The oxygen reduction reaction (ORR) is an important electrode reaction for energy storage and conversion devices based on oxygen electrocatalysis. This paper introduces the thermodynamics, reaction kinetics, reaction mechanisms, and reaction pathways of ORR in aqueous alkaline media. Recent advances of the catalysts for ORR were extensively reviewed, including precious metals, nonmetal-doped carbon, carbon–transition metal hybrids, transition metal oxides with spinel and perovskite structures, and so forth. The applications of those ORR catalysts to zinc–air batteries and alkaline fuel cells were briefly introduced. A concluding remark summarizes the current status of the reaction pathways, advanced catalysts, and the future challenges of the research and development of ORR.

Oxygen Reduction in Alkaline Media: From Mechanisms to Recent Advances of Catalysts

Waste biorefinery models towards sustainable circular bioeconomy: Critical review and future perspectives

This exhaustive review focuses on the fundamental principles and applications of heterogeneous electrochemical wastewater treatment based on Fenton’s chemistry reaction. The elementary equations involved in formation of hydroxyl radical in homogeneous electro-Fenton (EF) and photo electro-Fenton (PEF) processes was presented and the advantages of using insoluble solids as heterogeneous catalyst rather than soluble iron salts (heterogeneous electro-Fenton process) (Hetero-EF) was enumerated. Some of the required features of good heterogeneous catalysts were discussed, followed by the mechanisms of catalytic activation of H2O2 to reactive oxygen species (ROS) especially hydroxyl radical ( OH) by heterogeneous catalyst in Hetero-EF system. Extensive discussion on the two configuration of Hetero-EF system vis-a-vis added solid catalysts and functionalized cathodic materials were provided along with summaries of some relevant studies that are available in literature. The solid catalysts and the functionalized cathodic materials that have been utilized in Hetero-EF wastewater treatment were grouped into different classes and brief discussion on their synthesis route were given. Besides, the use of solid catalysts and iron-functionalized cathodic materials in bioelectrochemical system (BES) especially bioelectro-Fenton technology (BEF) using microbial fuel cells (MFCs) with concurrent electricity generation for Hetero-EF treatment of biorefractory organic pollutants was discussed. In the final part, emphasis was made on the challenges and future prospects of the Hetero-EF for wastewater treatment.

Heterogeneous electro-Fenton and photoelectro-Fenton processes: A critical review of fundamental principles and application for water/wastewater treatment

Recent advances in the use of different substrates in microbial fuel cells toward wastewater treatment and simultaneous energy recovery

Several industries are using dyes as coloring agents. The effluents from these industries are increasingly becoming an environmental problem. The removal of dyes from aqueous solution has a great potential in the field of environmental engineering. This paper reviews the classification, characteristics, and problems of dyes in detail. Advantages and disadvantages of different methods used for dye removal are also analyzed. Among these methods, Fenton process-based advanced oxidation processes are an emerging prospect in the field of dye removal. Fenton processes have been classified and represented as “Fenton circle”. This paper analyzes the recent studies on Fenton processes. The studies include analyzing different configurations of reactors used for dye removal, its efficiency, and the effects of various operating parameters such as pH, catalyst concentration, H2O2 concentration, initial dye concentration, and temperature of Fenton processes. From the present study, it can be conclude that Fenton processes are very effective and environmentally friendly methods for dye removal.

Degradation of dyes from aqueous solution by Fenton processes: a review

Sustainable ecological engineering systems for the treatment of domestic wastewater using emerging, floating and submerged macrophytes.

Catalytic microwave preheated co-pyrolysis of lignocellulosic biomasses: A study on biofuel production and its characterization.

Over the past few decades, access to abundant and easily available fossil sources aided in remarkable advancements in technologies and rapid urbanization. The unparalleled growth in population and migration of rural residents to the urban areas have transformed cities to hotspots for major anthropogenic activities, seminal contact points between natural and socio-economic activities, and areas responsible for generation of more than 80% of gross domestic product (GDP). This has placed cities at a crossroad of facing environmental grand challenges posed by population expansion, climate change, and depleting resources. Ushered by these problems, cities are directing the course of waste utilization towards sustainable production and consumption strategies by adopting the principles of circular economy (CE). This organic waste generated in huge quantities can be considered as a valuable resource in the urban biocycles. The present article highlights the importance of looping back this biogenic organic waste (domestic) to a certain extent in a decentralized way. It offers an eco-centric view to adopt circular urban food practices by constructing and operating a keyhole garden (KHG) as a case study. This approach works in synergy with nature and adopts the principles of biomimicry and cradle to cradle, wherein waste is reintroduced into the system as input resources or is metamorphosed to valuable materials. It underlines the role of CE approaches to spark this transformation and strategically direct the flow of valuable domestic waste resources to close the urban nutrient loops in a decentralized and regenerative approach. While the solutions to close the loop and recycle wastes address the end of pipe problems, the community-based innovation strategies aim at building resilience, producing food more locally, limiting the use of fertilizers, conserving water, and also combating climate change. Graphical Abstract

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Decentralized Urban Farming Through Keyhole Garden: a Case Study with Circular Economy and Regenerative Perspective

Conversion of carbon dioxide to value added products through anaerobic fermentation and electro fermentation: A comparative approach

/pdf/ecovillages-resilient-approach-to-sustainable-rural-56e8sodx8a.pdf

G. Velvizhi

Papers

Sustainable ecological engineering systems for the treatment of domestic wastewater using emerging, floating and submerged macrophytes.

Catalytic microwave preheated co-pyrolysis of lignocellulosic biomasses: A study on biofuel production and its characterization.

Decentralized Urban Farming Through Keyhole Garden: a Case Study with Circular Economy and Regenerative Perspective

Conversion of carbon dioxide to value added products through anaerobic fermentation and electro fermentation: A comparative approach

Ecovillages: Resilient Approach to Sustainable Rural Development In Indian Contex