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Textile and food industries produce a significant volume of effluents containing azo dyes and other pollutants. These effluents are serious environmental threats, and new methods for their treatment and for the degradation of azo dyes are thus attracting much attention. The current study deals with the oxidative degradation of azo dyes by meso‐tetrakis(1‐methylpyridinium‐4‐yl)prophyrinatoiron(III), [FeIII(tmpyp)], and meta‐chloroperoxy benzoic acid (m‐CPBA) in aqueous solution at room temperature. The catalytic degradation of azo dyes was investigated by using rapid‐scan stopped‐flow spectrophotometry as a function of solution pH, [catalyst], [m‐CPBA], [dye] and [surfactants]. To obtain mechanistic insight, the reaction between [FeIII(tmpyp)] and m‐CPBA was also studied in aqueous solution in absence of azo dyes. Spectral analyses and kinetic data show that [FeIII(tmpyp)] is transformed into the transient intermediate [FeIV(O)(tmpyp)].+ (a compound I analog) within 20–30 ms followed by the formation of relatively stable [FeIV(O)(tmpyp)] (a compound II analog). Batch experiments reveal that the dye degradation rate is influenced by the solution pH and the concentrations of [FeIII(tmpyp)], m‐CPBA, dye, and surfactants. On the basis of the kinetic and spectroscopic data, a mechanistic scheme for the dye degradation reaction and a steady‐state rate equation are proposed. The products resulting from oxidative degradation of the azo dye amaranth have been analyzed by HPLC‐UV‐HRMS. [ABSTRACT FROM AUTHOR]

Dyes in wastewater severely affect the nature and quality of water by inhibiting the sunlight penetration into the stream, which thereby reduces the photosynthesis reaction. This poses a serious environmental threat in many developing countries. Recently, new methods for the treatment of colored dye effluent streams have attracted much attention. The [MnIII(tmpyp)]/H2O2 system (tmpyp= meso-tetrakis(1-methylpyridinium-4-yl)porphyrinato) was now found to degrade various azo dyes with remarkably high efficiency under ambient conditions in aqueous solution at certain pH values. Main products of the catalytic degradation of the dye amaranth by [MnIII(tmpyp)]/H2O2 were analyzed. The reaction mechanism was studied in more detail by using rapid-scan stopped-flow spectrophotometry as a function of pH, [catalyst], [H2O2], [dye], and [surfactants]. Spectral analyses and kinetic data suggested rapid formation of an intermediate [MnIII(tmpyp)(OOH)] (a compound 0-type intermediate), followed by the formation of a relatively stable trans-dioxomanganese(V) porphyrin complex, [MnV(O)2(tmpyp)] (a compound I analog). The one-electron reduction of [MnV(O)2(tmpyp)] to [MnIV(O)(tmpyp)] (a compound II analog) was accelerated greatly by amaranth. On the basis of the kinetic and spectroscopic data, a reaction mechanism of the formation of reactive intermediates [MnIII(tmpyp)(OOH)], [MnV(O)2(tmpyp)], and [MnIV(O)(tmpyp)] was proposed. [ABSTRACT FROM AUTHOR]