Study On Treatments Of Thallium-containing Wastewater Based On Electrochemical Methods

Thallium(Tl),which has a bioaccumulation,is a virulent heavy metal.Tl(I)is the main oxidation state in the natural environment.With the development of industries,Tl-pollution is more and more serious due to Tl ore mining and smelting.it is a promising method for the treatment of Tl containing wastewater to oxidize the TI(I)which is with strong mobility to TI(III)and conduct situ-precipitation.Electrochemical technology which has attracted people's attention in recent years is efficient and easy to operate.However,there is no report about the treatment of Tl containing wastewater with this method.The present study based electrochemical technology achieved the efficient treatment of Tl containing wastewater with the aspect of power supply,anode materials and situ-precipitation.Aiming at the problem of large energy consumption for electrochemical technology,the microbial fuel cell(MFC)was used as a power supply with maximum power density of 518.5 mW/m2 and maximum voltage of 700 mV(1000 ?).With carbon felt and graphite plate used as anode and cathode respectively,initial Tl(I)concentration of 5 mg/L,pH of 2.0,and voltage of 600 mV,the oxidation efficiency of Tl(I)was as high as 80.5% within 4 h operation.After flocculation experiment,the total Tl removal efficiency was 82.3%.Result of X-ray photoelectron spectroscopy(XPS)indicated that Tl(III)was the main oxidation state in the precipitate.Anode materials played an important role for the electrochemical oxidation technology.In view of this question,the boron-doped diamond(BDD)was introduced as anode.With graphite plate used as cathode,initial Tl(I)concentration of 10 mg/L,pH of 2.0,and current density of 5 mA/cm2,the oxidation efficiency of Tl(I)was as high as 99.2% within 15 min operation.After flocculation experiment,the total Tl was removed completely.The XPS also revealed that Tl(III)was the final state of Tl.Moreover,the ·OH generated in the electrochemical process played a key role in the oxidation reaction.To solve the problem that the complete treatment of Tl containing wastewater still entails flocculation experiment after the electrochemical oxidation,the electrocoagulation process was used,achieving Tl of oxidation and flocculation by one-step.Compared Fe electrode,Al electrode was more suitable for Tl containing wastewater by electrocoagulation.With initial Tl(I)concentration of 10 mg/L,pH of 9.0,and current density of 5 mA/cm2,the total Tl removal efficiency was 86.4% within 60 min operation.XPS analysis indicated that Tl(III)was the main oxidation state of Tl in the precipitate collected in electrocoagulation experiment.In summary,the present study based on electrochemical technology achieved the efficient treatment of Tl containing wastewater.The use of microbial fuel cell as a power supply reduced the cost of electrochemical technology.The use of BDD electrode increased the efficiency of electrochemical oxidation technology.The use of electrocoagulation technology achieved one-step treatment of Tl containing wastewater.The results of the study offer a new direction and ideas for the treatment of Tl containing wastewater.