木虫 (著名写手)
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commandos2(金币+75,VIP+0):谢谢啊，虽然改动不多，但是也有帮助 3-16 08:15
3.2. Effect of sample dosage on the COD of wastewater
The effect of sample dosage ranging from 0.0 to 20 mg•mL-1 on the COD removal of wastewater is shown in Fig. 3. The COD removal increases significantly with the dosage of RHM or RHA when the dosage is less than 20 mg•mL-1. Thereafter, it changes slightly and maintains at 73% (RHM) or 66% (RHA). Compared with RHA, the COD removal of RHM is higher at identical dosages. For instance, the COD removal of RHM is ~18% higher than that of RHA when the sample dosage is 5 mg•mL-1. Moreover, the maximum COD removal of RHM (73.5%, at dosage of 15 mg•mL-1) is ~7% higher than that of RHA (66.5%, at dosage of 25 mg•mL-1).The surface area of RHA (433.90 m2•g-1) is twice as large as that of RHM (214.54 m2•g-1),so RHA should present stronger adsorption ability than that of RHM. The catalytic ability of RHM is stronger than that of RHA, due to the presence of MnFe2O4. Organics were adsorbed to the surface of RHM and catalysis degraded by the ferrite nanoparticles during the wastewater treatment, which is consistent with former researches [38, 41] .
3.3. Effect of microwave treatment on the COD of wastewater
The variations of the COD of wastewater as a function of microwave heating time is shown in fig.4. When the wastewater was treated by 20 mg•mL-1 RHM or RHA without microwave heating, the COD removal is less than 7%, which is attributed to the inadequate contract between RHM and organics. When the microwave radiation was added, the COD removal increases considerably in the first 3 min, from 41% to 72% for RHM and 19% to 60% for RHA. Thereafter, itl changes little and maintains at ~73% for RHM and ~65% for RHA.
Both RHM and RHA,as it is observedin microwave treatment ,will reach theirs maximum COD removal within 6 min under the assist of microwave radiation. There may be two reasons: first, microwave radiation will selectively heat and motivate some special materials such as active carbon and magnetic materials to be hotspots [43] which adsorb and catalytic degrade the organics of wastewater rapidly. Second, the quantum energy of microwave can motivate the rotation of molecules and decrease the activation energy of reactions, which facilitates the breaking of chemical bonds and the adsorption of RHM or RHA for organics [31, 44] . RHM reaches its maximum COD removal earlier than RHA does and the COD removal of RHM is higher than that of RHA at all periods, indicating that RHM is easier to be heated by the microwave radiation. It is still attributed to the presence of MnFe2O4. |
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