Oxidation of nonionic surfactant (Tween-80) by chromium(VI) in acidic medium

Abstract

The oxidation of Tween-80 by chromium(VI) in aqueous acidic solutions has been studied at different temperatures (30-60°C). The rates of disappearance of chromium (VI ) absorbance follow second order kinetics; first order each in

<span style="font-size:14.0pt;line-height:115%;font-family:" times="" new="" roman";="" mso-fareast-font-family:"times="" roman";color:black;mso-ansi-language:en-in;="" mso-fareast-language:en-in;mso-bidi-language:hi"="" lang="EN-IN">[Cr(VI )] and [Tw-80] at constant acidity. The reaction order with respect to [H⁺] increases from one to higher with increase in [HClO₄]. Interestingly, Tw-80 is not oxidised in absence of acid. The reaction is considered to proceed through the formation of a chromate ester between the chromium (VI) and primary - OH group of polyoxyethylene chain of Tw-80. The activation parameters calculated using Arrhenius and Eyring equations are: <i>E</i>_a= 46 kJ mol^-1 , Δ<i>H</i>^#= 44 kJ mol^-1 and Δ<i>S</i>^#= -200 JK^-1 mol^-1. . .</span>