Ultrafast capacitive deionization using rice husk activated carbon electrodes

Capacitive deionization (CDI) has attracted much attention as a promising desalination technology, since inexpensive carbon electrodes can be employed at a large scale. In this work, rice husk activated carbon (RHAC) was utilized to obtain electrodes for desalination. The RHAC materials were synthesized using different carbonization temperatures. After their physicochemical and electrochemical characterization, it was observed that the electrodes produced with the RHAC obtained at lower carbonization temperatures (450 or 650 degrees C) provided better desalination performance with a salt removal capacity of 15.5 mg g(-1) (1.2 V and C-0 = 600 mg L-1). However, the most remarkable feature of the RHAC electrodes was their ultrafast kinetics. To the best of our knowledge, here we report the fastest electrosorption rates observed for carbon electrodes applied for CDI (10.52 mg g(-1) min(-1)). From a simultaneous analysis considering the electrosorption/desorption kinetics and the electrosorption capacity, the RHAC carbonized at 600 degrees C displayed an outstanding value of 5.2 g of salt removed per gram of electrode per day. Importantly, the electrodes remained stable even up to 80 electrosorption/desorption cycles, with both the kinetics and the electrosorption capacities remaining close to the initial values.