Study On Microwave Absorption And Microwave Degradation Of Antibiotics For Two Typical Manganese Dioxides

The structure and property of natural birnessite were studied in the thesis.The results indicated that the natural manganese oxides(MOs)had excellent microwave absorption performance.In order to study the mechanism of microwave absorption for MOs,the representative MOs of birnessite with 1×? layered structure and cryptomelane with 2×2 tunnel structure were prepared.The influences of composition and morphology on microwave absorption performance of birnessite were investigated by controlling the acid-base and average oxidation state of birnessite,and the effects of microwave absorption mechanism towards the tetracycline(TC)degradation were also studied.The microwave absorption performance and degradation of TC by cryptomelane were explored by adjusting the intrinsic dipole moment,crystal symmetry and crystal morphology of as-prepared samples.The main contents and conclusions are listed as follows:(1)The Alkaline-Birnessite,acid-Birnessite and Cryptomelane were successfully prepared by coprecipitation method,and the structure and morphology were studied.The results showed that the birnessite had a layered structure,and the average oxidation state of obtained birnessites could be controlled by changing the adding amount of the lower valence of Mn.The crystal structure of Cryptomelane belonged to tetragonal system,and the morphology was nanofiber with diameter about 50 nm.After incorporation with Co and Fe,the crystal structure of Cryptomelane could be transformed from tetragonal to monoclinic,and the morphology was also changed simultaneously from nanofibers to the particles of micron level.(2)There are dielectric loss and magnetic loss under the microwave radiation.The dielectric loss was the main factor of Birnessite with higher average oxidation state,while the magnetic loss was the main contribution of Birnessite with lower average oxidation state,demonstrating that the spin magnetic moment of Mn was the key factor for affecting the dielectric loss or magnetic loss of birnessite.After doping Co/Fe into Cryptomelane,the microwave absorption performance was slightly reduced.However,due to the generation of inherent electric dipole moment by the transformation of crystal structure,the strongest reflection absorption peak was shifted to higher frequency(3)TC could be degraded by the natural Birnessite under microwave radiation.The main factor of this process was the physical adsorption.Compared with the natural birnessite,TC could be also degraded by prepared Alkaline-Birnessite under microwave radiation,and the removal amount was up to 16.9 mg/g.Compared with a series of Fe-Cryp,the raw Cryptomelane had the best microwave absorption performance,and the reflection loss could reach up to-35 dB.The results proved that the raw Cryptomelane had the best capacity to degrade TC and the degradation amount was 21.8 mg/g after 40 min.