Abstract
This work reports on the novel formation of caustic potash (KOH) directly on the MFC cathode locking carbon dioxide into potassium bicarbonate salt (kalicinite) while producing, instead of consuming electrical power. Using potassium-rich wastewater as a fuel for microorganisms to generate electricity in the anode chamber, has resulted in the formation of caustic catholyte directly on the surface of the cathode electrode. Analysis of this liquid has shown to be highly alkaline (pH>13) and act as a CO2 sorbent. It has been later mineralised to kalicinite thus locking carbon dioxide into potassium bicarbonate salt. This work demonstrates an electricity generation method as a simple, cost-effective and environmentally friendly route towards CO2 sequestration that perhaps leads to a carbon negative economy. Moreover, it shows a potential application for both electricity production and nutrient recovery in the form of minerals from nutrient-rich wastewater streams such as urine for use as fertiliser in the future.
Highlights
The growing consumption of fossil fuels is increasing the emissions of carbon dioxide, which is a major greenhouse gas (GHG), contributing to global warming
All Microbial Fuel Cell (MFC) generated catholyte that was collected in the syringe attached to the cathode half-cell, and it was shown to be directly related with the power output performance; activated carbon (AC) generated 20.8 mL ± 2.8 mL, microporous layer on carbon cloth (MPL) 16.7 mL ± 3.9 mL, Veil MPL 15.5 mL ± 0.2 mL and Veil 14.6 ± 1.8 mL (Fig. 2B)
During the MFC operation, the production of catholyte on the surface of the cathode electrode was a direct result of electricity generation, and power output has been correlated with catholyte volume
Summary
The growing consumption of fossil fuels is increasing the emissions of carbon dioxide, which is a major greenhouse gas (GHG), contributing to global warming. A recent method of sorbent regeneration from wastewater includes the use of bioelectrochemical systems (BES) where electrical power can be used to produce acid and alkali solutions (Zhu et al, 2013). This incorporates wastewater treatment and the recycling of its elements into useful products and chemicals with the use of microbial activity and external power input (Kelly and He, 2014) for example, to produce caustic soda in Microbial Electrolysis Cells (MEC) (Rabaey et al, 2010). Recovering potassium and its use as a carbon sink, followed by the mineralisation into bicarbonate, has a potential use as fertiliser as well as stabilising the carbon cycle
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