Surface Electrochemistry of Carbon Electrodes and Faradaic Reactions in Capacitive Deionization.

Recent advances in electrochemical desalination techniques have paved way for utilization of saline water. In particular, capacitive deionization (CDI) enables removal of salts with high energy efficiency and economic feasibility, while its applicability has been challenged by degradation of carbon electrodes in long-term operations. Herein, we report a thorough investigation on the surface electrochemistry of carbon electrodes and Faradaic reactions that are responsible for stability issues of CDI systems. By using bare and membrane CDI (MCDI) as model systems, we identified various electrochemical reactions of carbon electrodes with water or oxygen, with thermodynamics and kinetics governed by the electrode potential and pH. As a result, a complete overview of the Faradaic reactions taking place in CDI was constructed by tracing the physicochemical changes occurring in CDI and MCDI systems.

Enhancement in Desalination Performance of Battery Electrodes via Improved Mass Transport Using a Multichannel Flow System.

Desalination technologies have heavily been investigated to utilize the abundant salt water on Earth due to the global freshwater shortage. During recent years, the desalination battery (DB) has attracted attention for its low-cost, eco-friendly, and energy-efficient characteristics. However, the current DB system is subject to inevitable performance degradation because of the mass-transfer limitation at the electrode-electrolyte interface, particularly when the system is used to treat brackish water. Here, we present a novel strategy to overcome the intrinsic mass-transfer limitation of DB in brackish water using an effective cell design based on a multichannel flow system. Compared to the conventional DB that consists of one feed channel, the multichannel desalination battery (MC-DB) is configured using two side channels introducing a highly concentrated solution to the electrodes and one middle feed channel for water desalination. The MC-DB showed a desalination capacity of 52.9 mg g-1 and a maximum salt removal rate of 0.0576 mg g-1 s-1 (production rate of 42.3 g m-2 h-1) when a salinity gradient between the feed streams in the middle (10 mM NaCl) and side (1000 mM NaCl) channels was present, which were 3-fold higher than those in the case with no salinity gradient. In addition, the high concentration solution in the side channel significantly enhanced the rate capability of MC-DB, allowing the system to operate under a high current density of 40 A m-2 with a desalination capacity of 34.1 mg g-1. Considering the effect of electrolyte concentration on the battery electrode performance through electrochemical characterization, the highly saline medium at the side channel in the MC-DB creates an optimal environment for the battery electrode to fully capitalize the high desalination capacity, salt removal rate, and capacity retention of the battery electrodes.

Lithium recovery from brine using a λ-MnO2/activated carbon hybrid supercapacitor system.

Lithium is one of the most important elements in various fields including energy storage, medicine manufacturing and the glass industry, and demands for lithium are constantly increasing these days. The lime soda evaporation process using brine lake water is the major extraction method for lithium, but this process is not only inefficient and time-consuming but also causes a few environmental problems. Electrochemical recovery processes of lithium ions have been proposed recently, but the better idea for the silver negative electrodes used in these systems is required to reduce its cost or increase long term stability. Here, we report an electrochemical lithium recovery method based on a λ-MnO2/activated carbon hybrid supercapacitor system. In this system, lithium ions and counter anions are effectively captured at each electrode with low energy consumption in a salt solution containing various cationic species or simulated Salar de Atacama brine lake water in Chile. Furthermore, we designed this system as a flow process for practical applications. By experimental analyses, we confirmed that this system has high selectivity and long-term stability, with its performance being retained even after repetitive captures and releases of lithium ions.

Therapeutic potential of Gastrodia elata Blume for the treatment of Alzheimer's disease.

Several studies have demonstrated that the Chinese herb Gastrodia elata Blume can protect against amyloid beta-peptide (Aß)-induced cell death. To investigate the possible therapeutic effects of Gastrodia elata Blume on Alzheimer's disease, we established a rat model of Alzheimer's disease by injecting Aß25-35 into bilateral hippocampi. These rats were intragastrically administered 500 or 1 000 mg/kg Gastrodia elata Blume per day for 52 consecutive days. Morris water maze tests showed that Gastrodia elata Blume treatment significantly improved the spatial memory of Alzheimer's disease rats. Congo red staining revealed that Gastrodia elata Blume significantly reduced the number of amyloid deposits in the hippocampus of these rats. Western blot analysis showed that choline acetyltransferase expression in the medial septum and hippocampus was significantly increased by the treatment of Gastrodia elata Blume, while Ellman method showed significant decrease in the activity of acetylcholinesterase in all three regions (prefrontal cortex, medial septum and hippocampus). These findings suggest that long-term administration of Gastrodia elata Blume has therapeutic potential for Alzheimer's disease.

Gastrodia elata Blume and its pure compounds protect BV-2 microglial-derived cell lines against ß-amyloid: the involvement of GRP78 and CHOP.

OBJECTIVES: Gastrodia elata (GE) Blume (Orchidaceae) has been previously known for its therapeutic benefits against neurodegenerative diseases. Microglial activation and death have been implicated in the pathogenesis of a variety of neurodegenerative diseases, including Alzheimer's disease. In this study, GE and its pure components, gastrodin and 4-hydroxybenzyl alcohol (4HBA), were applied to ß-amyloid-induced BV2 mouse microglial cells. MATERIALS AND METHODS: Cell viability was assessed by the MTT assay and Western blotting was also performed. RESULTS: ß-amyloid-induced cell death was shown to be induced time- and dose-dependently. To examine the cell death mechanism, we confirmed the involvement of ER stress signaling. C/EBP homologous protein (CHOP), a pro-apoptotic ER stress protein, was expressed at high levels but glucose-regulated protein 78 (GRP78), an anti-apoptotic ER stress protein with chaperone activity, was only slightly affected by treatment with ß-amyloid. However, pretreatment with GE and its components inhibited the expression of CHOP but increased that of GRP78 in ß-amyloid-treated cells. This study also showed that a single treatment with GE extracts, gastrodin, or 4HBA induced the expression of GRP78, a marker for enhanced protein folding machinery, suggesting a protective mechanism for GE against ß-amyloid. CONCLUSIONS: This study reveals the protective effects of GE against ß-amyloid-induced cell death, possibly through the enhancement of protein folding machinery of a representative protein, GRP78, and the regulation of CHOP in BV2 mouse microglial cells.