| It is claimed in many researches that one of the promising ways to deal with dye wastewater is the electrochemically based. Electrocoagulation, known as an environmental-friendly technology, not only have been successfully demonstrated for removing pollutants in various industrial wastewaters, but also can cause less secondary pollution. However the large energy consumption hider the industrial applying of this technology and researches mainly concentrate on the removal performance but rarely consider the economical evaluation.This study focused on revealing the influencing factors of energy consumption, on the basis of which dedicating to scientific and effective energy-saving techniques. These impact factors are explored by the investigations of removal mechanism of pollutants, decisive experimental parameters, constituent of energy consumption and equivalent circuit of electrolyzation. Aiming at lowering the cost of the non-critical process without adverse to the removal efficiency and figure out ways to fully take advantage of the benefits of double-layer capacitor to decrease the costing energy. The main thesis content and innovative achievements include the following parts:Studied on the removal mechanism of the process and find the coagulation contributes most to the removing efficiency at the removal rate of more than 80%. The chroma removing rate of air floatation and anodic oxidation or reduction can only be no more than 1% and 3.5% respectively. But they could facilitate the adsorption of the pollutants and flotation of the floc.The decisive factors of the removal performance in the electrocoagulation were explored according to the removal mechanism. The best water quality always showed up at the certain electric quality no matter how much the current magnitude, electrolyte concentration, and plate area were. So the key factors are the electric quality. At the same time, the iron plate offered a better removal performance.Based on the energy consumption analysis of three different kinds of electrolysis, including direct current, periodic reversal current and pulse periodic reversal current, the results said that the constituent of energy consumption is solely in proportion to the electrolysis voltage. The consumption ratio of the electrode metal of electricity is P=kU, while the k is determined by metal atomic weight, valence of metal ions, and the price of the metal. Since the industrial electrolysis owns a fairly higher voltage, the energy-saving of electricity should obtain more attention.In order to decrease the energy consumption of the inessential factors, electrochemical impedance spectroscopy was used to calculate the equivalent-circuit parameters. In the conditions of 600mg/L X-6G reactive light yellow dyes, O.Olmol/L Na2SO4,24cm2 electrode plate area and lcm plate distance, the resistance of the electrolyte, cathode and anode polarization was 12.69Ω,2.08Ω, and 0.34Ω, and the electric double-layer capacitance was 28.63uF/cm2.Presented suggestions on energy-conservation by cutting down the resistance of these inferior parts, as electrolyte, anodic passivation and electrode polarization without interrupt electrochemical reaction. The methods of utilizing double-layer capacitance to decrease energy consumption were explored, which possess three energy-conservation benefits:Firstly, it restraints the polarization of the electrode; Secondly, it discourages the polarization of concentration; Thirdly, it recycles the electricity stored in the double-layer capacitance, which could reuse in a considerably higher efficiency due to without the resistance of the electrolyte. The contribution of double-layer capacitance cannot be ignored in pulse electrolysis. |
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