Hydrogen peroxide decomposition on manganese oxide (pyrolusite): Kinetics, intermediates, and mechanism
Hydrogen peroxide decomposition on manganese oxide (pyrolusite): Kinetics, intermediates, and mechanism
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DOI：
10.1016/j.chemosphere.2008.11.075
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发表时间：
2009-03-01
期刊：
影响因子：
8.8
通讯作者：
Kong, Sung-Ho
中科院分区：
文献类型：
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作者：
Do, Si-Hyun;Batchelor, Bill;Kong, Sung-Ho
本研究的目的是对过氧化氢在氧化锰(软锰矿)上的分解进行动力学解释，并解释包括过氧化氢/超氧阴离子在内的反应机理。在pH值为7时，过氧化氢在氧化锰上的分解符合准一级反应模型。在[H_2O_2]/[=MnO_2]为11.8时，当[H_2O_2]/[=MnO_2]在58.8~3.92时，观察到的一级反应速率常数的最大值为0.741分钟(-1)。在[H_2O_2]/[=MnO_2]范围内，拟一级反应速率常数k(MnO_2)的平均值为0.025(分钟mm)(-1)，标准偏差为0.003。当[H_2O_2]/[=MnO_2]为3.92时，反应速率常数(k(MnO_2))最大为0.061(Min Mm)(-1)。在大多数实验中，初始产氧速率随[H_2O_2]/[=MnO_2]的降低而增加，氧气总量略小于化学计量比(0.5)。然而，在低[H_2O_2]/[=MnO_2](即3.92和9.79)条件下，产氧量大于0.5。过氧化氢/超氧阴离子的相对生成量表明，随着[H_2O_2]/[=MnO_2]的降低，过氧化氢/超氧阴离子的生成量增加，阴离子的存在表明其机理包括与溶液中的过氧化氢/超氧阴离子等中间体的繁殖反应。此外，在碱性溶液中，[H_2O_2]的分解和阴离子的产生都被加速。在中性和碱性条件下，溶解到溶液中的锰离子几乎不存在，但在酸性条件下，溶解到溶液中的锰离子大大增加。(C)2008爱思唯尔有限公司。保留所有权利。
The objective of this study is the kinetic interpretation of hydrogen peroxide decomposition on manganese oxide (pyrolusite) and the explanation of the reaction mechanism including the hydroperoxide/superoxide anion. The decomposition of hydrogen peroxide on manganese oxide at pH 7 was represented by a pseudo first-order model. The maximum value of the observed first-order rates constants (k(obs)) was 0.741 min(-1) at 11.8 of [H2O2]/[= MnO2] when [H2O2]/[= MnO2] were ranged from 58.8 to 3.92. The pseudo first-order rate constants (k(MnO2)) approximated as the average value of 0.025 (min mM)(-1) with a standard deviation of 0.003 at [H2O2]/[= MnO2] ranged from 39.2 to 11.8. When [H2O2]/[= MnO2] was 3.92, the rate constants (k(MnO2)) was 0.061 (min mM)(-1) as maximum. Oxygen production showed that the initial rates increased with decreasing [H2O2]/[= MnO2] and the total amounts of oxygen was slightly less than the stoichiometric value (0.5) in most experiments. However, oxygen was produced at more than 0.5 in low [H2O2]/[= MnO2] (i.e. 3.92 and 9.79). The relative production of hydroperoxide/superoxide anion implied that the production increased with low [H2O2]/[= MnO2], and the existence of anions Suggested that the mechanism includes propagation reactions with intermediates such as hydroperoxide/Superoxide anion in solution. In addition, both [H2O2] decomposition and the production of anion were accelerated in alkaline solution. Manganese ion dissolved into solution was negligible in neutral and alkaline conditions, but it greatly increased in acidic conditions. (C) 2008 Elsevier Ltd. All rights reserved.