Synthesis and application of MnO2 and MnO2/FeOOH

• Main Authors: Ruo-LinHuang, 黃若琳
• Other Authors: Yao-Hui Huang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/92905556029603249526

碩士 === 國立成功大學 === 化學工程學系碩博士班 === 101 === This work successfully synthesized manganese dioxide through the chemical oxidation of manganese ions (Mn(II)) by hypochlorous acid. The result showed that increasing hypochlorous acid will improve the oxidation yield of manganese dioxide. The XRD patterns confirmed that the manganese dioxide majorly consisted of Akhtenskite (ε-MnO2) phase. The BET surface area of the manganese dioxide, determined by N2 adsorption, was 95.27 m2/g . The pHzpc of the manganese dioxide determined using a zeta potential meter was 3.4 0.5. To examine the synthetic manganese dioxides’ capability of acting as a catalyst and an oxidant. The experiments of hydrogen peroxide degradation and oxalic acid mineralization were then carried out. The 10 mM of hydrogen peroxide could be degraded by 0.1 g of ε-MnO2 in 20 minutes. The degradation of hydrogen peroxide was a second-order reaction and the reaction rate constant ( ) was 3.352 M-1•s-1. The 2.425 mM of oxalic acid also could be mineralized by 1 g of ε-MnO2 in 2 hours. On the other hand, a novel multi-functional MBT9 was prepared by deposition of the manganese dioxide onto an iron oxide, BT9; the amounts of deposition were optimized by the ratio of hypochlorous acid to manganese (II) (HOCl/Mn). By jar-test process, a maximum molar ratio of Mn to Fe was 0.18 by adjusting HOCl/Mn to 10. As HOCl/Mn was decreased to 1, the molar ratio of Mn to Fe was declined to 0.02. The manganese dioxide on MBT9 that underwent an additional oxidation of As (III) could substantially enhance the arsenic adsorption. M9BT9 with a 0.09 molar ratio of Mn to Fe could attain a maximum adsorption amount of As (III), 32.2 mg/g. The As (III) adsorption using M9BT9 followed a second-order behavior. The sorption isotherms could be well fitted with Langmuir model, revealing that As(III) adsorption capacity of M9BT9 was 32.2 mg/g, higher than that of BT9 (21.79 mg/g). The As (V) adsorption capacity of M9BT9 was 18.7 mg/g which was lower than that of BT9 (26.9 mg/g). High capacity of M9BT9 for As (III) was attributed to the surface manganese dioxide capable of oxidizing As (III) to As (V); however, low capacity of M9BT9 for As (V) was due to the relatively low surface potential than BT9.