Department Of Environmental Science And Technology
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Item Anode modification: An approach to improve power generation in microbial fuel cells (MFCs)(Elsevier, 2023-01-27T00:00:00) Rani, Gini; Jaswal, Vijay; Yogalakshmi, K.N.Global energy demand is continuously increasing and has become a matter of concern. At present, 86% of the energy demand are accomplished by fossil fuels, but these deliver harmful effects on the environment by releasing CO2 in the atmosphere. Contrary, though nonrenewable resources such as solar, wind, and bioenergy possess minimal carbon footprints, they suffer from limitations of higher installation cost, low efficiency, and complex operation system. Since the past two decades, a relatively new sustainable technology, the microbial fuel cells (MFCs) have emerged with potential to convert the bond energy of molecules present in organic/inorganic waste into electric energy with the help of microbes. The electricity produced through the release of electrons during microbial degradation of organic waste can be used to offset the running cost of wastewater treatment plants. The performance of the MFCs is influenced by a number of cofactors, viz. type of reactor, nature of feed, microbial consortia, electrode material, and mode of operation. Anode plays a significant role in the power enhancement. Across the globe, various research groups are working to enhance the efficiency and power output of anode through its modification using conductive polymers (polypyrrole and polyaniline), metal oxides, nanomaterials, and many others. MFC operated with the electrochemically reduced graphene oxide modified anode evidenced a power density enhanced by 17.5 times as compared to carbon cloth. In the past 5 years, power density ranging from 6.12 to 6119mWm?2 was observed with various modified anode. The chapter will throw light on anode materials popularly used in MFC, method/techniques used for its modification to enhance energy output and limitations that restrict its wide-scale application. � 2023 Elsevier Inc. All rights reserved.Item Statistical optimization of operating parameters of microbial electrolysis cell treating dairy industry wastewater using quadratic model to enhance energy generation(Elsevier Ltd, 2022-04-28T00:00:00) Rani, Gini; Banu, J. Rajesh; Kumar, Gopalakrishnan; Yogalakshmi, K.N.The performance of Microbial electrolysis cell (MEC) is affected by several operating conditions. Therefore, in the present study, an optimization study was done to determine the working efficiency of MEC in terms of COD (chemical oxygen demand) removal, hydrogen and current generation. Optimization was carried out using a quadratic mathematical model of response surface methodology (RSM). Thirteen sets of experimental runs were performed to optimize the applied voltage and hydraulic retention time (HRT) of single chambered batch fed MEC operated with dairy industry wastewater. The operating conditions (i.e) an applied voltage of 0.8 V and HRT of 2 days that showed a maximum COD removal response was chosen for further studies. The MEC operated at optimized condition (HRT- 2 days and applied voltage- 0.8 V) showed a COD removal efficiency of 95 � 2%, hydrogen generation of 32 � 5 mL/L/d, Power density of 152 mW/cm2 and current generation of 19 mA. The results of the study implied that RSM, with its high degree of accuracy can be a reliable tool for optimizing the process of wastewater treatment. Also, dairy industry wastewater can be considered to be a potential source to generate hydrogen and energy through MEC at short HRT. � 2022 Hydrogen Energy Publications LLCItem Electrode modification and its application in microbial electrolysis cell(Elsevier, 2022-02-04T00:00:00) Rani, Gini; Banu, J. Rajesh; Yogalakshmi, K.N.The microbial electrolysis cell (MEC) is a sustainable technology that degrades organic substrate to produce hydrogen, an important energy carrier. However, its large-scale practical application is hampered because of several factors including electrodes material, reactor designs, substrates, and high-cost catalysts. Electrodes in particular are fundamental components which determine redox reaction and transport of electric charge. The surface of the electrode is where the equilibrium of redox reaction is established between the electrode surface and the electrolyte (substrate). Therefore, modification of electrodes is emphasized much recently. Modified electrodes have wide application as electrochemical devices, chemical analysis, biosensors, and many more. The electrode modification is carried out to bring improved properties in the electrode by altering its morphology or molecular structure. Apart from high conductivity and low resistance, the modified electrodes develop increased sensitivity, selectivity, corrosion resistance, electrochemical, and chemical stability. They also possess large potential window. Moreover, electrode modification using nanomaterials and conductive polymers favors electrocatalysis process. Studies related to MEC using modified electrodes have reported improved wastewater treatment and hydrogen production along with enhanced energy recovery. In the present chapter, the mechanics of electrode in an electrochemical system, in general, is explained in detail. Moreover, the overview of different techniques for the modification of the electrodes and their applications in MEC has been expensively entailed. � 2022 Elsevier Inc.Item Graphitic carbon nitride for photocatalytic CO2 reduction. Energy and Air Pollution.(Elsevier, 2022-01-15T00:00:00) Teja, Y.N.; Sakar, M.; Yogalakshmi, K.N.Among the various emerging photocatalytic materials, graphitic carbon nitride (g-C3N4) has gained significant importance due to their two-dimensional (2D) structure, promising electronic, optical, and interfacial properties. The features such as narrow band gap energy, reduced recombination process, enhanced transportation of charge carriers to the surrounding, and appropriate band edge potential to produce the required redox species are making the g-C3N4 as a promising candidate for various photocatalytic applications, especially for CO2 reduction into hydrocarbon fuels. It should be noted that the CO2 conversion essentially involves two simultaneous process known as the CO2 reduction and protonation. The effectiveness in such simultaneous process requires the appropriate positioning of band edge potential in the system, which can be effectively engineered in g-C3N4-based materials as compared to the other metal oxide-based systems. Interestingly, in addition to the chemical induced redox process, the CO2 conversion properties of g-C3N4 can also be attributed to their physical structures such as 2D layers and porous structures, where it causes the shifting of band edge positions and enhanced CO2 adsorption in g-C3N4. To this end, this chapter provides a glimpse of structure-property relationship of g-C3N4 based materials towards their photocatalytic CO2 conversion properties, where it discusses the various g-C3N4 material systems and their efficiency towards the conversion of CO2 into various hydrocarbon fuels under light visible light/sunlight irradiations. � 2022 Elsevier Inc. All rights reserved.Item Biofiltration in wastewater treatment plants: An overview(Elsevier, 2022-01-15T00:00:00) Yogalakshmi, K.N.; Sharma, Avimanu; Mittal, SunilBiofilters or biological filters are a technology that uses attached biomass on a media to degrade and remove pollutants from the air, water, and wastewater treatment plants. They are natural systems which are engineered and simulated to remove a varied range of contaminants, that is, organic matter, suspended solids, natural organic matter, and organic micropollutants. Biofiltration systems are popular among wastewater treatment process due to its simple operation, robust nature, and low energy requirement. Trickling filters, aerated biological filters, and membrane bioreactors are some of the popular biofiltration systems used for wastewater treatment. The efficiency of the biofiltration systems depends on the nature, composition, and community structure of microorganisms in the biofilm developed on the medium. Immobilized biofilters are also popular in wastewater treatment. This chapter would provide an overview on the concept of biofiltration, the mechanism involved, types, and application of biofiltration process. The chapter will also throw light on the microbial ecology and community structure of the biological filters. Further, the different methods of identification of the microbial community will also be discussed in the chapter. � 2022 Elsevier Inc.Item Zero Waste Biorefinery: A Comprehensive Outlook(Springer Nature, 2022-01-12T00:00:00) Sachdeva, Saloni; Garg, Vinod K.; Labhsetwar, Nitin K.; Singh, Anita; Yogalakshmi, K.N.With the advancement in urbanization and industrialization, there�s sharp resource exhaustion along with instability in the global economy. Currently, most of the economies and industries follow a take-make-disposal pattern of production and consumption. This linear pattern magnifies the constraints on the availability of the resources and subsequently leads to hiked prices, unsustainable overuse, and economic volatility. Considering the circumstances, developed and developing nations are in lust after new, sustainable and carbon-free economic models to make the planet liveable. In pursuit of feasible advancements, the scientific community has already started exploring approaches to re-use or re-cycle different components across the production-consumption succession and put back the residue into the cycle of product generation, commonly conceptualized as a zero waste biorefinery. The researcher's expertise in this domain emphasis integrating the bioeconomy into a closed and re-circulating loop system to compensate for the burgeoning demands of humans. Biomass wastes from various industrial and agricultural operations have pushed the shortcomings into circular bioeconomy that not only adds auxiliary value but articulate social and environmental concerns as well. Henceforth, the present chapter provides a comprehensive outlook on various aspects of zero waste bio-refinery as a sustainable technology to process lignocellulosic wastes, algal waste, and residues into value-added products. � 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Enhancing the electrochemical performance of Fe3O4 nanoparticles layered carbon electrodes in microbial electrolysis cell(Elsevier Ltd, 2021-09-10T00:00:00) Rani, Gini; Krishna, Kadirvelu; Yogalakshmi, K.N.The present study assesses the performance of microbial electrolysis cell (MEC) to generate electric current using (I) uncoated/untreated electrodes and (II) Fe3O4 nanoparticles (FNPs) coated electrodes. The cyclic voltammetry (CV) reports highest conductivity of 58 Sm?1 in (II) while lowest (0.18 Sm?1) in (I) electrodes. The impedance spectroscopy confirms bulk resistivity of 375 k? in (I) electrodes while relatively lowest resistivity of 0.4 k? in (II) electrodes. Two sets of single chamber membraneless MECs is operated simultaneously at different applied voltage (300 mV, 500 mV and 700 mV): RI (uncoated electrodes) and RII, (FNP coated electrodes). The RII attains maximum current density and power density of 15.2 mAcm?1 and 10.6 mWcm?2 respectively at 0.7 V while RI achieves the maximum current density and power density of 4.03 mAcm?2 and 2.8 mWcm?2 respectively at same voltage. Moreover, the current density recorded in electrodes (II) is significantly higher compared to electrodes (I) measured using CV. The result suggests FNP to be an excellent catalyst which improves biosynthesis of electric current. The biologically active environment consisting of anaerobic electrogenic microbes supported biosynthesis/generation of high electric current along with other metabolites produced from the microbes mediated redox reaction. � 2021 Elsevier LtdItem Photosynthetic Microbial Fuel Cells: From Fundamental to Potential Applications(Springer Singapore, 2021-02-09T00:00:00) Jaswal, Vijay; Rani, Gini; Yogalakshmi, K.N.In photosynthetic microbial fuel cell (MFC), algae and photosynthetic bacteria undergo photosynthesis to generate electricity by harnessing the solar energy. The microorganisms on absorbing solar energy initiate a series of reactions to generate protons (H+ ions), electron, and oxygen through splitting of water. The energy from these reaction series is harnessed by placing photosynthetic organisms in anodic chamber separated from cathodic chamber by a semipermeable membrane selective for hydrogen ions. The electrons generated in an anodic chamber by photosynthetic activity of microbes travel through an outer circuit to the cathodic chamber, where they combine with protons and oxygen at the reductive electrode (cathode) to generate water. This technology has huge potential for converting solar energy into electrical energy and might also help to reduce the carbon footprint. The chapter discusses the concept, fundamentals, process design and operation of photosynthetic MFC. Furthermore, the role of photosynthetic organisms in MFC, various bottlenecks faced by MFC systems and their potential applications are also outlined in the chapter. � Springer Nature Singapore Pte Ltd. 2020.Item An Insight into Biological Photovoltaic Cell Based Electrochemical System(Springer Singapore, 2021-02-02T00:00:00) Rani, Gini; Jaswal, Vijay; Banu, Rajesh; Yogalakshmi, K.N.Biological photovoltaic cells can be called as living solar cells. They use oxygenic photoautotrophs such as cyanobacteria and algae, instead of silicon, to capture light energy for photolysis. The organisms such as cyanobacteria and algae capture light energy during the process of photosynthesis and perform charge separation of water molecules (photolysis), producing protons, electrons, and oxygen molecules. The electrons thus produced are transferred to the anode and through external circuit they move to cathode to get reduced to water, producing electric current. Biophotovoltaic (BPV) are different from traditional silicon based solar photovoltaics (SPV) cells in a number of ways. Unlike SPV, the presence of water is imperative in BPV for the algae/cyanobacteria to perform photolysis. The BPV are self-renewing in nature and do not require any external carbon source for growth. The technology of BPV can be incorporated in bioelectrochemical systems (BES) to generate green energy. BPV based electrochemical technology can be used as solar bio-battery or bio-solar panel. It can also be utilized in low powered devices such as alarm clocks. Despite the multiple advantages of BPV, still they are in the threshold of its development due to its energy conversion efficiency. The chapter would comprehensively explain the principle, working, and application of biological photovoltaic systems. � Springer Nature Singapore Pte Ltd. 2020.Item Degradation of n-hexanoyl homoserine lactone with quorum quenching bacteria immobilised magnetic nanocomposite beads(Taylor and Francis Ltd., 2020-08-20T00:00:00) Kaur, Jaskiran; Yogalakshmi, K.N.N-acyl homoserine lactones (AHLs) based quorum sensing controls various phenotype expressions, including biofilm formation, hence its interruption is considered to be an ideal option for membrane biofouling control. Bead entrapped quorum quenching bacteria was reported to be an efficient approach for degradation of signal molecules in recent years. In the present study, we investigated the potential of quorum quenching (QQ) bacteria immobilised magnetic nanocomposite beads (IMN) in degradation of signalling molecule, n-hexanoyl homoserine lactone (C6-HSL). Three QQ bacteria, named Acinetobacter baumannii JYQ2, Pseudomonas nitroreducens JYQ3 and Pseudomonas JYQ4 isolated from dairy industry waste activated sludge (WAS) were immobilised in the magnetic nanocomposite (IMN) beads. The scanning electron microscopy (SEM) of the IMN beads has indicated the successful entrapment of QQ bacteria within the alginate matrix. The GC-MS analysis showed that all the QQ bacteria immobilised magnetic nanocomposite (IMN) beads degraded the signalling molecule, n-hexanoyl homoserine lactone (C6-HSL) within 72 h of incubation. The nanocomposite beads containing the QQ bacteria Pseudomonas JYQ4 showed the maximum degradation percentage of 97 � 0.13% leaving a residual HSL of 0.7 mg/L. All the other isolates showed C6-HSL degradation percentage in the range of 87% to 95%. The data suggest the potential of C6-HSL degradation by QQ bacteria IMN beads. Hence, the study offers possibilities of controlling biofilm developed on the membrane surface during wastewater treatment processes. � 2020 Informa UK Limited, trading as Taylor & Francis Group.