Formation, characteristics, and applications of environmentally persistent free radicals in biochars: A review

Xiuxiu Ruan, Yuqing Sun, Weimeng Du, Yuyuan Tang, Qiang Liu, Zhanying Zhang, William Doherty, Ray L. Frost, Guangren Qian, Daniel C.W. Tsang

Research output: Journal article publicationReview articleAcademic researchpeer-review

271 Citations (Scopus)


Due to abundant biomass and eco-friendliness, biochar is exemplified as one of the most promising candidates to mediate the degradation of environmental contaminants. Recently, environmentally persistent free radicals (EPFRs) have been detected in biochars, which can activate S 2 O 8 2− or H 2 O 2 to generate reactive oxygen species for effective degradation of organic and inorganic contaminants. Comprehending the formation mechanisms of EPFRs in biochars and their interactions with contaminants is indispensable to further develop their environmental applications, e.g., direct and indirect EPFR-mediated removal of organics/inorganics by biochars. With reference to the information of EPFRs in environmental matrices, this article critically reviews the formation mechanisms, characteristics, interactions, and environmental applications of EPFRs in biochars. Synthesis conditions and loading of metals/organics are considered as key parameters controlling their concentrations, types, and activities. This review provides new and important insights into the fate and emerging applications of surface-bound EPFRs in biochars.

Original languageEnglish
Pages (from-to)457-468
Number of pages12
JournalBioresource Technology
Publication statusPublished - Jun 2019


  • Contaminant degradation
  • Engineered biochar
  • Green/sustainable remediation
  • Stabilized radicals
  • Waste valorization/recycling

ASJC Scopus subject areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal


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