| Nitrate is one of the most concerning contaminants due to eutrophication.Biological denitrification is a relatively economical denitrification technology.However,organic carbon source is often required in the traditional denitrification,which is likely to cause secondary pollution.The photoanode in the microbial photoelectrochemical cell will generate photogenerated electron-hole pairs under the excitation of light,and provide electrons to the denitrification process in the cathode chamber.It provides a new idea for autotrophic denitrification.In this work,TiO2-NTs electrode was modified with polyaniline by anodizing method to enhance the visible light response and photocurrent output.The prepared PANI/TiO2-NTs were used as photoanodes in the microbial photoelectrochemical cell,and their denitrification and the performance of nitrogen removal and electricity generation were systematically studied.The main results are as follows:?1?The acclimation time of autotrophic denitrifying bioelectrode was shortened by pre-attachment biofilm.After 16 days of domestication,the average removal rate of NO3--N was about 0.68 mg·L-1·h-1.The proportion of functional genus such as denitrifying bacteria and electrogenic bacteria reached 51.59%.?2?PANI/TiO2-NTs electrode was prepared,and the optimal loading time of polyaniline was determined.The crystal phase and conductive characteristics of PANI/TiO2-NTs was analyzed by XRD,XPS and electrochemical tests.PANI/TiO2-NTs showed obvious light response in visible light range than TiO2-NTs.When the loading time of polyaniline was 20200 s,the photocurrent output of PANI/TiO2-NTs is better than that of TiO2-NTs.The optimal loading time was 80 s.When the electrode potential was 2 V,the photocurrent of the PANI/TiO2-NTs reaches 2.43 mA,which is 80.1%higher than that of the TiO2-NTs.The presence of polyaniline and titanium dioxide in the composite electrode was determined.The modification of polyaniline did not change the crystal phase of TiO2,and the composite electrode was an n-type semiconductor.?3?PANI/TiO2-NTs and denitrification bioelectrode were used as photoanode and cathode in the microbial photoelectrochemical cell.The performance of nitrogen removal and electricity generation was investigated.It was found that the average removal rate of nitrate in the treatment system reached 0.97 mg·L-1·h-1,while the faraday efficiency was between 36.7%and 53.8%,the system current between 1.2 and1.5 mA.The treatment system was well to adapt to the change of nitrogen initial concentration,and the average removal rate of nitrate is between 0.911.04 mg·L-1·h-1.High photocurrent input could increase the denitrification capacity and reduce the accumulation of nitrite.The addition of trace organic carbon source in the cathode chamber can enhance the denitrification treatment and inhibit the accumulation of nitrite.The average nitrate removal rate can reach 34.08 mg·L-1·h-1.High-throughput sequencing results showed that the trace organic carbon sources inhibited some autotrophic denitrifying bacteria in the cathode chamber,but denitrifying bacteria and electrogenic bacteria were still in dominant position,and the abundance accounted for53.2%.The microbial photoelectrochemical cell with PANI/TiO2-NTs photoanode has stable autotrophic denitrification capacity,which provides a technical approach for efficient deep denitrification of wastewater. |
PDF Full Text Request