| Although internal micro-electrolysis(IME) has been widely studied in the field of refractory organic wastewater treatment, some of the fundamental questions regarding the functions of cathodes and anodes(e.g., iron and granular active carbon) and what happens when numerous particles(microscopic galvanic cells) are combined in the wastewater treatment of an IME reactor still not be clearly addressed, also the enhanced IME treatment technologies for specific refractory organic wastewater should been further developed. In this thesis, we focused on the electrochemical behaviors of the cathode and anode, the power generation characteristics of the simulated and simplified single group IME, and also the degradation of refractory organism in cathode and anode cell, respectively, with specifically designed and manufactured electrolysis reactor with separated cathode and anode cells, specific reactor for tests of group-effect. With these experiments, the phenomena of leakage of current between cathode and anode in an IME, dual-reduction of 2,4-dichlorophenol(2,4-DCP), and group-effect of voltage of open circle were discovered, respectively. It was believed that all above phenomenon were commonly existed in an internal micro-electrolysis reactor, and were contributed to the high removal efficiency of organism by traditional internal micro-electrolysis process and possible enhanced internal micro-electrolysis process with aeration. Based on above results, the internal micro-electrolysis method was enhanced to be integrated processes of traditional internal micro-electrolysis and internal micro-electrolysis with aeration, which were further designed in the application of specific wastewater treatment. The sequence internal micro-electrolysis was specifically designed for mature landfill leachate under the design concept of combine reductive and oxidative processes in one reactor with automation technology of PLC. And an engineering project using intergated IME complied with biological contact oxidation process to treat pharmaceutical wastewater has been successfully designed, build and operated in Shandong, China. A new cathode material of copper foam had also been introduced in the study of electrolysis with external power in order to provide sufficient electron for reaction. It was used as cathode in a gas diffusion electrode reactor to treat X-3B. The degradation of X-3B was much more efficient than traditional copper cathode. It degradation pathway and mechanism had also been discussed. Main parts of the research are as below:(1) The reduction and oxidation mechanism in an internal micro-electrolysisThe redox reactions of 2,4-DCP on graphite cathode, in which 2,4-DCP have a sharp reductive peak, has been verified thought the CV curves of graphite in 2,4-DCP aqueous solution by Autolab potentiostats and galvanostat. And the voltage of open circles for couple iron-graphite electrodes had been detected with this Autolab workstation. The result show that those voltages are high enough for 2,4-DCP degradation. The power generation characteristics had also been test, in which low FF values had been found for most IME. It showed that leakage of current must be commonly existed in IME reactor. Additionally, both of cathode and anode cells had been could degrade 2,4-DCP. 2,4-DCP in anode cell could probably be reduced by ferrous iron or the leaked electron from iron corrosion which should be transferred to graphite cathode. It is supported by the calculations of degradation rate in both cathode and anode cells. Group-effect of voltage which is a great increase of the voltages of open circle only by insert one or two unconnected groups of additional electrode couples into the electric field line of detected electrode couple. It means that a high voltage probably exist in IME when numerous particles mixed together in the reactor, which is not possible from previous opinion derived classic understanding of the IME reactor based on isolated electrode couple. With this high voltage, some organic compounds with high redox potential could be reduced in IME reactor which was believed impossible previously. 4×10-4 M H2O2 has been detected in an IME reactor with aeration, which supports the strong oxidative reaction mechanism of IME-Fenton.(2) Treatment of mature landfill leachate with sequencing batch internal micro-electrolysis reactor(SIME)The mature landfill leachate was extraordinary resisted to oxidation process and extremely stable. Therefore, common treatment was noneffective to mature landfill leachate. The sequencing batch internal micro-electrolysis reactor was specifically designed for mature landfill leachate, in which a reductive process of IME followed by oxidative process of IME with aeration, which is also called IME-Fenton. The result shows that the combined process was effective to treat mature landfill leachate, which is much better than that of single IME and IME-Fenton. The SIME reactor is also complied with automation technology of PLC, with which a simple operation could be possible. A practical engineering of treating pharmaceutical wastewater with enhanced internal micro-electrolysis with biological contact oxidation process had been designed, build and operated successfully. The capacity of the treating facility is 80 m3 day-1.(3) Treatment of simulated wastewater of acid brilliant red X-3B by gas diffusion electrode method with copper foam electrode under low voltage electrolysis.The electron supply in internal micro-electrolysis reactor is still in-sufficient at most operation conditions. The external power was introduced to treatment system in order to provide sufficient electron for reduction and further modified oxidation process. However, a new cathode with high surface area is urgently needs. The copper foam electrode is made by powder sintering method. It is character by porous structures while it also has good electrical conductivity. The result showed that it is much better than common copper electrode as a cathode in gas diffusion electrolysis reactor. Much more H2O2 has been detected in gas diffusion electrolysis reactor with copper foam cathode. It was also enhanced by ferrous and ferric iron. The samples from degradation process were tested by UV-Vis and LC-MS. The result showed that X-3B is degraded while the ring in it was broken by the electrolysis process, which is probably due to hydroxyl radical produced by Fenton process in it.The phenomena of dual-reduction and group-effect, which were discovered in this thesis, were commonly existed in all internal micro-electrolysis processes. And both of them, especially the group effect phenomenon, contribute to the degradation of organisms in internal micro-electrolysis. With possible high redox potential provided by the group effect in internal micro-electrolysis reactor, organism with high redox over-potential still could be reduced which was believed impossible previously. Therefore, the group effect of potential provides a brand new opinion of potential in internal micro-electrolysis system which improves the principle of internal micro-electrolysis method. The methods of internal micro-electrolysis was further developed to be enhanced sequencing batch internal micro-electrolysis reactor and internal micro-electrolysis complied with biological contact oxidation process, which were successfully applied to mature landfill leachate and pharmaceutical wastewater treatment, respectively. External power was introduced in order to provide sufficient electron, together with porous copper foam electrode. The preliminary experimental results suggested that the new electrode was very good gas diffusion electrode and probably have a good application foreground in the field of wastewater treatment by electrochemical method. |
PDF Full Text Request