Research On The Treatment Of Pharmaceutical Wastewater By Heterogeneous Electro-Fenton

Pharmaceutical wastewater is difficult to degrade,because it has some characteristics such as:high concentration of organic matter,high volume and poor biodegradability.Nowadays,heterogeneous electro-Fenton process received extensive attention due to its high oxidizability.This thesis is based on heterogeneous electro-Fenton process.First,Rhodamine B(RhB)was employed as model wastewater to optimize the electro-Fenton system.The cathode,anode and catalyst were studied.Finally,pharmaceutical wastewater was used to test the system.Our research aims at improving the treatment efficiency,and helping companies realize "zero release".The detailed abstract is as below.To fabricate the cathode,the electrochemical and degradation performance of graphite felt(GF),graphite sheet and pyrolytic graphite sheet were compared,and GF was selected.Four methods(electrodeposition carbon and carbon nanotubes,polytetrafluoroethylene carbon and carbon nanotubes)were used to modify the cathode,and the degradation of RhB was studied.As a result,the polytetrafluoroethylene-carbon(PTFE-CB)modified cathode was proved to have the best performance.Afterwards,the surface properties of PTFE-CB modified cathode were characterized by SEM,BET and contact angle.The stability of PTFE-CB modified cathode was studied by consecutive cycles.Based on GC/MS analysis,a proposed degradation pathway of RhB was put forward.To reduce the cost of anode and improve its electrochemical property,Ti based PbO2 electrode(PbO2-Ti)and Ti based SnO2 doped with Sb electrode(SnO2/Sb-Ti)were prepared.Linear Sweep Voltammetry,cyclic voltammetry,Tafel and electrochemical impedance spectroscopy were conducted to examine the electrochemical properties of the anodes(Pt,PbO2-Ti,SnO2/Sb-Ti and Ti).These assessments showed that PbO2-Ti had the best performance.Moreover,PbO2-Ti showed smooth surface and exhibited long service lifetime(approximately 4000 h).Based on PbO2-Ti,the operating parameters(electrolyte types and current density)were optimized.To prepare a high-efficiency heterogeneous electro-Fenton catalyst,6 commercial ferruginous materials(Fe-C,zero-valent iron powder,sponge iron,pyrite,vanadium-titanium magnetite and magnetite)were compared through degradation 20 mg/L RhB solution.Result showed that Fe-C,zero-valent iron powder and sponge iron exhibit high catalytic efficiency.In addition,sponge iron exhibit less iron leakage,which indicated that sponge iron show satisfactory durability.To promote the durability of sponge iron,PTFE was modified on the surface of it.The PTFE modified sponge iron showed low iron leakage and high decolorization performance.Finally,the technology conditions were optimized.To study the effect of home-made heterogeneous electro-Fenton on pharmaceutical wastewater,the PTFE-CB,PbO2-Ti and PTFE modified sponge iron were employed.Orthogonal test and response surface analysis was used to optimize the technology parameters(including dosage of catalyst,current density,pH and time).The multivariate second degree polynomial mode between COD removal and parameters was built.The impact of parameters in the order of the following:time>current density>dosage of catalyst>pH.About 80%COD was removed at a current density of 50 A/m2,catalyst dosage of 0.5 g/L and neutral condition after 100 min degradation.A first-order kinetics equation of COD removal was built.According to the GC-MS analysis,most organics were degraded after treatment.