Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 562, Issue -, Pages 517-525Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2016.03.248
Keywords
Biochar; Heavy metal; Pyrolysis temperature; Mechanisms; Sorption characteristics
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Funding
- Ministry of Science and Technology of China [2012BAC17B03-02]
- CN-USA International Cooperative Fund [2010DFB33960]
- Ningbo science and Technology Bureau [2012C10003]
- Fundamental Research Funds for the Central Universities [2014FZA6008]
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The objective of this study was to investigate the mechanisms of cadmium (Cd) sorption on biochars produced at different temperature (300-600 degrees C) and their quantitative contribution. The sorption isotherms and kinetics of Cd2+ sorption on biochars were determined and fitted to different models. The Cd2+ sorption data could be well described by a simple Langmuir model, and the pseudo second order kinetic model best fitted the kinetic data. The maximum sorption capacity (Q(m)) obtained from the Langmuir model for CIB500 was 188.8 mg g(-1), which was greater than that of biochars produced at other temperature. Precipitation with minerals, ion exchange, complexation with surface oxygen-containing functional groups, and coordination with pi electrons were the possible mechanisms of Cd2+ sorption on the biochars. The contribution of each mechanism varied with the pyrolysis temperature. With increasing pyrolysis temperature, the contribution of surface complexation and metal ion exchange decreased from 24.5% and 43.3% to 0.7% and 4.7%, while the contribution of precipitation and Cd2+-pi interaction significantly increased from 29.7% and 2.5% to 89.5% and 5.1%, respectively. Overall, the precipitation with minerals and metal ion exchange dominated Cd2+ sorption on the biochars (accounted for 73.0-94.1%), and precipitation with minerals was the primary mechanism of Cd2+ sorption on the high-temperature biochars (>= 500 degrees C) (accounted for 86.1-89.5%). (C) 2016 Elsevier B.V. All rights reserved.
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