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Capacitive deionization (CDI) is an emerging desalination technology which utilizes porous electrodes to remove ions in water by electrosorption. Similar to electric capacitors, energy is stored and released during charging and discharging cycles, respectively. In this study, a nanoporous activated carbon coupled flow-through CDI device was used to evaluate energy consumption and recovery under various operational conditions by charging and discharging the cell at a constant current, respectively. Results indicated that the charging/discharging current, salt concentration and water flow rate were major factors impacting electrosorption and energy consumption, by changing the structure of the electrical double layer (EDL) and how ion transport occurs between the interface and bulk solution. A porosity-based EDL theory was applied to explain the experimental observations. Between 30 and 45% of the energy consumed during charging could be recovered depending on operational conditions, although thermodynamically more than 98% of the total energy should be recoverable. Results indicated that overpotential and faradaic reactions induced irreversible energy are the major reasons for gaps in observed energy losses. Energy consumption for reducing the salinity of brackish water from 32.7 to 5.5 mM by our device could be as low as 0.85 kWh/m 3 under most optimized conditions (dependent on materials used and cell configuration). The energy consumption can be dramatically reduced by employing more electron-conductive and Faradaic-resistant electrode materials. Increasing demand for freshwater is driving the need for energyefficient and cost-effective technologies to generate potable water from unconventional sources such as brackish water.1 Due to its simplicity and reliability, capacitive deionization (CDI) has attracted a growing interest for water desalination.1-7 Capacitive deionization utilizes highly porous electrodes to remove charged ions in water by electrosorption (Figure 1). During charging, an electric voltage is applied and ions are driven to oppositely charged electrodes by electrostatic force and entrapped at the electrode-water interface by the formation of an electric double layer (EDL). After removing the ions, the electric voltage is removed or reversed to discharge and regenerate the electrodes. Ions return to solution and the concentrated brine is discarded. Desalination is realized by means of consecutive charging/discharging cycles to separate influent water into freshwater and brine (concentrate) streams.Energy consumption is a major factor driving the synthesis of new CDI electrode materials. Energy-efficient CDI devices are required for up-scaling the process and for broader adoption of this technology for potable or agricultural water treatment. An important feature of CDI is that part of the energy consumed during charging can be recovered during discharging, a process similar to charge/discharge in electric capacitors.6,8 CDI could become more cost competitive compared with well-established desa...

In contrast to many nanotoxicity studies where nanoparticles (NPs) are observed to be toxic or reduce viable cells in a population of bacteria, we observed that increasing concentration of TiO2 NPs increased the cell survival of Bacillus subtilis in autolysis-inducing buffer by 0.5 to 5 orders of magnitude over an 8 hour exposure. Molecular investigations revealed that TiO2 NPs prevent or delay cell autolysis, an important survival and growth-regulating process in bacterial populations. Overall, the results suggest two potential mechanisms for the disruption of autolysis by TiO2 NPs in a concentration dependent manner: (i) directly, through TiO2 NP deposition on the cell wall, delaying the collapse of the protonmotive-force and preventing the onset of autolysis; and (ii) indirectly, through adsorption of autolysins on TiO2 NP, limiting the activity of released autolysins and preventing further lytic activity. Enhanced darkfield microscopy coupled to hyperspectral analysis was used to map TiO2 deposition on B. subtilis cell walls and released enzymes, supporting both mechanisms of autolysis interference. The disruption of autolysis in B. subtilis cultures by TiO2 NPs suggests the mechanisms and kinetics of cell death may be influenced by nano-scale metal oxide materials, which are abundant in natural systems.

Excessive nitrate in surface waters poses a great threat to the health of human beings. Traditional measuring tools require either hazardous chemicals or organic matter compensation. In this work, we proposed an online microfluidic device incorporated with a miniaturized capacitive deionization cell that separates organic matter and nitrate ions before the measurement and afterwards determines the nitrate concentration with a 235-nm LED. The optimal operational parameter setting, which is a combination of 600-s charging duration and 0.5-V cell potential, was also obtained in order to achieve the maximum fractionation of nitrate ions. Promising results were obtained by our new approach, revealing that this device could serve as a functional and effective tool for the determination of nitrate concentration in surface water.