N-doped citrate-sludge-derived carbon (NCSC) effectively promotes peroxymonosulfate activation for perfluorooctanoic acid (PFOA) removal with surface-mediated electron transfer mechanism

Shiyuan Fu; Yi Zhang; Xiangyang Xu; Yingyu Tan; Liang Zhu

doi:10.1016/j.ecoenv.2023.115592

N-doped citrate-sludge-derived carbon (NCSC) effectively promotes peroxymonosulfate activation for perfluorooctanoic acid (PFOA) removal with surface-mediated electron transfer mechanism

Ecotoxicol Environ Saf. 2023 Nov 1:266:115592. doi: 10.1016/j.ecoenv.2023.115592. Epub 2023 Oct 13.

Authors

Shiyuan Fu¹, Yi Zhang¹, Xiangyang Xu², Yingyu Tan³, Liang Zhu⁴

Affiliations

¹ Institute of Environment Pollution Control and Treatment, College of Environmental and Resource Science, Zhejiang University, Hangzhou 310058, China.
² Institute of Environment Pollution Control and Treatment, College of Environmental and Resource Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Province Key Laboratory for Water Pollution Control and Environmental Safety, Hangzhou 310058, China; Zhejiang Provincial Engineering Laboratory of Water Pollution Control, Hangzhou 310058, China.
³ Zhejiang Ecological Environment Scientific Design and Research Institute, Hangzhou 310007, China.
⁴ Institute of Environment Pollution Control and Treatment, College of Environmental and Resource Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Province Key Laboratory for Water Pollution Control and Environmental Safety, Hangzhou 310058, China; Zhejiang Provincial Engineering Laboratory of Water Pollution Control, Hangzhou 310058, China. Electronic address: felix79cn@zju.edu.cn.

PMID: 37837698
DOI: 10.1016/j.ecoenv.2023.115592

Abstract

In traditional wastewater treatment methods, the removal of emerging contaminants including perfluorooctanoic acid (PFOA) can be challenging. To address this, biochar is commonly utilized as an activator for peroxymonosulphate (PMS) to effectively eliminate organic pollutants. Sewage sludge has shown potential as a biochar precursor, but its complex composition and variable iron content, as well as the low specific surface area of the product limit the practical use of iron-dominated sludge-derived catalysts. To overcome this limitation, N-doped citrate-sludge-derived carbon (NCSC) was synthesized, possessing a low iron content (0.29 at%) and a large specific surface area (315.31 m² g^-1). As a comparison, Fe-/N-doped citrate-sludge-derived carbon (Fe-NCSC) was prepared by introducing exogenous iron, resulting in a higher iron content (2.12 at%) but a significantly reduced specific surface area (73.87 m² g^-1). In performance evaluation, the NCSC/PMS system achieved impressive removal efficiency, effectively eliminating 99.8% of PFOA (at an initial concentration of 2 mg L^-1) within 60 min, while Fe-NCSC/PMS only achieved 84.6%. The slightly lower reaction rate per specific surface area of NCSC/PMS proved that large specific surface area was NCSC's key advantage. The lower sensitivity of NCSC to pH and water substrates than FeNCSC suggested different activation mechanisms. Further analysis of reactive sites and species showed that the main oxidation mechanism of NCSC/PMS was forming the surface-bound PMS-NCSC complexes at the N sites, followed by PFOA donating electrons to the complexes to be oxidized, which was different from the Fe/N-dominated singlet oxygen mechanism of Fe-NSC/PMS. Furthermore, the reusability of the NCSC was demonstrated, with the removal rate decreasing to only 90.1% after four cycles and recovering to 94.8% after heated regeneration. In conclusion, this study provides a viable method for the elimination of emerging contaminants such as PFOA in water remediation.

Keywords: Carbonaceous materials; Nonradical reaction; Persulfate activator; Water purification.

MeSH terms

Carbon* / chemistry
Citrates
Citric Acid
Electrons
Iron / chemistry
Peroxides / chemistry
Sewage*
Water

Substances

peroxymonosulfate
biochar
Carbon
Sewage
perfluorooctanoic acid
Citric Acid
Peroxides
Iron
Citrates
Water