Design and operation of microbial fuel cells for sustained electric power generation from sugar industry effluents.

The present study reports about the fabrication of a three-dimensional (3D) macroporous steel-based scaffold as an anode to promote specifically bacterial attachment and extracellular electron transfer to achieve power density as high as 1184 mW m–2, which is far greater than that of commonly used 3D anode materials. The unique 3D open macroporous configuration of the anode and the microstructure generated by the composite coating provide voids for the 3D bacterial colonization of electroactive biofilms. This is attributed to the sizeable interfacial area per unit volume provided by the 3D corrugated electrode that enhanced the electrochemical reaction rate compared to that of the flat electrode, which favors the enhanced mass transfer and substrate diffusion at the electrode/electrolyte interface and thereby increases the charge transfer by reducing the electrode overpotential or interfacial resistance. In addition, bacterial infiltration into the interior of the anode renders large reaction sites for substrate oxidation without the concern of clogging and biofouling and thereby improves direct electron transfer. A very low overpotential (−27 mV) with a very low internal resistance (7.104 Ω cm2) is achieved with the fabricated microbial fuel cell (MFC) that has a modified 3D corrugated electrode. Thus, easier and faster charge transfer at the electrode–electrolyte interface is confirmed. The study presents a revolutionary practical approach in the development of highly efficient anode materials that can ensure easy scale-up for MFC applications.

The present paper reports for the first time the development and application of novel Zn wetted CeO 2 (Zn/ CeO 2 ) composite galvanic zinc coating to combat microbial induced corrosion (MIC). Zinc metal−metal interaction causes the effective incorporation of composite into the galvanic coating and accordingly increases the active sites for antibiofouling activity. The developed coatings are explored for their anticorrosion/antibiofouling characteristics toward MIC induced by cultured seawater consortia. Enhanced antibiofouling activity of the composite galvanic coating is achieved due to the tuned content of 28 wt % Zn and 34 wt % of Ce. High charge transfer resistance as high as 4.0 × 10 14 Ω cm 2 and low double layer capacitance as low as 3.99 × 10 −8 F are achieved by tuning the structure and composition of the coating. The synergistic effect of Zn and Ce ensures the stability and corrosion resistance of the coatings in a corrosive bacterial environment. Evident decreases in the bacterial attachment and biofilm formation are illustrated using antibiofouling assay. The antibiofouling activity is attributed to the effective reduction of Ce 4+ to Ce 3+ and the shuttling characteristics of oxidation state of CeO 2 . This impairs the cellular respiration and results in bacterial death. Thus, it can be used as an effective coating to protect the steel based equipment in corrosive marine environments to combat marine microorganisms and their interactions. The present study also paves the scope for exploration of similar effective protective systems.

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The present paper reports for the first time the construction of a sugar cane bagasse-mediated double-chambered microbial fuel cell (MFC), consisting of a novel bioanode of an iron/titanium Ni–P composite. This anode could facilitate uninterrupted extracellular electron transfer (EET) from bacteria (mixed culture). The Ni–P composite anode had a significant corrosion resistance and enhanced electrocatalytic activity. The corrosion rate was reduced to 0.187 mmpy, which was 3 times less than that of the noncomposite anode. A steady decrease in internal resistance from 3.84 × 103 Ω to 2.94 × 102 Ω was achieved with the incorporation of the iron/titanium-based composite on the anode surface. The presence of Fe (III) ion centers in the composite surface favored electroactive biofilm formation and enhanced the capacitive nature of the anode, thereby accelerating EET. The constructed MFC showed an internal resistance as low as 1.12 × 10–2 Ω in comparison with the control MFC. This led to a very high power density of ∼2.1 W/m2, which was 20% higher than that of the control MFC, while a stacked MFC obtained a maximum open-circuit potential of 3.2 V with power density and current density outputs of 6.3 W/m2 and 2.7 mA/m2, respectively. Even though an extensive amount of literature is available in this field, this report is the first of its kind because it includes such a simple reproducible system that can be extended to other similar systems.

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Microorganisms tend to colonize on solid metal/alloy surface in natural environment leading to loss of utility. Microbiologically influenced corrosion or biocorrosion usually increases the corrosion rate of steel articles due to the presence of bacteria that accelerates the anodic and/or cathodic corrosion reaction rate without any significant change in the corrosion mechanism. An attempt was made in the present study to protect hot-dip galvanized steel from such attack of biocorrosion by means of chemically modifying the zinc coating. W-TiO2 composite was synthesized and incorporated into the zinc bath during the hot-dipping process. The surface morphology and elemental composition of the hot-dip galvanized coupons were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The antifouling characteristics of the coatings were analyzed in three different solutions including distilled water, seawater, and seawater containing biofilm scrapings under immersed conditions. Apart from electrochemical studies, the biocidal effect of the composite was evaluated by analyzing the extent of bacterial growth due to the presence and absence of the composite based on the analysis of total extracellular polymeric substance and total biomass using microtiter plate assay. The biofilm-forming bacteria formed on the surface of the coatings was cultured on Zobell Marine Agar plates and studied. The composite was found to be effective in controlling the growth of bacteria and formation of biofilm thereafter.

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