Comparative assessment of biochars from multiple sources based on persulfate activation capability: Role of iron component in enhancing thermal treatment effect on carbocatalytic performance

• Published in: Applied catalysis. B, Environmental Environmental, 2023-08, Vol.330, p.122647, Article 122647
• Main Authors: Suh, Sae In, Woo, Heesoo, Song, So-Yeon, Park, Dongjoo, Ahn, Yong-Yoon, Kim, Eunju, Lee, Hongshin, Kim, Dong-Wan, Lee, Changha, Ok, Yong Sik, Lee, Jaesang
• Format: Article
• Language: English
• Subjects: Biochar; Carbon-encapsulated iron; Non-radical oxidation; Persulfate activation; Thermal annealing
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2023.122647

In this study, we explored the correlation between the catalytic activity of UK Biochar Research Center biochars (BCs) and their physicochemical properties, suggesting a potential role of endogenous iron in promoting their persulfate activation capability by heat treatment. A steady improvement in the persulfate activation efficiency with increasing annealing temperature was observed exclusively for iron-containing BCs (e.g., sewage sludge (SS) BCs). Along with increasing the Brunauer–Emmett–Teller surface area, thermal annealing formed carbon-wrapped iron particles on the SS BC surfaces, produced crystalline elemental iron and iron carbides, and caused an sp3-to-sp2 conversion in the carbon phase. Comparing the annealed SS BCs in terms of the open circuit potential shift, electrical conductivity, and thermodynamic binding parameters showed that the heat-initiated modification enhanced the electron transfer-mediating capacity and surface affinity toward persulfate, which led to the beneficial effect of annealing on the carbocatalytic activity of iron-containing BCs for non-radical persulfate activation. [Display omitted] •UKBRC standard biochars were assessed in terms of persulfate activation capability.•Enhancing effect of thermal annealing was unique to iron-containing biochars.•Heat-induced iron-carbon interaction produced elemental iron and iron carbides.•Endogenous iron catalyzed carbon phase transformation during thermal annealing.•Thermal modification improved electrical conductivity and binding affinity.