp mineral was dependent on the level of ion exchange. This mechanistic study confirmed that 3-D ion exchange was the most important path for heavy metal removal from aqueous solution and immobilization in BC mineral matrix, and put forward a novel and sustainable remediation strategy for Cd removal in wastewater and soil clean-up.

Keywords: Bone char (BC); Cadmium (Cd); Carbonated hydroxyapatite (CHAp); Heavy metal; Ion-exchange; Remediation.

MeSH terms

Adsorption
Cadmium* / chemistry
Durapatite* / chemistry
Phosphorus

Substances

Durapatite
Cadmium
Phosphorus