The ratio of H/C is a useful parameter to predict adsorption of the herbicide metolachlor to biochars

Lan Wei, Yufen Huang, Lianxi Huang, Yanliang Li, Qing Huang, Guizhi Xu, Karin Müller, Hailong Wang, Yong Sik Ok, Zhongzhen Liu

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51 Citations (Scopus)


Biochar adsorbent was produced by pyrolyzing traditional Chinese medicinal herb residue at 300, 500 and 750 °C (referred to as biochar-300, biochar-500 and biochar-750). Basic physical and chemical analyses, Fourier transform infrared spectroscopy (FT-IR), and thermodynamic analyses were performed to elucidate adsorption and properties of biochar. Biochar adsorption capacity of herbicide metolochlor, as measured by batch-type adsorption experiments by Freundlich constant Kf (mg1−n Ln kg−1), followed the order: biochar-750 > biochar-300 > biochar-500. Thermodynamic analysis suggested that adsorption of metolachlor on biochar was a spontaneous process. The adsorption isotherm for the biochar produced at the highest pyrolysis temperature was characteristic for adsorption process driven by a high surface area of biochar (85.30 m2 g−1), while the adsorption process for the biochar produced at the lowest temperature was controlled by its higher content of organic matter (39.06%) and abundant functional groups. The FT-IR spectra also showed that the biochar prepared at the lowest temperature had the highest number of surface groups. In general, pore-filling induced by the large surface area of the biochar was the dominant adsorption mechanism. When the H/C value was >0.5, the adsorption mechanism of biochar was dominated by surface chemical bond, while pore-filling played a major role when the H/C value was <0.5.

Original languageEnglish
Article number109324
JournalEnvironmental Research
Publication statusPublished - 2020 May

Bibliographical note

Funding Information:
This work was supported by Pearl River S&T Nova Program of Guangzhou , China ( 201610010131 ); the National Natural Science Foundation of China ( 41401353 , 41571313 , 41807454 , 21577131 ); Natural Science Foundation of Guangdong Province , China ( 2015A030313570 , 2016A030313772 , and 2017A030311019 ); Department of Science and Technology of Guangdong Province , China ( 2017B020203002 , 2016B070701009 , and 2016A020210034 ); and President Foundation of Guangdong Academy of Agricultural Sciences, China ( 201716 ); Special fund for scientific innovation strategy-construction of high level Academy of Agriculture Science ( R2016PY-QY010 , R2016PY-JX006 ).

Publisher Copyright:
© 2020 Elsevier Inc.


  • Adsorption mechanism
  • Chinese medicinal herb residue
  • Functional groups
  • H/C ratio
  • Pore-filling

ASJC Scopus subject areas

  • Biochemistry
  • General Environmental Science


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