Study On Activated Carbon Regeneration By High Voltage Pulse Discharge

The high voltage pulse discharge regenerator could produce many active species including hydroxyl radical, hydrogen peroxide, ozone, uv, etc., which brought the integrated physical and chemical effects to degrade the toxic adsorbate on the surface of activated carbon making the activated carbon regenerate. The new method of regeneration on activated carbon had more incomparable advantages than the traditional methods because of its advantages such as low energy consumption, short regeneration time, high regeneration efficiency, and simple equipments, etc.. The regeneration on activated carbon(AC) and activated carbon fiber(ACF) by high voltage pulse discharge were studied in this thesis as well as their regeneration mechanisms.Granule activated carbon(GAC) regeneration was studied in gas-liquid series electrical pulse discharge regenerator, in which the optimum value between the panel of earth pole and the high voltage pole was chose 18mm(the liquid phase height was 12mm, the gas phase height was 6mm) and the optimum oxygen flow value rate was 0.09m3/g. Main factors effecting regeneration efficiency were discussed including the regeneration time, temperature, solution pH and conductivity, the pulse discharge voltage and frequency, particle size of activated carbon, regeneration times and oxidant. Higher regeneration efficiency was achieved for smaller particle size of activated carbon at extended time and higher temperature; the more pulse discharge voltage and frequency had the benefit on the activated carbon regeneration within a certain range, but the efficiency of the regeneration would decline. when the voltage and frequency of pulse discharge were 46kV, 100pps, the efficiency of regeneration was best; For pH of the solution, pH showed to some extent effect on regeneration efficiency; The activated carbon regeneration efficiency firstly increased, and then declined with the conductivity of solution increasing, the optimum of conductivity was chose 500μs/cm; Regeneration efficiency decreased a little but kept above the level of 85% when activated carbon was recycled 6 times. H2O2 which was added to the solution had a little influence on the regeneration efficiency at the preliminary stage of the regeneration, but not at the end of the regeneration.The experimental results showed the regeneration of activated carbon fiber was higher than activated carbon because of its unique pore structures and surface characteristics. TiO2/ACF composite materials regeneration rate should be higher than the individual activated carbon fiber regeneration, the results of which was attributed to make full use of ultraviolet light produced by pulse discharge. In the pulse discharge process, the surface acidic functional groups of activated carbon and activated carbon fiber had more substantial increase in the number while the number of basic functional groups almost kept the same level, specific surface area and pore volume changed to some degrees because of oxidation of various kinds of oxides.Regeneration of AC was attributed to desorption and the degradation of the adsorbate on the surface of AC. During the early stage of regeneration, Oxidative decomposition of organic adsorbate was the controlling step in the regeneration process,in which the surface alkaline functional groups of act as catalyzer. Afterwards, desorption of organic adsorbate from inner to exterior surface of AC was the controlling step.