Preparation Of High-performance Magnetic Activated Carbon And Its Adsorption To Methylene Blue

In today’s energy crisis and environmental problems,the quest for cheap raw materials to prepare high performance magnetic activated carbon is gaining increasing attention.Activated carbon fugitive magnetization can effectively solve the problem of difficult separation and recovery of activated carbon,with high magnetic content and strong magnetism in magnetic activated carbon,as well as simple and low cost process.In this paper,sesame straw,an agricultural waste,was used as raw material to prepare magnetic biomass activated carbon adsorbent for adsorption of methylene blue(MB)solution by low temperature solid phase method milling of the adsorbent and its tube furnace(magnetization and activation)in one step.Not only improve the shortcomings of the traditional adsorbent is not easy to recover,to avoid secondary pollution,and the use of KOH to chemically modify it,containing iron,cobalt,nickel and other salts for magnetic materials before the preparation of magnetic biomass activated carbon(MAC)adsorbent adsorption effect is good,the application of a wider prospect.The effects of the initial concentration of dye,adsorption time,adsorbent dosage,adsorption temperature and p H on the adsorption effect were explored individually,and orthogonal and response surface tests were used to improve the adsorption process.The adsorbents were characterised according to FT-IR and SEM,BET was used to determine the adsorption efficacy of the materials,XPS was used to determine the elements contained in the materials,thermogravimetry(TG)was used to study the thermal stability and components of the materials,and adsorption kinetics and isothermal adsorption models were used to study the adsorption mechanism.The main results are as follows:1.Sesame straw activated carbon,sesame straw ferromagnetic activated carbon,sesame straw nickel magnetic activated carbon and sesame straw cobalt magnetic activated carbon were prepared by low temperature solid phase milling,and their structures and properties were analysed by SEM,XPS,VSM,TG and BET specific surface area and other modern analytical methods to further understand the relevant structures of the activated carbon.2.The process of adsorption of methylene blue(MB)dye wastewater from the above activated carbon was optimised by orthogonal as well as response surface methodology.The optimum preparation conditions for sesame straw activated carbon(AC)were:potassium hydroxide,sesame straw biochar at a mass ratio of 4:1,activation temperature of800°C,activation for 30 min,adsorption capacity of 798 mg/g;sesame straw ferromagnetic activated carbon(Fe-MAC)at a mass ratio of potassium hydroxide,sesame straw biochar and ferric chloride hexahydrate of 4:1:0.4,activation temperature 800°C,activation for 30 min,adsorption capacity of 895 mg/g;sesame straw nickel magnetic activated carbon(Ni-MAC)potassium hydroxide,sesame straw biochar,nickel chloride hexahydrate by mass 4:1:0.4,activation temperature 800°C,activation for 30 min,adsorption capacity of992 mg/g;sesame straw cobalt magnetic activated carbon(Co-MAC)best preparation conditions were: Potassium hydroxide,sesame straw biochar,cobalt chloride hexahydrate in the mass ratio of 4:1:0.4,activation temperature of 800°C,activation for 30 min,adsorption capacity of 1078 mg/g.3.The surface structural characteristics of the three magnetic activated carbons were observed by SEM;the chemical states of the elements contained in the activated carbons were analysed by XPS;the thermal stability of the sesame straw activated carbon and the three magnetic activated carbons were compared by TG;the BET specific surface area of the sesame straw activated carbon(AC)was 2362.08 m2/g,the BET specific surface area of the sesame straw ferromagnetic activated carbon(Fe-MAC)was 2347.09 m2/g for sesame straw ferromagnetic activated carbon(Fe-MAC),2367.60 m2/g for sesame straw nickel magnetic activated carbon(Ni-MAC)and 2517.64 m2/g for sesame straw cobalt magnetic activated carbon(Co-MAC);the saturation magnetization intensity was 18.3Aemu/g for sesame straw ferromagnetic activated carbon(Fe-MAC)and 2517.64 m2/g for sesame straw cobalt magnetic activated carbon(Co-MAC).The saturation magnetisation intensity of sesame straw nickel magnetic activated carbon(Ni-MAC)was 5.92 Aemu/g and the saturation magnetisation intensity of sesame straw cobalt magnetic activated carbon(Co-MAC)was 21.50 Aemu/g.4.The adsorption mechanism of methylene blue(MB)adsorption by the above activated carbons was investigated by adsorption kinetic and adsorption thermodynamic models.The adsorption kinetic model: all four activated carbons were in accordance with the quasi-secondary kinetic model;adsorption thermodynamic model: all four activated carbons were in accordance with the Langmuir isothermal adsorption model.The results show that the adsorption of methylene blue(MB)on all four activated carbons is unilateral and that the adsorption proceeds spontaneously.This experiment provides a new method for the preparation of magnetic activated carbon and its adsorption of methylene blue(MB)dye,and a new method for the preparation of magnetic activated carbon;the investigated adsorption of methylene blue(MB)dye provides data reference for the treatment of dye wastewater by activated carbon.