Oxidative degradation of non-ionic surfactant (TritonX-100) by chromium(VI)

Abstract

Degradation of polyoxyethylene chain of non-ionic surfactant (TritonX-100) by chromium(VI) has been studied spectrophotometrically under different experimental conditions. The reaction rate bears a first-order dependence on the [Cr(VI)] under pseudo-first-order conditions, [TritonX-100] ≫ [Cr(VI)] in presence of 1.16 mol dm −3 perchloric acid. The observed rate constant ( k obs) was 3.3 × 10 −4 to 3.5 × 10 −4 s −1 and the half-life ( t 1/2) was 33–35 min for chromium(VI). The effects of total [TritonX-100] and [H +] on the reaction rate were determined. Reducing nature of non-ionic TritonX-100 surfactant is found to be due to the presence of –OH group in the polyoxyethylene chain. It was observed that monomeric and non-ionic micelles of TritonX-100 were oxidized by chromium(VI). When [TritonX-100] was less than its critical micelle concentration (cmc) the k obs values increased from 0.76 × 10 −4 to 1.5 × 10 −4 s −1. As the [TritonX-100] was greater than the cmc, the k obs values increases from 2.1 × 10 −4 to 8.2 × 10 −4 s −1 in presence of constant [HClO 4] (1.16 mol dm −3) at 40 °C. A comparison was made of the oxidative degradation rates of TritonX-100 with different metal ion oxidants. The order of the effectiveness of different oxidants was as follows: permanganate > diperiodatoargentate(III) > chromium(VI) > cerium(IV).