Risk evaluation of biochars produced from Cd-contaminated rice straw and optimization of its production for Cd removal

Zhengtao Shen, Xiaoliang Fan, Deyi Hou, Fei Jin, David O'Connor, Daniel C.W. Tsang, Yong Sik Ok, Daniel S. Alessi

Research output: Contribution to journalArticlepeer-review

56 Citations (Scopus)


Based on the “waste-treat-waste” concept, biochars were produced from cadmium (Cd)-contaminated rice straw (CRSBs) at 300, 500, and 700 °C (CRSB300, CRSB500, and CRSB700). The risks of the Cd remaining in CRSBs were evaluated and the optimal biochar pyrolysis temperature for Cd removal was investigated. It was observed that 41% of the total Cd in the raw rice straw was exchangeable, which may pose significant risks to crops and humans. Pyrolyzing at 300 °C did not significantly alter the Cd fractions, while the exchangeable fraction of Cd greatly dropped to 5.79% at 500 °C and further to 2.12% at 700 °C. Increasing the highest pyrolysis temperature resulted in CRSBs with higher pH values, greater surface area, and smaller pore sizes, thus providing more rapid and efficient removal of Cd from aqueous solutions. For Cd removal tests, increasing pyrolysis temperature (300–700 °C) increased the total (24.8–55.1 mg/g) and non-exchangeable (18.9–52.8 mg/g) Cd concentrations immobilized on the CRSBs and significantly decreased the exchangeable Cd fraction (23.7%–4.85%). It is suggested based on the study from aqueous solutions that CRSB700 was the most suitable for the remediation of Cd contaminated soil on site due to the lowest risks of remained Cd from feedstock, fastest and highest Cd removal, and most stable immobilization of Cd.

Original languageEnglish
Pages (from-to)149-156
Number of pages8
Publication statusPublished - 2019 Oct

Bibliographical note

Funding Information:
This work was supported by China's National Water Pollution Control and Treatment Science and Technology Major Project (Grant No. 2018ZX07109-003 ), and the National Key Research and Development Program of China (Grant No. 2018YFC1801300 ). The first author would like to thank the Killam Trusts of Canada for kindly providing the Izaak Walton Killam Memorial Postdoctoral Fellowship.

Publisher Copyright:
© 2019 Elsevier Ltd


  • Cadmium removal
  • Cadmium rice
  • Green/sustainable remediation
  • Pyrolysis temperature
  • Sustainable waste management
  • Waste valorization/recycling

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Pollution
  • General Chemistry
  • Health, Toxicology and Mutagenesis
  • Environmental Engineering
  • Environmental Chemistry


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