cImproving the performance of graphite anode in a Microbial Fuel Cell via PANI encapsulated α-MnO2 composite modification for efficient power generation and methyl red removal

Synthesis of novel PANI/PVA-NiCu composite material for efficient removal of organic dyes

The present work aims the synthesis of a novel, low cost, and environmentally friendly PANI/PVA-CuNi composite by chemical oxidative polymerization of aniline monomer and polyvinyl alcohol (PVA) as film matrix; several percentages of copper (Cu) and Nickel (Ni) were used. UV-Visible spectroscopy, FTIR, SEM-EDX, and TGA were used to characterize the nanocomposites. While PANI/PVA-CuNi nanocomposites were investigated in adsorption experiments of methylene blue (MB) under different controlled conditions (time reaction, adsorbent dosage, initial dye concentration, stirring speed, temperature, and pH of the medium) also various kinetic models were employed to evaluate the efficiency of the adsorption. The results revealed that the10 mg of PANI/PVA-Cu₅₀N_i50 and PANI/PVA-Ni composites Catalyst removed (94% and 93% of methylene blue in 180 min respectively at 10^-5 M initial concentration of dye, pH of 13, stirring speed of 150 rpm, the temperature of 301 k. the kinetics data were properly fitted with the pseudo second-order model with a correlation coefficient of 0.98262 and 0.95881 using PANI/PVA-Cu₅₀N_i50 and PANI/PVA-Ni, respectively.

Electrochemical Removal of Nitrogen Compounds from a Simulated Saline Wastewater

In the last few years, many industrial sectors have generated and discharged large volumes of saline wastewater into the environment. In the present work, the electrochemical removal of nitrogen compounds from synthetic saline wastewater was investigated through a lab-scale experimental reactor. Experiments were carried out to examine the impacts of the operational parameters, such as electrolyte composition and concentration, applied current intensity, and initial ammoniacal nitrogen concentration, on the total nitrogen removal efficiency. Using NaCl as an electrolyte, the N_TOT removal was higher than Na₂SO₄ and NaClO₄; however, increasing the initial NaCl concentration over 250 mg·L^-1 resulted in no benefits for the N_TOT removal efficiency. A rise in the current intensity from 0.05 A to 0.15 A resulted in an improvement in N_TOT removal. Nevertheless, a further increase to 0.25 A led to basically no enhancement of the efficiency. A lower initial ammoniacal nitrogen concentration resulted in higher removal efficiency. The highest N_TOT removal (about 75%) was achieved after 90 min of treatment operating with a NaCl concentration of 250 mg·L^-1 at an applied current intensity of 0.15 A and with an initial ammoniacal nitrogen concentration of 13 mg·L^-1. The nitrogen degradation mechanism proposed assumes a series-parallel reaction system, with a first step in which NH₄⁺ is in equilibrium with NH₃. Moreover, the nitrogen molar balance showed that the main product of nitrogen oxidation was N₂, but NO₃^- was also detected. Collectively, electrochemical treatment is a promising approach for the removal of nitrogen compounds from impacted saline wastewater.

Study on the Changes in the Microcosmic Environment in Forward Osmosis Membranes to Reduce Membrane Resistance

Osmotic microbial fuel cells (OsMFCs) are an emerging wastewater treatment technology in bioelectricity generation, organic substrate removal, and wastewater reclamation. To address this issue, proton-conductive sites were strengthened after using the forward osmosis (FO) membrane by reducing the membrane resistance. The mechanism of improving electricity generation was attributed mainly to the unique characteristics of the membrane material and the water flux characteristics of the FO membrane. In particular, only when the concentration of catholyte was greater than 0.3 M was the membrane resistance the main contributor to the overall internal resistance. Meanwhile, through the simulation of the concentration inside the membrane, the changes in the membrane thickness direction and the phase transition of the internal structure of the membrane from the dry state (0% water content) to the expansion state (>50%water content) were analyzed, which were influenced by the water flux, further explaining the important role of the membrane’s microenvironment in reducing the membrane impedance. This further opens a novel avenue for the use of OsMFCs in practical engineering applications.

Microbial-Inspired Surface Patterning for Selective Bacterial Actions for Enhanced Performance in Microbial Fuel Cells

The performance of any bio-electrochemical system is dependent on the efficiency of electrode-microbial interactions. Surface properties play a focal role in bacterial attachment and biofilm formation on the electrodes. In addition to electrode surface properties, selective bacterial adhesion onto the electrode surface is mandatory to mitigate energy loss due to undesired bacterial interactions on the electrode surface. In the present study, microbial-patterned graphite scaffolds are developed for selective bacterial-electrode interactions. A power density as high as 1105 mW/m² is achieved with mG-E (a graphite electrode patterned with Escherichia coli), which is about 3 times higher than that of the pristine graphite electrode (370 mW/m²). Initial mechanical pre-treatment of the graphite electrode, followed by bacterial patterning, results in the formation of a unique cobblestone topography with a tuned surface area of 127.12 m²/g. This provides suitable morphology with enhanced active sites for selective bacterial intercalation in graphite layers. This cannot be otherwise achieved by any mechanical or other means. A unique methodology of symbolic regression is adopted to validate a genetic algorithm suitable for predicting a perfect correlation between surface characteristics and electrochemical characteristics with a minimum root-mean-square error of 0.08. The bacterial intercalation onto the graphite electrode causes protuberance of the graphite layers that reduces the surface potential and resistance, leading to high electron transfer. The study presents a unique bacterial-inspired surface patterning on the anode, which is critical for the performance of a microbial fuel cell.

Advancements in Bioelectricity Generation Through Nanomaterial-Modified Anode Electrodes in Microbial Fuel Cells

The use of nanotechnology in bioelectrochemical systems to recover bioelectricity and metals from waste appears to be a potentially appealing alternative to existing established procedures. This trend exactly characterizes the current renewable energy production technology. Hence, this review focuses on the improvement of the anode electrode by using different functional metal oxide-conducting polymer nanocomposites to enhance microbial fuel cell (MFC) performance. Enhancement of interfacial bioelectrocatalysis between electroactive microorganisms and hierarchical porous nanocomposite materials could enhance cost-effective bioanode materials with superior bioelectrocatalytic activity for MFCs. In this review, improvement in efficiency of MFCs by using iron oxide- and manganese oxide-based polypyrrole hybrid composites as model anode modifiers was discussed. The review also extended to discussing and covering the principles, components, power density, current density, and removal efficiencies of biofuel cell systems. In addition, this research review demonstrates the application of MFCs for renewable energy generation, wastewater treatment, and metal recovery. This is due to having their own unique working principle under mild conditions and using renewable biodegradable organic matter as a direct fuel source.

Polyaniline on Stainless Steel Fiber Felt as Anodes for Bioelectrodegradation of Acid Blue 29 in Microbial Fuel Cells

This study investigated the advantages of using low-cost polyaniline-fabricated stainless steel fiber felt anode-based microbial fuel cells (PANI-SSFF-MFCs) for azo dye acid blue 29 (AB29) containing wastewater treatment integrated with an aerobic bioreactor. The findings of electrochemical impedance spectroscopy (EIS) and polarization studies showed that the PANI–SSFF anode considerably decreased the MFC internal resistance. The highest power density of 103 ± 3.6 mW m−2 was achieved by PANI-SSFF-MFCs with a decolorization efficiency of 93 ± 3.1% and a start-up time of 13 days. The final chemical oxygen demand (COD) removal efficiencies for integrated PANI–SSFF–MFC–bioreactor and SSFF–MFC–bioreactor set-ups were 92.5 ± 2% and 80 ± 2%, respectively. Based on 16S rRNA gene sequencing, a substantial microbial community change was observed in MFCs. The majority of sequences were from the Proteobacteria phylum, accounting for 72% and 55% in PANI–SSFF–anodic biofilm and suspension, respectively, and 58 and 45% in SSFF–anodic biofilm and suspension, respectively. The relative abundance of the seven most abundant genera (Pseudomonas, Acinetobacter, Stenotrophomonas, Geothrix, Dysgonomonas, Shinella, and Rhizobiales) was higher in PANI–SSFF–MFCs (46.1% in biofilm and 55.4% in suspension) as compared to SSFF–MFC (43% in biofilm and 40.8% in suspension) which predominantly contributed to the decolorization of AB29 and/or electron transfer. We demonstrate in this work that microbial consortia acclimated to the MFC environment and PANI-fabricated anodes are capable of high decolorization rates with enhanced electricity production. A combined single-chamber MFC (SMFC)-aerobic bioreactor operation was also performed in this study for the efficient biodegradation of AB29.