A Study Of The Degradation Effect And Mechanism For Chlorophenol Wastewater By A Novel Tubular Magnetic Film Photocatalysis System

Chlorophenols?CPs?were widely used as the raw materials or intermediates in wood antiseptic,insecticidal and bactericide,pesticide and veterinary medicine,textile and dyeing,paper and chemical industry due to their excellent broad-spectrum bactericidal and antiseptic effects.However,CPs will pollute the aquatic ecosystem and threaten human health uder improperly discharged for its environmental persistence,bioaccumulation and biological toxicity.In China,2,4-dichlorophenol?2,4-DCP?has been listed as a control pollutant by the State Environmental Protection Administration.Among the advanced oxidation technologies,photocatalytic oxidation technology has many advantages,such as simple and efficient,easy to operate,no secondary pollution and so on.However,the wide application of photocatalysis technology is limited due to the restriction of key factors such as light source,catalyst recovery and photoreactor structure.In this paper,the magnetic nano photocatalyst Fe₃O₄@SiO₂@TiO₂?FST?with core-shell structure was successfully prepared by microwave hydrothermal method.A novel tubular magnetic membrane photocatalysis system was built for CPs pollutants in water.The main results are as follows:?1?The core-shell photocatalyst FST with good activity and uniform particle size was successfully prepared by microwave hydrothermal method.Microwave solvothermal method is efficient and low consumption.It can not only obtain high magnetic and high purity Fe₃O₄nanospheres,but also quickly obtain the outermost TiO₂ layer with good crystal form,which significantly simplifies the synthesis process and is more environmentally friendly.Finally,the FST composite photocatalyst with an average particle size of 149 nm and MS of 23.2emu/g was prepared.?2?Based on the self-made FST composite photocatalyst,a novel tubular magnetic film reactor was designed and constructed.The comparation between the conventional photocatalysis reactor and the tubular magnetic film reactor was analyzed for the photocatalytic degradation of 2,4-dichlorophenol?2,4-DCP?.The experimental results indicated that the light utilization ratio of immersion light source is higher than that of external light source.The traditional suspended catalyst photoreactor reduces the light utilization due to the"light shielding effect"between particles,and the photocatalyst needs to separate by another unit,which limits the application of photocatalysis technology.In this paper,the tubular magnetic film photocatalyst was proposed to form FST film under the action of external magnetic field,which not only solves the"light shielding effect",but also avoids the recovery operation and loss of nano photocatalyst,so as to achieve efficient and stable photodegradation effect for organic pollutants.A tubular magnetic film reactor was used to treat 2,4-DCP with an initial concentration of 10 mg/L.the average removal rate of effluent for 10 times was 98.15%.?3?The photocatalytic degradation of chlorophenols?2-CP,2,4-DCP,2,4,6-TCP?was studied with different initial concentrations in water,and the photodegradation kinetics of CPs in single component system and multi-component system were investigated.The oxidative degradation mechanism of 2,4-DCP in this photocatalytic reactor was analyzed by adding corresponding quenching agents of different active groups(h⁺?·O^2-?·OH).In addition,the effects of SO₄^2-and Cl^-on the degradation of 2,4-DCP were also analyzed.?4?The doped La FST magnetic composite photocatalyst was successfully prepared.Its photocatalytic activity was significantly improved and its photocatalytic effect was stable.Dosing La-FST into the tubular magnetic film photoreactor to treat 2,4-DCP?10 mg/L?,the removal rate arrived at 99.59%after 40 minutes of photocatalysis,and the average degradation rate was 99.20%for 10 times of effluent.