Study On Enhanced Flocculation Of Natural Organic Matter Based On Regulation Of Hydrolysate Transformation Of High Valent Iron

Natural organic matter（NOM）was the complex mixture which existed in natural water and had a great impact on water treatment and human health.Recently,coagulation,oxidation,adsorption and membrane filtration technologies were the main methods for NOM treatment.Ferrate（Fe（Ⅵ））had been widely used to treat pollutants due to its characteristic of oxidation,coagulation and disinfection.In spite of Fe（Ⅵ）could oxidize pollutants,it was difficult to completely oxidize and remove the colloidal particles in NOM,and had a serious influence on water quality.Most researches were focused on oxidation of Fe（Ⅵ）and usually ignoring the flocculation and adsorption of hydroxyl complex.So how to regulate the generation and transformation of iron species,coordinate the relationship between oxidation and coagulation to further enhance the removal of colloidal particles was the problem need to be solved urgently.Firstly,in-situ UV differential spectroscopy was utilized to identify the intermediate hydrolysate such as FeOH²⁺、Fe（OH）₂⁺、Fe₂（OH）₂⁴⁺、Fe₃（OH）₄⁵⁺.The effects of p H and ferrate concentration on the transformation of iron species were investigated and found that FeOH²⁺was promoted to convert to polynuclear in acidic and neutral environment.The synergistic and antagonism between in-situ oxidation and flocculation were illustrated by comparing the measured removal efficiencies and predicted values.The results showed that Fe（Ⅲ）could accelerate Fe（Ⅵ）self-decomposition and promoted the synergistic of Fe（Ⅵ）oxidation and Fe（Ⅲ）flocculation.In case of HA was abundance,Fe（Ⅵ）could not oxidize organic matter sufficiently and the dissociated quinone moieties will reduce Fe（Ⅲ）to Fe（Ⅱ）,which inhibited the formation of flocs and weakened the flocculation.Secondly,our study used the chemical quinone electronic intermediator and physical magnetic field to intervene the oxidation and hydrolysis process,in order to regulate the transformation of polynuclear hydroxide and enhance the flocculation of colloidal particles.Results indicated that benzoquinone（BQ）promoted FeOH²⁺converted to Fe（OH）₂⁺,Fe₂（OH）₂⁴⁺and Fe₃（OH）₄⁵⁺which benefited for adsorption between particles.Interestingly,quenching studies suggested polynuclear Fe hydroxide（PnFe-H）derived from the high-valence iron species which were the active components by BQ activation,was proved the vital factor for removing HA.According to the analysis of interaction energy,BQ weakened the polar property and increased hydrophobicity of compounds,further benefited for adsorption with lower Lifshitz-van del Waals（LW）and Lewis acid-base（AB）interfacial energy between PnFe-H-contaminant compounds.Compared with the chemical method with electronic intermediator,magnetic field could influence the structure of pollutants without substances additional.Results showed that magnetic field enhanced intermolecular hydrogen bonding and caused more polar group binding with iron ions,further controlled Fe（Ⅲ）transformed to amorphous iron hydroxide rather than crystalline iron oxide.The pollutants were removed by adsorption and co-precipitation.Based on the classical nucleation theory and interfacial interaction,the mechanism of contaminant selective removal by ferric hydroxide was clarified.Although ferrate could efficiently treat the complex contaminant,additional work will need to do to complete the process with depth treatment technologies such as membrane technology in order to satisfy the water quality standards.Finally,this study combined ferrate pretreatment with ultrafiltration technology and investigated the synergistic effects of ferrate oxidation and hydroxide coagulation on particles scales.Ferrate oxidized conjugated C=C double bounds and aromatic structures,and formed precipitates which result in increased proportion of particles at 100-500 nm.The correlation between micro-particle and meso-particle and membrane fouling was established to reveal the core mechanism of serious irreversible fouling which caused by the unique characteristic of meso-particle.The interfacial fouling behavior and dynamic pollution which caused by different particles were analyzed by the characterization of particles.The research was expected to provide relevant information on preventing and controlling membrane fouling according to the regulation and characteristics of meso-particles and micro-particles.