Fresh water shortage is one of the most concerning problems for several areas of the world that do not have direct access to clean water. To tackle this problem, many technologies such as as reverse osmosis and thermal processes, have been developed to remove salt from sea and brackish waters. The main issues related to such technologies are the high energy consumption and high economical and environmental costs. Capacitive deionization (CDI) is a novel alternative technology currently gaining increasing attention. CDI systems could be used to produce fresh water from brackish sources, with reduced energy consumptions and environmental impact. CDI relies on the use of porous electrodes which, once connected to a power source, electrostatically adsorb ions. Electrodes can be manufactured from a wide range of carbon-based matrices as aerogels, nanotubes, electro-spun graphene or biomass-derived activated carbons (AC). This latter category is receiving increasing attention due to the abundance of source and the simple and economic production process. In the present work, AC electrodes prepared via phisical activation in CO2 were manufactured and then tested at different water flow rates, in order to tailor the best operation parameters to achieve the highest adsorption from a saline (NaCl) solution. The system consisted of two carbon electrodes of 42X27 mm2 surface area each, connected to a 1.2V power supply. A 500 mg L-1 NaCl solution was circulated in a closed loop from a 50 mL beaker to a channel between the two electrodes, at different water flow rates. Conductivity and total dissolved solids were continuously measured through a conductivity meter. Results showed an absorption of 150 ppm of salts with a 10 ml min-1 water flow rate during two hours operation which resulted in electrodes absorption capacity of 5-6 mg of salts per g of electrodes material.

Assessing flow rate parameters on capacitive deionization of NaCl solution using biomass-derived activated carbon electrodes

2019 Fall National Meeting

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