Preparation Of Ferrate (Ⅵ) And Its Removal Of Sulfapyridine And Acetaminophen

Ferrate（Ⅵ）,which possesses the function of oxidation,disinfection and coagulation,is a green water treatment agent and has tremendous application foreground in the field of water treatment.However,due to the main shortcomings of low concentration,poor stability and high cost,its large-scale application is still restricted.Pharmaceuticals and personal care products（PPCPs）are one kind of emerging micropollutants in the aquatic environment,which have the potential hazard toward aquatic organisms and public health.Along with the more frequent detection in water bodies,people are attaching more importance to PPCPs.The paper achieved good results that high concentration of ferrate（Ⅵ）was synthesised by electrochemical way and the self-made ferrate（Ⅵ）was also used for the removal of two common PPCPs（sulfapyridine and acetaminophen）.The effects of NaOH concentration,electrolytic temperature,current density and anode materials on the electrolytic preparation of sodium ferrate（Ⅵ）were investigated.Results showed that the optimum concentration of Na OH solution was 17 mol/L and low temperature and current density would contribute to get higher ferrate（Ⅵ）concentration.Besides,iron electrode could reach higher ferrate（Ⅵ）concentration than iron electrode and the regular replacement of anode could improve the sodium ferrate（Ⅵ）generation obviously.The resulting sodium ferrate（Ⅵ）could reach 0.39 M for the conditions found from this study: the electrolyte of 17 M NaOH,the thermostatic bath temperature of 13 oC,the reaction time of 5 h,4 iron mesh electrodes（single effective area of62.1 cm2）,the regular anodic replacement（replacing at 1 h,3 h,4 h）,the S/V value of 2.484 1/cm and current of 8.4 A.The influence of different initial concentrations（0.079⁰.359 mol/L）of ferrate（Ⅵ）and the presence of different ions(PO₄^3-,ClO^-,SiO₃^2-)on the stability of sodium ferrate（Ⅵ）solutions were investigated.Results showed that higher initial concentration of ferrate（Ⅵ）had the faster decomposition rate,and the best effect of ClO-on the stability of ferrate（Ⅵ）got.The effects of ferrate（Ⅵ）dosage,solution pH values and the presence of humic acid（HA）on the removal of sulfapyridine（SPY）and acetaminophen（AAP）by ferrate（Ⅵ）were studied.Results showed that the increasing ferrate（Ⅵ）would improve the removal rate of SPY and AAP,but acid and alkaline environment had the opposite effects.Low concentration of HA could promote the removal of SPY and AAP but then inhibited with increasing in HA contents.When the ferrate（Ⅵ）dosage was 9.2 mg/L（as Fe）and 5 mg/L（as Fe）,the removal rates of AAP（initial concentration 1 mg/L）at 60 min and SPY（initial concentration 500 μg/L）at 15 min were 99.6% and 100 %,respectively.The kinetics of the reaction between ferrate（Ⅵ）and AAP was pseudo third-order and the pseudo rate constant was 1.4x10-5L2/mg2·min.Three oxidation products were identified and then the probable pathways of AAP degradation were proposed.The presence of 0.2⁵ mmol/L K⁺,Na⁺,Mg²⁺,Ca²⁺ could promote the removal of AAP,but Al³⁺,CO₃^2-and PO₄^3- had a significant inhibitory effect on the removal of SPY and AAP.