Study On Degradation Of Sulfachloropyridazine By Ferrate(?)

In recent years,emerging organic pollution like PPCPs?pharmaceuticals and personal care products?and EDCs?Endocrine disrupting chemicals?have received increased attention due to their impact on water environment.Sulfonamades are broad-spectrum antibiotics,which are used in animal husbandry and aquaculture.Sulfonamades are not readily biodegradable and have been widely detected in animal waste,farmland soil,surface water and wastewater effluents.Sulfonamades can accumulate in the biological chain and promote the emergence of drug-resistant bacteria.Because they belong to refractory organics,it is particularly important to find a safe and effective way to remove the sulfonamides.Ferrate???is recognized as a green water purifier with a powerful oxidizing property and do not produce toxic disinfection by-products.In this paper,sulfachloropyridazine?SCP?is used as target pollutant and it is degraded by the self-produced potassium ferrate???.The removal performance and the reaction mechanism of SCP by ferrate???has been studied.First of all,the degradation of SCP at different pH levels and ferrate dosage was studied.The experimental results showed that when the initial concentration of SCP was 0.2mmol/L,the molar ratio of ferrate to SCP was 10:1,the removal of SCP reached the highest rate of about95.6%at pH=5.Flocculation can only remove about 20%of the SCP,therefore the oxidation of ferrate dominated in the removal of SCP.The removal rate of TOC also follows this pattern.When the molar ratio of ferrate to SCP was 10:1 at pH 5,SCP is not completely mineralized,the removal of TOC was only 50.3%.However,BOD₅/COD_Crr of the water samples before and after treatment was increased from 0.053 to 0.38?molar ratio of ferrate to SCP=8:1,pH=5?,which meet biological standards and can be followed up for routine biological treatment.The cytotoxicity of water samples after treatment was tested.The result showed that the biotoxicity of the product was significantly reduced after the reaction,whichreduced harm to human body and other animals.After treated by ferrate???,there is no iron detected in the water sample,it means that using ferrate???as purifier will not bring new pollution into water.The reaction knietics of potassium ferrate???and SCP was studied by using initial rate method in pH=9 buffer solution at 25?.Ferrate???and SCP conform to second-order reaction,the second-order rate constant k was determined to be 0.5933L·mol^-1·s^-1.According to this rate constant,1.25h is needed to gain 95%removal in the 0.2mmol/L of SCP solution with the dosage of ferrate???in molar ratio of 10:1.However,in the improved method,after ferrate???was put into the sample solution,dilute sulfuric is added at a speed of 90-360?mol/min until pH=5,then the removal of SCP can be more than 95%within 30 minutes.The reactive products was detected by gas chromatography-mass spectrometer?GC-MS?after extraction and enrichment.The electrostatic potential on the molecular structure of SCP was calculated and analyzed.The results show that ferrate???firstly attack electron-rich groups on the SCP molecule,so the S-C bond,S-N bond and N-C bond were easy to be broken.The amido group was oxidized into nitro,and the intermediate product was formed to be p-nitrophenol?C₆H₅O₃?,Amino-6-chloropyridazine?ACP?and sulfanilamide?C₆H₆N₂O₄S?.Then,the intermediate products were oxidized,and the ring of benzene and chlorpyridine were opened,which was decomposed into alcohols and carboxylic acids.In summary,ferrate???can remove SCP efficiently and no secondary pollution was introduced.Potassium ferrate???can destroy the antibiotic properties of SCP.In practical water treatment,application of this process can reduce the drug resistance of bacterial caused by low dose and long exposure of antibiotics in water.