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化学学报
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化学学报 ›› 2003, Vol. 61 ›› Issue (9): 1346-1351. 上一篇    下一篇

研究论文

高碘酸盐氧化硫脲的非线性动力学行为和机理

林娟娟;王舜;高庆宇;王新红;徐良芹   

  1. 温州师范学院化学与材料科学系;中国矿业大学化工学院
  • 发布日期:2003-09-15

Nonlinear Kinetic Behavior and Mechanism of the Oxidation of Thiourea by Periodate

Lin Juanjuan;Wang Shun;Gao Qingyu;Wang Xinhong;Xu Liangqin   

  1. Department of Chemistry and Material Science, Wenzhou Teachers' College;College of Chemical Engineering, China University of Mining and Technology
  • Published:2003-09-15

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被引次数

16 | 3

在酸性介质中，高碘酸盐氧化硫脲的非线性反应呈现多种不同的化学计量方程 式。当[KIO_4]_0/[SC(NH_2)_2]_0 > 4时，计量方程为4IO_4~- + SC(NH_2)_2 + 3H_2O = 4IO_3~- + SO_4~(2-) + CO_3~(2-) + 2H~+ + 2NH_4~+；当[KIO_4]_0/ [SC(NH_2)_2]_0 = 8:7时，计量方程为8IO_4~- + 7SC(NH_2)_2 + 17H_2O = 4I_2 + 7SO_4~(2-) + 7CO_3~(2-) + 6H~+ + 14NH_4~+；而当[KIO_4]_0/[SC(NH_2)_2] _0 < 1时，反应的主要计量方程为IO_4~- + 4SC(NH_2)_2 + 8H_2O = I~- + 4S + 4CO_3~(2-) + 8NH_4~+。同时反应体系在氧化剂过量的条件下碘钟产生的诱导期 与1/[H~+]~2成正比；而当还原剂过量时，体系I_2逐渐累积至极值的诱导期与体系 初始pH呈线性关系。运用包含质子平衡反应、碘化合物自身反应、碘化合物-硫化 合物反应以及硫-硫反应的15步反应机理较好地模拟出封闭体系中pH，[I~-]以及 [I_2]的准振荡行为。

关键词: 振荡化学反应, 高碘酸盐, 硫脲, 氧化, 反应动力学, 反应机理

The reaction between periodate and thiourea in acidic medium has been investigated in a batch. The stoichiometries of the reaction are: 4IO_4~- + SC(NH_2)_2 + 3H_2O = 4IO_3~- + SO_4~(2-) + CO_3~(2-) + 2H~+ + 2NH_4~+ ([IO_4~-]/[SC(NH_2)_2]_0 > 4) (1) 8IO_4~- + 7SC(NH_2)_2 + 17H_2O = 4I_2 + 7SO_4~(2-) + 7CO_3~(2-) + 6H~+ + 14NH_4~+ ([IO_4~-]/ [SC(NH_2)_2] ≈ 8:7) and mixed reaction of (l) and (2) (8/7 < [IO_4~-]/ [SC(NH_2)_2]< 4 ), respectively. In closed systems the reaction is autocatalytic in H+ and I" , and can be characterized by two different induction periods. In excessive periodate, the induction period defined as the time between the beginning of reaction and the appearance of a red-brown colour, indicating the product of iodine, has a linear relation with 1/[H~+ ]~2. In excessive thiourea, the induction period from the start of reaction to maximal [l2] is directly proportional to the initial pH. A fifteen-step mechanism, including iodine-iodine reactions, iodine-sulfur reactions and sulfur- sulfur reactions, simulated the observed kinetics.

Key words: OSCILLATION CHEMICAL REACTION, PERIODATE, THIOUREAS, OXIDATION, REACTION KINETICS, REACTION MECHANISM

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