| In recent years, the concentration of antibiotics increases in theenvironmentdue to their abuse, which threatens to both human health and ecological safety. Because of their good antibacterial activity, antibiotics are difficult to be degraded with conventional biological processes.However, Electro-Fenton technology is an efficient and clean advanced oxidation technology, which is considered as an ideal choice for the treatment of antibiotic wastewater. The production of H2O2 and the performance of the catalyst are the key factorsthat influence the treatment of organic pollutants in the Electro-Fenton system. Therefore, developing new efficient and cost-saving reactors becomes a major research focus in the field. The main contents are as follows:1.We developed a novel Electro-Fenton reactor for wastewater treatment, in which a rotating graphite disk electrode as the cathode.Results indicated that the optimal conditions for H2O2 generation werecathodic potential of-0.8 V vs. SCE, rotating speed of 400 rpm and pH of 3. Under the optimal conditions, H2O2 generation rate reached 0.90 mg?L-1?h-1?cm-2. The degradation of tetracycline was investigated in this reactor and the results confirmed that this reactor had the excellent ability totreat organic pollutants in the absence of aeration. With the 1.0 mM ferrous ion as catalyst,tetracycline of 50 mg?L-1 could be removed in 2 h.The analysis of Chronoamperometry demonstrated that the diffusion coefficients of dissolved oxygenwasl9.45x10-5 cm2/s, which was greater than other researchs due to the rotation of the cathode. In addition, the calculation indicated that the oxygen is able to diffuse through theaqueous film on the graphite within the contact time.This study provides a promising method for degrading organic pollutants by the combination of rotating disk technology with Electro-Fenton reactor.2.An electro-Fenton reactor was built with the rotating gas diffusion electrode as cathode, which was efficient for H2O2 production.After a series of optimization, the best preparation conditions for electrode were identified:graphite and PTFE quality ratio of 2:1, the molding pressure of 15 Mpa, pressing time of 30 min and pore-forming agent Na2SO4 addition amount of 0.5 g. When the condition is set as pH=3, cathode voltage of-0.8 V vs. SCE, and the rotating speed of 300 rpm, the accumulation of H2C>2was up to249.7 mg?L-1 after 120 min electrolysis, with maximum generation rate of 12.8mg?L-1?h-1?cm-2.In addition, the cathode exhibited good stability after 10 runs,3.We developed a new electro-Fenton system with a Fe3O4/gas diffusion electrode (Fe3O4/GDE) as the rotating cathode, in which Fe3O4 was pre-immobilized on the activated carbon. In this system, H2O2 was firstly electro-generated by the rotating mode and the porous structure of the gas diffusion cathode, and then in suit activated to hydroxyl radical by the immobilized Fe3O4. It was proved that 50 mg?L-1 of tetracycline was almost completely degraded in 120 min, with the total organic carbon removal efficiency of 56.7%, which was accelerated by 1.7 times compared with the mobilized Fe3O4 as catalyst. Thisenhancement was attributed to the increased catalytic ability of immobilized Fe3O4 in the presence of electric field. The effects of some important parameters such as Fe3O4 loading, initial pH, applied potential and the rotation speed on the tetracycline removal were evaluated. Further investigation indicated that the immobilized Fe3O4 contributed to the decomposition of H2O2 predominately, while the effectsof leaching iron could be ignored. The hydroxyl radical was considered as theprimary reactive oxidants, and the degradation mechanism of tetracycline was proposed by the analysis of intermediates by ion chromatograph technology.4. It is confirmed that the rotating disk electro-Fenton reactor can improve oxygen diffusion process, thus improving the degradation of tetracycline. However, there are also some drawbacks, such as the poor O2mineralization ability. In order to enhance the efficiency of Electro-Fenton system, UV was introduced to create a photoelectro-Fenton coupling rotating disk system. Investigations on the pH, voltage and rotating speed were conducted to improve the generation of H2O2 in this system, and the results showed that H2O2 concentration could achieve 51.5 mg?L-1 under the pH of 3, rotation speed of 400 rpm and a potential of-0.8 V vs. SCE in 75 min. Tetracycline of 50 mg?L-1 was totally degraded after the operation of photoelectro-Fenton coupling rotating disk system for 45 min with the catalyst of 1.0 mmol?L-1 Fe2+. The degradation ability of this system was superior to the traditional Electro-Fenton system. Further experiments showed that the ferric ions could be photo-converted to ferrous ions, inhibiting the loss of catalyst. In addition, the direct excitation of hydrogen peroxide into the hydroxyl radical by UV contributed to the fast removal of tetracycline. |
PDF Full Text Request