Study On The Hydrolysis Process Of Ultraviolet Activated Ferrate And Its Application In Water Treatmen

Ferrate（Fe（Ⅵ））is mainly used as a highly efficient oxidant/disinfectant for pollutants selective removal.Fe（Ⅵ）can be converted into Fe（OH）₃,Fe₂O₃,Fe OOH and other amorphous iron oxides during the oxidation process,which can further enhance the pollutants removal.Ultraviolet（UV）activation can convert low-energy reactants into high-energy activated complexes,and then the activated complexes release energy to form products,which have been applied to strengthen the oxidation of Fe（Ⅵ）.Most researches were focused on the oxidation of UV-activated Fe（Ⅵ）,and little attention had been paid to the flocculation and adsorption of Fe（Ⅵ）during the activation process.Therefore,it was necessary to explore the transformation and formation of the dominant form of iron during the hydrolysis of Fe（Ⅵ）,coordinate the relationship between the oxidation of high-valent iron and the flocculation of ferric iron,and achieve enhanced pollutants removal in natural surface water.First,in situ UV differential spectroscopy was used to study the changes of iron species during UV-activated Fe（Ⅵ）hydrolysis and oxidation.The results showed that UV activation significantly promoted the hydrolysis of Fe（Ⅵ）,which converted Fe（Ⅵ）into intermediate high-valence iron with higher reactivity,and accelerated the hydrolysis rate of Fe（III）.The transformation of the mononuclear oligomer Fe OH²⁺to the polynuclear hydroxyl complexes with good flocculation performance such as Fe（OH）₂⁺,Fe₂（OH）₂⁴⁺and Fe₃（OH）₄⁵⁺was made faster.In addition,the UV-activation of Fe（Ⅵ）was affected by its concentration,and the increase of the concentration will reduce the efficiency of UV activation.And the transformation of oligomeric hydroxy complexes to higher polymeric states was inhibited under weak acid conditions.Secondly,it was investigated the effects of UV activation on Fe（Ⅵ）treatment of natural surface water.The results showed that UV activation can effectively improve the protein and humic acid organic matter removal in natural surface water.The analysis of reactive oxygen radicals found that activation can effectively promote the generation of hydroxyl radicals and superoxide radicals,thereby increase the oxidative capacity of the reaction system.In addition,in the characterization analysis of the ferrate hydrolyzate,it was found that a large number of amorphous iron hydroxides and ferrihydrites would be formed on the crystal surface after activation,which had high surface activity and can significantly improve the pollutant adsorption s.Finally,this study combined UV/Fe（Ⅵ）pretreatment with ultrafiltration technology and investigate the effect of UV/Fe（Ⅵ）pretreatment process on membrane fouling.The results showed that UV/Fe（Ⅵ）can effectively slow down the flux attenuation and reversible fouling resistance during filtration of humic acid（HA）,bovine serum albumin（BSA）,sodium alginate（SA）and natural surface water.The correlation analysis by particle scale and fouling resistance showed that the main factor of irreversible fouling was mesoscale particles.In the process of UV-activated Fe（Ⅵ）oxidation and coagulation,the particle size of pollutants can be increased.The aggregation of meso-scale particles into micro-scale particles can be promoted,which was to mitigation of membrane fouling and inhibited the generation of irreversible fouling effectively.And through the analysis of the membrane-particle interface interaction,the different membrane interface fouling behaviors caused by the particle scale were explained.This paper will provide theoretical guidance for the scientific and efficient using of Fe（Ⅵ）in deep water purification process by exploring the application of UV/Fe（Ⅵ）technology in membrane process.