Experimental Study On The Acid Orange 7 Degradation Based On Reverse Electrodialysis Technology

Large amounts of organic wastewater and waste heat are generated in some industrial production and daily life.On the one hand,large quantities of high concentrated and salinity organic wastewater resistant to biological processes that can be discharged into the environment without treatment,which will cause serious harm to the human body and the environment.Various advanced oxidation processes have been adopted to treat such organic pollutants.But,the technologies also have problem of high energy consumption,which restricts their further large-scale application.On the other hand,large quantities of low-grade waste heat existing in some industrial production processes is discharged into the environment because it is difficult to be effectively utilized,resulting in energy waste.The utilization of low-grade waste heat driven to the treatment of organic wastewater resistant to biological processes has a positive effect on reducing the energy cost of organic wastewater treatment and improving energy efficiency.The basic working principle is:based on the reverse electrodialysis(RED)technology,the low-grade thermal energy that needs to be discharged is converted into the solution concentration gradient energy firstly by the thermal separation methods,and then the solution concentration gradient energy can be converted into the energy used to organic wastewater degradation with the RED reactor.In this paper,the azo dye used commonly,acid orange 7,was used as the simulated organic pollutant of electrode solution in the anode and cathode chambers.The strong oxidants generated by the cathode electro-Fenton reaction and the anode reaction can be used to degrade the organic wastewater.The experimental research on the oxidation degradation of organic wastewater with the RED reactor was carried out.This paper includes the four aspects:firstly,the orthogonal experiment is designed to analyze the influencing factors of the electrode solution independent cycle degradation experiment with the single RED reactor.Secondly,the orthogonal experiment is designed to analyze the influencing factors of the electrode solution joint cycle degradation experiment with the single RED reactor,and the two processes of joint cycle were studied.The two methods including independent cycle and joint cycle were compared.Thirdly,the degradation experiment by one-time flowing through electrode chambers with the multiple RED reactors in series was studied.Fourthly,the research on the joint cycle degradation experiment with the multiple RED reactors in series was carried out.The experimental results show that the independent cycle and the joint cycle degradation experiments of electrode solution have their own advantages and disadvantages under the certain experimental conditions.For the electrode solution independent cycle degradation experiment,the degradation rate is higher than the joint cycle degradation experiment of the electrode solution,because the organic wastewater through the two electrode chambers circulating independently does not interfere with each other.However,the disadvantage of the independent cycle degradation experiment is that the cathode chamber of the RED reactor needs to be added with acid continuously to maintain the reaction of the electro-Fenton reaction.Meanwhlie,the anode continuously generates acid due to the reaction.The anode organic wastewater needs to be taken certain measures like adding with additional alkali to change its pH that it can be discharged into the environment,while the anode organic wastewater reaches the discharge standard.All these measures will increase the processing costs.For the electrode solution joint cycle degradation experiment,the cathode electro-Fenton reaction utilizes the HCl produced by the anode reaction,and that can reach balance between the production and consumption of H~+in the two electrode chambers without requiring adding with acid or alkali.However,the disadvantage is that the electrode reaction products of the anode and the cathode in the RED reactor interfere with each other,resulting in a decrease of the degradation rate of the acid orange 7 organic wastewater.At the same time,the concentrated and the dilute solution still have a certain concentration difference after flowing through the single RED reactor,so the organic wastewater can be degraded with the multiple RED reactors in series to improve the utilization rate of the solution concentration gradient energy.The numbers of the RED reactor that can be connected in series at different currents is different.Under the same conditions,the smaller the current is,the more the RED reactor numbers can be connected in series.The change of current has great influence on the degradation of organic wastewater in the syetem of multiple RED reactors in series.Within a certain current range,the larger the current is,the higher the degradation rate of organic wastewater is.