Investigation And Application Of Micro-arc Oxidation Catalytic Technology In Wastewater Treatment

As is well known that TiO2 exhibits superior catalytic effect in the cooperation with plasma to improve the production of ·OH, and when Ti or Ti alloys is used as an anode, a catalytic adhesive TiO2 film will be made on it during the micro-arc oxidation (MAO) process. Compared with traditional catalysts dissolved or suspended in the electrolyte, this liquid discharge plasma-electrode catalytic system naturally formed on the anode is proved to be much more centralized, efficient and promising.In order to enhance discharge and wastewater treatment effect, based on the former investigation, in this paper Ti-Al alloy electrodes are used to discharge by MAO in organic wastewater simulated by Rhodamine B, optimize discharge by the means of optimizing oxidation films and discharge bubbles, and then carry on studying characteristics and mechanism of discharge, the main content of this paper is as follows:1. Through the test of variation of voltage and current during MAO with AC power supply and Ti-Al alloy electrodes, characteristics of U-I are compared from both the deviation degree of peak value and the deformation of U-I curve under the condition of different electrolytes, different electrode materials and whether discharge is happened or not. It has been found that the phase of an increasing impedance caused by film formation and the phase of a decreasing impedance caused by film-breakdowns are alternately predominate under different experimental conditions during different stages of every single period of AC power supply.2. Influence of characteristics of oxidation film on MAO-electrode catalysis is investigated by changing power supply mode (alternate discharge under bipolar rectangular wave power supply mode and intermittent discharge under monopolar rectangular wave), moreover experiments are carried out in order to investigate the static effect after discharge. It has been found that better decoloration rate of Rhodamine B is acquired under narrow wave width, and alternate effect and intermittent effect are both beneficial to discharge; combined with static effect, optimum experimental conditions in this paper is obtained.3. Films formed on electrode surfaces under different discharge conditions (alternate discharge, intermittent discharge and continuous discharge) are examined and analyzed by SEM and XRD, and it has been found that in alternate discharge, the structure of oxidation is seriously destroyed so that more weak places are offered for the benefit of discharging;moreover both TiO2 of rutile and anatase are generated which ensures better and diversified catalysis in plasma environment.4. By modification of the experimental devices, the influence of bubble rises and placement of electrodes, it has been found that distribution and diffusion pattern of the bubbles generating on electrodes are influenced by different placements and depths of electrodes. The addition of discharge promoter is beneficial to the decoloration effect, but has little effect on the initial voltage and stablitilized voltage of discharge.