Preparation Of Wood-based Magnetic Activated Carbon And Its Adsorption Characteristics On Methylene Blue

In order to achieve efficient removal of methylene blue from printing and dyeing wastewater,activated carbon prepared from agricultural and forestry biomass with high cellulose content and rich cell structure has been widely used,which has large specific surface area,rich pore size structure and high adsorption efficiency,and in the problem of achieving rapid and efficient separation after adsorption of activated carbon,some researchers have proposed the preparation and synthesis of magnetic adsorbent.However,the application of magnetic adsorbents in real-life and commercial production is still limited due to the high cost of raw materials,complicated operation process and low reusability in the preparation process.Therefore,it is of great significance to find a new magnetic adsorbent and a new technology that can effectively remove methylene blue from printing and dyeing wastewater with a simpler preparation process,better adsorption effect,easy recovery and multiple reuse after regeneration.Therefore,a series of new activated carbon and magnetic activated carbon adsorbent materials were prepared by activators（H₃PO₄,KOH）and hydrothermal methods using agricultural and forestry biomass materials as raw materials,and they were applied to remove methylene blue in printing and dyeing wastewater to test the adsorption performance of the samples.The research content and important results of the paper are as follows:（1）Preparation and structural characterization of iron oxide loaded magnetic activated carbon.The ACs,M1ACs and M2ACs were successfully prepared by one-step and two-step hydrothermal magnetization methods using juniper wood chips under low-temperature activation with H₃PO₄,and all of them had a large number of microporous and mesoporous structures,among which AC2,M2AC1 and M2AC2 prepared by two-step activation method and two-step hydrothermal magnetization method had high specific surface areas of 1111.0 m²/g,1135.6 m²/g and 1012.4 m²/g,respectively.The structural characterization demonstrated that the magnetic activated carbon MACs were successfully loaded with fine iron oxide particles,of which Fe³⁺dominated in the prepared magnetic activated carbon materials,which could provide more adsorption sites for the adsorption of methylene blue,and the overall magnetization effect of M2ACs was stronger than that of M1ACs,indicating the strong magnetic properties of M2ACs.The powerful magnetic properties of M2ACs,which are more favorable for the repeated sustainable use of magnetic activated carbon.（2）Adsorption performance of iron oxide loaded magnetic activated carbon on methylene blue.In the adsorption tests of methylene blue in printing and dyeing wastewater,ACs,M1ACs and M2ACs were applied,and it was found that all samples showed high selective adsorption capacity for MB at p H 10.0 and concentration of 100 mg/L.Among them,AC1 and M2AC2 showed the strongest adsorption effect with the final adsorption amounts of 535 mg/g and 540 mg/g,respectively.The adsorption of methylene blue was in accordance with the Freundlich model and pseudo-second-order kinetic model,indicating that the sites on the surface of the adsorbent materials were heterogeneous and mainly surface chemisorption.In addition,after five repeated adsorption-desorption regenerable tests,the adsorption rate of methylene blue by M2AC2 was as high as 79.8%.Therefore,the magnetic activated carbon prepared by the two-step method is conducive to efficient carbonization activation and has good stability of methylene blue adsorption,which is of practical value in the adsorption application of printing and dyeing wastewater.（3）Preparation and structural characterization of iron-cobalt oxide-loaded magnetic activated carbon.Based on the results in Chapters 2 and 3,activated carbons N-AC800,N-AC900 and N-AC1000 with higher specific surface area and rich pore structure and two different easily recyclable and reusable magnetic adsorption materials Fe-N-AC and Co-N-AC were successfully prepared by urea doping,KOH activation and hydrothermal treatment of Fe-Co-oxide.-AC900 and Co-N-AC both exhibited high specific surface areas of 2779.7 m²/g and 2076.8 m²/g,respectively.The successful loading of iron oxide and cobalt oxide on the surfaces of the magnetic adsorbent materials Fe-N-AC and Co-N-AC,respectively,was verified by structural characterization,which proved their strong magnetic properties and facilitated the easy recovery and renewable use.（4）Adsorption performance of iron-cobalt oxide loaded magnetic activated carbon on methylene blue.By applying the prepared high specific surface area adsorbent materials N-AC900,Fe-N-AC and Co-N-AC to methylene blue adsorption tests,it was found that all three samples exhibited good adsorption of methylene blue at p H values of 3-10.Meanwhile,the highest adsorption rates of methylene blue were up to 99.0%,98.5%and 99.6%for N-AC900,Fe-N-AC and Co-N-AC,respectively,at different initial concentrations of methylene blue solution.The adsorption isotherms and adsorption kinetics of all samples were in accordance with the Freundlich model and the proposed secondary kinetic model,which proved that the adsorption mechanism of methylene blue by the adsorbent was mainly controlled by chemisorption in the multilayer adsorption.In addition,the adsorption rates of Co-N-AC on methylene blue were 90.9%after five repeated adsorption-resolution regeneration tests,which further demonstrated that the magnetic adsorbent prepared in this test has good desorption,regeneration and recovery properties.