Iridium nanoparticles with high catalytic activity in degradation of acid red-26: an oxidative approach

Nanocatalysis using metal nanoparticles constitutes one of the emerging technologies for destructive oxidation of organics such as dyes. This paper deals with the degradation of acid red-26 (AR-26), an azo dye by hexacyanoferrate (abbreviated as HCF) (III) using iridium nanoparticles. UV-vis spectroscopy has been employed to obtain the details of the oxidative degradation of the selected dye. The effect of various operational parameters such as HCF(III) concentration, pH, initial dye concentration, catalyst and temperature was investigated systematically at the lambda(max), 507 nm, of the reaction mixture. Degradation kinetics follows the first order kinetic model with respect to AR-26 and Ir nano concentrations, while with respect to the HCF(III) concentration reaction it follows first order kinetics at lower concentrations, tending towards zero order at higher concentrations. Thermodynamic parameters have been calculated by studying the reaction rate at four different temperatures. The UV-vis, high performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS) analysis of degradation products showed the formation of carboxylic acid and substituted carboxylic acids as major degradation products, which are simple and less hazardous compounds. The big advantage of the present method is the recovery and reuse of iridium nanoparticles. Moreover, turnover frequencies for each catalytic cycle have been determined, indicating the long life span of Ir nanoparticles. Thus, the finding is a novel and highly economical alternative for environmental safety against pollution by dyes, and extendable for other contaminants as well.