Dye reduction-based electron-transfer activity monitoring assay for assessing microbial electron transfer activity of microbial fuel cell inocula

Microbial fuel cells (MFC) utilize microbes as catalysts to convert chemical energy to electricity.Inocula used for MFC operation must therefore contain active microbial population.The dye reduction-based electron-transfer activity monitoring (DREAM) assay was employed to evaluate different inocula used in MFCs for their microbial bioelectrical activity.The assay utilizes the redox property of Methylene Blue to undergo color change from blue to colorless state upon microbial reduction.The extent of Methylene Blue reduction was denoted as the DREAM assay coefficient.DREAM assay was initially performed on a microbial culture along with the growth curve and estimation of colony forming units (CFUs).DREAM coefficient correlated to the CFU/m L obtained over time as growth progressed.The assay was then extended to water samples (domestic sewage,lake and a man-made pond) serving as inocula in MFCs.Domestic wastewater gave the highest DREAM coefficient (0.300±0.05),followed by pond (0.224±0.07) and lake (0.157±0.04) water samples.Power density obtained conformed to the DREAM coefficient values,with the three samples generating power densities of 46.45±5.1,36.12±3.2 and 25.08±4.3 m W/m^2 respectively.We have also studied the role of addition of various carbon sources and their concentrations towards improving the sensitivity of the assay.The DREAM assay is a rapid,easy-to-perform and cost-effective method to assess inocula for their suitability as anolytes in terms of electron transfer potential in MFCs.

Rapid degradation of dyes in water by magnetic Fe^0/Fe_3O_4/graphene composites

Magnetic Fe^0/Fe3O4/graphene has been successfully synthesized by a one-step reduction method and investigated in rapid degradation of dyes in this work. The material was characterized by N2 sorption–desorption, scanning electron microscopy（SEM）, Fourier transform infrared spectroscopy（FT-IR）, vibrating-sample magnetometer（VSM） measurements and X-ray photoelectron spectroscopy（XPS）. The results indicated that Fe^0/Fe3O4/graphene had a layered structure with Fe crystals highly dispersed in the interlayers of graphene, which could enhance the mass transfer process between Fe^0/Fe3O4/graphene and pollutants. Fe^0/Fe3O4/graphene exhibited ferromagnetism and could be easily separated and re-dispersed for reuse in water. Typical dyes, such as Methyl Orange, Methylene Blue and Crystal Violet, could be decolorized by Fe^0/Fe3O4/graphene rapidly. After 20 min, the decolorization efficiencies of methyl orange, methylene blue and crystal violet were 94.78%, 91.60% and 89.07%, respectively. The reaction mechanism of Fe^0/Fe3O4/graphene with dyes mainly included adsorption and enhanced reduction by the composite. Thus, Fe^0/Fe3O4/graphene prepared by the one-step reduction method has excellent performance in removal of dyes in water.

Catalytic bubble-free hydrogenation reduction of azo dye by porous membranes loaded with palladium nanoparticles

Catalytic bubble-free hydrogenation reduction of azo dye by porous membranes loaded with palladium （Pd） nanoparticles was studied for the first time. The effects of Pd loading, dye concentration and reuse repetitions of membranes were investigated. In reduction, the dye concentration decreased whereas the pH rose gradually. An optimal Pd loading was found. The catalytic membranes were able to be reused more than 3 times.