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Plant-substrate biochar properties critical for mediating reductive debromination of 1,2-dibromoethane

Authors: Jonathan H. Lindhardt,Peter E. Holm,Yong-Guan Zhu,Changyong Lu,Hans Christian B. Hansen
Journal: Journal of Environmental Sciences
Publisher: Elsevier BV
Publish date: 2025-1
ISSN: 1001-0742 DOI: 10.1016/j.jes.2023.09.018
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The study effectively highlights the significance of biochar properties like quinone functional groups and elemental composition (e.g., nitrogen, nickel, and zinc) in facilitating reductive debromination. It’s intriguing to see such strong correlations emerge from the analysis. However, I’m curious; did the authors explore or consider potential mechanistic studies, such as real-time electron transfer measurements or spectroscopic techniques, to directly observe the role of these functional groups or elements during debromination? Additionally, given the environmental emphasis, how do you envision scaling this approach while managing potential challenges like metal leaching or biochar longevity in diverse remediation scenarios?

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3 months, 4 weeks ago

You derive significant positive correlations for N, Ni, P, Zn, and quinones (Table 3) and build a 3‑predictor multiple linear model (Eq. 4, R² = 0.98) using only the 6 most reactive biochars (n=6). With three predictors, the degrees of freedom are just 2—this model is almost certainly overfitted and has no predictive power. Why were the other 24 low‑reactivity biochars excluded from this regression? Including them would provide the necessary variance and statistical power; excluding them introduces severe selection bias and renders your p‑values meaningless.

You fit a pseudo‑first‑order model (Eq. 2) that asymptotically forces complete (100%) conversion of DBA to ethylene. However, your maximum observed debromination extent (ε₇d) is only 27%, and for SOYM6 adsorption accounts for just ~3% of removal. Fitting a model that assumes 100% conversion severely distorts the rate constant *k* (explaining why BARST6 with low ε₇d shows a high *k*). More critically, what happens to the remaining ~70% of DBA in the SOYM systems? The reaction stalls, yet you do not discuss GR passivation, product inhibition, or irreversible surface binding—so your derived *k* values are not true reaction rates but artifacts of a flawed asymptotic assumption.

2 weeks, 3 days ago

. The abstract states the highest first-order rate constant is 0.082 h⁻¹, and the conclusion attributes the highest *k* to BARST6. But Fig. 3B shows ZOST8 ≈ 0.026 h⁻¹, BARST8 ≈ 0.003 h⁻¹, SOYM6 ≈ 0.001 h⁻¹. Please give the exact *k* values and clarify whether 0.082 h⁻¹ belongs to a biochar with negligible ε₇d. If so, it cannot be presented as the main kinetic result.
. Text says SSA range is 2–378 m²/g and the highest is WHST8; Table 2 lists FAVA8 = 407 m²/g, higher than WHST8 = 318. Text says FAVA8 C = 77%; Table 2 appears to show ~71%, with WHST8/BARST8 higher. Table 2 is also almost unparseable—missing decimal points/units and column alignment. Provide a corrected table with units.
. Table 3 and the abstract report quinone groups as significantly positively correlated with ε₇d (p = 0.034), but the Discussion says the expected quinone/sp² correlation “could not be confirmed.” Which statement is correct?
. Eq. (4) is statistically and stoichiometrically unclear. The N coefficient 0.43 × 10⁻³ conflicts with Table 3’s N slope 0.00265 and with the claim that N is “critical.” With only 6 reactive BCs and 3 predictors, R² = 0.98 suggests overfitting; report adjusted R², per-term p-values, VIF, validation, and the missing Eq. (5). Also clarify units for Ni, Zn, and N.
. Methods 1.3 writes Fe₄ᴵᴵFe₄ᴵᴵ(OH)₁₂SO₄·yH₂O, and Fig. 1 caption says Feᴵᴵᴵ–Feᴵᴵᴵ hydroxide green rust. The correct sulfate green rust is Fe₄ᴵᴵFe₂ᴵᴵᴵ(OH)₁₂SO₄·yH₂O. Fig. 2/3 captions also use FeᴵᴵᴵGR inconsistently.
. Text says adsorption reaches ≈80% for WHST, but Fig. 3A shows WHST8 with roughly 50% adsorbed. Text says SOYM adsorption is ~3%, but the bars appear higher. Clarify.
. “rate constants … were very low … explaining their relatively large rate constants” is logically impossible. Likely you meant ε₇d was very low.

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