| Electro adsorption technique is a new type of desalination technology, attracting widespread attention home and abroad at present. Many scientific research institutions have invested a lot of energy for the technology to explore and analyze, without any industrialized application. Based on the characteristics of the principle and performance advantage of device, Electro adsorption is expected to be used in a variety of industrial sector for the sewage purification. This paper focuses on the salinity of circulating cooling water in the thermal power plant, the desalination performance of Electro adsorption and how to improve the working ability of the electrode materials, etc, hoping to make full use of the practical application of Electro adsorption, and further more, to perfect relevant desalination adsorption theory. The following research work has been carried out based on Electro adsorption electrode, optimization of the module working conditions and the improvement of the performance of the Electro adsorption mechanism, etc.(1) Based on the electric double layer theory of Electro adsorption, combining adsorption dynamics model to analyze the motion of charged particles on the surface of the electrode conditions, the main factors influencing the interface adsorption capacity have been concluded, and meanwhile, optimized through the field pilot tests to actual working parameter. 1.6 V is selected as the optimal voltage for Electro adsorption modules on combined working condition; and 500 L/h is chosen as the optimal flow rate. Raw water conductivity in pilot experimental is 2300 μS/cm on average, and the average product conductivity is 730 μS/cm, chloride ion concentration in raw water 270-300 mg/L, water average production 60 mg/L, and power consumption of per tons water production 1.1 kWh/t, which proves that Electro adsorption module can meet the requirements of industrial wastewater reuse.(2) A series of improvement of Electro adsorption module is conducted, mainly including the selection of electrode materials, the size of the module, and the design of flow channel structure and related research of the experiment process, with the choice of electrode material as the key point. This paper chose carbon fiber felt with stable conductive performance and physical structure as the basis, first modifying polyacrylonitrile (PAN) based carbon fiber mat by HN03 liquid chemical oxidation and thermal oxidation process, and preparing modified electrode and to contrast against untreated carbon fiber electrode. The results show that PAN based carbon fiber felt can still achieve the best desalination under the voltage of 1.6 V, and show stronger sensitivity on voltage transformation comparing with the untreated carbon fiber electrode. Modified electrodes get into the state of equilibrium in 40 minutes. PAN base carbon fiber felt electrode modified by Liquid phase oxidation showed better desalination adsorption ability, which can at most reduce electrical conductivity of raw water with 1780 μS/cm to 430 μS/cm, while the carbon fiber electrode can only make it to 605 μS/cm; The thermal oxidation modification of carbon fiber electrodes show the better adsorption ability to organic matter, and removal rate of raw water COD reaches up to 80%, significantly exceeding that of carbon fiber electrode, but two kinds of electrodes cannot work under high COD.(3) Considering the uniqueness of microcosmic structure of carbon nanotubes and the conductive ability, chemical vapor deposition method was selected to prepare carbon nanotubes/PAN based carbon fiber composite electrode (CNTs/PCF). By contrast experiment, CNTs/PCF electrode has a better desalination performance than carbon fiber felt electrode, which suggests that electrodes performance upgrade afte increasing significantly the surface modification of specific surface area and conductivity. In addition, in order to overcome the defect that composite electrode can’t desalt under high COD, channel aperture for the materials has been re-chosen combining with the double electrical layer model. polypyrrole/PAN based carbon fiber felt (PPy/PCF) composite was prepared as Electro adsorption electrode materials. Because of its large number of pore distribution in the structures, which is up to 100 nm, this electrode can guarantee the desalting efficiency under the water quality whose COD is more than 300 mg/L. It can simplify the pretreatment unit construction, reduce the processing cost. Thermal power plant circulating water---on the condition of initial conductivity 1500 μS/cm, PPy/PCF as electrodes---when the voltage increases, desalting ability and the removal of COD enhance synchronously. The optimum working voltage is 1.4-1.6 V. At the same time, comparing to carbon nanotubes and PCF, the working voltage of PPy/PCF can be lowered to 1.4 V, to reach energy-saving purpose. |
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