Study On Three-dimensional Electrode Reactor For Kinds Of Organic Simulated Wastewater Treatment

Organic substance is one of the most serious pollutants that affect the water quality and water ecological environment. Pollution caused by organic substance is a typical feature of global water pollution, which not only leads to a series of environmental pollution, but also seriously imperils people's life and health. As a result, the treatment of organic wastewater has been an urgent problem to be solved. A method of three-dimensional electrode (TDE) which applied to wastewater treatment has high electric current efficiency and desired treatment effect. However, the technique, at present, is immature and there are some key problems to be solved. For example, systematical and thorough research is deficient in the study on the optimization of particle electrode, main electrode and the optimization of various operational parameters.Moreover,an agreement about the reaction process of electrochemistry and the mechanism of TDE degrading organic substance have not been reached. Therefore, a study on TDE treating organic wastewater has tremendous significance and value. This dissertation studies the effect of TDE,degrading mechanism of TDE, degrading regularity of TDE and degrading reaction kinetics when TDE is used to treat simulated organic wastewater. In addition, a TDE-Fenton method is explored in the dissertation. The main research content and research result include:1. Experiment of using TDE to treat wastewater containing polyacrylamide(PAM)(1) In order to study the main electrode and particle electrode of TDE, the COD removal ratio comparison by experimentally and scanning electron microscopy (SEM) is carried out. The result shows that the main electrodes made of stainless iron have the best COD removal efficiency. Moreover,electrodes made of stainless iron are the most resistive to the corrosion and active carbon packed in TDE has indeed lead to a particle electrode.(2) Studying various factors that affect TDE to remove PAM contained in wastewater shows that the COD removal ratio by TDE treating wastewater is significantly influenced by the main electrode material, space between the main electrode, electrolysis time and electrolysis current. Under the optimum operational condition, TDE has a satisfied effect of degrading wastewater containing 0.1% PAM, The COD of simulated wastewater containing 0.1%PAM is reduced from the initial of 1120.0mg/L to 96mg/L, and the COD removal efficiency reaches 91%. Morever PAM containing in wastewater also decreases from 1000mg/L to 47mg/L. The degrading reaction of 0.1%PAM is considered as a second order reaction by using TDE.2. Study on mechanism of TDE degrading wastewater containing PAMIn order to make clear the mechanism of TDE degrading wastewater containing PAM, infrared spectrum of insoluable substance in sample after treatment is analyzed. A method referred to Ti(Ⅳ)-5-Br-PADAP and the colorimeter test for the existence of H2O2 and·OH free radicals in sample after treatment are employed. It is found that the insoluable substance is the formation of imide group via cyclization. The existence of HCO3-, H2O2 and·OH indicates that the PAM molecule is completely degraded into CO2,H2O and that the generation of insoluable substance and H2O2 and·OH are responsible for the decrease of PAM concentration and COD. At last, the possible reaction process of·OH free radical degrading PAM is deduced.3. Study onTDE treating L-leucine contained wastewater(1)The experiment studies the relationship between the COD removal ratio and L-leucine degrading ratio. It is demonstrated that when TDE treats wastewater containing 1.0g/L leucine, the higher degrading ratio of L-leucine results in, the bigger COD removal efficiency.(2) The study on the electric potential distribution of TDE shows that the electric potential distribution is uneven in the reactor, which is significantly affected by the wastewater concentration, main electrode material and the terminal voltage of electrobath has something to do with the COD removal ratio.(3) The experiment studies the influence of factors on the treating efficiency of TDE with different packed particles (activate carbon, ceramic particle). Through orthogonal experiment, the optimum operational condition of TDE packed with either activate carbon or ceramic particle is obtained for treating the simulated wastewater containing 1.0g/L- leucine. Under this condition, the COD removal efficiencies are 90% and 88%, respectively. With TDE treating low-concentration and high-concentration wastewater containing L-leucine, the degrading reaction is a first order reaction and a zeroth order reaction, respectively.4. Study on TDE treating wastewater containing multi-component amino acid(1) The study on TDE treating wastewater containing multi-component amino acid illustrates that the higher the general degraddation ratio of wastewater containing multi-component amino acid is, the higher COD removal efficiency is. The degraddation of different components of amino acid becomes difficult fowling the order from difficult to easy: L-leucine>L-tyrosine>L-arginine >L-histidine>L-cysteine.(2) Treating mixed wastewater of containing multi- component amino acid mixed shows that when mixing two-component amino acids, the degrading ratio of L-leucinie mixing with L-cysteine or mixing with L-tyrosine is the highest or the lowest, the COD removal ratio is the highest or the lowest,relevantly. When mixing three-component amino acids, the general degrading ratio (55%) and the COD removal ratio (90%) of wastewater containing L-leucine and L-tyrosine and L-cysteine is higher than those of wastewater containing L-leucine and L-tyrosine and L-arginine. When mixing 4 or 5 component amino acids,the general degrading ratio and COD removal ratio of wastewater containing 4-component amino acids are 51% and 88%, respectively,higher than the degrading ratio 47%and COD removal ratio 86% for 5- component..(3)Based on the molecule structure of amino acid, and the feature of the reaction of·OH radical with organic substance, and different energy-gap of frontier orbital of amino acid,the reason why different amino acids in wastewater under the same condition has different degrading effects has been explained.5. Study on TDE-Fenton methodThe experiment studies the effect of factors influencing the COD removal ratio of TDE-Fenton method. Under the optimum conditions, the COD removal ratio of TDE-Fenton method treating simulated organic wastewater containing hydroquinone can reach 92%. Under the same conditions, the TDE-Fenton method has a better degrading effect than either Fenton agent or TDE. The COD removal ratios are 89%,53% and 41% for TDE-Fenton,Fenton and TDE,respectively, demonstrating that the TDE-Fenton method has definite a feasibility.6. The feasibility study of TDE on teat wastewater (1)TDE is used to treat a real wastewater containing amino acid and wastewater containing polymer statically. The COD removal ratios are 68% and 83%,respectively While treating a real wastewater containing polymer dynamically by TDE,the COD removal ratio is 87%.(2) When TDE is used to treat a real wastewater containing amino acid and polymer statistically, the maximum electrical consumption is 9kW·h/kgCOD and 8kW·h/kgCOD respectively and the space-time yield is both 3.0kgCOD/h·m3.The Faradic current efficiencies are 13756% and 1450%,respectively. When TDE is utilized to treat the real wastewater containing polymer dynamically, the maximum electrical consumption is 12kW·h/ kgCOD. The Faradic current efficiency is 1003%. Higher the original COD in wastewater is, higher the Faradic current efficiency is, whereas smaller the maximum electrical consumption is.