Multifunctional iron-biochar composites for the removal of potentially toxic elements, inherent cations, and hetero-chloride from hydraulic fracturing wastewater

Yuqing Sun, Iris K.M. Yu, Daniel C.W. Tsang, Xinde Cao, Daohui Lin, Linling Wang, Nigel J.D. Graham, Daniel S. Alessi, Michael Komárek, Yong Sik Ok, Yujie Feng, Xiang Dong Li

Research output: Journal article publicationJournal articleAcademic researchpeer-review

284 Citations (Scopus)


This paper evaluates a novel sorbent for the removal of potentially toxic elements, inherent cations, and hetero-chloride from hydraulic fracturing wastewater (FWW). A series of iron-biochar (Fe-BC) composites with different Fe/BC impregnation mass ratios (0.5:1, 1:1, and 2:1) were prepared by mixing forestry wood waste-derived BC powder with an aqueous FeCl3 solution and subsequently pyrolyzing them at 1000 °C in a N2-purged tubular furnace. The porosity, surface morphology, crystalline structure, and interfacial chemical behavior of the Fe-BC composites were characterized, revealing that Fe chelated with C–O bonds as C–O–Fe moieties on the BC surface, which were subsequently reduced to a C[dbnd]C bond and nanoscale zerovalent Fe (nZVI) during pyrolysis. The performance of the Fe-BC composites was evaluated for simultaneous removal of potentially toxic elements (Cu(II), Cr(VI), Zn(II), and As(V)), inherent cations (K, Na, Ca, Mg, Ba, and Sr), hetero-chloride (1,1,2-trichlorethane (1,1,2-TCA)), and total organic carbon (TOC) from high-salinity (233 g L−1 total dissolved solids (TDS)) model FWW. By elucidating the removal mechanisms of different contaminants, we demonstrated that Fe-BC (1:1) had an optimal reducing/charge-transfer reactivity owing to the homogenous distribution of nZVI with the highest Fe0/Fe2+ ratio. A lower Fe content in Fe-BC (0.5:1) resulted in a rapid exhaustion of Fe0, while a higher Fe content in Fe-BC (2:1) caused severe aggregation and oxidization of Fe0, contributing to its complexation/(co-)precipitation with Fe2+/Fe3+. All of the synthesized Fe-BC composites exhibited a high removal capacity for inherent cations (3.2–7.2 g g−1) in FWW through bridging with the C–O bonds and cation-π interactions. Overall, this study illustrated the potential efficacy and mechanistic roles of Fe-BC composites for (pre-)treatment of high-salinity and complex FWW.

Original languageEnglish
Pages (from-to)521-532
Number of pages12
JournalEnvironment international
Publication statusPublished - Mar 2019


  • Engineered biochar
  • Fracturing wastewater treatment
  • Metals/metalloids
  • Mineral-carbon composites
  • Sustainable remediation

ASJC Scopus subject areas

  • Environmental Science(all)

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