Electrochemical response of titania, zirconia, and alumina electrodes to phosphate adsorption

Suppression of phosphorus release from eutrophic lake sediments by sediment microbial fuel cells

Sediment microbial fuel cells (SMFCs) have served as an alternative technique to suppress phosphorus release from lake sediments to water bodies and thus mitigate eutrophication. However, the phosphorus regulation mechanism remains unclear. The purpose of this research was to understand the electrochemical influence of an SMFC on the phosphorus concentration in interstitial water. In this study, a lab-scale SMFC was applied to acetate-spiked sediments (ace+) and unspiked sediments (sed) with closed-circuit (CC)/open-circuit (OC) columns, and the circuitry was switched to investigate the relationship between electron transfer and phosphorus concentration. The dissolved total phosphorus (DTP) concentration in the sediment interstitial water in CC columns significantly decreased to below 0.1 mg/L, whereas the DTP in OC columns remained high for nine weeks. After switching the circuit, the DTP in OC→CC columns dropped but that in CC→OC columns increased within one week. At the end of the experimental period, the DTP concentrations in CC/sed, CC/ace+, OC/sed, and OC/ace+ columns were 0.10 ± 0.02, 0.03 ± 0.00, 0.82 ± 0.01, and 1.66 ± 0.12 mg/L, respectively. The respective estimated anode capacitances of those columns were 2.05 ± 0.49, 5.15 ± 0.14, 0.72 ± 0.19, and 0.71 ± 0.12 nF. We concluded that the phosphorus may have been electrochemically attracted and retained on the anode in the sediment because the adsorbed DTP contents and the increased anode capacitances were strongly correlated. Thus, SMFCs can be used for suppressing phosphorus release from eutrophic lake sediments.

Trace-Level Sensing of Phosphate for Natural Soils by a Nano-Screen-Printed Electrode

Phosphate as one of the most essential components of living systems, robust analytical techniques available for phosphate sensing in natural waters and soils are essential for monitoring and predicting water quality and agronomic evaluation of phosphate. Using cyclic voltammetry, a point-of-use electrochemical sensor zirconium dioxide/zinc oxide/multiple-wall carbon nanotubes/ammonium molybdate tetrahydrate/screen printed electrode (ZrO₂/ZnO/MWCNTs/AMT/SPE) was applied to explore the electro-redox reaction of phosphomolybdate complexes on the surface of electrode, which produced a quantitative electrochemical response of phosphate anions. The modification of the electrode surface with ZrO₂/ZnO/MWCNTs nanocomposites is able to generate the electroactive species via chemical reaction between molybdenum (Mo(VI)) and the targeted phosphate anions, leading to a sensitive detection technique for trace phosphate with a lower detection limit (LOD = 2.0 × 10^-8 mol L^-1), higher reproducibility, anti-interference, and precision in different soil sources. This system will be of great potential to advance the trace-level understanding of phosphate especially in field environmental analysis.