Study On Treatment Of MBR Effluent Leachat By PMS,H₂O₂ Double Oxidant Catalystied By CoFe@MgAl Hydrotalcite

Leachate is a kind of dangerous wastewater with a complex and high concentration of pollutants,and it can be a serious threat to the soil and groundwater water if not treated well.Now,combination of biological and advanced leachate treatment processes are widely being used in China.In advanced leachate treatment,membrane treatment technology mainly is used,but this technology can only concentrate the pollutants but not to degrade the pollutants,so it will generate a large amount of leachate concentrate.So,there is no ideal methods for leachate treating yet.In this research,the researcher propose the advanced oxidation of fixing transition metals Co and Fe on the MgAl-hydrotalcite(MgAl-LDH)to catalyst double oxidant: Potassium peroxymonosulfate(PMS)and H2O2 to deal with MBR leachate effluents.The structure of hydrotalcite greatly reduce the metal ion leaching,proposed to be as environmental friendly catalyst.Moreover,advanced oxidation method did not produce leachate concentrated.The main research contents and results are as follows:(1)CoFe@MgAl-LDH is prepared using precipitation.Then ICP-AES,Specific Surface Area(BET),Scanning Electron Microscopy(SEM),X-ray Diffraction(XRD)and Fourier Transform Infrared(FT-IR)analysis were employed to characterize the surface properties,morphology and crystal structure of the catalyst.It is found that the catalyst has the structure of MgAl-CO3 hydrotalcite and has good crystal shape and large surface area.(2)Using Fe,Cu and Zn transition metal fixed on MgAl-LDH and MgFe-LDH to catalyst H2O2 as the reaction system.And the system is optimized through the selection of catalyst,oxidant amount,temperature and so on.It is found that using the best catalyst is Cu@MgAl-LDH at the optimum conditions,the removal rate of COD was the highest 44.36%,but the processing cost was 65.74 yuan/t,and it is not suitable to the actual project.(3)Using Co,Fe,Cu and other transition metal fixed on MgAl-LDH to catalyst PMS and H2O2 double oxidant as the reaction system.And the system is optimized through the selection of catalyst,oxidant amount,temperature,time and so on.It is found that PMS and H2O2 play a synergistic effect and make a better treatment.When choose CoFe@MgAlLDH catalyst,hydrogen peroxide dosage is 0.5 mol/L,dosage of PMS is 5g/L,catalyst dosage is 1g/L,the reaction time of 2h,leachate MBR effluent COD removal rate is almost 60%,and when the catalyst was reused three times,the removal rate of COD could still reach 47%.But processing costs is 66.01yuan/t,and it is still too high.(4)In order to further reduce the processing cost,choose coagulation as the pretreatment on leachate MBR effluent.Using polymeric ferric sulfate(PFS),ferric chloride(FC),polyaluminium chloride(PAC)three kinds of flocculant,choose COD and chroma(CN)as the indicators.Results show that using dosage of PFS is 1000 mg/L without adjusting the pH,and the COD removal rate is 45%~48%,chroma removal rate was 84%.(5)Combining Coagulation and heterogeneous oxidation.The effluent of leachate MBR was pretreated with PFS flocculant,and then using CoFe@MgAl catalyst,H2O2 and PMS double oxidant as forward treatment.It is found at the optimal treatment,the coagulation PFS dose of 1000 mg/L,adding the PMS for 2g/L,H2O2 dosing quantity is 0.2mol/L and the catalyst is 1g/L.By coagulation leachate MBR effluent COD removal rate as 42%,after oxidation of COD removal rate as 65%,the processing cost is 22.47 yuan/t.The research has plore a new way for the popularization and application of advanced oxidation.