Abstract
Being constituents of the effluents of many industries, heavy metals cause severe environmental pollution due to their recalcitrance and persistence in the environment. Conventional remediation strategies used to treat heavy metals loaded wastewater are neither economical nor environmentally friendly. To overcome these challenges, the rise of a new process that combines energy conservation and recovery was mandatory. Microbial fuel cells have been recognized as an emerging technology to mitigate environmental pollution; it provides a solution to wastewater treatment and the removal and/or recovery of heavy metals. Microbial fuel cells can be defined as bioelectrochemical systems that utilize the catalytic activity of microorganisms organized in biofilms to oxidize organic or inorganic compounds by producing electric current thus providing a new opportunity for sustainable energy production and bioremediation. The removal of metals, such as chromium, vanadium, arsenic, copper, silver and gold has been studied using both single and double chambered MFCs. The fact that some heavy metals have high redox potential makes it possible to utilize them as effective electron acceptors instead of oxygen in the cathodic chamber of microbial fuel cells. Biotic/Abiotic cathode chambers can not only remove but also recover heavy metals. However, a number of challenges such us: low production rates and limited efficiencies make the application of this technology restricted to lab scale only. In this chapter, we review the treatment of metal-containing effluents using microbial fuel cells. We’ll first summarize the principle of metal removal/recovery in microbial fuel cells, and then provide an overview of literature that attempted to treat metal loaded effluents in both single and double chambered microbial fuel cells while discussing power output, heavy metal removal efficiency and mechanisms involved in the process. Furthermore, the primary challenges and opportunities for scaling-up of microbial fuel cells and their future applications in the treatment of heavy metals contaminated wastewater will be outlined.
Highlights
Water is a precious commodity that suffers from various forms of pollution and degradation: ecosystems and people’s health are directly impacted
Any compound with a comparable or higher redox potential than oxygen can be reduced at the cathode, elements like permanganate, ferricyanide, nitrate, persulfate, dye molecules, and most importantly heavy metals were used and proven to be efficient electron acceptors in the cathode of Microbial fuel cells (MFCs) (Mathuriya and Yakhmi, 2014; Wang and Ren, 2014; Nancharaiah et al, 2015; Modestra et al, 2017)
With the performance of the electrodes significantly affected by the type of material they are fabricated with, all throughout the last decade, many researchers focused on the electrode material because the performance of a MFC directly depends on the kinetics of its electrodes (Mustakeem, 2015)
Summary
Water is a precious commodity that suffers from various forms of pollution and degradation: ecosystems and people’s health are directly impacted. Various physical, chemical, and biological treatment approaches for the removal of heavy metals from wastewater have been largely practiced These methods include chemical precipitation, coagulation-flocculation, adsorption, membrane filtration, and electrochemical treatment technologies (Fu and Wang, 2011). Microbial fuel cells (MFCs) have been proven to be a promising technology to harvest energy and treat wastewater owing to their low-cost and sustainability (Chouler et al, 2016). In their simplest form, MFCs consist of an anodic and a cathodic compartment that are generally separated by a proton exchange membrane (PEM) to avoid the migration of electrolytes from one chamber to the other (Ho et al, 2018). This review gives an insight into the major challenges holding back the application and the scaling-up of the MFC technology, including the thermodynamic limits, heavy metals biotoxicity, pH imbalance, and membrane biofouling
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