Study On Application Of Bipolar Three-dimensional Electrode Method In Treating Wastewater Containing Triphenylmethane Dye

With the rapid development of production and manufacturing,the dye wastewater produced by the printing and dyeing industry has become a very serious problem in the pollution of natural water resources.Printing and dyeing wastewater has the characteristics of deep coloration,high concentration of organic pollutants,poor biodegradability,and large emission.It is hard to degraded and conventional wastewater treatment technology is difficult to degrade effectively.TPM dyes are the third largest dye after azo dye and fluorene dye.The wastewater has the common characteristics of printing and dyeing wastewater,as well as the complex composition and many dye systems.The three-dimensional electrode method is based on the two-dimensional electrode method.It is advanced oxidation wastewater treatment technology developed by filling the reactor with conductive particles to form a third pole.When using a relatively high-impedance activated carbon material as the filling in the case of particles,each particle is polarized under the action of an electric field to form a microelectrolytic cell,also called a"bipolar three-dimensional electrode method."The bipolar three-dimensional electrode method has the advantages of fast mass transfer,simple equipment,large amount of processing.It has been a popular spot in the field of electrochemical research in recent years,but the disadvantages of poor versatility,high energy consumption,numerous operating conditions,and strong coupling restrict its application.In order to further promote and apply three-dimensional electrode method,the authors carry out research on the application of bipolar three-dimensional electrode in dye wastewater treatment systematically by exerting the advantages of advanced oxidizing ability of bipolar three-dimensional electrode to solve the problem of refractory degradation of triphenylmethane wastewater,which has become an important research direction recently.In this paper,three representative systems of triphenylmethane dyes:Malachite green,Crystal violet,and Acid blue are used as the active components of the simulated wastewater to be treated.According to the oxidation mechanism of the method,activated carbon or modified activated carbon was used as the filling material to make a bipolar three-dimensional electrolysis reactor and an experimental study on the treatment of simulated waste water of triphenylmethane dyes was carried out.Explore the application of bipolar three-dimensional electrode treatment of triphenylmethane dyestuff wastewater,the impact of various operating conditions on the degradation efficiency and the interaction between the operating conditions,optimize The operating conditions;Research three-dimensional electrolysis reactor dye wastewater treatment including the dynamic operation process,organic matter degradation kinetics and degradation mechanism;For the purpose of improving the electrode efficiency from the essence of the electrode reaction,the activated carbon is modified by loading different materials,and the modified activated carbon is used as a bipolar three-dimensional electrode reactor.The effects of degradation and energy consumption of organics when using different modified activated carbons as particle electrodes are investigated.Based on small-scale experiments,pilot-scale experiments have been conducted to treat the methyl blue wastewater from a chemical company by three-dimensional electrode method.The main conclusions obtained are as follows:1.Separately applied voltage,electrolysis time,electrolyte concentration,pH value,and aeration as single-factor variables,the effects of various variables on the electrolysis process were examined,and COD degradation rate and energy consumption were used to analyze the operating conditions of the electrolysis process.The current amplification experiment was carried out by increasing the applied voltage to investigate the degradation rate and energy consumption of organic pollutants when the wastewater was treated by three-dimensional electrode method.From the experimental results,the current is higher,the degradation rate is faster,and the current efficiency cannot be effectively improved.When inquiring into the mutual influence of each operating variable,orthogonal experiments were conducted to select three factors for the degradation of three dye simulated wastewaters:applied voltage,electrolysis time,electrolyte concentration,p H value and aeration.The factors affecting the degradation efficiency of organic pollutants are as follows:time>pH value>applied voltage>electrolyte concentration>aeration.In the orthogonal experiment of three kinds of dye wastewaters,the highest removal rate of pollutants in wastewater was taken as the target.Taking into account the degradation efficiency and energy consumption of organics in wastewater,the optimum degradation conditions for the three dye simulated wastewaters were determined.2.Taking the bipolar three-dimensional electrode process as the research object,the electric field distribution and oxidation-reduction potential in the electrolysis reactor are measured to study the parameter distribution of the three-dimensional electrode reactor during the operation from the macroscopic point of view.According to the electric field distribution measurement data,the potential at the anode is the highest,the potential at the cathode is the lowest,and the potential is parallel to the different depths of the anode and cathode.The electrode potential is the same,and the equipotential lines are parallel.The redox potential measurement results show that with the progress of the electrolysis reaction,the redox potential near the anode continuously increases,the value of the redox potentialnear the cathode continuouslydecreases,andthe oxidation-reduction potential near the middle position of the anode and cathode both basic constant.In the process of simulated wastewater degradation,the macroscopic kinetics of the dye degradation process was studied.The kinetics of the three dye degradation processes show a high degree of similarity and the macroscopic kinetic equations for the degradation of the three dyes were obtained by fitting the experimental data.The electrolysis process is a comprehensive process including adsorption/desorption and oxidative decomposition.It is repeatedly carried out according to the law of adsorption-decomposition-desorption.It is proposed that the treatment of triphenylmethane dyes with bipolar three-dimensional electrode is an adsorption/desorption-decomposition mode.Combined with the microscopic kinetic model,the rate control step is the adsorption/desorption process,and the kinetic equation can be represented by the Langmuir adsorption isotherm.The degradation of triphenylmethane dyes was studied through the analysis of the UV-Visible scanning wastewater degradation products.The degradation mechanism of triphenylmethane dyes can be determined based on the characteristics of the maps.The clumps first fell off;the bonds between the three benzene rings and the central carbon atoms were broken,and the central carbon atoms were oxidized to carboxylic acids;the detached side-chain groups and the benzene ring were broken open and gradually decomposed into CO₂ and nitrogen oxides.3.Four types of modified activated carbon were used as the filling material for the three-dimensional electrode reactor to degrade triphenylmethane simulated wastewater.The effect of different modified activated carbons as particle electrodes on the degradation process of dye wastewater was investigated.Current efficiency analysis method was adopted to calculate the current efficiency of each group.Current efficiency and COD degradation efficiency were used to evaluate the effect of dye wastewater treatment with different modification activities as particle electrodes.Modified activated carbon mixed with ordinary activated carbon as particle electrode,the degradation effect is better than pure modified activated carbon as particle electrode effect.Among the four modified activated carbons,the PTFE-AC shows the best degradation effect when mixed with ordinary activated carbon.4.The treatment process and pilot plant such as bipolar three-dimensional electrode reactor were designed to conduct pilot tests on the wastewater treatment.The pilot plant was commissioned with wastewater treatment capacity,electrolysis voltage,pH and aeration as variables.The results of the pilot tests showed that the effects of wastewater treatment volume,electrolysis voltage,and pH on the electrolysis process are consistent with the effects of small-scale experiments.Due to the large setting of the aeration change gradient,the aeration adjustment experiment did not show the same pattern as the small experimental experiment.The ammonia nitrogen and COD in wastewater were in better removal by this process and the biodegradability of wastewater is significantly improved.Three-dimensional electrolytic method as a pretreatment process,combined with a simple biochemical treatment process can achieve the best effect of printing and dyeing wastewater treatment.Although this study has gained certain recognition,there are still many deficiencies.Further follow-up will be further studied,providing more theoretical support and data support for the efficient and clean treatment of dye wastewater.