Study Of The Efficiency And Mechanism Of Heterogeneous Fenton Technology

The large amount of industrial wastewater and domestic wastewater always pose a threat to environment,because of discharging without remediating completely.In recent years,some emerging contaminants have been detected by researchers in water resources.Although the researchers only find them exist in water with low concentrations,they can become the potential hazard as the refractory and ecotoxicity characteristics of these contaminants.In the last thirty years,advanced oxidation processes?AOPs?have already attracted increasing attention,which can be used to treatment recalcitrant pollutants as the promising technology.So far,fundamentals treatment of conventional methods such as Fenton,photo-Fenton,electro-Fenton,ultrasound-Fenton,ultrasound-photo-Fenton,ultrasound-electro-Fentonand electro-photo-Fenton are widely used.This review use ultraviolet and ultrasound assisted TiO₂@foam nickel/H₂O₂ Fenton-like system for degrading target pollutants.Enhancing the effect of Nitrosomonas europaea on degrading Triclosan by using improved heterogeneous Fenton-like reaction.?1?Heterogeneous Fenton system was composed of TiO₂@foam nickel with hydrogen peroxide,and ultrasound and ultraviolet were introduced to investigate the effect of the combined technology to degrade rhodamine B.we set the corresponding experiment in order to investigate the degradation performance of rhodamine B in ultrasonic environment by nickel foam/H₂O₂ process.The results showed that the system had the good degradation effect.In order to acquire the optimum experimental conditions,such as initial pH values and the dosage of hydrogen peroxide,we set the single factor experiments.The mechanism of degrading RhB by ultrasound/H₂O₂ system was the hydroxyl radicals'oxidation.The system mainly relied on the cavitation of the ultrasonic which could accelerate the decomposition of H₂O₂ to produce hydroxyl radicals.The nickel foam provided more cavitating nucleis to ultrasonic cavitation,so the generation of hydroxyl radicals was accelerated.Making a thorough inquiry of the degradation efficiency by using the photo-assisted nickel foam/H₂O₂ system when the photocatalysts existed.We could conclude that the photo-generated holes played a leading role during the treating process of UV/TiO₂/nickel foam/H₂O₂ system through adding various free radical scavengers in solution.The problems of difficult recovery and secondary pollution could be avoided through loading the TiO₂ on nickel foam.The influence of pretreatment of nickel foam and SiO₂ layer for loading TiO₂ were studied.The amount of TiO₂ loaded on the nickel foam could be increased after preprocessing of nickel foam.The removal rate has enhanced from 36.61%to 49.85%when the TiO₂/SiO₂ films as composite photocatalyst were loaded on nickel foam.Ultrasound/TiO₂@nickel foam Fenton-like system had great treatment effect on the rhodamine B,and its removal rate reached to 72.91%.If ultraviolet was introduced,the removal rate of the rhodamine B could reach to 81.88%.Hence,it indicated that the combination of the ultraviolet and ultrasound could improve the degradation of the rhodamine B.?2?Four Fenton systems were designed and compared with each other to investigate the effect of heterogeneous Fenton-like Reaction on N.europaea cells.They are ultrasound alone,nickel foam alone,ultrasound and nickel foam and ultrasound,nickel foam combined with hydrogen peroxide.The membrane fluidity was used as an indicated parameter.The order of effect of Fenton reaction ranked as US/NF/H₂O₂>US/NF>US>NF because free radicals in solution increased obviously.After treated by Fenton-like reaction,N.europaea surface exhibits higher roughness than that of the native bacterium and the bulges on cell surface became irregular.The effect on N.europaea cells in acid medium is weakened in alkaline medium.The quencher can capture free radical·OH and weakened the effect.2.50 mg/L Ni²⁺dissociated from NF during Fenton process but Ni²⁺didn't take action.?3?The N.europaea could degrade triclosan to obtain energy and nutrients.The cell membrane fluidity of N.europaea had been changed after treatment by heterogeneous Fenton-like reaction.The Fenton reaction could affect the N.europaea absorbed triclosan.To detect the changes of metabolic energy of N.europaea cell and to determine the ability for degrading the triclosan.As a result,the metabolism of N.europaea became more active.In the case of N.europaea with 0.35 polarization value,the degradation efficiency of triclosan was improved.When the polarization value increased to 0.52,the metabolism of N.europaea was inhibited and biodegradation of triclosan by N.europaea ceased.