Mechanistic insights and multiple characterizations of cadmium binding to animal-derived biochar

Sicong Lei; Ling Zhu; Cong Xue; Chengyi Hong; Junliang Wang; Lei Che; Yongfeng Hu; Yuping Qiu

doi:10.1016/j.envpol.2019.113675

Mechanistic insights and multiple characterizations of cadmium binding to animal-derived biochar

Environ Pollut. 2020 Mar:258:113675. doi: 10.1016/j.envpol.2019.113675. Epub 2019 Nov 25.

Authors

Sicong Lei¹, Ling Zhu¹, Cong Xue¹, Chengyi Hong², Junliang Wang³, Lei Che⁴, Yongfeng Hu⁵, Yuping Qiu⁶

Affiliations

¹ State Key Laboratory of Pollution Control and Resources Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, International Joint Research Center for Sustainable Urban Water System, Shanghai, 200092, China.
² State Key Laboratory of Pollution Control and Resources Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China.
³ College of the Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
⁴ School of Engineering, Huzhou University, Huzhou, 313000, China.
⁵ Canadian Light Source Inc., Saskatoon, SK S7N 2V3, Canada.
⁶ State Key Laboratory of Pollution Control and Resources Reuse, Ministry of Education Key Laboratory of Yangtze River Water Environment, College of Environmental Science and Engineering, Tongji University, Shanghai, 200092, China; Shanghai Institute of Pollution Control and Ecological Security, International Joint Research Center for Sustainable Urban Water System, Shanghai, 200092, China. Electronic address: ypqiu@tongji.edu.cn.

PMID: 31812527
DOI: 10.1016/j.envpol.2019.113675

Abstract

Cattle-derived biochar (CB), which is derived from industrial pyrolysis of cattle carcasses in harmless treatment plants, is a naturally occurring mineral form of carbonate-bearing hydroxyapatite (CHAP) with a small amount of elemental carbon. CB has 4.02% of carbonate content, which falls under the B-type substitution of CHAP. In this work, the Cd(II) sorption capacity of CB was determined to be 0.82 mmol/g, with 97.6% of the Cd(II) uptake contributing to CHAP and only 2.36% of the Cd(II) uptake contributing to the elemental carbon component. The calculation and linear combination fitting (LCF) of Cd L₃-edge X-ray absorption near-edge structure (XANES) analysis indicated that the contributions of Cd(II) species to CB presented the following order: ion exchange (57.6%-61.0%) > precipitation (24.4%-29.9%) > surface complexation (12.5%-13.4%). The depth dependent X-ray photoelectron spectroscopy (XPS) showed the presence of ion exchange, which is accompanied by intraparticle diffusion. LCF of XANES and Rietveld analysis of X-ray diffraction (XRD) demonstrated that Cd(II) was precipitated in the form of Cd₅H₂(PO₄)₄·4H₂O on the CB surface. Furthermore, the precipitate was directly observed and identified by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Consequently, we revealed the intricate binding mechanism of Cd(II) to CHAP-rich CB and confirmed the importance of surface precipitation.

Keywords: Animal-derived biochar; Hydroxyapatite; Precipitation; Quantitative analysis; XANES.

MeSH terms

Adsorption
Animals
Cadmium / chemistry*
Cattle
Charcoal / chemistry*
Environmental Pollutants / chemistry*
Models, Chemical

Substances

Environmental Pollutants
biochar
Cadmium
Charcoal