Kinetics of the self-decomposition of ozone and the ozonation of cyanide ion and dyes in aqueous solutions.

Abstract

Kinetic studies on the self-decomposition of ozone in water, the decomposition of CN~and CNO~, and the decolorization of several dyes by ozone were performed over a wide range of pHusing a stopped-flow apparatus under homogeneousconditions at 298 K. The rate of selfdecomposition of ozone was measured in the pH range from 1 to 13.5, and it was found that in the pH range above 8 the rate was expressed bywhile in the acidic region the concentration dependence of the rate was complicated, and a simple rate expression could not be obtained. The purpose of this paper is to obtain the intrinsic reaction kinetics of the ozonation of several typical contaminants such as cyanide and cyanate ions and dyes in water using a stopped-flow technique under homogeneous conditions. The rate of self-decomposition of ozone in water, which is closely related to the degree of ozone utilization, was also investigated over a wide range of pH. ExperimentalKinetic measurements were performed by meansof a spectrophotometric method.Therates of reactions other than the self-decomposition of ozone at low pH were quite fast, and were measured by a stopped-flow apparatus (Union Giken RA-110). Water containing a known amount of ozone, prepared by bubbling ozone through deionized water, was mixed with the same volume of a buffer solution adjusted to the desired values of pHand of the concentration of a substrate in a cylindrical cell having 2 mmor 10 mmlight-path length, and the time-course of the absorbance of ozone or the reactant was followed. The self-decomposition of ozone at pH below 9 was followed by an ordinary spectrophotometer equipped with a glass-stoppered cell of 10 mmpath length. Calibration charts of the relation between absorbance and ozone concentration were prepared on the basis of the usual analytical method employing potassium iodide. The absorption 383

Ozone treatment of textile effluents and dyes: effect of applied ozone dose, pH and dye concentration

“…The cleavage of CÐC double bonds and other functional groups will shift the absorption spectra of the molecule out of the visible region. 20 Researchers have observed that some dye-containing wastewater undergoes a pseudo®rst order reaction with respect to dye concentration and the rate of decolorization decreases with increase in dye concentration. 12,13 Results have showed that ozonation can improve the biodegradability of the wastewater by converting the high molecular compounds of the dye into lower molecular organics.…”

“…Color is caused by chromophores in the molecules (usually double bound systems) which are oxidized by ozonation to single bonds thus losing the ability to absorb visible light. 20 The lower DOC and COD removal compared with the color removal can be explained by incomplete oxidation of organic materials. COD and DOC removal ef®ciencies for Sample A at several ozone dose applications for a 15 min ozonation time were in the ranges 15±46% and 10±20% respectively.…”

Decolorisation of effluent with ozone and re-use of spent dyebath

“…81,89 During the study of the self-decomposition of ozone in aqueous solution for a pH range from 1 to 13.5, it was observed that the rate was related to the total amount of ozone consumed. 90 It was noticed that decolorisation efficiency was strongly dependent on the pH of the solution during decolorisation of dyes other than Naphthol Yellow, for which the rate of decolorisation was almost independent of the pH. 90 Interestingly, one acid dye, C.I.…”

Energy efficient—Advanced oxidation process for treatment of cyanide containing automobile industry wastewater

“…H 2 O 2 , a strong oxidizing agent, oxidizes CN to nontoxic compounds via cyanate (CNO − ) following hydrolysis reaction. CN destruction using a O 3 /CN system has been employed for a number of bench scale studies [12][13][14][15][16][17][18][19][20] that demonstrated the first reaction to be extremely rapid while the second reaction of cyanate oxidation by O 3 to be a slower one. The use of O 3 offers a specific advantage over H 2 O 2 that little secondary products are formed after the treatment.…”