THE CHEMISTRY OF PERSULFATE .1. THE KINETICS AND MECHANISM OF THE DECOMPOSITION OF THE PERSULFATE ION IN AQUEOUS MEDIUM
THE CHEMISTRY OF PERSULFATE .1. THE KINETICS AND MECHANISM OF THE DECOMPOSITION OF THE PERSULFATE ION IN AQUEOUS MEDIUM
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DOI：
10.1021/ja01151a024
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发表时间：
1951-01-01
影响因子：
15
通讯作者：
MILLER, IK
中科院分区：
文献类型：
--
作者：
KOLTHOFF, IM;MILLER, IK
证明过硫酸钾在水溶液中热分解有两个反应：(A)O-O键对称断裂，生成两个硫酸盐自由基，与水反应放出氧而消失；(B)酸催化反应，包括HS2OS~+的O-O键不对称断裂，生成四氧化硫和硫酸氢盐。在稀酸溶液中，四氧化二硫迅速分解生成氧和硫酸，而在2-5M的高氯酸或硫酸溶液中，四氧化二硫迅速水解，生成卡洛酸(H_2S_05)。过硫酸盐离子的热分解动力学方程为-d&Oa‘/dz=fcit&Os-]+é2[H+][S208-]。在50℃离子强度为0.4时，k值和k%分别为6.0×10~(-6)min~(-1)和3.5×10~(-3)min~(-3)。非催化反应的活化能为33.5kcal。酸催化反应为26.0kcal。非催化反应的速率与离子强度无关，但酸催化反应的速率随着离子强度的增加而减小。非催化反应释放的氧气来自水，而酸催化反应释放的氧气来自过硫酸盐离子。自1878年Berthelot发现过硫酸(H_2S_2O_3)以来，有关过硫酸和过硫酸盐的性质和反应的文献已有3篇之多。ELBS和Schónherr4发现，过硫酸在水溶液中不稳定，在稀硫酸溶液中分解，释放氧气，而在浓度较高的硫酸溶液中生成过氧化氢，而不是氧气。Caro6a观察到强酸过硫酸盐溶液生成一过硫酸(H_2SO_3)，而Palme6b后来的工作表明，这种酸是过硫酸在强酸溶液中分解生成过氧化氢的中间产物。因此，过硫酸盐在水溶液中的分解涉及反应
Evidence is given that potassium persulfate decomposes thermally in aqueous solutionsby two reactions,(a) a symmetrical rupture of the 0-0 bond to form two sulfate free-radicals which disappear by reaction with water to liberate oxygen, and (b) an acid-catalyzed reaction involving the unsymmetrical rupture of the 0-0 bond of the HS2Os~ ion to form sulfur tetroxide and bisulfate. In dilute acid solutions sulfur tetroxide decomposes rapidly to form oxygen andsulfuric acid while in solutions 2 to 5 M in perchloric or sulfuric acid sulfur tetroxide hydrolyzes, rapidly to Caro’s acid (H2S05). The kinetics of the thermal decomposition of the persulfate ion are described by the equation— d&Oa'/dZ= fcit&Os-]+ é2 [H+][S208-]. The values of k, and k%, respectively, are 6.0 X 10 “6 min.-1 and 3.5 X 10-3 (min.^ Xm./l.)-1 at an ionic strength of 0.4 at 50. The activation energy for the uncatalyzed reaction is 33.5 kcal. and for the acid-catalyzed reaction 26.0 kcal. The rate of the uncatalyzed reaction is independent of ionic strength but the rate of the acid-catalyzed reaction decreases with increasing ionic strength. The oxygen liberated by the uncatalyzed reaction comes from the water while the oxygen liber-ated by the acid-catalyzed reaction comes from the persulfate ion.Since the discovery of persulfuric acid (H2S2O3) in 1878 by Berthelot, 3 numerous papers have appeared concerning the properties and reactions of persulfuric acid and persulfates. Elbs and Schónherr4 found that persulfuric acidis unstable in aqueous solutions, decomposing in dilute sulfuric acid solutions with liberation of oxygen while in more concentrated sulfuric acid solutions hydrogen peroxide rather than oxygen is formed. The formation of monopersulfuric acid (H2SO3) by strongly acid persulfate solutions was observed by Caro6a while later work by Palme6b showed that this acid is an intermediate in the decomposition of persulfuric acid in strongly acid solutions to form hydrogen peroxide. Thus the decomposition of persulfate in aqueous solutions involves the reactions