Influence of C/N ratios on treatment performance and biomass production during co-culture of microalgae and activated sludge.

Novel phycosphere associated bacteria processes are being regarded as a potential and cost-effective strategy for controlling anthropogenic contaminants in wastewater treatment. However, the underlying concern with the process is its vulnerability to improper organic or nutrient intake. This study established a synergistic interaction between microalgae and activated sludge in a three-photobioreactor system (without external aeration) to understand how pollutants could be mitigated whilst simultaneously yielding biomass under different C/N ratios of 1:1, 5:1 and 10:1. The result showed that the superior biomass productivity was facilitated at a C/N ratio of 5:1 (106 mg L-1 d-1), and the high degradation rate constants (kCOD = 0.25 d-1, kTN = 0.29 d-1, kTP = 0.35 d-1) was approximated using a first-order kinetic model. The removal of pollutants was remarkably high, exceeding 90% (COD), 93% (TN), and 96% (TP). Nevertheless, the C/N ratio of 1:1 resulted in a threefold drop in biomass-specific growth rate (µ = 0.07 d-1). Microalgal assimilation, followed by bacterial denitrification, is the major pathway of removing total nitrogen when the C/N ratio exceeds 5:1. Activated sludge plays an important role in improving microalgae tolerance to high concentration of ammonia nitrogen and boosting nitrification (light phase) and denitrification (dark phase). The use of phycosphere associated bacteria could be a promising strategy for controlling nutrients pollution and other environmental considerations in wastewater.

Ni2P nanocrystals embedded Ni-MOF nanosheets supported on nickel foam as bifunctional electrocatalyst for urea electrolysis.

It's highly desired but challenging to synthesize self-supporting nanohybrid made of conductive nanoparticles with metal organic framework (MOF) materials for the application in the electrochemical field. In this work, we report the preparation of Ni2P embedded Ni-MOF nanosheets supported on nickel foam through partial phosphidation (Ni2P@Ni-MOF/NF). The self-supporting Ni2P@Ni-MOF/NF was directly tested as electrode for urea electrolysis. When served as anode for urea oxidation reaction (UOR), it only demands 1.41 V (vs RHE) to deliver a current of 100 mA cm-2. And the overpotential of Ni2P@Ni-MOF/NF to reach 10 mA cm-2 for hydrogen evolution reaction HER was only 66 mV, remarkably lower than Ni2P/NF (133 mV). The exceptional electrochemical performance was attributed to the unique structure of Ni2P@Ni-MOF and the well exposed surface of Ni2P. Furthermore, the Ni2P@Ni-MOF/NF demonstrated outstanding longevity for both HER and UOR. The electrolyzer constructed with Ni2P@Ni-MOF/NF as bifunctional electrode can attain a current density of 100 mA cm-2 at a cell voltage as low as 1.65 V. Our work provides new insights for prepare MOF based nanohydrid for electrochemical application.