Many rivers in tropical and subtropical karst regions are supersaturated with respect to CaCO3 and have high water hardness. After flowing through waterfall sites, river water is usually softened, accompanied by tufa ...Many rivers in tropical and subtropical karst regions are supersaturated with respect to CaCO3 and have high water hardness. After flowing through waterfall sites, river water is usually softened, accompanied by tufa formation, which is simply described as a result of water turbulence in fast-flowing water. In this paper, a series of laboratory experiments are designed to simulate the hydrological conditions at waterfall sites. The influences of air-water interface, water flow velocity, aeration and solid-water interface on water softening are compared and evaluated on a quantitative basis. The results show that the enhanced inorganic CO2 outgassing due to sudden hydrological changes occurring at waterfall sites is the principal cause of water softening at waterfall sites. Both air-water interface area and water flow velocity increase as a result of the 'aeration effect', 'low pressure effect' and 'jet-flow effect' at waterfall sites, which greatly accelerates CO2 outgassing and therefore makes natural waters become highly supersaturated with respect to CaCO3, consequently resulting in much CaCO3 deposition and reduction of water hardness. Aeration, rapidly increasing air-water interface area and water flow velocity, proves to be effective in reducing water hardness. This study may provide a cheap, safe and effective way to soften water.展开更多
Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for wate...Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.展开更多
基金This research was supported jointly by the CRCG Seed Grant of the University of Hong Kongthe National Natural Science Foundation of China(Nos.90202003 and 40303014)
文摘Many rivers in tropical and subtropical karst regions are supersaturated with respect to CaCO3 and have high water hardness. After flowing through waterfall sites, river water is usually softened, accompanied by tufa formation, which is simply described as a result of water turbulence in fast-flowing water. In this paper, a series of laboratory experiments are designed to simulate the hydrological conditions at waterfall sites. The influences of air-water interface, water flow velocity, aeration and solid-water interface on water softening are compared and evaluated on a quantitative basis. The results show that the enhanced inorganic CO2 outgassing due to sudden hydrological changes occurring at waterfall sites is the principal cause of water softening at waterfall sites. Both air-water interface area and water flow velocity increase as a result of the 'aeration effect', 'low pressure effect' and 'jet-flow effect' at waterfall sites, which greatly accelerates CO2 outgassing and therefore makes natural waters become highly supersaturated with respect to CaCO3, consequently resulting in much CaCO3 deposition and reduction of water hardness. Aeration, rapidly increasing air-water interface area and water flow velocity, proves to be effective in reducing water hardness. This study may provide a cheap, safe and effective way to soften water.
基金supported by international cooperation program for science and technology funded by the Ministry of Science,ICT&Future Planning(NRF-2014K1A3A1A09063208)
文摘Electrochemical water treatment is an attractive technology for water desalination and softening due to its low energy consumption. Especially, capacitive Deionization(CDI) is promising as a future technology for water treatment. Graphene(rGO) has been intensively studied for CDI electrode because of its advantages such as excellent electrical conductivity and high specific surface area. However, its 2D dimensional structure with small specific capacitance, high resistance between layers and hydrophobicity degrades ion adsorption efficiency. In this work, we successfully prepared uniformly dispersed Fe3O4/rGO nanocomposite by simple thermal reactions and applied it as effective electrodes for CDI. Iron oxides play a role in uniting graphene sheets, and specific capacitance and wettability of electrodes are improved significantly;hence CDI performances are enhanced. The hardness removal of Fe3O4/rGO nanocomposite electrodes can reach 4.3 mg/g at applied voltage of 1.5V, which is 3 times higher than that of separate r GO electrodes.Thus this material is a promising candidate for water softening technology.
