Toxicity monitoring signals analysis of selenite using microbial fuel cells.

Microbial fuel cells (MFCs) based biosensors are widely studied to environmental monitoring. The suitable responsive signal is important for microbial electrochemical sensors. However, the responsive signals of toxins have not been investigated in detail. Using sodium selenite as a toxic substance, the different response signals are analyzed over a concentration range from 0 to 150 mg/L in the double chambered. The output voltage and power density had the opposite trend between 0 and 2.5 mg/L and 2.5-150 mg/L. To analyze the reasonable signal of Se(IV) monitoring sensor, correlation analysis of concentrations and responsive signal data (maximum voltage, maximum power density, coulombic recovery, coulombic efficiency, and normalized energy recovery, etc.) has been accomplished. The high concentration of exogenous selenite (2.5-100 mg/L) is negatively correlated with maximum voltage (r = -0.901, p < 0.01) and max power density (r = -0.910, p < 0.01). The low concentration of exogenous selenite is positively correlated with average voltage, max power density, coulombic yield (r = 0.973, 0.999 and 0.975, respectively. p < 0.05). Furthermore, Illumina sequencing results indicate that the addition of sodium selenite solution changes the anode community structure, thereby affecting the removal efficiency of organic matter, which may be the reason why coulombic efficiency and normalized energy recovery are not suitable as sensing signal. Overall, based on the analysis of experimental data, the maximum power density is the best response signal, which provides a reference for the selection of sensor response signal based on microbial fuel cells.

Architecting an indirect Z-scheme NiCo2O4@CdS-Ag photocatalytic system with enhanced charge transfer for high-efficiency degradation of emerging pollutants.

Bimetallic oxides with spinel structure show great prospects in the photocatalysis owing to many active sites. Herein, a novel 500NiCo2O4@CdS-5%Ag composite was fabricated via a feasible strategy. Interestingly, the combination with NiCo2O4 could significantly enhance the absorption ability of CdS for visible light. Benefiting from the formation of heterojunction structure between NiCo2O4 and CdS, the recombination of photogenerated electrons and holes was remarkably restrained. As an effective mediator, deposition of Ag could further promote the transfer of photogenerated charge carriers, thereby accelerating the reaction rate. Meanwhile, light absorption capacity of composite was also improved, owing to the surface plasmon resonance effect of metallic Ag. More importantly, 500NiCo2O4@CdS-5%Ag composite with great stability displayed an excellent performance in the photocatalytic degradation of OFX, and its highest removal efficiency was as high as 99.14%. Possible degradation pathways of OFX were given, and most of OFX could be degraded into CO2, H2O and other by-products with no toxicity. Significantly, the separation and transfer of photogenerated charge carriers followed indirect Z-scheme heterojunction mechanism. The O2-, OH and 1O2 were main active species in photocatalytic reaction system. All in all, current work inspired some new ideas for designing novel photocatalytic system in wastewater treatment.

Treatment of Oil Wastewater and Electricity Generation by Integrating Constructed Wetland with Microbial Fuel Cell.

Conventional oil sewage treatment methods can achieve satisfactory removal efficiency, but energy consumption problems during the process of oil sewage treatment are worth attention. The integration of a constructed wetland reactor and a microbial fuel cell reactor (CW-MFC) to treat oil-contaminated wastewater, compared with a microbial fuel cell reactor (MFC) alone and a constructed wetland reactor (CW) alone, was explored in this research. Performances of the three reactors including chemical oxygen demand (COD), oil removal, and output voltage generation were continuously monitored. The COD removals of three reactors were between 73% and 75%, and oil removals were over 95.7%. Compared with MFC, the CW-MFC with a MnO2 modified cathode produced higher power density and output voltage. Maximum power densities of CW-MFC and MFC were 3868 mW/m³ (102 mW/m²) and 3044 mW/m³ (80 mW/m²), respectively. The plants in CW-MFC play a positive role for reactor cathode potential. Both plants and cathode modification can improve reactor performance of electricity generation.