Rapid removal of PFOA and PFOS via modified industrial solid waste: Mechanisms and influences of water matrices

Hongyi Wan, Rollie Mills, Kai Qu, James C. Hower, M. Abdul Mottaleb, Dibakar Bhattacharyya, Zhi Xu

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Emerging perfluoroalkyl and polyfluoroalkyl substances contaminate waters at trace concentrations, thus rapid and selective adsorbents are pivotal to mitigate the consequent energy-intensive and time-consuming issues in remediation. In this study, coal combustion residuals-fly ash was modified (FA-SCA) to overcome the universal trade-off between high adsorption capacity and fast kinetics. FA-SCA presented rapid adsorption (teq = 2 min) of PFOX (perfluorooctanoic acid and perfluorooctanesulfonic acid, collectively), where the dynamic adsorption capacity (qdyn = qm/teq) was 2–3 orders of magnitude higher than that of benchmark activated carbons and anion-exchange resins. Investigated by advanced characterization and kinetic models, the fast kinetics and superior qdyn are attributed to (1) elevated external diffusion driven by the submicron particle size; (2) enhanced intraparticle diffusion caused by the developed mesoporous structure (Vmeso/Vmicro = 8.1); (3) numerous quaternary ammonium anion-exchange sites (840 µmol/g), and (4) appropriate adsorption affinity (0.031 L/µmol for PFOS, and 0.023 L/µmol for PFOA). Since the adsorption was proven to be a synergistic process of electrostatic and hydrophobic interactions, effective adsorption ([PFOX]ini = 1.21 µM, concentration levels of highly-contaminant-sites) was obtained at conventional natural water chemistries. High selectivity (>85.4% removal) was also achieved with organic/inorganic competitors, especially compounds with partly similar molecular structures to PFOX. In addition, >90% PFOX was removed consistently during five cycles in mild regeneration conditions (pH 12 and 50 °C). Overall, FA-SCA showed no leaching issues of toxic metals and exhibits great potential in both single-adsorption processes and treatment train systems.

Original languageEnglish
Article number133271
JournalChemical Engineering Journal
Volume433
DOIs
StatePublished - Apr 1 2022

Bibliographical note

Funding Information:
This work was supported by China Postdoctoral Science Foundation [2020M681204]; the National Natural Science Foundation of China [21908054 & 22075076]; and NIEHS-SRP grant [P42ES007380]. We highly appreciate the collaborations with the UK superfund center and the UK CAER

Funding Information:
This work was supported by China Postdoctoral Science Foundation [ 2020M681204 ]; the National Natural Science Foundation of China [21908054 & 22075076]; and NIEHS-SRP grant [P42ES007380]. We highly appreciate the collaborations with the UK superfund center and the UK CAER

Publisher Copyright:
© 2021 Elsevier B.V.

Keywords

  • Co-existing competitors
  • Fly ash
  • PFAS removal
  • Quaternary ammonium
  • Rapid adsorption

ASJC Scopus subject areas

  • Chemistry (all)
  • Environmental Chemistry
  • Chemical Engineering (all)
  • Industrial and Manufacturing Engineering

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