Enhancing Stable Electricity Generation and Assimilative Ammonium-N Removal in Photosynthetic Algae–Microbial Fuel Cells Using a Chlorella Biofilm-Loaded ZnO-NiO@rGO Carbon-Fiber Composite Cathode

Nur Konflikte, die die Publikation selbst zeigt, jeweils am Text geprüft.

• Innerhalb der Publikation Control cathode (R1) achieved higher peak NH₄⁺–N removal during light than modified cathodes, yet modified cathodes are presented as superior.

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  R1 peak removal 54.1% during light period (Section 3.2, Figure 3b)

  “peak 54.1% at 144 h”

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  R2 and R3 average light-period removal 43.1–44.7%, lower than R1's 51.2% (Section 3.2)

  “the average removal efficiencies of R2, R3, and R1 during the light period were 43.1 ± 1.6%, 44.7 ± 2.2%, and 51.2 ± 1.0%, respectively”

  Einordnung der Autoren. Authors resolve this by reframing the advantage: modified cathodes reduce diurnal variability (32% lower fluctuation) and improve stability rather than peak capacity. The 'primary advantage of the ZnO₀.₂–NiO@rGO cathodes lies in improving the stability of the diurnal response under continuous-flow operation rather than increasing the peak removal capacity' (Section 3.2).

Konkrete Lücken in dieser Publikation, jeweils mit einem Experiment, das sie schließen würde.

• Hoch No monitoring of other nitrogen species (NO₃⁻, NO₂⁻, N₂O, organic-N) or gaseous losses; nitrogen mass balance incomplete.

  Authors state: 'nitrogen removal was assessed as the net decrease in NH₄⁺–N between the influent and cathode effluent. Other nitrogen pools, biomass-bound nitrogen, and potential gaseous losses were not quantified' (Section 3.2). This prevents attribution of removal to assimilation vs. denitrification or other pathways.

  Versuch. Measure NO₃⁻, NO₂⁻, N₂O, and total dissolved nitrogen; perform ¹⁵N tracing to partition assimilation vs. reduction; quantify biomass-N and gaseous-N loss.

• Hoch No measurement of cathode potential, anode potential, or overpotential; only cell voltage reported.

  Cell voltage alone (0.34–0.38 V) does not reveal cathode operating potential or oxygen reduction kinetics. Authors report polarization curves from prior work but not for this system under continuous flow.

  Versuch. Install reference electrodes (Ag/AgCl) in both chambers; measure cathode and anode potentials vs. SHE; construct polarization curves under light and dark conditions at steady state.

• Hoch No quantification of dissolved oxygen (DO) or pH dynamics at the cathode during light–dark cycling; only mentioned qualitatively.

  Authors note: 'cathodic pH gradients, which weakens oxygen reduction reaction kinetics' (Introduction) and cite prior work showing DO increased from 250 to 750 µmol/L and pH from 6.7 to 8.8 (Section 1), but do not measure these in their own system.

  Versuch. Install DO and pH probes in cathode chamber; log at 5 min intervals during light–dark cycling; correlate with voltage and NH₄⁺–N removal.

• Mittel No SEM imaging of biofilm architecture or quantification of attached vs. suspended algal biomass on cathode surface.

  Authors state: 'SEM imaging of the cathodic algal biofilm after PAMFC operation was not performed in this work' (Section 2.1) and note that 'differences may be associated with the influence of electrode surface properties on the proportions of attached algae and suspended algae' (Section 3.2).

  Versuch. Image cathode biofilm by SEM at end of operation; quantify biofilm thickness and coverage; measure suspended algal concentration in effluent; correlate with 18S community composition.

• Mittel No variation of hydraulic retention time (HRT), influent NH₄⁺–N concentration, or light intensity to define operating windows.

  Only one HRT (1.0 d), one influent concentration (~1.44 mg/L NH₄⁺–N), and one light intensity (3000 lux) tested. No exploration of C/N ratio, loading rate, or light-dependent thresholds.

  Versuch. Vary HRT (0.5–2.0 d), influent NH₄⁺–N (0.5–3.0 mg/L), and light intensity (1000–5000 lux); measure removal efficiency, voltage, and community composition; identify optimal operating window.

• Mittel No investigation of anode conditions, organic carbon supply, or anode-derived CO₂ contribution to photosynthesis.

  Anode fed acetate (2.13 g/L) and NH₄Cl (0.1 g/L); CO₂ from anode mentioned as driver of photosynthesis in introduction, but not quantified or manipulated.

  Versuch. Measure anode CO₂ production; vary acetate concentration (C/N ratio); measure cathode CO₂ uptake and photosynthetic rate; assess whether anode-derived CO₂ is limiting.