Phenolphthalein Anilide Based Poly(Ether Sulfone) Block Copolymers Containing Quaternary Ammonium and Imidazolium Cations: Anion Exchange Membrane Materials for Microbial Fuel Cell

Specific gaps in this paper, with an experiment that would close each.

• High No nitrogen cycling data (nitrification, denitrification, ammonia recovery, N2O production) reported despite focus on bioelectrochemical systems. Paper does not measure or discuss nitrogen species (NO₃⁻, NO₂⁻, NH₄⁺, N₂O) in anode or cathode chambers.

  The MFC experiments use acetate (CH₃COONa 3.28 g/L) and NH₄Cl (0.23 g/L) in media but only measure voltage and power; no nitrogen balance or speciation analysis provided. This is a major gap for an MES paper focused on nitrogen cycling.

  Try. Measure NO₃⁻, NO₂⁻, NH₄⁺, and N₂O concentrations in anode and cathode effluent over time using ion chromatography and gas chromatography; vary C/N ratio (acetate:NH₄Cl) and cathode potential to map denitrification vs. nitrification windows.

• High Cathode potential and anode potential not independently controlled or reported. Paper does not specify applied voltage, cathode potential vs. Ag/AgCl reference, or anode potential during MFC operation.

  Section 2.9 describes MFC setup with Ag/AgCl reference electrode but only reports OCV, CCV, and power density via LSV polarization curves. No potentiostatic control or potential-dependent nitrogen transformation data.

  Try. Operate MFC in potentiostatic mode at fixed cathode potentials (e.g., −0.2, −0.4, −0.6 V vs. Ag/AgCl) and measure nitrogen species, current, and power output to identify optimal window for denitrification or ammonia recovery.

• High Dissolved oxygen (DO) in cathode chamber not controlled or measured. Potassium ferricyanide used as electron acceptor instead of oxygen, preventing assessment of aerobic nitrification or oxygen-dependent processes.

  Section 2.9 states 'catholyte was added potassium ferricyanide (0.1 M, 0.323 g/L) for the reduction reaction of protons' but does not mention DO control or aeration. This eliminates a key variable for nitrogen cycling studies.

  Try. Test MFC with aerated cathode (air or O₂ sparging) to enable nitrification; measure DO, NO₃⁻ production, and power output as functions of aeration rate and cathode potential.

• Medium Catholyte pH not reported or controlled. Paper does not specify pH in cathode chamber during MFC operation, which is critical for nitrification (optimal pH 7–8) and denitrification (optimal pH 6.5–7.5).

  Section 2.9 states anolyte and catholyte both contain '50 mM phosphate buffer (pH 7.0)' initially, but no pH monitoring or control during operation is mentioned. Membrane conductivity and ion transport may alter local pH.

  Try. Monitor and control pH in both chambers during MFC operation; measure nitrogen species and power output at pH 6.5, 7.0, 7.5, and 8.0 to identify optimal windows for nitrification vs. denitrification.

• Medium Hydraulic retention time (HRT) and current density not systematically varied. Paper does not report HRT, flow rate, or current density during MFC operation, limiting ability to assess kinetic trade-offs.

  Section 2.9 describes static batch MFC operation (no flow mentioned) with 250 mL chambers. No data on how HRT or current density affects nitrogen transformation rates or selectivity.

  Try. Operate MFC in fed-batch or continuous mode with varying HRT (e.g., 12, 24, 48 h) and measure nitrogen removal efficiency, N2O accumulation, and power output to identify optimal residence time.

• Medium Nitrite (NO₂⁻) and N2O accumulation not measured. Paper does not report whether denitrification is complete (to N₂) or partial (accumulating NO₂⁻ or N₂O), which is critical for assessing nitrogen recovery and environmental impact.

  No gas chromatography or ion chromatography data provided for nitrogen species. Only electrical output measured.

  Try. Measure N₂O and NO₂⁻ in gas and liquid phases using GC-ECD and IC; vary cathode potential and HRT to map conditions favoring complete denitrification vs. partial reduction.