| As a kind of fundamental resource, the water of scarcity becomes serious bottlenecks constraining economic and social development. Water is vital resource for human that is becoming scarce due to population, industrial development and environmental pollution, thus efficient and low-cost strategies for sewage treatment and desalination are needed. Capacitive deionization (CD1) only requires an electric potential change without the need for a chemical reaction or phase state transformation during ion removal from salty water. This suggests CDI is a cost-effective and environmentally-friendly deionization technology.The principle of CDI process is uncomplicated, where salty water is passed through a space between different electrodes with the opposite charges, and cations and anions from the saltwater are adsorbed onto the porous surface of the cathode and anode electrode, respectively, yielding fresh water. As a derivative of CDI, membrane capacitive deionization (MCDI) was studied. The MCDI cell consists of porous carbon material and ion exchange resin, where the major difference between CDI and MCDI is that ion exchange membranes (IEMs) are placed on the cathode and anode electrode, respectively. Because IEMs have abundant charged groups such as sulfonic acid groups and quaternary amine groups, IEMs selectively adsorb counter-ionsand repel co-ions. Several studies have discussed ion transport and storage in porous electrodes, and because the membranes block co-ion migration, the macropores within the carbon material are available as extra storage space for ions, which contributes to the increased adsorption capacity of MCDI, compared to CDI.The restacking-inhibited N-doped graphene (GN) is prepared for supercapacitor material. While, the graphene oxide (GO) is reduced by melamine-resorcinol-formaldehyde (MRF). The reduced graphene oxide (RG) is characterized with the UV absorption spectrum, Raman spectra and X-ray diffraction. Moreover, the morphology of GN is measured by SEM, TEM and nitrogen adsorption. The doped N content is confirmed by elemental analysis and X-ray photoelectron spectroscopy. The result shows that GO are reduced by resorcinol derivatives. Laminated GN with 2.5 wt% GO exhibits the outstanding specific capacitance (245 F g-1), and superior cycle stability (94.8% retention after 2000 cycles). In sum, the method presented in this work could open up a general route to prepare the laminated electrode material with highly promising application in energy storage. A cross-linked quaternised polyvinyl alcohol (QPVA) membrane and a Nafion membrane were used as ion exchange membranes for MCDI. The microstructure and properties of the membrane were characterized by elemental analysis, FT-IR, X-ray diffraction, DSC, TG and SEM. The electrochemical influences of QPVA on activated carbon electrode were examined by cyclic voltammetry and electrochemical impedance spectroscopy. And electrosorption performance of the composite electrode was investigated by NaCl capacitive deionization test. The results showed that the structure order degree, ion exchange capacity and moisture content of QPVA decreased with an increasing degree of cross-linking. Accompanied by lower electric resistance, the carbon electrode with a compressed membrane exhibited a higher specific capacitance than the coated membrane. The cross-linked QPVA membrane (0.8 mL 5 wt% glutaraldehyde solutions and 0.5 g QPVA) was compressed onto an active carbon (AC) electrode and provided the optimum conditions of deionization with the adsorption capacity of 15.6 mg g-1, and the adsorption kinetics of NaCl onto the composite electrodes was affirmed by the Lagergren’s pseudo-first-order model. In short, the material and method presented in this work could open up a route to prepare composite electrode with highly promising application for water treatment. |
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