本研究針對亞錳離子(Mn2+)，首先利用次氯酸化學氧化法合成二氧化錳(MnO2)，並藉由增加次氯酸劑量以提升產率。產物以XRD、EDS做定性分析，確認所合成二氧化錳為ε-MnO2(Akhtenskite)，以BET儀器測得其比表面積為95.27 m2/g，以雷射界面電位分析儀分析此材料之pHzpc = 3.4 0.5。
在應用方面，本研究將上述合成的ε-MnO2應用於降解雙氧水與礦化草酸。研究結果顯示，針對10 mM之雙氧水，使用0.1 g/L之ε-MnO2即可於20分鐘內達99 %的去除率，動力為二階反應，反應速率常數 = 3.352 M-1•s-1;另一方面，使用1 g/L之ε-MnO2可於2小時內礦化99 %濃度為2.45 mM之草酸。
接下來，本研究試圖將次氯酸氧化亞錳離子所得的二氧化錳披覆於鐵氧化物-FeOOH(BT9)表面，以合成核殼型的錳/鐵雙成分氧化物(MBT9)。研究發現藉由改變次氯酸劑量與反應時間，可控制二氧化錳於MBT9表面之披覆量，當HOCl/Mn = 10(莫耳比)時，反應6小時以後，其錳/鐵莫耳比約為18 %。錳/鐵莫耳比會跟隨氧化劑量的減少而降低，當HOCl/Mn = 1時，反應6小時以後，錳/鐵莫耳比下降至2%。
最後，本研究試圖將上述一系列不同錳/鐵含量的MBT9應用於吸附除三價砷(As(III))與五價砷(As(V))實驗中，發現除砷效果受錳/鐵含量的影響，有其最適值錳/鐵莫耳比約為9 %(M9BT9)，故後續的研究以此做為除砷的吸附劑，發現As(III)去除效率隨增加M9BT9劑量而提升，5 g/L M9BT9之用量可使10 ppm之As(III)在20小時內降至0.01 ppm以下，符合WHO飲用水標準的要求。在吸附動力方面符合二階吸附動力模式(R2 = 0.99)，在等溫吸附實驗中較符合Langmuir Model(R2 = 0.99)，研究結果顯示M9BT9對於As(III)最大吸附量為32.2 mg/g大於改質前的BT9對As(III)的最大吸附量(21.79 mg/g)，推測原因為M9BT9表層披覆的二氧化錳可以將As(III)氧化成As(V)，進而被BT9所吸附；但M9BT9對於As(V)的最大吸附量為18.7 mg/g反而小於改質前的BT9對As(V)的最大吸附量(26.9 mg/g)，推測其原因為表面電位，BT9(pHzpc =6)於反應過程中(pH = 3)，表面電位為帶正電性，相較M9BT9其表層二氧化錳(pHzpc =2.8)為帶負電或不帶電，BT9較易吸附帶負電的五價砷(H2AsO4-)。

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.

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