Study On Ethyl Acetate Removal By Integrated System With Microbial And Photo-electrochemical Catalysis

Volatile organic compounds（VOCs）,precursors of O₃ and PM_2.5,which aggravated regional air pollution in China.The massive VOCs emitted in industrial processes are discharged into the atmosphere,posing potential harm to ecological environment and human health.The current individual VOCs treatment techniques cannot simultaneously meet the needs of decontamination and energy conservation,but the hybrid techniques are more attractive to comply with new tendency for control of VOCs pollution due to the environmental and economic benefits created by them.Integrating microbial fuel cell（MFC）and photo-electrochemical catalysis（PEC）is an innovative technology that can realize air purification and energy conversion under normal temperature and pressure conditions,and its application and development are more practical.The in-situ generation of electricity by MFC is used to drive the separation of photoinduced electron-hole pairs,synergistically promoting the pollutants degradation and energy production.In this thesis,the coupled system（MFC-PEC and bio-trickling MFC-PEC）was constructed,which integrated microbial and photo-electrochemical catalysis by connecting bio-anode and modified Bi VO₄ catalytic cathode.The continuous flow gaseous ethyl acetate（EA）removal and electricity output in the coupled system under visible illumination were studied.Besides,the possible VOCs removal mechanism was proposed.In view of multistage cascade VOCs treatment,the scale-up configuration concept was also designed for practical application.The main results are summarized as follows:（1）Mo S₂-Bi VO₄ p-n heterojunction catalyst was synthesized by hydrothermal method and used as catalytic cathode material for constructing MFC-PEC system.The effect of gaseous EA(initial concentration 5.9～7.9 g m^-3)removal in this coupled system was investigated.Under optimal experimental conditions with 20 wt%Mo S₂-Bi VO₄ catalytic cathode and 500Ωexternal resistance,the MFC-PEC system could maintain the EA removal efficiency of71.98%～81.58%（average～77.73%）during 2 h operation,and the average elimination capacity reached 24.68 g m^-3 h^-1.In addition,simulated water circulation trickling mode was implemented at the bio-anode.When the EA concentration was about 5.1 g m^-3 and the catalysts loading was 2.5 mg cm^-2,74.77%～83.64%of EA was removed and stable cell voltage（～244m V）was obtained.The maximum power density was 1214.1 m W m^-3 in this system.Based on the structure of Mo S₂-Bi VO₄ p-n heterojunction,it was inferred that the decomposition of EA in the MFC-PEC system was attributed to the oxidation by·OH,·O₂^-and photogenerated h⁺.（2）The catalysts of Co-Bi VO₄,Cu-Bi VO₄ and Co-Cu-Bi VO₄ were prepared using impregnation-calcination method.And a novel bio-trickling MFC-PEC system was established to explore the effect of metal doped Bi VO₄ catalytic cathode on EA removal.The highest EA(393.3～786.7 mg m^-3)average removal efficiency of 90.83%was achieved in the bio-trickling MFC-PEC system with the optimal catalyst of bimetal doped 3 wt%Co-3 wt%Cu-Bi VO₄ and500Ωexternal resistance.It was noted that it respectively increased by 26.18%,14.43%and14.14%,compared to the system of adsorption,bio-trickling MFC-EC and bio-trickling PC.Besides,the maximum power density of 1127.5 m W m^-3 was also obtained.Two-stage cascade operation could constantly remove 97.85%～99.13%of the high concentration EA(～6940 mg m^-3)in 5 h duration time.EPR results indicated that both·O₂^-and plentiful·OH were produced in bio-trickling MFC-PEC system,so that EA was degraded due to the oxidation by·OH,·O₂^-and photogenerated h⁺.In scale up considerations to suit practical engineering,three concept designs with tubular configuration for bio-trickling MFC-PEC,such as multistage parallel form,multistage series form and spray tower form were proposed.