Study On The Catalytic Degradation Of Anionic Dye Wastewater By ?-FeOOH And Its Composite Materials

Dyestuff wastewater has the characteristics of high concentration of organic matter,deep color,poor biodegradability,large biological toxicity,large variation in water quality and water content,complex composition,and stable chemical properties,resulting in poor treatment of traditional wastewater treatment methods and becoming a major wastewater treatment problem.At present,adsorption and chemical oxidation are effective ways to treat printing and dyeing wastewater.Adsorption can recover dyes,save the cost of dyes while purifying water,and chemical methods can break the hard-degradable dye molecules into small molecules and eventually even mines.Turn into CO2 and H2O to reduce the harm to the environment.As a natural mineral,?-FeOOH is widely found in soil water and sediments.It has special tunnel structure,stable physical and chemical properties,large specific surface area,and ultra-fine granular structure.It is used in the adsorption of environmental functional materials.There are broad prospects for the development of catalytic materials.At present,Fenton degradation reaction and photocatalytic degradation reaction of organic printing and dyeing wastewater based on ?-FeOOH is rarely reported.P-FeOOH as a functional material with great development potential needs further development in the treatment of dye organic wastewater.Therefore,in this paper,?-FeOOH was prepared by hydrothermal synthesis method,and its morphological structure was characterized.The application of ?-FeOOH in the treatment of anionic dye wastewater was systematically studied including the following three aspects:1)P-FeOOH Adsorption removal of acid orange ?(AOII),methyl orange(MO),reactive brilliant blue(KN-R);2)Degradation of AOII by ?-FeOOH/H2O2/hydroxylamine hydrochloride heterogeneous Fenton system;3)Preparation of visible light photocatalyst ?-FeOOH/TiO2 composite material and its effect on the treatment of acidic AOII.The research results can provide theoretical basis for the research and application of P-FeOOH as an environmental functional material.The main results of this work are as follows:(1)The XRD results confirmed that the hydrothermal synthesis sample is ?-FeOOH with good crystallinity.The SEM results showed that the ?-FeOOH particle size is uniform and the dispersion was good.The average length is about 250 nm and the average width is about 60 nm.P-FeOOH has positive removal effect on anionic dyes AOII,MO and KN-R,and can reach equilibrium in a very short time.The maximum adsorption amounts are 283.67,174.38 and 256.33 mg·g-1,respectively.FeOOH has negative adsorption effect on the cationic dye MB,and the adsorption amount was only 20.66 mg·g-1.The kinetics of adsorption of AOII by P-FeOOH accords with the pseudo-second order kinetics equation.The main adsorption process are chemical adsorption and physical adsorption.The adsorption isotherms at 15,35,and 55? are more in line with the Langmuir model.It is a monolayer adsorption process.The ?-FeOOH has good adsorption effect on AOII in acidic,neutral and weak alkaline conditions.(2)When the concentration of H2O2 is 2.5 mmol·L-1 and hydroxylamine hydrochloride 0.5 mmol·L-1 in ?-FeOOH/H2O2 heterogeneous system,the degradation rate of AOII reaches more than 90%within 40 min.The AOII can be rapidly degraded from pH 3.0 to 6.0;Cl-and N03-hardly have any effect on pre-adsorption but have a positive effect on the catalytic degradation.S042-has a gradually increasing effect on pre-adsorption with the increase of concentration,but it has no significant effect on catalytic degradation.However,H2PO4-almost completely inhibited the adsorption and catalytic degradation of AOII by P-FeOOH.The active species of this system is OH derived from the homogeneous Fenton reaction and the heterogeneous Fenton reaction.After four cycles of P-FeOOH catalyst,the degradation rate of AOII is still as much as 87.56%.(3)When the content of ?-FeOOH in the composite is 75%,the initial pH value of the reaction solution is 3.05,and the H2O2 concentration is 10 mmol-1,the catalytic effect of AOII is the best and the highest degradation rate was 99.61%.The mechanism analysis indicates that the active species of the system may have four sources:1)direct decomposition of H2O2 under UV light conditions;2)photocatalytic reaction of ?-FeOOH/TiO2 and H2O2 system under light irradiation;3)heterogeneous Fenton reaction of ?-FeOOH in composite materials FeOOH/TiO2 and composition on its surface;4)Fenton reaction of iron ions dissolved from ?-FeOOH and H2O2 in solution.